AC Grounding &/or Bonding

[Traveler 45C]

It seems that Hatt used the bonding ckts as the AC grounding path (green wire) in the older boats.

I replaced the water heater last night. Hatt supplied the hot and neutral wires in the usual fashion, but no grounding (green) wire. The heaters case was connected to the bonding ckt.

Is this the correct method of grounding/bonding by today’s standards? Or do I need to also run an additional grounding wire (green)?

[Traveler 45C]

Does Hat in their prints perhaps show where the ac ground goes?

Yes. My schematic clearly shows a connection between the heaters grounding (green) wire and the ship's ground bus bar. However, no such wire was connected to the heater, only the bonding wire (also shown on the schematic).

Given that the bonding ckt should also be connected to the ship's ground bus bar, electrically the heater is grounded. But something about this method bothers me. If something should go wrong with the bonding ckt there would not be a safe path for fault currents back to ground. It seems to me that having a redundant grounding wire ran directly to the ship's grounding bus would be safer. I just don't know if it is required or not.

[Nonchalant1]

It matters when your boat was made. Earlier Hatts did not have the isolation transformers so they were made with real grounding wires. In any case there is a difference between "ground" and bonding wires. AC and DC ground should be connected to the bonding system only at one single point on the boat.

[REBrueckner]

The above posts are essentially correct.
Nigel Calder has always called for the same essential ground to bonding connections for at least 30 years, isolation transformer or not. But there existed for a while a two wire system aboard some boats, called a floating ground used with an isolation transformer....in that case the negative is NOT grounded....its just brought back to the isolation transformer secondary. My prior 1961 Matthews had that system.

All ac ground wires should be brought together at an ac bus bar; all dc ground wires should be brought together at a dc bus bar. Then a single heavy wire is connected from each of those bus bars directly to a single point on the bonding system, usually to the thru hull bolt which is connected to an external copper ground plate if there is one.

The reason that a single point of connection is utilized between electrical grounds and the bonding circuit is to minimize stray electrical voltages and resulting currents which may cause zincs to deterioriate and underwater metals to suffer.

[Trojan]

At the panel in older boats not using an isolation transformer both black and white wires exiting the panel are terminated through a pair of breakers. All of the AC circuits are isolated. In the panel ahead of the breakers. The white and green wires are tied together. The green is used as a safety wire and for electrolysis protection.
With the use of the isolation transformer the white and green are still tied together and are treated the same except that the electrolysis protection is not required or provided.
It does not make any difference whether the voltage is 120 V or 240 VAC. They still require twin breakers for circuit isolation. The green is still used as a safety ground wire.
BILL

[Traveler 45C]

You are correct; the neutral and grounding wires should not be tied together onboard when power is supplied direct from the dock. However, they will be if power is supplied through an isolation transformer (at the secondary), the generator or inverter.

I don't have an iso xfmr.

It is my understanding that all equipment should have an insulated return to a common grounding point. Also that all equipment in contact with the water should be bonded.

In the event of a fault, the grounding wire would become current carrying and have a direct path to the grounding bus. If no grounding wire is connected, only a connection from the heater case to the bonding system (my boat's original setup), all bonded metal becomes hot.

Even though a connection to the bonding ckt is 'electrically' the same as connecting a separate grounding (green) wire, on a boat this shouldn't be done. No equipment should be using the bonding system as a ground return as these connections could possibly be at different electrical potentials due to the physical connections varying resistances and could induce stray voltages in the bonding ckt. A separate grounding wire direct to the grounding bus avoids inducing any stray currents.

Knowing all of this, it surprised me that there was no grounding wire provided for the water heater, only a bonding connection. Now that I'm thinking about it, there are no grounding wires to ANY elec outlet or the A/C system, I bet the fridge and stove are the same.

Maybe Hatt didn't know about stray currents back in '72.

[TedZ]

[QUOTE=Traveler 45C;143348]You are correct; the neutral and grounding wires should not be tied together onboard when power is supplied direct from the dock. However, they will be if power is supplied through an isolation transformer (at the secondary), the generator or inverter.


Well said but this is NEC talk and has been debated here to tears. The ABYC says one thing and depicts another. Many folk feel differently on these issues. TZ


I don't have an iso xfmr.

It is my understanding that all equipment should have an insulated return to a common grounding point. Also that all equipment in contact with the water should be bonded.


Agreed but this can become very confusing by not using the term "neutral" and "neutral buss." TZ


In the event of a fault, the grounding wire would become current carrying and have a direct path to the grounding bus. If no grounding wire is connected, only a connection from the heater case to the bonding system (my boat's original setup), all bonded metal becomes hot.


Well this trips breakers in allegedly all but the dock side power scenerio. Naturally one can see why it would be nice to wire grounds through to dockside in marine situations. It really boils down to whether our power pedestals in a marine world are really a sub panel. My contention, put a little differently is that the power pedestal source is our utility supply to the environment, our boats and should not be considered a sub panel. Then it becomes simple and safe. TZ


Even though a connection to the bonding ckt is 'electrically' the same as connecting a separate grounding (green) wire, on a boat this shouldn't be done. No equipment should be using the bonding system as a ground return as these connections could possibly be at different electrical potentials due to the physical connections varying resistances and could induce stray voltages in the bonding ckt. A separate grounding wire direct to the grounding bus avoids inducing any stray currents.


Of course. Again, "neutrals." TZ


Knowing all of this, it surprised me that there was no grounding wire provided for the water heater, only a bonding connection. Now that I'm thinking about it, there are no grounding wires to ANY elec outlet or the A/C system, I bet the fridge and stove are the same.

Maybe Hatt didn't know about stray currents back in '72.[/QUOTE

I don't know what Hatteras knew but it is a dynamic world and through mistakes and sometimes tragedies, standards get updated. TZ

Ted

[Traveler 45C]

Sorry, but not the neutrals TedZ. I was specifically referring to the grounding (green) wire, not the white one.

Without an iso xfrm, the neutrals on my boat should not be connected onboard.

[TedZ]

Great.

This confuses me...

"Knowing all of this, it surprised me that there was no grounding wire provided for the water heater, only a bonding connection. Now that I'm thinking about it, there are no grounding wires to ANY elec outlet or the A/C system, I bet the fridge and stove are the same."

and

"It is my understanding that all equipment should have an insulated return to a common grounding point. Also that all equipment in contact with the water should be bonded."


So you mean here that there are not two green wires assuming the bonding wire is green also. And the outlets only have a white and a black wire?

OK I wouldn't have guessed that was what you meant. My fault.

Ted

[Traveler 45C]

So you mean here that there are not two green wires assuming the bonding wire is green also. And the outlets only have a white and a black wire?

The heater has a hot (black), neutral (white) and bonding wire (green, connected to the bonding ckt), no grounding wire (green, insulated return to the common ground point). The outlets only have hot and neutral.

Sorry if I wasn't more clear or got my wire names crossed :)

[Brian Degulis]

So the cable that runs from the panel to your water heater is a 2 conductor cable just white and black? Then there is a seperate green wire running to the bonding circuit (the copper strips in the bilge)? If that's the case it's hard to believe Hat wired the boat this way.


