Isolation Transformers question

As part of my refit, I am looking at adding in an isolation transformer, rather than galvanic isolators.

Is it advisable to just have an isolation transformer?
Can you parallel isolation transformers?
Any recommendations on the brand/model/etc for the transformers or isolators?

I was looking at the victron isolation transformer, but need to have about 20kw of shore power.

Thank you

You want a single isolation transformer on the shorepower inlet.

20 kW? The maximum you can get out of a 50A/220V shorepower receptical is 50*220 = 11 kW.

David

DavidM said:

You want a single isolation transformer on the shorepower inlet.

20 kW? The maximum you can get out of a 50A/220V shorepower receptical is 50*220 = 11 kW.

David

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Yes, but 100A x 220V = 22kw

If you have a isolation transformer there is no need for galvanic isolators.

You want a isolation transformer to match the shore power line and isolation transformer standard sizes do just that.

Do not parallel isolation transformers, and there is not any reason to do so. Just buy the correct one for your shore power inlet.

sndog said:

Yes, but 100A x 220V = 22kw

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Is that two 50A cords, or a single 100A. If two cords, then on 12kva isolation transformer for each. If a single cord then a single 25kva.

twistedtree said:

Is that two 50A cords, or a single 100A. If two cords, then on 12kva isolation transformer for each. If a single cord then a single 25kva.

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Acme/Hubble make good isolation transformers including taps so you can wire a selector switch to boost 208V shore power when needed. They also make an auto sensing and boosting model, but considerably more expensive.

twistedtree said:

Acme/Hubble make good isolation transformers including taps so you can wire a selector switch to boost 208V shore power when needed. They also make an auto sensing and boosting model, but considerably more expensive.

Click to expand...

Thank you

twistedtree said:

Is that two 50A cords, or a single 100A. If two cords, then on 12kva isolation transformer for each. If a single cord then a single 25kva.

Click to expand...

Still deciding between the two. Any pros/cons?

sndog said:

Still deciding between the two. Any pros/cons?

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100A dock outlets will only be in places expecting big boats - say 70' or bigger, and probably more in the 100'+ range. 50A outlets will be MUCH more common So based on that I'd go with two 50s.


That said, if you have two 50s, then you need to split up your loads between the two. Dedicating one to HVAC, and the other to everything else is common, but certainly not the only way to do it. But it has the advantage of letting you run the boat off a single 50A outlet as long as you don't need HVAC.


Just as one example, I have three load panels in the boat; Inverter loads, which is pretty much everything, non-inverter loads which is only the hot water heater and shore chargers, and HVAC. Then I have two 50A shore cords, and I can any of my load panels to either shore cord. So I can run off one cord or two, with loads split up in a number of different ways. It's relatively easy to do in a new build, but could be a lot harder in a refit.