Isolation Transformer shorted out?

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Turning Point

Turning Point

Veteran Member
Joined
Aug 22, 2019
Messages
32
Location
USA
Vessel Name
Turning Point
Vessel Make
67’ Ed Monk Pilothouse Trawler
Help!
Yesterday the circuit breaker on the dock popped. Through a process of elimination, it appears the Charles Industries isolation transformer is the cause.
This has been in the system, working fine for over ten years. There are no moving parts. Has anyone heard of these shorting out?
Still waiting for Charles Ind. to respond...
Thx.
Duncan
 
Ground fault, not inrush. I disconnected the output leads and it still pops immediately. When I initially disconnected the input leads, everything was fine, so it’s not the cord, plug or faulty circuit breaker.
(Old school shorepower, no GFI)
 
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I had a Westinghouse or a GE isolation transformer (forgotten) and it gave up the ghost after about 15 years. I think its partly because we tend to spec the smallest we can get away with (cheaper) instead of a larger unit and then heat becomes the issue.
 
Yes, likely an insulation failure. The best diagnostic instrument is the Fluke 1503, which I have 6 feet away. But, with no output connected, and it trips out a 30 or 50 Amp breaker, I think that is all the real test you need. It's bad....
Most of the intrinsic value is copper, not iron, so rewinding is likely not a consideration.
 
Thanks Xsbank,
I don’t think it was overloaded. It’s a robust (235 lb.) unit rated for 50Amps. I remember it getting lukewarm at most. I’m curious how yours failed....did it short out or ?
 
I'd check the incoming ground wire and connections. It should be connected to the internal shield of the isolation transformer (not the output ground of the transformer). Measure resistance of the incoming ground to the incoming power wires (with shore power disconnected of course). If the short is truly internal to the transformer, it would need to be replaced.
 
diver dave said:
Yes, likely an insulation failure. The best diagnostic instrument is the Fluke 1503, which I have 6 feet away. But, with no output connected, and it trips out a 30 or 50 Amp breaker, I think that is all the real test you need. It's bad....
Most of the intrinsic value is copper, not iron, so rewinding is likely not a consideration.
Click to expand...

Thanks Diver Dave,
I’m still in the grieving process here. I just started shopping for a replacement ?
I’ve had drug habits cheaper than this!
 
Turning Point said:
Thanks Diver Dave,
I’m still in the grieving process here. I just started shopping for a replacement ?
I’ve had drug habits cheaper than this!
Click to expand...

Try calling Charles, if you haven’t already, to see if they can suggest a cause. I was told by an ABYC electrician who installed many of these units that they don’t often fail but a replaceable circuit board is often the cause when they do. Please post what you learn.
 
Angus99,
I just got off the phone with a great guy in customer support. After my description, it sounds dead to him. He said a bench test with a “variac “ (sp)
could confirm it but doesn’t look good.
BTW: this is an older unit with no circuit board, basically just a big copper coil.
 
I sold Charles isolation transformers for over 10 years. I stopped selling it a few years ago because of too many warranty issues and news that Charles is discontinuing production soon.

The transformer is held in the case with a rubber like potting material, no fasteners. The potting material does not go all the way down to the bottom. There is a 2 or 3 inch space at the bottom. Heat causes the potting material to come loose from the case and the transformer drops sometimes breaking wires.

Also had issues with the transformer quitting shortly after installation and received a few with low output voltage.

I now sell the Victron Energy isolation transformers. They don't have a 50 amp unit yet but the 30 amp manual transformer is less than $700
 
syjos said:
I sold Charles isolation transformers for over 10 years. I stopped selling it a few years ago because of too many warranty issues and news that Charles is discontinuing production soon.

The transformer is held in the case with a rubber like potting material, no fasteners. The potting material does not go all the way down to the bottom. There is a 2 or 3 inch space at the bottom. Heat causes the potting material to come loose from the case and the transformer drops sometimes breaking wires.