Brian

[Angela]

So the cable that runs from the panel to your water heater is a 2 conductor cable just white and black? Then there is a seperate green wire running to the bonding circuit (the copper strips in the bilge)? If that's the case it's hard to believe Hat wired the boat this way.


Brian

Yep...that's the way Hatt made mine too.

[Traveler 45C]

So the cable that runs from the panel to your water heater is a 2 conductor cable just white and black? Then there is a seperate green wire running to the bonding circuit (the copper strips in the bilge)? If that's the case it's hard to believe Hat wired the boat this way.


Brian

Brian, you are correct. Like I said above, the air conditioners are wired the same, as well as all the elec outlets.

Hatt must have thought that using the bonding ckt as the AC grounding return (green, bare wire) was ok to do. It is 'electrically' the same point after all.

I'll be correcting the heater and AC ground returns today. I'll run an additional wire to the AC ground return bus that I'll be installing, then connect that to the DC grounding bus the way Calder suggests.

[Brian Degulis]

Wow that's weird I've never seen that. When I got my first Hat I was impressed that even the DC equiptment was wired with 3 conductor cable including a green ground back to the ground bus in the panel many manufacturers don't do that.

Well good luck sounds like your tackling it the right way the safe way. The frustrating thing about jobs like that is that you do a lot of work for no noticible improvement but you do get get piece of mind.


Brian

[TedZ]

As far as i can remember, Romex with a bare ground wire came around in the 50's. It was not connected to a ground prong like a three prong outlet but wrapped around the precursor to MC wire, BX or put on a ground lug or a green screw in the boxes. Hatteras in the early 60's likely used this system. Insulated green wires and three pronged outlets started showing up in the 60's to the best of my recollection.

Knowing the reluctance to embrace change - a good thing most of the time - on manufacturer's part, i have no trouble believing that the green ground conductor was slow in coming on the boats, probable as late as the early 70's but on some even later. They bonded for electrolysis purposes for sure and that may have been it. On my 1972 43DC there are three prong outlets with bare ground wires on the green screws and green bonding. Best of my knowlege it is original.

Ted

[Traveler 45C]

The schematic is correct, they just didn't wire the boat as per the drawing. I couldn't believe it myself, that's why I was questioning it here.

Thanks All!

[Trojan]

So the cable that runs from the panel to your water heater is a 2 conductor cable just white and black? Then there is a seperate green wire running to the bonding circuit (the copper strips in the bilge)? If that's the case it's hard to believe Hat wired the boat this way.


Brian


All the Hat boats are wired this way. The green wire is only joined to the white in the panel. and by rights one or the other feed breakers will trip if there is a overload. Where else would you like to attach the green. Its got to be grounded somewhere. We must have 200 post on this same thing in the past.

BILL

[Traveler 45C]

You got it right.

The bonding ckt gets tied to the common ground point (DC gnd, AC grounding and bonding ckt).

[TedZ]

Many will say, and i am one of them, that the UK article is not right. One reason is that it does not take into account that neutrals and grounds are bonded in many scenerios boat side, and if other boats are plugged in at a marina, on the dock side.

Ted

[Brian Degulis]

All the Hat boats are wired this way. The green wire is only joined to the white in the panel. and by rights one or the other feed breakers will trip if there is a overload. Where else would you like to attach the green. Its got to be grounded somewhere. We must have 200 post on this same thing in the past.

BILL

No they aren't What are you smoking? Almost all boats use 3 conductor cable black white and green. for 120V black is hot white is neutral green is ground. All conductors run to the panel and are conected to Black (breaker) White (neutral bus) green (ground bus). THAT'S THE WAY MOST ARE AND SHOULD BE WIRED

I've never seen a boat wired with 2 conductor cable and a seperate green wire going directlly from the the case of whatever is being powered to the bonding system. THAT'S THE WRONG WAY TO DO IT FOR A WHOLE BUNCH OF REASONS.

Brian

[REBrueckner]

Craig posts: "You may disagree all you want, but wiring a boat using an isolation transformer not wired as they show will defeat the purpose of the transformer. After all the reason for isolation is to do just that isoloate you from the dock and other boats..."

That has nothing to do with the point Ted is making. Ted is referring to on board wiring only, not a connection between shore side and boat side of the transformer (I hope).

and "I am not so sure ac units should be grounded directly to the bonding system."

In general, connecting ac and dc grounds to the bonding system, all at a single connection point, often a thru hull bolt to an exterior ground plate, is a necessity.....otherwise a fault may not trip your circuit breaker.

Also: Brit's have traditionally called for a different arrangement on the boat side of an isolation transformer....ABYC still calls for ground/neutral connection at isolation transformers for the US....that's what Calder shows (1996) page 103. The Brits may still use the floating on board system I referred to in my earlier post that was used onboard my 1961 wood Matthews. [That may be related (I am not sure about this) that virtually everything over there is 220volts.]

When you run your on board genny or on board inverter, those units automatically make the ground to neutral contact...as we have discussed here innumerable times. And the secondary of the isolation transformer, no matter how it is wired should be disconnected from your on board system when you flip your selection from "shorepower" and select some other arrangement.

On bonding: You CAN isolate any given underwater silicon bronze hardware you wish from the bonding system...I've posted previously the pros and cons..and the considerations....in general, if your fiberglass boat is already bonded, leave it that way and be sure your zincs are adequate. Anything other than an ABYC wiring arrangement will not be understandable to people working on your boat and only a few old time (wood boat) surveyors MAY understand it...

I've posted about this before and explained how such isolation can provide protection aboard wood boats where lignen (cell walls) in the wood may be destroyed by galvanic protection (zinc) currents. It also reduces the possibility that a lightning strike will destroy that fitting(s) and reduces the antenna array effect whereby bonding systems pick up stray currents in salt water (like a radio antenna picks up a radio signal) and bring them aboard where they can use up zincs and destroy underwater fittings.

[Brian Degulis]

I haven't been in the forum long enough to read 200 posts, not yet anyway.

The site I posted earlier today explains the grounding quite well, when an isolution transformer is used. Without an isolution transformer never never tie green to white. The correct way is to have a 3 conductor wire with white, black, and green included, black is hot (line) white is neutral, and grren is ground aka safety ground. My understanding of bonding is to help eliminate electrolysis, I am not so sure ac units should be grounded directly to the bonding system. All through hulls, and the like should of course be tied to the bonding system.

Be aware white is not ground, it is neutral, and a reference for the hot.

If I am not understanding all this correctly, more info will be welcomed.

Craig

White and grren are never tied together after the panel. They are tied together at the point of distribution. That would be the panel that supplies your dock pedastal and your genset. I've seen it tied together on some boats at the boats main panel also I'm not sure if that's right or not.

There are some experts not to many that do make a connection from the secondary or an isolation transformer's ground to the shore pedastal ground and I think they do the same with the neutral. That defeats the isolation and changes the transformer to a balancing transformer. Then they ad a diode or Zinc Saver to the ground line. They do it because they're worried about 2 things first a short in the transformer's secondary winding will not trip the shore power breaker or any other breaker. Second they worry about a diffrence in potential between shore neutral and ground and the boats neatral and ground. I've never heard of any boat experiencing these problems. I would use the original Hat Isolation wiring.

