AC Grounding &/or Bonding

[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. 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. 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