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Old 04-03-2017, 11:03 AM   #1
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Charles 30 Amp Isolation Transformer

I have purchased and am preparing to install a Charles 30 Amp Isolation Transformer (93ISOG26A) on one of my 30 amp inputs. We only use one of the 30 amp sources as all loads can be accommodated with one. Obviously this will be installed somewhere inside the boat. The input is located behind the washer dryer and there is a tangle of copper plumbing behind there. Also, based on feedback from other KK42 owners, you pretty much have to decommission the stacked washer/dryer unit in order to get back there. I'd like to leave that for another time. The issue:

These units are heavy (70 lbs inside a plywood packing case) but compact. You just can't locate them any old place. I was thinking of locating it where the old freedom inverter charger was located aft of the fuel tank as the backing is sufficiently beefy. I would guess there would be a wire run of some 20 feet to that location and another 20 feet back to the AC panel. Since we are talking about 120 AC, is there any problem with the length of these wire runs?

Second: I assume that the old galvanic isolator should be decommissioned?

Jim
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Old 04-03-2017, 11:35 AM   #2
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I don't know about KK's but I recently installed a galvanic isolator to prevent problems with upgraded marinas in the NW.

I have a bow and stern shore power plug and it was recommended I get an isolator for each...I asked why we couldn't wire it to the selector switch so it would work with both plugs, whichever plug that was selected. All agreed that was a good idea and that was what we did, It works well.

We put it inside the pilothouse near the Plug 1, Plug 2, Gen selector switch.
It did cause electronic problems with compass-autopilot...requiring we relocate the compass sensor.
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Old 04-03-2017, 11:45 AM   #3
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Ken: I already have a galvanic isolator. My question concerns an "Isolation Transformer" that completely isolates the boat from the shore-side power. This especially includes the "ground". As a consequence, I believe the galvanic isolator should be decommissioned.

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Old 04-03-2017, 11:47 AM   #4
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Sorry..I mis-wrote...should have read isolation Transformer--just installed last July.

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Old 04-03-2017, 12:27 PM   #5
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I was thinking about doing the same thing - adding an Isolation Transformer and putting it where my Galvonic Isolator is located. I don't see any need for both.
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Old 04-03-2017, 01:30 PM   #6
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With an isolation transformer, you don't need a galvanic isolator. Such a transformer "isolates" the ground from the shore power supply, keeping DC from being transmitted from the shorepower ground to your boat's electrical system.

Your shore power wiring almost certainly is 10 gauge which is what you should use to wire up the new isolator.

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Old 04-03-2017, 04:55 PM   #7
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Originally Posted by JDCAVE View Post
I have purchased and am preparing to install a Charles 30 Amp Isolation Transformer (93ISOG26A) on one of my 30 amp inputs. ...............................

I would guess there would be a wire run of some 20 feet to that location and another 20 feet back to the AC panel. Since we are talking about 120 AC, is there any problem with the length of these wire runs?
OK, so far, nobody has mentioned this:

The ABYC requires overcurrent protection on the incoming wiring within ten feet (measured along the length of the wire) of the inlet. You are planning on adding 40 feet of cable and this far exceeds the ABYC requirement. You will need to install a double pole breaker (breaks the hot and neutral conductors) somewhere within the first ten feet from the inlet.

I would look for a better place for the transformer even if you have to get behind the washer/dryer.
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Old 04-03-2017, 04:59 PM   #8
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I have a bow and stern shore power plug and it was recommended I get an isolator for each. ............
You have to learn who to take recommendations from and who not to. Web forums are the worst for this because anyone can be an expert on the Internet.

The galvanic isolator is not needed with a properly installed isolation transformer.
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Old 04-03-2017, 07:56 PM   #9
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Pretty much every diagram I have seen of isolation transformers use the shore powers ground to ground the transformers case.

Because of that, the isolator (wired between the shore and the transformer) would actually insert a ground fault and the transformers case would not be properly grounded.
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Old 04-03-2017, 09:00 PM   #10
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I don't think so. The Charles installation diagram has the load side ground connected to the case but not the shore power side.

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Old 04-03-2017, 09:20 PM   #11
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I installed a 50-amp 120/240-volt ISOBoost last year and it, too, is a beast to move--a 250-lb basketball. As Wes notes, I installed a 50-amp double-pole breaker within 10 feet (actually three ft.) of the shore power inlet. Another breaker On the load side of the transformer provides over-current protection.

This may not help you much, but I installed the ISOBoost on a bulkhead in the ER. I had some stainless steel "staples" made that poke through the bulkhead from the opposite side and distribute the considerable weight better than bolts and washers.






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Old 04-04-2017, 08:44 AM   #12
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wiring diagram attached

For those interested in this minutia, attached is a page from Charles installation instructions showing the wiring diagram. The shorepower ground is wired to a primary shield (perhaps for RF control) and is indicated to be insulated from case. The secondary (load) ground is tied to the case and the neutral side of the winding. This is allowed (and necessary) as the transformer secondary is the source in NEC terms.

I learned about all of this when I discovered that my Mainship 34T had an open ground. It turns out that when Mainship installed the isolation transformer, they never connected the ground to the case. Anyone who owns a Mainship built in the mid 2000s and has an isolation transformer should check this as others were miswired this way.