Brian

[Trojan]

No they aren't What are you smoking? Almost all boats use 3 conductor cable black white and green. for 120V black is hot white is neutral green is ground. All conductors run to the panel and are conected to Black (breaker) White (neutral bus) green (ground bus). THAT'S THE WAY MOST ARE AND SHOULD BE WIRED

I've never seen a boat wired with 2 conductor cable and a seperate green wire going directlly from the the case of whatever is being powered to the bonding system. THAT'S THE WRONG WAY TO DO IT FOR A WHOLE BUNCH OF REASONS.

Brian


You had better notify Hatteras so they can make there electrical schematic match yours along with there boats. My whole boat is wired that way by Hatteras.
Every 6 months we go through this same stuff. Every 6 months we get a new expert.:D Oh well.

BILL

[TedZ]

Craig posts:

"You may disagree all you want, but wiring a boat using an isolation transformer not wired as they show will defeat the purpose of the transformer. After all the reason for isolation is to do just that isoloate you from the dock and other boats."

First, no one should have much of an expectation about isolation transformers actually isolating anything. This is not my say so, it is common knowlege. Google it.

They obviously facilitate voltage changes and do protect the DOCK power (common mode rejection) from on board problems but don't do much for the boat in that voltage spikes, RFI, jitter, ripple etc. are transformed blissfully from the primary to the secondary.

The notion that your neutral and green grounds are electrically isolated either on the boat or dockside all of the time is simply not right. Boat side many plugged in appliances bond neutral and green. Your genny and inverters should do it also. If you have a dockside boat with plugged in appliances bonded, then the whole marina is bonded. No sense guessing. Use a good meter and check it. Certainly where the power comes into the marina there is a bond. That is the code. As you migrate away from the supply source, there may be a ground loop, i.e. a difference in potential on the neutral and the ground but it is small.

We have discussed this a lot here and i know folks are adamant in their positions and that is great. Occasionally it is nice to let a little science triumph over superstition and with a meter any one of us can do exactly that.

I'm sure Craig and others have got a ton of experience with electricity and are very qualified to draw schematics for the rest of us and that is great also. What gives me a little insecurity is anyone who attributes properties to isolation transformers that they simply do not possess. There are electrical/electronic devices that do all of the isolation one could want but they really are not necessary unless you have a lot of sensitive equipment on board and are getting a lot of electrical noise through the door.

Once again, my $.02

Ted

[Brian Degulis]

You had better notify Hatteras so they can make there electrical schematic match yours along with there boats. My whole boat is wired that way by Hatteras.
Every 6 months we go through this same stuff. Every 6 months we get a new expert.:D Oh well.

BILL

I don't claim to be an expert I think as time goes on you just get more and more confused.

My boat and every other Hat I've seen is wired the way I describe 3 conductor cable to everything one white one black and one green in a single cable the green ground goes directly to the ground bus in the panel. The schematic shows that also.

So your telling me that your AC circuits are supplied by 2 conductor cable. So your hot (black) and your White (neutral) are the only conductors that go back to the panel. Your green (ground) is seperate from the supply cable and it goes directly from what's being powered to the bonding system (copper straps in the bilge) IS THAT WHAT YOUR TELLING ME IS THAT HOW YOUR BOAT IS WIRED? If so your describing what the original poster is describing and that's fine. But please don't tell me that's the way it should be or all Hats are that way

Brian

Brian

[REBrueckner]

Brian posts:
"My boat and every other Hat I've seen is wired the way I describe 3 conductor cable to everything one white one black and one green in a single cable the green ground goes directly to the ground bus in the panel. The schematic shows that also."

That IS how my 1972 48 Hatt YF is wired....guaranteed.

I can remember identifying the separate ac and dc grounds buses...they were in fact behind the main electrical panel and I used them as intended when I added new equipment.....

[TedZ]

Craig,

I understand, i think, the issue. The hope is to use iso xformers to isolate the boat's ground plane from the dock side ground plane and they do that if wired correctly. Is this what we want?

My point is that neutrals and grounds are bonded on both sides of the xformer intentionally or not and many iso's have a significant difference in voltage between dock side ground and boat side ground because of neutral-ground bonds. In as much as it is pretty well agreed they don't really isolate anything, why isolate grounds and get a buzz or worse when you are standing on a metal dock and grab a bonded piece on the boat?

Having a transformer on a boat is great for voltage adjustment. Calling it an iso xformer raises the price and gives an impression it is doing a task that it really isn't. And God knows which side of the xformer grounds you bond the cage. No one agrees on that including all of the "experts."

So i contirue to say, as do some others, to bond the whole mess together. That is after you are careful to eliminate all neutral-ground bonds which may not be easy. People immediately say "that destroys the isolation" which is a huge non-sequitor as there is no isolation in the first place above an ordinary transformer. Trust me the mini-Farady cage does nothing of significance but confuse the discussion. The advantage of this besides safety is when a boat plugs in with neutral-ground bonds something will happen, i.e. a breaker will trip like a GFI.

But this is a lot of trouble so we all take the easy way out and when someone says " i get a shock when xxxxx" we all give a ton of advice. The classic arrives when someone says "when on the hard, make sure you drive a stake in the ground and ground your boat to it, otherwise if you are standing on the ground and touch metal on the boat you get zapped!!" Well that about covers the neutral-ground bonds and their undesirability! And that certainly tells you that you have a voltage impressed on your neutral-ground plane that has to be coming from the iso.

Once again, is this what we want?

Sorry so long.

Ted

[Brian Degulis]

But this is a lot of trouble so we all take the easy way out and when someone says " i get a shock when xxxxx" we all give a ton of advice. The classic arrives when someone says "when on the hard, make sure you drive a stake in the ground and ground your boat to it, otherwise if you are standing on the ground and touch metal on the boat you get zapped!!" Well that about covers the neutral-ground bonds and their undesirability! And that certainly tells you that you have a voltage impressed on your neutral-ground plane that has to be coming from the iso.

Once again, is this what we want?

Sorry so long.

Ted

The problem with the above is that no one seems to be having any trouble at all with the standard Hat Isolation Transformer wiring. We all seem to be seeing good isolation minimum zinc wastage minimum elctrolysis and no shocks or fires or any problems at all ever being atributed to the Isolation transformer wiring. At least I can't recall ever seeing a post on it?

Brian

[Trojan]

No they aren't What are you smoking? Almost all boats use 3 conductor cable black white and green. for 120V black is hot white is neutral green is ground. All conductors run to the panel and are conected to Black (breaker) White (neutral bus) green (ground bus). THAT'S THE WAY MOST ARE AND SHOULD BE WIRED

I've never seen a boat wired with 2 conductor cable and a seperate green wire going directlly from the the case of whatever is being powered to the bonding system. THAT'S THE WRONG WAY TO DO IT FOR A WHOLE BUNCH OF REASONS.