Also had issues with the transformer quitting shortly after installation and received a few with low output voltage.

I now sell the Victron Energy isolation transformers. They don't have a 50 amp unit yet but the 30 amp manual transformer is less than $700
Click to expand...

Thanks syjos,
I’m not sure what is going on. Charles support told me there is usually scorched electrical smell. I have none of that and this afternoon I bypassed the unit and shorepower is driving my inverter crazy. My shorepower is 240v but the wiring is suspect. Tomorrow I research that ? That would be the cheapest cure.
 
50 amps isn’t really very much - a heater or two, a/c, hot water tank, lighting, battery charger? It adds up pretty fast. If you add too much load the voltage drops and it starts to heat up, then the resistance rises...

When you are on your boat, all snug in the warmth, tied up at the dock, stick your volt meter in any 120 volt outlet and read the voltage. Anything below the voltage at the dock pedestal and you are overloaded. Unplug something.
 
Acme Transformer General Purpose Encapsulated 15KVa, multi voltage in, 120/240 out, price about $1000 US. As good as any you'll get. Sorry the model# isn't handy, find it easy enough...
 
EngNate said:
Acme Transformer General Purpose Encapsulated 15KVa, multi voltage in, 120/240 out, price about $1000 US. As good as any you'll get. Sorry the model# isn't handy, find it easy enough...
Click to expand...


:thumb: And they now have models with the proper dual/isolated grounding for marine use. And don't be scared by the "Acme" name. It's quality stuff, not roadrunner junk, and now part of Hubbell.
 
twistedtree said:
:thumb: And they now have models with the proper dual/isolated grounding for marine use. And don't be scared by the "Acme" name. It's quality stuff, not roadrunner junk, and now part of Hubbell.
Click to expand...

I had an Acme isolation transformer on the previous boat and it worked without issue for 14 years.

They need to be mounted on top of a rubber pad to isolate hum.
 
Turning Point said:
Thanks syjos,
I’m not sure what is going on. Charles support told me there is usually scorched electrical smell. I have none of that and this afternoon I bypassed the unit and shorepower is driving my inverter crazy. My shorepower is 240v but the wiring is suspect. Tomorrow I research that That would be the cheapest cure.
Click to expand...

I'd recommend you sort out why you're having dock power and inverter issues with IT bypassed. On most vessels, an onboard IT should ideally be in place to deal with dock wiring issues not boat wiring. Are the docks you're plugged into the new marina code GFIC setups?
 
A failed transformer may not have smell or visual indications. In bypassing your transformer you have likely left the Neutral floating - the incoming N is not used with the transformer and would have to be wired.

These encapsulated models from Acme have been shielded (a ground wire comes out from the windings, isolated from the case) for as long as I've put them in- some 25 years.

Here is a connection diagram, from Canada's Ships' Electrical Standards for Inspected Vessels:
 

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Oh! You're right!, wrong page...
 

Attachments

  • Transformer wiring.pdf
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Thank you everyone for your input. My current situation is as follows:
I’ve wired passed the both the IT and the Outback inverter and all loads function normally.
(For some reason the transfer switch in the inverter refuses to function on shorepower but works fine with generator power)
I’m shopping for a new Acme/Hubbell IT but waiting for an explanation to the electrical gremlins first.
Thx
Duncan
 
I can help. PM me if interested.
Nate
 
Just saw at FLIBS

I just saw a booth at FLIBS with a sign that said they had Charles transformer repair solutions. I spoke briefly with the guy but didn’t take a card. Turns out they’ve found a way to bypass the failures with the electronics of the Charles isoboosts and switching systems.
 
Kapn said:
I just saw a booth at FLIBS with a sign that said they had Charles transformer repair solutions. I spoke briefly with the guy but didn’t take a card. Turns out they’ve found a way to bypass the failures with the electronics of the Charles isoboosts and switching systems.
Click to expand...

Thanks Kapn,
Mine is an older unit consisting of copper coils and no moving parts.

Duncan
 
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