Ac System Failure Problem

[summer75time]

Yesterday, we disconnected the dock's anti-electrick shock breaker and everything inside the boat worked!

After a few minutes, we discovered that the problem was caused by a faulty kenyon inverter (used to transform the 12Vdc to 110Vac and vice versa) which was bypassing the main ac panel, and overheated dangerously. So, logically, our next step will be to locate the inverter's connections and unmount it from the system. Hopefully, this will solve my problem and let me enjoy at last, the comfort of electricity in my boat.

Thank you all, for your help and suggestions over the previous week.

Thank you for the update! Very happy that things are coming right.

[Harbor_Pilot]

summer75time,

I am very glad to hear that you found the source of the problem.

I have been busy, and haven't been on here for a few days. Reading the posts, everybody that knew anything about something wanted to help. Of course we all want to help.

There were a few posts that suggested looking in the wrong place, but oh well, that doesn't matter any more. We were at a big disadvantage with not knowing the complete system and trying to solve it via the internet. Even with two electricians on site it was a big mystery.

If you ever have to resort to to finding an electrical problem by disconnecting or taking apart the system, keep a few things in mind. 1) Start at the Source, The head, not the tail end and test it as you go. 2) Split the system if you can, e.g. AC from DC and panel #1 from panel #2, and so on. 3) Compare the working to the non working and find the differance.

Now Life should be better in your world!

[Trim50]

Can someone explain the logic to me why ABYC requires AC & DC to share a common ground?

[Lighthouse]

I don't understand.

AC ground is a "leak" to earth - to dissipate a short, spike or leak. The AC "ground" is a third wire that is neither live nor neutral.

DC ground is a common live circuit.

Surely, if you tie these two 'grounds" together you are looking for disaster on your 12v side if there is a spike in the AC circuit.

I am no expert however.

[Trim50]

My point exactly!

I just had my boat surveyed for new insurance, and the surveyor is telling me that ABYC requires the AC ground and the DC ground to be linked which it is not on my boat...never has been. I've since talked with my friend who owns a Swan and he says his boat does not tie them together either and he says it is something thjat European standards and American standards dissagree on.

To me it make no sense....and I'm certainly not going to fix something that isn't broke.

[MMNETSEA]

Does this site clarify the question on grounding (Earthing in British terminology)

Click on ACDC Grounding

[KG4JXT]

I don't think a common ground is a problem. When I installed an isolation transformer on my boat for the AC shore power input, I had two transformer output leads and I wondered to myself which one was the "hot" lead. Well it turns out it was totally up to me! With some trepidation I picked one and grounded it. Voila! the other lead is 110 volts AC hotter than the ground circuit. The boat was connected to marina shore power for several years after that and I never experienced any problems with stray currents causing electrolysis nor was I ever electrocuted while cleaning the bottom and bronze thru-hull fittings. The wiring is consistent with diagrams in a boat electrical system book by Charlie Wing (don't recall the title now). Anyway, just my 2-cents.

[redbopeep]

With an isolation transformer in place, in theory, the shorepower ground should go to a faraday shield on the isolation transformer so a really high voltage spike on the shore power side should short to the faraday ground (shorepower ground) which should trip the shorepower circuit w/o affecting anything on the boat.

Conversely, some boats have galvanic isolators rather than more expensive isolation transformers. A galvanic isolator will make it such that a small (AC source from the marina) current will flow to AC ground unless over a certain threshold. The galvanic isolatiors typcially have two .7V diodes so often the threshold is 1.4V. Therefore anything over that threshold would then bleed through and the boat will have AC current passing through the ground system. If this is tied into the DC system, then there will be AC current flowing on the DC ground. Thus, a boat with galvanic isolator probably shouldn't have the two grounds tied together whereas one with an isolation transformer should be able to handle it. With the galvanic isolator, if the AC and DC grounds are tied together, one path of the current leaked across the 1.4V diodes can go through the water--creating a hazard in the water.

If you have a piece of AC equipment on the boat that is improperly wired, and both AC/DC grounds are tied together, then there is a potential hazard having nothing to do with isolation from the shore power. However, there is a much lower chance that the AC current from the defective equipment will leak into the water because there is unlikely to be a second path to the water outside the boat. Well, unless you've got multiple bonded thru-hulls, zincs and so forth...

A good source in the USA of inexpensive marine isolation transformers is Bridgeport Magnetics. They don't typically sell to the end user (thus, their good pricing I suppose) so you need to know what you want when ordering from them and be willing to wait 3 to 6 weeks for delivery via a freight service. We purchased one last fall to replace an older Triplite isolation transformer and are pleased with the quality of the new Bridgeport Magnetics one. They use a toroidal transformer. By design toroidal transformers are quite a bit lighter than a traditionally stacked transformer. So, instead of having 80-100lb's hanging on the bulkhead, we've got a smaller 50lb box. Nice.

Fair winds,