electrolysis

[egaito]

I'm aware that the GFI's protect downstream. To think otherwise would be nonesense.

Hatteras and others go through the trouble to bond everything in the boat and to continue that bonding to the shore power. Most of us operate in that mode.

For some reason when using isolation transformers you advise abandoning that philosophy when it is unnecessary and can be dangerous. It is simply based in a misunderstanding the role of the modern isolation transformer.

Electrolysis, which is the subject of this thread, is not prevented by unbonding the boat from shore power in any scenerio and attempting to make an "electrical island" out of your boat when docked at a marina is doomed to fail in some way.

Using an isolation transformer to protect against stray currents can work as well as protecting against transients, but it has nothing to do with the bonding of the neutral or lack thereof.

Ted

I can't thing of the specific reason at the moment, but while shopping for what is now Sanctuary, we looked at a '58 that had horrible corrosion problems on all of the through-hulls. The fins on the stabs had been eaten off the boat as well.

A surveyor friend of mine gave me the number of a Hatt electrical engineer from that vintage, who told me that the problem was likely that the neutral ground to shore power had probably been "restored" by an unknowing technician. I was told that these boats were not grounded to shore by design, but often are "fixed" by folks that don't know that. Wish I could remember why....

 

[TedZ]

That is a little confusing...the word "restored."

Here is what a previous post in this thread said:

"I will dig this thread up once more. I talked with an electrical expert at Hatteras. He pulled a copy of my blueprint from their file.(Try that with any other boat builder after 20years; I am impressed). He said that our 36 is wired exactly the same way as every new Hatteras is today. They do not believe in isolating the shore grounds from the ships bonding system. They do isolate all ac neutrals from those grounds. They also don't recommend galvonic isolators. They claim that the galvonic isolator will help make zincs last longer but if the diodes fail, as they do, you no longer have an ac ground. That is bad. They also say that normal zinc consumption in Florida is 3 sets per year. They also don't like adding more zincs, they don't even approve of the fish we hang over the side.
This folks is the word from our friendly manufacturer."

So it seems like Hatteras is saying what i have been saying.

Ted

 

[Genesis]

I'm aware that the GFI's protect downstream. To think otherwise would be nonesense.

Hatteras and others go through the trouble to bond everything in the boat and to continue that bonding to the shore power. Most of us operate in that mode.

Hatteras and others do this on boats that have no isolation transformer because it is NECESSARY in that configuration, especially if there are no GFIs involved.

For some reason when using isolation transformers you advise abandoning that philosophy when it is unnecessary and can be dangerous. It is simply based in a misunderstanding the role of the modern isolation transformer.

Nonsense.

It is no more "dangerous" than it is to run a GENSET on board.

A Generator is a power source. So is an isolation transformer.

Do the following:

1. Take EITHER a genset OR an isolation transformer secondary.
2. DO NOT connect any pole of the output to ground (you have three bare wires sticking out - black, white and green - assuming 120V output)
3. Sitting on your boat, immerse ANY of the three wires in the water (not more than one however!)

NOTHING HAPPENS. No current flows. NONE! Not even if you stick the HOT wire in the water! Not even if you GRAB the hot wire and stick your FOOT in the water. (BTW, I explicitly recommend against grabbing the wire, because if there is a connection between neutral and ground that you don't know about - like a 220V dryer that is wired the "old way" - you will DIE!)

Why not? Because there is no return current path. There is nowhere for the energy to go! For current to flow there must be a COMPLETE CIRCUIT. The transformer (or genset) prevents that circuit from existing, as there is an "open" in the middle.

Now, connect your GREEN wire (from either the genset or the isolation transformer outlet) to the shoreside GREEN wire. NOW immerse the hot. You get a HUGE current flow through the water, back to your submerged underwater metals, and back to shore. This is a fault condition. If you're lucky you trip a breaker. If not you fry things - including those metals. If YOU come between that hot and water, YOU FRY.

So why do people make noise about the difference between an "isolation" and "polarization" transformer? Because it is possible for the TRANSFORMER ITSELF to have a fault in it - specifically, there can be a short in the windings between the primary and secondary side. An isolation transformer has a shield between those windings that can take the entire fault current and dump it back to the primary side's ground without melting. The design parameters necessary to do this are complex because doing so tends to interfere with the magnetic flux in the core of the transformer and thus special design considerations must be made to accomodate it.

