Install Isolation Transformer

[LenBuchanan]

I believe that Defender is still carrying the Charles Iso Transformer.
As for installation, as I said, I have two shore power inlets on both port and starboard side of the boat. At my home dock, I tie up Port side to. So I installed two Iso Transformers, one for each inlet on the port side. If I am at a marina where I am tied up on the starboard side, I run my shore power cords to the port side, so I am always running through the iso transformers.
Our marina was hit by an electrical strike at the end of 2018, which blew out the underground sprinkling and fried the electronics on the sailboat next to me. I had no issues. My dock mate had a marine electrician over to his boat and we were discussing the strike and I mentioned that I had installed the iso transformers. He said that that was what saved my boat from damage.

 

[Comodave]

I bought 2 of them from Defender and have them mounted and most of the wiring run. Have to figure out how to get the wiring from the inlets to the new breaker box that I am installing.

 

[Newtrawlerowner]

-665mV, AC or DC and where is this being measured, on the SP cord? Of AC and on the SP cord, the GI will not stop that, it only blocks DC, and as long as it does not originate on your vessel, there's nothing you can do about it. Was it measured with SP breakers on or off? If off, and there is little or no difference between on and off, it's not from your vessel.

Steve,
The tests are all DC Mv readings. I have RED lead connected to engine, BLACK lead connected to a submerged silver/silver-chloride electrode.

As posted first reading was SP cord plugged in, pedestal off. No change. Then with SP plugged in, pedestal on, no change. Then SP plugged in, shore power on, vessel breakers on, nothing on the vessel turned on. Readings go down to -650Mv. I understand this may be a DC issue.

Thank you for your responses. I'm still learning. I'll continue looking and testing.

 

[Steve DAntonio]

If it is DC then the GI is either not working or it's been inadvertently bypassed.

As an aside, buying a non-boosting transformer has some undesirable side effects, detailed here https://stevedmarineconsulting.com/wp-content/uploads/2019/12/ShorePowerTransformers181-04.pdf The most important of which is when plugging into 208, you will end up with 208/104 aboard, your outlets, refirg, microwave etc. will have 104. Without a transformer, on 208, you will have 208/120 aboard.

 

[EngNate]

Here's a possibility - metallic inlet, mounted with thru-bolts and nuts and a bonding wire attached on the back side, bypassing the GI.

 

[Steve DAntonio]

Bounding a shore power inlet would be very unusual, and incorrect since it is already connected to the AC safety ground, but yes, that would bypass the GI.

 

[boomerang]

Following up on this thread and a post I made about wanting to install an isolation transformer on our boat, I did in fact find an Acme 3kW transformer on ebay. It was advertised as used and bent up from being in storage but working. I offered $135 (it was free shipping too and the damn thing weighs over 50 pounds). I figured that maybe I would get lucky and that it was worth gambling $135 because a new one is $4-500. I received it and sure enough, it was definitely bent. I took a hammer to the case and straightened it so the cover fit. I think it was never used because the knockouts were still intact and the wiring looked as it had never been connected to anything. I mocked it up & tested it before going to the trouble building a shelf & installing it. It worked so now it's installed & I'll have a little more confidence when we stay at a marina with a GFCI shore pedestal.
No, the transformer isn't hanging upside down! Sorry about the typical skewed iphone pictures but I'm on a chromebook right now and can't do any editing. The hardest part was getting the heavy bugger under the cockpit, over the exhaust hose all the way outboard. At least I know my hernia operation a year ago was a success.

 

[Comodave]

I put 2 of the Charles transformers in our boat. One was mounted on the deck where the old house battery bank was so it was pretty easy. The other one had to be mounted on the bulkhead so with the weight it was very difficult to get mounted. But we got it done so all is good now.