Brian

I didn't say I had 2 conductor cable. I have 3 conductor. Except that both black and white have a breaker in each line and the green is grounded at the panel.

BILL

[TedZ]

Brian,

There is a 10/21/09 post for example. Search for "electric shock."

There are many posts on grounding boats on the hard.

There are many plug meltdown posts. Some are overload, some are not. When you see ground/neutral meltdown be suspicious. Overloads should affect hot and neutral equally.

There are drowning deaths every season at marinas. We have kids who swim at our marina. I check for stray voltage when i see that but it is not always a definitive check.

The savings grace here is that there are not a lot of marinas where you can get in between a conductive dock and the boat. Not as difficult when on the hard.

My continued feeling is that i would feel awful if someone on the forum or at my marina got hurt or worse and i could have prevented it.

Ted

[Brian Degulis]

I didn't say I had 2 conductor cable. I have 3 conductor. Except that both black and white have a breaker in each line and the green is grounded at the panel.

BILL

My original commemt was to the original poster who said he has 2 conductor cable and a seperate green wire going directly to the bonding system. I said that was strange and not a good way to wire. You told me all Hats are wired that way.

Your not understanding the conversation I'm done

Brian

[Brian Degulis]

Brian,

There is a 10/21/09 post for example. Search for "electric shock."

There are many posts on grounding boats on the hard.

There are many plug meltdown posts. Some are overload, some are not. When you see ground/neutral meltdown be suspicious. Overloads should affect hot and neutral equally.

There are drowning deaths every season at marinas. We have kids who swim at our marina. I check for stray voltage when i see that but it is not always a definitive check.

The savings grace here is that there are not a lot of marinas where you can get in between a conductive dock and the boat. Not as difficult when on the hard.

My continued feeling is that i would feel awful if someone on the forum or at my marina got hurt or worse and i could have prevented it.

Ted

We've seen lots of posts on shocks and wiring problems but I've never seen or heard of one that was caused by the Iso tranformer wiring. I could be wrong maybe you can point one out to me?

I'm not saying your posts are without merit you make some good points. But I think defeating the isolation would create more problems than it solves. I think with thousands of Hats and other boats all wired to isolate some 30 or more years old the record speaks for itself.

Brian

[TedZ]

Its funny you mention 30 years. We have a very popular saying in our company because we have people who tell us "it has to be your fault, i've been doing this for thirty years!" Our answer is "you've been doing it wrong for 30 years and it finally bit you in the butt."

I really expected someone to ask, "How do you check for stray current to protect swimmers, metal etc.?"

I hate to bury this post here but it is so important i can always post it again.

There is a guy Dave Rifkin who is a USN ret., a Captain and an ABYC consultant on electolysis from time to time. I know a lot of people do not have clamp-on amp meters but they are cheap and you all may want to buy one when you read this.

THESE ARE ALL HIS WORDS:
"Here's a question for you. You go up to boat on shore power, and using an AC clamp meter you clamp the whole shore cord. It reads 5amps. What is the significance of this reading and where is this current flowing? This is something most electricians have not thought of."

AND HIS ANSWER:
"Here's the answer. The clamp always reads an imbalance. If there is "missing" current when you clamp the whole shore cord, it means that what are reading is going into the water. If the boat is not in the water, it will always read exactly zero, unless, of course, there is different grounding path provided and there is a ground fault. This works on 120 or 240v shore cords. Essentially you are reading the current that is NOT coming back on the cord.

If you get a reading, you just turn the pedestal breaker off. If the current goes away, it's due to fault on the boat you are clamping. If the meter continues to read, then the source of current is somewhere else (faults on other boats or ground-neutral currents which are using that boat as return path to the source).

This is a key tool in doing electrical safety checks on boats."


Please, please read the above at least twice. If you have an imbalance as described you have a potentially dangerous situation for you or for others. I maintain that many of the problems you will encounter are from isos and improper or confused bonding. Ground faults and leakage can happen on any boat but the chances of problems on boats with isos are magnified by the very isolation they describe as a good thing! The reason of course is different neutral potentials and goofy bonding philosophies.

I know we beat this to death and this covers it i would say. Do what you think works.

Ted

[Traveler 45C]

So your hot (black) and your White (neutral) are the only conductors that go back to the panel. Your green (ground) is separate from the supply cable and it goes directly from what's being powered to the bonding system (copper straps in the bilge)

Not exactly.

I have a 2 conductor cable (black and white) running from a double pole breaker to the heater and a green bonding wire running to the bonding ckt. There was no green grounding wire attached. I installed that myself. I also had to install a new grounding bus that all the green grounding wires from other AC equipment will be attached. The A/C's are wired the same, no green grounding wire, only 2 conductor and bond. I attached the new AC grounding bus to the DC ground bus.

If any of your appliances have the neutral and grounding wire internally connected, Calder recommends disconnecting these.

I like the test method you described TedZ and will use it next time I'm on board.

[TedZ]

Thanks but i did not think of it, it was Capt. Rifkin.

I mentioned quite a few times that undesirable bonding occurs through appliances on both sides of the power pedestal. I did not know that Calder reccommended taking them apart and disconnecting something, but disconnecting what? The only safe thing is to isolate the neutral, not disconnecting the green/ground.

Make the test and keep unplugging stuff or turning off breakers to see if you can get rid of unbalances or you will have the whole boat apart! Then just fix the offending items.

The part that i continue to find so surprising in the state "experts" minds is grounding the boat when on the hard. Trust me if you can get a shock when on the hard there is no difference in the impressed voltage on your ground/bond system when in the water. Get the wrong situation on a dock or with a swimmer -we do fall in on occasion - and very bad things can happen.

Ted

[Brian Degulis]

Ted The Iso transformer produces a power source that is in and of itself. Your genset does the same thing and has no conection to shore ground. Are you sugesting we should stop using our gen sets for fear of shock? Yes we all go in the water and we aren't getting shocks. I understand you have a point of view and I agree it has merit. But it's not the only point of view nor the only one that has merit. No system is perfect in all respects it's always a balance of risk and function. The only way you eliminate all risk is to turn off the power.


Brian

[Brian Degulis]

On a truly isolated system the only place the green ground from the pedistal should be tied is the primary side of the isolation transformer where the manufacturer indicates it should be go. If it is tied to case ground of the transformer the the case should not be tied to ships ground.

If you are working on an isolated circuit and touch earth ground you should not get a shock because the isolated circuit is not reference to ground. Botton line, this is why and isolation transformer is used in the first place.

Sorry to be so wordy, but not being a teacher I am not always the best at explaining things.

Try to remember except for the problems of electrolysis, ships power is no different than the power in you house. (Quote Craig)

On most of our boats with Iso transformers the only thing that gets a hard wire conection to shore ground is the recepticle where the shore cord plugs in and the transformers sheild. Everything else is grounded to sea water. IMHO the reason the system is safe and we don't get shocks caused from diffrences in potential is because Sea Water and Earth ground should be at the same potential or very close.