David
Attached Files
File Type: pdf Charles Isolation Transformer Wiring.pdf (1.91 MB, 62 views)
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Old 04-04-2017, 09:01 AM   #13
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Quote:
Originally Posted by djmarchand View Post
I learned about all of this when I discovered that my Mainship 34T had an open ground. It turns out that when Mainship installed the isolation transformer, they never connected the ground to the case. Anyone who owns a Mainship built in the mid 2000s and has an isolation transformer should check this as others were miswired this way.
Please refresh my memory here David. Did they screw up by not connecting the "internal" ground (on the boat-side of the xformer) to the xformer case? Or was the problem on the "shore side" ground (which appears to connect to the xformer shield)?

And what tipped you off that they'd messed the install up?

Dave
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Old 04-04-2017, 09:07 AM   #14
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Originally Posted by djmarchand View Post
For those interested in this minutia, attached is a page from Charles installation instructions showing the wiring diagram. The shorepower ground is wired to a primary shield (perhaps for RF control) and is indicated to be insulated from case. The secondary (load) ground is tied to the case and the neutral side of the winding. This is allowed (and necessary) as the transformer secondary is the source in NEC terms.

I learned about all of this when I discovered that my Mainship 34T had an open ground. It turns out that when Mainship installed the isolation transformer, they never connected the ground to the case. Anyone who owns a Mainship built in the mid 2000s and has an isolation transformer should check this as others were miswired this way.

David
It's not "minutia" if you are actually installing one of these transformers. A properly installed isolation transformer is a good thing. An improperly installed isolation transformer may be worse than the original problem that someone is trying to correct.


The attachment makes it all pretty clear.
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Old 04-04-2017, 05:34 PM   #15
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shield, I meant shield.

Drats too late.

As Trump said the other day, sometimes you hit a clunker.

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Old 04-04-2017, 05:43 PM   #16
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Wire length should be an issue. Just install breakers in the right places, and use heavy enough wire.

My isolation transformers came mounted on rubber isolation mounts, and now I know why. Last year I installed an auto transformer to get 240V service from my 120V inverter service, and when turned on, the auto transformer makes a pretty good humming sound. I heat the isolation transformers too, but not nearly as much. I now have some isolation mounts for the auto transformer to install this summer.
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Old 04-04-2017, 06:25 PM   #17
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Please refresh my memory here David. Did they screw up by not connecting the "internal" ground (on the boat-side of the xformer) to the xformer case? Or was the problem on the "shore side" ground (which appears to connect to the xformer shield)?

And what tipped you off that they'd messed the install up?

Dave
I bought a plug in polarity and ground tester and was somewhat shocked that all outlets had no ground. This was on a two year old boat. I suspected the isolator transformer; it was a standard Mainship item on that boat. So I downloaded the Charles installation instructions, the one I attached a page out of, and noticed that the ground on the boat side, the load side was open, ie not connected.

It was easy to fix, just connect the green wire to the screw on the case which I determined was also appropriately connected to the neutral side of the transformer.

David
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Old 04-05-2017, 09:06 AM   #18
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......... The secondary (load) ground is tied to the case and the neutral side of the winding. This is allowed (and necessary) as the transformer secondary is the source in NEC terms............
This is the key. Just as the neutral and ground are connected together at the electric panel (the "source") in your home, the secondary of the isolation transformer is considered the source on your boat. The neutral and ground are connected together there.

It's surprising and a real shame to find a production boat wired incorrectly. Maybe this was a dealer installed option.
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Old 04-05-2017, 10:14 AM   #19
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It's surprising and a real shame to find a production boat wired incorrectly. Maybe this was a dealer installed option.
Nope, the isolator was a standard factory installed item, not even an option. That is why I encourage all Mainship owners of boats built in the mid 2000s to check, well heck everyone- you never know what yahoo wired your boat. The consequences can be deadly.

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Old 04-05-2017, 10:47 AM   #20
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Thanks people for your experiences and advice on the installation of an Isolation Transformer (IT). I had figured that the Galvanic Isolator was unnecessary and have confirmed that with Collier's book on corrosion where it is explicitly stated. Wes: Thanks for your points on the GCFI. That is not shown on the installation instructions I had downloaded the from the Charles site but it does make sense. However wouldn't the breaker on the shore power pedestal serve that purpose (hopefully not too dumb a question)? I had also noticed the ground to the case. I presume, though, that the ground on the boat is isolated from the shore ground as that would seem to be the whole purpose of the installation. From the diagram, it would seem that everything, including the generator would go through the IT.

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You have to learn who to take recommendations from and who not to. Web forums are the worst for this because anyone can be an expert on the Internet.
That's true for enough, but I did learn something about Ken's particular installation: that a rotary switch could be installed to allow both shore connections to be utilized. Not sure if I will go down that route, but that and where he located his unit and some of the problems he encountered (compass interference issues) are useful to know.

So why ask questions on this forum, since I will be having this professionally installed? A number of reasons. First there are well informed people (Dave, Wes, Peter and others) on this forum who have valuable information to provide and who challenge my own limited knowledge. Second, I get information on what others have done, expert or not on site locations and the like. So when it comes to the actual installation, what the electrician does is obvious, and some time (think $) can potentially be saved as some of the issues have been thought through before hand. Finally, I can be at least somewhat informed so that if the electrician does something I don't understand, at least I will know enough to ask for an explanation.

Thanks all!

Jim
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