However, in point of fact this is a quite-rare fault. It can be covered with a GFI instead of a shield, if you wish to.

Electrolysis, which is the subject of this thread, is not prevented by unbonding the boat from shore power in any scenerio and attempting to make an "electrical island" out of your boat when docked at a marina is doomed to fail in some way.

Yes it is UNLESS the electrolysis is caused by a fault ON YOUR OWN BOAT.

If the fault is on your boat then isolating the grounds will do nothing.

However, if the fault is on a NEIGHBORS boat then it will stop YOUR (but not his) damage. If he is leaking current down the ground conductor on HIS boat then your "ground" will be at some potential ABOVE ground. That voltage is then present on ALL the ground wires in the marina. The closer you are to the fault, the more of the current your boat sinks. As it sinks that current back to the actual ground your zincs erode at an accelerated rate.

Using an isolation transformer to protect against stray currents can work as well as protecting against transients, but it has nothing to do with the bonding of the neutral or lack thereof.

Ted

You don't bond neutral, you BOLT neutral.

Neutral (grounded conductor) and ground (safety ground) MUST BE BOLTED at one and only one place - it is to be done at an energy source.

Therefore, your Genset must have neutral and ground bolted together at the genset and when running on generator your boat MUST NOT connect ship's ground to shore ground. This is why your genset breaker or rotary switch on the AC panel has THREE poles and not TWO. Your isolation transformer, if it is operating as an isolation transformer, has NO ground connection to shore; it is an energy source and thus neutral and ground are BOLTED at the transformer secondary.

If you are running on shroe power and have NO isolation transformer than you MUST NOT connect neutral and ground together on board the boat ANYWHERE. Doing so is a very serious error and raises both shock risks as well as CREATING electrolysis not only in your boat but also in those around you at the marina, because there typically is a 2-3V (not millivolt, VOLT!) offset between the grounded conductor (neutral) and safety ground, depending on the amount of load present on that wire.

If you bolt neutral and ground when they should not be, you will cause that ground offset to appear on ALL of your underwater metals!

 

[Trojan]

What qualifies the guy at Hatteras to be an expert? You can lead a hoarse to water but you can't make him drink. Karl IS correct. Why is it that every other paragraph in this thread repeats it self. Come on guys pay attention. Every time it repeats you bring in another so called expert that likes something else. You guys need to learn to read a new schematic. Hatteras electrical schematics are HOW OLD. GfIs did not exist when these schematic were designed and isolation transformers were a special thing. Not a norm. Just because our boats were built in the past. We don't need to keep our electral in the past. Lets up grade. OUCH




BILL

How about we make a mass purchase of calders electrical book.

 

[TedZ]

Well i suppose that comment could be applied to any "expert" that doesn't agree with you.

This link is good

http://www.yachtsurvey.com/corrosion_in_marinas.htm

and says in part...

In case you’ve heard of that crazy solution of disconnecting your green, grounding wire, consider that quite a few people have been electrocuted as a result of this half-baked idea. The green is there to protect people against electric shock and electrocution, so don’t defeat its purpose.

I wouldn't waste any more time on this if it weren't that certain practices can create serious risk of injury.

Ted

 

[Genesis]

Pascoe is absolutely correct if you have no transformer and/or GFIs on the boat.

Of course, taken out of context, you'd conclude that running your genset at the dock is a recipe for instant death, since the correct configuration of shipboard wiring will (and must!) disconnect the shore ground when you switch the vessel over to "generator".

Again, the NEC requires GFIs in "wet locations" (and has for quite some time) because grounding is not sufficient protection in such an environment and, in fact, it can actually create risk. Arguably the safest configuration in a wet environment is known as a bifilial supply, however, for historical and cost reasons the power grid in the United States relies on an "earth" reference.

You can wire your boat any way you'd like; my view of it, Nigel Calder (widely acknowledge as "the" expert when it comes to "small vessels" like ours), and the NEC all agree.

Taking quotes out of context is extremely dangerous and when applied to AC circuits can get people killed.

Please take the time to understand what you're looking at before you act on it.

 

[MikeP]

WOW! This is the first time I read any of this thread and it makes my hair hurt!!