Something I just learned recently (on this forum) is that even though your Iso transformer makes power in and of itself it's still important to ground the boat when it's hauled. You would think that with the Iso transformers output having no relationship to earth ground when hauled then it would not be possible to get a shock unless you were in contact with a hot and the boats neutral or ground. In other words when hauled there is no path from the boats hot to earth ground. It still presents a hazard because of inductance which I can't explain but is real. Bottom line you can get zaped if there were a fault in your boat and your were in contack with earth. So ground the boat when it's hauled.

Brian

[Traveler 45C]

Calder says that some appliance manufacturers connect the neutral to case ground internal to the appliance for safety reasons. He says that this connection should be broken.

To summarize: The neutral and grounding wires should not be connected on board if brought on board from ashore.

The neutral and grounding wires should be connected on board if using the genny, an inverter, or an iso xfmr. These ckts are isolated from shore power.

DC ground, bonding ckt, and AC grounding (green) should be tied together at a common grounding point aboard.

[TedZ]

Brian:
I am saying you should not use your genny at the dock with the boat still plugged in, yes. Same with inverters.

Craig:
If you turn the power off and you get a reading it is due to no voltage on hot and neutral AND a voltage on the ground! Not good.

There is no isolation in the first place so you are not defeating anything. If you think there is isolation, arc the primary! Iso transfromers are "feel good" devices that really do almost nothing. I am not saying there is no use for transformers for changing voltage. Every transformer is to some degree an isolation device. Wire them according to the NEC.

Unless your house has an isolation transformer, there is a big difference in some ship's wiring and your home.

Brian:
If your bonded items were isolated from the neutrals it would not be necessary to ground anything. If they are not isolated you are shorting the iso's neutral by driving a stake in the earth. Check the plug after a few days. I have heard on this forum folks who say, "I blow breakers when my boat is on the hard!" No kidding!

Suggesting that our boats are grounded to mother earth through the water is bad thinking. For one thing that might work in salt water, not so hot in fresh. Also how about the swimmer who gets in that electrical field in salt or fresh water. Some say fresh is worse BTW? There are marina drownings. Many are "unexplained." That is the dirty little secret at marinas...unexplained deaths in the water. Google it.


All very good comments and good thoughts. These are mine only. As i have said many do not agree. I think you can be confident that boats with isos are going to be subject to new regulations soon if they aren't already. IMHO it simply is too dangerous to have what you all agree is a voltage grid some voltage above or below earth ground aboard your vessel and likely bonded to all metal on board.

Best to all.

Ted

[TedZ]

Craig

Clamp-on meters traditionally read on one conductor at a time. To measure amperage you always clamps on to one wire. They inductively couple to the field that is around each conductor - right hand rule remember?

I have never put a clamp-on around multiple conductors in say a cord as you always read zero EXCEPT if there is an unbalance in the line. With no power on the hot and neutral - the breaker does not open the ground - and a ground fault say on the dock the green will be energized. As long as there is power in a conductor a clamp-on will register. It does not have to be going anywhere but in the case of the dock-side ground fault your meter will read with the pedestal off and it is going to your boat. Maybe it is stopped at the iso, maybe not. Depends on boat-side bonding.

This is Rifkin's test. I wasn't smart enough to figure that out.

You have got to understand this because it is VERY important and a test i think a marina owner should make on all of the boat supply cords.

Ted

[Brian Degulis]

OK once again for what it's worth, an isolation transformer is used to isolate ground. This being said. The primary side of the transformer is grounded to shore ground, that is the only thing on the boat that should be grounded to shore ground. The secondary actually has no earth ground, ground and neutral are tied together as a reference for the or to the hot side. Ground, and neutral are tied together on the secondary (output side) to eliminate potential (voltage) difference between them. You should read voltage between the white/green to the black. A test to see if you are truly isolated, connect one side of your ac meter to earth ground coming from the pedistal and the other lead to to the hot side of any outlet inside the boat, if you get any significant reading you are not isolated. You will find most so called isolated boats will fail this test, because some doo doo conected ground to the primary side of the transformer, usually a installed not familiar with isolated circuits.

Remember when you read hot to neutral you are not truly reading to ground you are reading the difference between the two. Yes you will read voltage hot to ground as utlimately they are tied together at the power source. On the same token you can read voltage neutral to ground, if fact that voltage should be under about 1.4 volts, if it is higher you are probably eating zincs. Most marinas do not pull in neutral on the 120 pedistals, they do usuaally pull it in on the 220 outlets. This is the reason the larger boats using 220 power use the isolation transformers and your plugs are 4 conductor (2 hots, 1 neutral, one ground) instead of 3 on the 120 (1 hot, 1 neutral, 1 ground.

Brian I'll have to look into the thing about being grounded on the hard, I am not sure about it. If no power is hooked to the boat, I doubt it is needed although lightening protection could be a factor.

Ted, your comments still confuse me. Put a clamp on meter on the cord turn off power from the pedistal and read something? Please explain to me how you can get any current flow with a clamp on meter with only one conductor connected to something (in this case ground), for many reasons this does not compute, at least to me.

I agree we are beating this subject to deaf, but it's not all bad, hopefully we are all learning something about an important issue.

On this subject I don't offer up opinions, I try very hard to stick to the techinical facts.

I sincerely hope this helps everyone

Grounding on the hard to prevent a shock hazard is only needed when the boat is plugged in on the hard.

Testing for isolation by reading voltage from a boats hot to earth ground won't work. You'll always get a reading because your boats Iso secondaries are conected to sea water ground which is in fact earth ground. You may not read full voltage but your going to get a reading for sure. It depends on the salinity of the water and the distance between the shore panel ground rod and the water.

Brian

[Trojan]

Ted I like the Rifkin's test you presented. I think it's a good easy test. I will be at the boat Sat and I'm going to check my panel. Being away from the boat it's sometimes hard to remember just how things are wired for sure. When you have been in many panels you tend to expect that all panels are wired correctly and it may not be the case. The electrical panels in some 30+ year old boats leave something to be desired.
I have never checked but are the battery chargers output isolated? I know the DC ground and the green ground are tied together.
This has been a good read. I sometimes don't give all the information I should and take things for granted. I sometimes think that we are all on the same technical plane.

BILL

[TedZ]

Brian said:

"Grounding on the hard to prevent a shock hazard is only needed when the boat is plugged in on the hard.

Testing for isolation by reading voltage from a boats hot to earth ground won't work. You'll always get a reading because your boats Iso secondaries are conected to sea water ground which is in fact earth ground. You may not read full voltage but your going to get a reading for sure. It depends on the salinity of the water and the distance between the shore panel ground rod and the water."


Naturally you have to be plugged in to have any issue with voltage on the ground plane. This grounding of boats on the hard is not my concept, i have seen folks like Roger of Jarrett Bay and others discuss it. It seems to me it is a safety precaution anticipating improper bonding boat-side like appliances etc.

I am not following your second paragraph. Where is the measurement you discuss taken? What i understand to be a test for isolation, if that is desirable, is to measure continuity from ground on the pedestal to ground on the boat. If it is open, the grounds are isolated.

