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Old 12-07-2015, 20:36   #1
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Isolation Transformer-- Does Anybody Use One?

I am in the process of putting together a manual charger for my 48v bank, (so I can do a proper equalization charge when needed... my regular charger is a solid state automatic smart charger) and started thinking, just for general electrical safety reasons, about adding an isolation transformer to feed the 3kva Variac which is basically a variable-secondary autotransformer with no isolation from AC source. Fine. But then I started thinking about actually installing an isolation transformer at my shore power connection, too, and the possible advantages thereof related to safety, galvanic issues, etc. Does anybody else here use one, who made it and who sells it, and what sortt of current do you draw through it from shore power? I looked it up in Nigel Calder's book and apparently this is thought to be a pretty good idea, but there were no specifics or fine details mentioned. FWIW I am set up for a single 30a 120v connection and have a separate enclosed breaker feeding my AC switchboard. Most boats I have owned had no proper AC system, just jury rigged ad hoc stuff but I put in a more or less proper system in Mr. Wiggles with full GFCI protection, etc, but I didn't think at the time an isolation transformer was all that important, since I didn't already have one on hand in my junk pile.

Howls of outrage for not hiring a professional electrician are the only replies I will ignore. All other comments or ideas or actual knowledge are welcome!
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Old 13-07-2015, 00:48   #2
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Re: Isolation Transformer-- Does Anybody Use One?

most boats don't have them because they are somewhat big, heavy, and expensive. but they are good to have.


a few different companys make them.


Charles marine ones are pretty common in north America.


I think victron makes one.


mastervolt makes one but it sucks with 120v. you need to buy one twice as big.
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Old 13-07-2015, 01:48   #3
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Re: Isolation Transformer-- Does Anybody Use One?

On my boat I don't use a seperate islation transformor, but instead use the charger as one. All AC power used onboard always comes from the inverter. And an inverter, if you don't have one already, is often cheaper as an isolation transformer.
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Old 13-07-2015, 03:35   #4
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Re: Isolation Transformer-- Does Anybody Use One?

An isolation transformer is great if you are going to Europe. Just change the jumper and you are compatible.
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Old 13-07-2015, 06:09   #5
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Re: Isolation Transformer-- Does Anybody Use One?

Boats in our brand -- at least those between 38' and 50' -- started being built with isolation transformers standard sometime between 2002 (I.e., after ours) and 2006 (my best guess). That might have been because all those boats require 50-amp shorepower service. Some of those are 50-amp/250v boats but with no 220v appliances on board (38' and 42') while the larger 45' and 50' both had a couple 220v systems


Dunno, about the smaller 33' to 36' boats, which routinely used twin 30s.

I'd guess that probably affected all 5 brands in the group, one of which was Hunter.

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Old 13-07-2015, 06:10   #6
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Re: Isolation Transformer-- Does Anybody Use One?

I would consider Victron over Charles. Victron uses a torrid core and is about 1/2 the weight.

http://www.victronenergy.com/upload/...formers-EN.pdf
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Old 13-07-2015, 06:13   #7
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Re: Isolation Transformer-- Does Anybody Use One?

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Originally Posted by rooiedirk View Post
On my boat I don't use a seperate islation transformor, but instead use the charger as one. All AC power used onboard always comes from the inverter. And an inverter, if you don't have one already, is often cheaper as an isolation transformer.
Does your setup provide galvanic isolation? (shore ground is not connected to the boat ground)
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Old 13-07-2015, 06:45   #8
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Re: Isolation Transformer-- Does Anybody Use One?

I don't see how you could go wrong installing an isolation transformer. I have one and it results in normal zinc consumption even if my dock mates are leaking electrons all over the place. Down there in the warm water it might even be more beneficial.
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Old 13-07-2015, 07:19   #9
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Re: Isolation Transformer-- Does Anybody Use One?

A galvanic isolator and earth leakage device cover most of the issues.

If your going around the world and want to be able to plug into 230 and 110 then the isolation transformer is a great idea to step up or down


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Old 13-07-2015, 08:35   #10
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Re: Isolation Transformer-- Does Anybody Use One?

As far as I know the isolation trnsaformer is used as galvanic isolator, I remeber having built one for a Hanse 65. To my knowledge they are not normally incorporated into sail boats.
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Old 13-07-2015, 08:50   #11
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Re: Isolation Transformer-- Does Anybody Use One?

Hi I cannot speak highly enough of the value of an isolation transformer. This transformer will allow you to set any voltage from European to US standards as well as preventing any galvanic corrosion because the ground is not required to be tied to the boat it completely isolates the shore power. They are not specifically built for the marine industry and in fact you can contact a number of commercial electrical supply places for a less expensive version.
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Old 13-07-2015, 09:59   #12
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Re: Isolation Transformer-- Does Anybody Use One?

Yes, Truemettle is right, normally an Isolation TRX is relation 1:1 so input Voltage equals output vVoltage
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Old 13-07-2015, 10:38   #13
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Re: Isolation Transformer-- Does Anybody Use One?

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Originally Posted by sotavento View Post
Yes, Truemettle is right, normally an Isolation TRX is relation 1:1 so input Voltage equals output vVoltage
Victron's 3600W Auto handles different input and output voltages. This negates the need for an additional autotransformer.
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Old 13-07-2015, 10:41   #14
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Re: Isolation Transformer-- Does Anybody Use One?

Quote:
Originally Posted by rooiedirk View Post
On my boat I don't use a seperate islation transformor, but instead use the charger as one. All AC power used onboard always comes from the inverter. And an inverter, if you don't have one already, is often cheaper as an isolation transformer.
Looking at the Victron pricelist I see that a charger + inverter combo even comes in cheaper than an isolation transformer + multi.

And this gives you clean 230V 50Hz everywhere, regardless of the quality of the shore power. In my opinion indeed the best solution, as long as your needs don't stray in to the territory where you need multiphase high amp hookups...
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Old 13-07-2015, 10:54   #15
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Re: Isolation Transformer-- Does Anybody Use One?

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Originally Posted by LakeSuperior View Post
An isolation transformer is great if you are going to Europe. Just change the jumper and you are compatible.

Kind of compatible. The transformer will change voltage IE 230V to 120 V or vice versa (at least mine will) but does not change frequency, EU 50 Hz to US 60 Hz.

For some electrical equipment using the correct frequency is necessary.
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