As you all know, I am 3500 miles from our boat, my Calder book, and Brigadoon's blueprints/wiring diagrams. ASSUMING the (1980 53MY) 120/240V systems are oem (which I believe they are), does anyone know if the oem Hatt connections to the isolation transformers and associated equipment is correct per this discussion?

Note- I just did a google earth plot and found that I'm NOT 3500 miles from our boat. I'm only 2200 miles!!!. I feel so much better.

 

[egaito]

Pascoe is absolutely correct if you have no transformer and/or GFIs on the boat.

Yep, the paragraph quoted is part of a discussion of solutions, galvanic isolators and isolation transformers being discussed before he suggests the latter as a bad alternative:

For small boats with aluminum drives, galvanic isolators are available that work only with the grounding circuits, and not the main power feeds. These are okay for boats that are only running something like a battery charger on AC current. For larger boats with higher power demands, it is necessary to have a full sized isolation transformer.

In case you’ve heard of that crazy solution of disconnecting your green, grounding wire, consider that quite a few people have been electrocuted as a result of this half-baked idea. The green is there to protect people against electric shock and electrocution, so don’t defeat its purpose.

Taking quotes out of context is extremely dangerous and when applied to AC circuits can get people killed.

Please take the time to understand what you're looking at before you act on it.

Amen!

 

[Genesis]

Again, out of context.

Yes, "disconnecting your green wire", standing alone, is unwise.

Pascoe recommends an isolation transformer. By definition an isolation transformer does not bring dock ground on board beyond the shield of the transformer. If your system does, then it is NOT WIRED AS AN ISOLATION TRANSFORMER!

You guys REALLY need to learn about this stuff before playing with it. If you don't understand how it works then don't screw with it and find someone who does!

I've read Pascoe's entire article (along with virtually everything else he has written.) He's correct but you must understand the context of his words in order for them to make sense!

IF you have current flowing in your "ground" (green) wire from shore, something is wrong either on your boat or another boat near yours in the marina. If the problem is not on your boat then it IS either on another boat or in the dock wiring itself. In either case you are VERY unlikely to be able to fix whatever it is that is broken, and in most cases you won't even be able to identify where the problem is without active cooperation of everyone else at the marina, which you may not be able to achieve.

The problem here is that MEASURING the voltage potential on the green wire requires lifting it and if there is a fault somewhere that all on its own can get you killed if done without due caution.

AC systems are not something to play with unless you understand them.

If you believe that Pascoe is saying that an isolation transformer equipped boat brings shore ground on board beyond the primary of the isolation transformer, then you do not understand the principles involved because it is not possible to both bring shore ground on board and have an isolation transformer setup on your boat.

 

[SKYCHENEY]

I've stayed away from this duel but here is my observation from my boat which is OEM Hatteras with isolation transformers. I have 2 transfromers, one for each 240v shore source. There is no ground wire in either of the shore cords. They do not have the metal outer band at the plug to carry the ground as some cords do. So, the ground stops at the shore stand and is not even carried down the cord to the boat.

 

[egaito]

I've stayed away from this duel but here is my observation from my boat which is OEM Hatteras with isolation transformers. I have 2 transfromers, one for each 240v shore source. There is no ground wire in either of the shore cords. They do not have the metal outer band at the plug to carry the ground as some cords do. So, the ground stops at the shore stand and is not even carried down the cord to the boat.

Right. This is what the Hatt engineer of that era told me was correct from the factory, and was often "fixed" by folks that believed it was either an oversight or a hack by another technician.

Since all the experts are wrong, or being taken out of context, I think I'll just stick to what the factory says, and what's worked. Earning an EE to plug in my boat just doesn't seem a good use of time that could be better spent on the water

 

[Genesis]

That's because Hatteras knew what they were doing originally

 

[Maynard Rupp]

WOW...I sure opened a kettle of fish with this thread. I think it would be easier for me to just replace anodes. Seriously though, all of you sure helped all of us and gave us the nikel tour through electricity. I know I have learned alot and I hope everyone has also.

 

[34Hatt]

Maynard Rupp WOW...I sure opened a kettle of fish with this thread. I think it would be easier for me to just replace anodes.

It sure has I have one question has your battery charger been addressed???
A bad or crappy charger can raise hell with zinc's. Well if anything it one more Idea too keep you up at night