Forget about ground rods at a marina. They are likely hundreds of feet away and ground loops almost certainly develop which will give a differing reading from hot to ground depending on how far away you are from the main panel. The NEC requires regrounding with a certain distance away from the main panel but i don't know if that applies to marinas. Probably does but i have never done it because it is hard to drive ground rods when you are over water!

The concept of iso secondaries, the hot(s) and neutral, being tied to sea water grounds implies that the grounds and bonds are tied together AND apparently to the neutral? I don't think that is what you want but it is likely quite common.

Ted

[TedZ]

Craig said:

"Tying the secondary of an isolated system to the ships bonding or grounding system, defeats the reason for the transformer. Now the question becomes and I can see a discussion comming, should the the secondary on an isolated boat be tied to ships ground? My training and experience tells me it should not."

I couldn't agree more, that is why i said:

"The concept of iso secondaries, the hot(s) and neutral, being tied to sea water grounds implies that the grounds and bonds are tied together AND apparently to the neutral? I don't think that is what you want but it is likely quite common."

To go further, i don't think the boat side grounds and bonds should be tied together except when USING a genny or inverter.

Ted

[Brian Degulis]

Brian Posted,

Testing for isolation by reading voltage from a boats hot to earth ground won't work. You'll always get a reading because your boats Iso secondaries are conected to sea water ground which is in fact earth ground. You may not read full voltage but your going to get a reading for sure. It depends on the salinity of the water and the distance between the shore panel ground rod and the water.

Brian,

I agree totally with what you, and given that, one has to ask, is the boat truly isolated?

Tying the secondary of an isolated system to the ships bonding or grounding system, defeats the reason for the transformer. Now the question becomes and I can see a discussion comming, should the the secondary on an isolated boat be tied to ships ground? My training and experience tells me it should not.

That would go against all common knowledge and I don't think any builder does it that way. That would be a completly floating system and would be almost impossible to acomplish. It would mean that the housings on your air conditioning compressors would be floating (no wired ground) yet seawater is flowing thru them creating a crude seawater ground. I can't see how it would work. Isolation on a boat means isolated from shore supply not isolated from sea water ground. The main purpose is to prevent electrical leakage from another boat or dock from finding ground through your boat which will happen if your hard wire conected to shore ground and shouldn't happen if you aren't.

Brian

Brian

[Traveler 45C]

I put the clamp on meter on my shore power cord and read .5a on the AC scale. Switching to the DC scale the reading was higher. Which is the correct scale to use for this test?

I shut down the breakers at the dock panel and the reading did not change.

I'm not exactly understanding this stray current ckt path and the effect of shutting off the breakers. How are you able to determine the problem is on the dock by shutting off the breakers? I would think that the stray current is on the grounding wire but could it also be flowing on the neutral?

[Traveler 45C]

Hmmm, I don't think this is all that complicated...

The reading should have been zero even with all the systems turned on as they were. I took readings on a few different power cords and they all were zero.

I'm in salt water.

There is definitely a problem somewhere. I already know that I've got some Hatteras induced wiring issures (AC grounding) and my bonding ckts are not in the best of shape. A galvanic isolator would block this current and I'll get one installed soon.

I'll try to do some further troubleshooting on Sunday.

[REBrueckner]

Traveler: You can go to YANDINA.com and check their electrolysis testing procedure....I've recommended their site several times...any questions to their website used to elicit a prompt reply...these folks make isolators (or used to) for West Marine and are real boaters. All you need is a volt ohm meter and maybe an hour....

http://www.yandina.com/electrolysis.htm


Brian's post #57 reply is correct....but I will mention again that floating secondaries, meaning onboard ungrounded two wire systems have been used in the past...my 1961 wood Matthews had such an isolation transformer based system.....Nigel Calder also mentions them......

[Brian Degulis]

I am not following your second paragraph. Where is the measurement you discuss taken? What i understand to be a test for isolation, if that is desirable, is to measure continuity from ground on the pedestal to ground on the boat. If it is open, the grounds are isolated.

Forget about ground rods at a marina. They are likely hundreds of feet away and ground loops almost certainly develop which will give a differing reading from hot to ground depending on how far away you are from the main panel. The NEC requires regrounding with a certain distance away from the main panel but i don't know if that applies to marinas. Probably does but i have never done it because it is hard to drive ground rods when you are over water!

The concept of iso secondaries, the hot(s) and neutral, being tied to sea water grounds implies that the grounds and bonds are tied together AND apparently to the neutral? I don't think that is what you want but it is likely quite common.

Ted


If I'm going to test for anything I need solid parameters. If I have to wonder wether contiuity I'm reading is a fault in my isolation or a ground rod that's close to seawater( Like at my home) then the test is worthless.

Brian

[Brian Degulis]

I think we need to understand the purpose of using a transformer in a boat. My understanding of it is this.

The ability to use 120V shore cord and have limited 240V on the boat

The ability to boost dock voltage which is often low

To isolate and create a power source that is unique to your boat one that does not share neutral or hot with anything on shore and shares ground only to the extent that seawater and earth ground are common. The benifit to isolation is that an electrical leak from another boat or shore supply does not use your boat to find ground because your boat is not conected to shore ground. Your boat is working on a seawater ground only. This is exactly what your gen set does it has no conection to earth ground or any other power source.

If you agree with the above then what would be the advantage to isolating secondary neutral and seawater ground from each other. It's my understanding that the two are conected on land based supplies for safty purposes. With the neutral and ground conected at a single point neutral is always at ground potential.

Basicly on your boat your transfomer is your power company and your boat is the grid and end user. So IMHO follow the same guidlines as your power company does.

Brian

[Traveler 45C]

Trav,

I hope I am understanding you correctly. with power connected to the boat and something running you should read the current that is being used. What do you mean you should get nothing? What am I missing here.

Think about a 2 conductor power cord. If you were to clamp only one of the wires you would read the current through that wire. If you clamped both of them, your reading the positive and negative current at the same time, which is effectively zero (+1a + -1a = 0, for example).

If you've got one, clamp a 2 conductor power cord and see. If you have a 3 conductor cord, we know that the 3rd wire, the grounding wire is non-current carrying. Since we know the reading should be zero, any reading must be coming from the grounding wire and shouldn't be there. If it is, something is wrong.

Rob, I'm familiar with that website.

[TedZ]

I think we need to understand the purpose of using a transformer in a boat. My understanding of it is this.

The ability to use 120V shore cord and have limited 240V on the boat

The ability to boost dock voltage which is often low

To isolate and create a power source that is unique to your boat one that does not share neutral or hot with anything on shore and shares ground only to the extent that seawater and earth ground are common. The benifit to isolation is that an electrical leak from another boat or shore supply does not use your boat to find ground because your boat is not conected to shore ground. Your boat is working on a seawater ground only. This is exactly what your gen set does it has no conection to earth ground or any other power source.

If you agree with the above then what would be the advantage to isolating secondary neutral and seawater ground from each other. It's my understanding that the two are conected on land based supplies for safty purposes. With the neutral and ground conected at a single point neutral is always at ground potential.

Basicly on your boat your transfomer is your power company and your boat is the grid and end user. So IMHO follow the same guidlines as your power company does.

Brian

That is absolutely the way it is done now EXCEPT the power company doesn't put 60 or 70 VAC on a manufactured ground above the real ground potential of zero. That is what we are doing in most instances with an iso. Which is back to the beginning. As long as the ship's ground plane doesn't come in contact with the dock-side ground plane all is fine for 30 years! Get a swimmer in the water or a metal dock or hand rail in the rain and watch out.

Making 240 VAC out of 120 VAC great...half the ampacity but fine. Buck-boosting with xformers fine if you have the switches and many do. You just need to understand this is not without some risk - what isn't - i know. Many will say, "that's life with a xformer" and that is ok if that is what you accept. There are transformers that are wound in such a way as to not have neutral/ground secondaries that are above the real earth ground by more than a fraction of a volt or a few volts tops. If with a meter you read a voltage between the boat's bonded items and shore ground that is say 30 volts or more - meter on a boat's handrail if bonded and the green conductor in the power pole RECEPTICAL - then some thought has to be given to safety. That is all this is about.

Ted

[Brian Degulis]

Then you must see the same safty problems when running on the gen set Right?

I think you grossly underestimate the seawater ground and it's relationship to earth ground. They are the same most of the time or within a volt or 2. I read 0 volts between my bonding system and shore ground. The problems you describe simply aren't happening because the seawater ground is better than you think it is.


Brian

[TedZ]

Well make the measurement.

Don't tell me the secondary neutral is within a volt or two of the primary's neutral. It isn't right and you won't find one EE who will agree with you. If you are bonded on the ship's side correctly i.e. no neutral ground connectiuons, there will be no voltage difference ground to ground...couldn't agree more.

BUT as we have said ad nauseum, if you have ship side neutral-ground connections such as appliances present, then what you say is not correct and is a dangerous assumption.

If your boat is perfect in that regard, wonderful. Congratulations. Most are not.

Ted

[Brian Degulis]

On our boats the secondary neutral and seawater ground are conected at a single point in the panel. Seawater ground is at or very close to earth ground eliminating the problems you describe.

I notice you keep avoiding any comment at all as to why running an iso transformer is any different than running your gen set as far as no earth ground is concerned. I'd like to hear your thoughts on that?


Brian

[TedZ]

Sorry. Don't mean to avoid it i thought i was very clear that the genny and inverters bond neutral to ground and to not run them when plugged in at the dock.

If you are asking do gennys manufacture a neutral, they do not nor do inverters. These devices are primary supply units and the neutral and ground are supposed to be bonded together. Accordingly, there is the correct voltage between the legs and neutral/ground. I install BIG generators and i always ground them to mother earth. If it were a problem i would have pyrotechnics!

Unless you get a transformer that has for example, a 120 VAC primary and two 120 VAC secondaries to form the 240 VAC secondary, then the neutral is going to be arbitrary with respect to the primary's neutral. It depends on how it is wound and likely no two are exactly the same. Ask a transformer manufacturer if there is any question on this issue.

Hope this answers the question.

Ted

[Brian Degulis]

You seem to think that neutral from the Iso secondary is not bonded to ground. On our boats Neutral from the Iso secondary is bonded to seawater ground the exact same way our generators are. That's why there is very little or no diffrence in potential between shore neutral and ground and the boats neutral and ground. That's why no one is experiencing the problems you speak of. There is no avoiding being in contact with earth ground and our boats ground. Our railings are bonded only to the boats seawater ground and of course anything on the dock like the power pedastal is bonded to earth ground. If things actually were as you suggest we would being getting shocks all the time in fact most of us would probably be dead by now.


Brian

[TedZ]

Well it seems to me that Brian and Craig need to get their thoughts resolved.

Brian says his neutral is bonded to the "sea water" ground, i.e the ships bonding system.

Craig says bonding the iso secondary in any way defeats the isolation. He feels that isos are 1:1 devices.

I guess those two smart and respected boaters' posts tell the story of isos and how little they are understood.

First, isos are not necessarily 1:1 devices. They have taps like most transformers for varying voltages.

Second, the assumption that a sea water ground is the same potential as a dock ground is not true nor is there any guarantee that it is ever true. Sea water is resistive just like fresh water but less so.

This is crazy. Measure it and report back here. So simple. Open your iso and check the neutral to neutral voltage, i.e primary's neutral to secondary's neutral. To be totally accurate, you should disconnect the secondary neutral as it could be being sunk by various grounding philosophies but try it the simple way first.

If there is a voltage difference then decide where it is being dissipated if it is, or where it exists ship side and what is energized with this voltage.

If you have an iso it is the only responsible thing to do.

Good luck.

Ted

[Brian Degulis]

I'm not talking theory here or hypothetical's our secondary neutrals are bonded to seawater ground. I don't have to check the Iso neutral against shore neutral I'm not disputing that they may be different. I have checked my boats seawater ground against shore ground and they're at the same potential. As I said before If they weren't we would all be getting shocks on a regular basis simply by grabbing a rail on the boat and a shore ground. I think this shows how a well respected EE gets so immersed in theory that simple truths and realities are ignored.

Brian

[Traveler 45C]

I think you guys all have your wires crossed :)

I wasn’t able to do any testing yesterday as I planned; other repairs had to get done. But I did find this pic.

It pretty much says it all. It clearly shows the isolation xfmr secondary’s neutral tied to ground (the ship’s ground plate, in the water) as it should be. The generator should be wired the same as the xfmr. Notice the inverters output neutral is also tied to ground. That connection is made when the inverter is the primary power source. When not, that connection is switched out*. The bonding ckt should be tied to ground also. Note if no iso xfrm is used and operating from shore power, neutral and ground should not be tied together on board.

The article from which I pulled the pic can be found here:
Grounding and Circuit Protection for Inverters and Battery Chargers
http://www.jamestowndistributors.com/userportal/document.do?docId=114&title=Grounding+and+Circuit+Protection+for+Inverte rs+and+Battery+Chargers

Here are some other good reads:

Preventing Hazardous Ground Faults on Boats
http://www.jamestowndistributors.com/userportal/document.do?docId=121&title=Preventing+Hazardous+Ground+Faults+on+Boats

*Neutral (White) to Ground (Green) Bond Switching
http://www.jamestowndistributors.com/userportal/document.do?docId=95&title=Neutral+%28White%29+to+Ground+%28Green%29+Bo nd+Switching

[Traveler 45C]

I don’t get it. Did I offend you somehow? If I did, sorry, it was meant as a joke. With all the differences in the terms and methods you guys were discussing I thought it be funny. Again, sorry. Didn’t mean to step on your toes.

I don’t have an iso xfrm so I can’t measure what you’ve asked. Thinking about it though, I can see that there would be a reading. With the meter across the xfmr from sec hot to pri ground I would think you’d see the full voltage. The meter would be making a connection from shore to boat.

So what are you saying, that under normal ckt conditions wiring according to the pic above is incorrect? Why? Are you saying a difference of potential exists between shore and the boat? They are both held at earth potential but there is no connection on the hot or neutrals so no current flow, which is what you want. Should a fault occur the breaker should pop. You’re protected from shock and the boat is protected from stray currents.

[TedZ]

You folks are all very nice...appreciated.

The Jamestown picture is wrong, i don't know why...as i said very misunderstood. ABYC E-11 doesn't show it that way nor do other experts.

Why don't you all consider looking at http://qualitymarineservices.net/ and look at #4 "Understanding the Neutral to Ground Connection." Maybe you will relate to it. Also check out the drowning deaths...very interesting.

If you think this is theory and "reality" is different that is your privilege. I respect that...happens often. However, when someone posts that his ground connector is burned off in his shore plug, or his GFI's are tripping all over the place, i don't want to be the one who tells him it is not really happening! Just bad theory! :--)

Good luck. Been fun. Hope we educated by either accepting the info or by rejecting it!!

Ted

[Canuck Dennis]

All generator neutrals are tied to centre pin of the isolation transformer, as is the neutral of any inverter.
Generator engines are grounded to ships ground as is ground from inverter.

All ships neutrals are switched when going from shore to ship power.

Pretty simple..
.the experts here in Vancouver are still "out" on galvanic isolators
for shore grounds, fears of electrical fires on shore power connections.

My 2c

[SKYCHENEY]

I don't understand how you can test the potential between the primary neutral and the secondary neutral when the neutral from the shore cord ends at the boat inlet connection. There is no neutral at the primary of the transformer just two hots and a ground.

[Brian Degulis]

I think you guys all have your wires crossed :)

I wasn’t able to do any testing yesterday as I planned; other repairs had to get done. But I did find this pic.

It pretty much says it all. It clearly shows the isolation xfmr secondary’s neutral tied to ground (the ship’s ground plate, in the water) as it should be. The generator should be wired the same as the xfmr. Notice the inverters output neutral is also tied to ground. That connection is made when the inverter is the primary power source. When not, that connection is switched out*. The bonding ckt should be tied to ground also. Note if no iso xfrm is used and operating from shore power, neutral and ground should not be tied together on board.

The article from which I pulled the pic can be found here:
Grounding and Circuit Protection for Inverters and Battery Chargers
http://www.jamestowndistributors.com/userportal/document.do?docId=114&title=Grounding+and+Circuit+Protection+for+Inverte rs+and+Battery+Chargers

Here are some other good reads:

Preventing Hazardous Ground Faults on Boats
http://www.jamestowndistributors.com/userportal/document.do?docId=121&title=Preventing+Hazardous+Ground+Faults+on+Boats

*Neutral (White) to Ground (Green) Bond Switching
http://www.jamestowndistributors.com/userportal/document.do?docId=95&title=Neutral+%28White%29+to+Ground+%28Green%29+Bo nd+Switching


Well my wires aren't crossed your diagram is exactly the way I said it should be wired. And exactly the way Hat wires they're boats so we're in full agreement.

Sky what Ted is saying is that an Iso neutral will be at a diffrent potential than the iso pimaries neutral. Right ours don't have neutral on the primary side but you could do the test using the iso's earth ground on the primary side since earth ground (green) and neutral (white) are tied together in the panel that supplies the shore pedastal.

I have no idea what the point is in doing that test. They're may very well be a diffrence in potential who realy cares. The iso secondary neutral is tied to the boats seawater ground so everthing on the boat is bonded to seawater ground. It's exactly the same thing Ted say's he's doing on land based iso's except he's using earth ground instead of a seawater ground.

This seawater ground arrangement on the iso is exactly the same as your gen set no hardwire conection to earth ground. Is anyone getting shocked using they're gen set? Has anyone ever noticed swimmers floating face down and beginning to de compose around your boat while your using your gen set. Has anyone been keeping there boats hard wired to earth ground with a 200 mile teather?

If you have answered no to the above then you can only conclude this. Hat and ABYC have a safe workable arangement for Iso wiring. It's not perfect and ted may have some valid points. But IMHO ted is missing something perhaps our transformers are built diffrently than what he's familiar with for land based aplications I don't know. But I do know that testing from my boats ground to earth ground shows no diffrence in potential. And I know that the hazards he speaks of simply aren't happening.

Brian

[Traveler 45C]

Well Brian I didn't mean to piss you off either.

Didn't you guys see the smiley face next to the 'wires crossed' statement? :)

I would have enjoyed it if Hatt had wired my boat like they did all the rest. This post would never have gotten started. Since it's not, has no iso xfmr or AC safety grounds and lots of mistakes from PO's, I've got to trace all the wires I'm working with just to make sure they go where they're supposed to. I've found lots of wire nuts, elec tape, wires connected together with a nut and bolt just hangin' there, AHG!!! The boat originally had two 30a shore cords. Sometime in its past it was rewired to a single 50a, and they didn't bother to update the schematics. I hope they did that job right. I've got to go through the whole boat to check everything.

[Canuck Dennis]

Hope you have Calders book....

[Traveler 45C]

I do :)

[Brian Degulis]

Well Brian I didn't mean to piss you off either.

Didn't you guys see the smiley face next to the 'wires crossed' statement? :)

I would have enjoyed it if Hatt had wired my boat like they did all the rest. This post would never have gotten started. Since it's not, has no iso xfmr or AC safety grounds and lots of mistakes from PO's, I've got to trace all the wires I'm working with just to make sure they go where they're supposed to. I've found lots of wire nuts, elec tape, wires connected together with a nut and bolt just hangin' there, AHG!!! The boat originally had two 30a shore cords. Sometime in its past it was rewired to a single 50a, and they didn't bother to update the schematics. I hope they did that job right. I've got to go through the whole boat to check everything.

You didn't piss me off at all.

Brian

[Brian Degulis]

Not sure what your asking most of our boats are set up to run on 240V Or 120V shore power.

Brian

[Brian Degulis]

I'm trying to figure out when or why they decided to put isolation transformer on the boat. It seems like only the larger boats have them. Mine is 2 30amp 120 from Hat.

Brian, are you in Apollo Beach? I am in North Tampa+

Yes I'm in Apollo beach on the south side Were in N Tampa are you?

Yes it is mostly larger boats I guess they figure more equiptment more wiring just more to protect and the cost is a smaller percentage of the whole with a bigger boat.

I've had several boats without them and 3 with and there's a big diffrence in electrolysis problems and vinc wastage. And they sure come in handy to boost voltage. Seems like everyplace we go has low voltage problems. So many marinas are using 3 phase so your starting with 208V and then encountering the typical losses on the way to your boat.

Brian

[Brian Degulis]

We take the boat over to Jackson's in Tampa for lunch and dinner pretty often. You can tie at the hotel pier if it's open and no one's watching or at the convention center piers. I'll give you a heads up next time we're planning to go?

Brian

[captddis]

Brian'

Seems there are plenty of Hat owners in the bay area, maybe we can get a party going. Even if we go by land (yuck)


I have suggested a West Coast FL rendezvous or weekend but never much interest. Lets try again. I know of a number of local Hatt owners who would participate. Brian himself would need two slips.

[Brian Degulis]

Hopefully just one will work. We are coming to the end of the 60C project I hope to have it on the market by the end of the month.

Brian