Isolation Tranformer Image

Isolation Tranformer

Isolation Transformer

Hey there,

I work on a 49 ft steel sailboat. We have an old isolation transformer on board when the boat was purchased rated for 240V 50 Amps of service. We want to replace it with a Victron product, however, according to the Victron Datasheet, the highest Amp rating is 32 Amps at 7000W. Would the isolation transformer work if we purchased two 32Amp isolation transformers and attached them in parallel?

Any suggestion on setup or product advice is greatly appreciated.



oliviaritter asked
oliviaritter answered ·

2 Answers

Isolation transformer connecting Multiplus

Could be a dumb question but : I am currently retrofitting a steel boat, there is a 4000VA isolation transformer installed (torroid type with inrush limiter) On secondary side the PE (Ground) is connected to Neutral as it should be according to the transformer manual. (Primary PE is not connected to shore)Directly after the isolation transformer i would like to install a Multiplus II 24/3000/70. Since the Neutral is allready connected to PE. Do i need to put a PE wire into the inlet of the multiplus (which essentialy is the neutral) or can i just put Line and Neutral in the power inlet? Or can i make the PE to N loop at the multiplus terminals? What is the right way to connect the Multiplus? (Answer would be greatly appreciated)


manta asked
manta commented ·

2 Answers

Isolation transformer earth connection

Hi all,

Just confirming here that when my boat is floating on the water there should be a link from the input PE terminal to J34a.

So, the earth wire from the shore power supply flex is connected to the input PE terminal and I make a small wire up with a female spade connector from this input PE terminal and connect it to J34a?

This transformer is not the auto 115v - 230v switching model

Many thanks

metal-snapper asked
h2operator commented ·

8 Answers

High Lines Voltage with Isolation transformer and Multiplus

System Description on sailboat:

  • Isolation Transformer 3600VA
  • Multiplus 24/300/70
  • Shore power 120V (nominal)
  • System Power 220V (nominal)

The only load on the transformer is the Multiplus.

We currently are in a location where the lines voltage is running right at the very top of the USA grid specification (127V). Coming out of the transformer we have 272V. This is over the maximum high voltage cutoff for the Multiplus (270V), so it stays in "Inverting" mode.

My understanding is that applying a load on the transformer output will drop the voltage to something like (127*2*1.05)= 267V which is still high, but would allow the Multiplus to make its line connection and charge our batteries and pass through AC power. Unfortunately, without extensive rewiring there is no way to apply a non-voltage sensitive load to the transformer.

Is there any other way to make this connection work? I have reviewed previous posts on similar issues, and it seems the answer is "no," but maybe something specific to my situation is possible? It frustrating to have to run the generator while shore power is available, but just 1 or 2 Volts too high (but still within local grid power specification!)

I appreciate that the usual issue with marina shore power is LOW voltage and this might be the reason for the 5% voltage boost out of the isolation transformer, but this is not the first time we have had this issue and the high voltage problem has been much more often the issue for us.

billknny asked
pwfarnell answered ·

2 Answers

Help with Isolation Transformer and Quattro Voltages

We are in a marina in the Dominican Republic that provides a very clean but high voltage of 135.6 volts at the pedestals. Obviously, this is higher than spec but they say they do it so that everyone on the docks has the voltage needed for their vessels.

The problem is that our Victron Isolation Transformers take that 135.6 voltages and add an additional 5% per its specifications. This new voltage of about 142 volts is obviously quite high and exceeds the Quattro maximum input voltage by two volts - having the result that it won't then start the charge our batteries.

Looking for solutions here.

atarlecky asked
pwfarnell commented ·

3 Answers

Isolation Transformer 3600 Fan

If the cooling fan is operating when shore power is disconnected does the fan stop? If not where is it powered from.

Thank you

John Siggs asked

0 Answers

Isolation Transformer cooling fan broken?

How can I tell if my 3600W Isolation Transformer’s cooling fan is working? I have never seen it on, even when the unit is obviously hot and running near max load for some time. It’s a 5 year old unit and I’ve been using it for several months now.

I read that the transformer should shut down if it overheats, but fortunately that hasn’t happened either.

kdagley asked
wanderer answered ·

3 Answers

Welding a vessel on water

Hi Guys,

Just wondering if anyone could help answer my following concern.

I want to do some welding repairs on my steel boat (She is using shore power in a marina in Aust), I'm concerned about stray current damaging my boat (and others nearby).

Can someone tell me if it is safe to weld using sore power via isolation transformer, the theory/concept behind why, and anything/indications to watch out for ?

I thought there was a description about welding in one of the Victron publications but I cannot find it...

Kind Regards


brynwatson asked
Paul B answered ·

1 Answer

Are the Isolation Schematics on the Victron Website Wrong?

This question has been asked before (@Charmcityboater) but not really answered:

It seems like the Victron diagrams below show the Multiplus BEFORE the Isolation Transformer in the chain from shore power to loads? I thought that the isolation transformer would be the first and only thing directly connecting to shore power and the multiplus would connect to the Isolation Transformer?


msg43 asked
wkirby answered ·

1 Answer

Isolation Transformer buzzing on electric heated blanket

Hello All, very confused. Victron I.T 3600w 115/230v on a boat connected to shorepower. Very happy and (almost) quitly doing its thing until i plug in the electrical heating blanket. The buzzing is too much and changes with the setting of the heating from low = annoying to high = unbearable. The blanket is an Inventum HN1312V with a draw of 60w. Very curious why this is and if there is a way to still be warm at night and being able to sleep.

goyow asked
Alexandra answered ·

1 Answer

Is it possible to put 230v via a switch directly between transformer output and multiplus input


I would like to use an isolation transformer to convert from 120v to 230v.

Is it possible to put 230v via a switch directly between transformer output and multiplus input like in the picture?

What if 120v is connected on the 230v output side because the switch position is wrong. Will the transformer and the Multiplus switch off or will there be damage?

Exactly the same question what happens if the input voltage is bridged differently than actually present?

This is unfortunately not described in the manual


service-1 asked
Mike Dorsett answered ·

1 Answer

3600W output Isolation step up voltage incorrect, possible failure?

Hello I currently have a Victron 3600W 115v/230v(not auto)isolation transformer. I have the jumper above the inputs set properly for 115v In(measured: L-120v/N-0v/PE-0v) and I have the output jumper set correctly(middle two spades) for 230v output but the output voltage is messured: L-77v/N-65v/PE-0v which makes no sense to me at all. If any one has a suggestion as to what may be causing this I would greatly appreciate it.


Image Caption


I do not have the J33 and J21 jumpered, will this make a difference?

miller76 asked
wkirby answered ·

1 Answer

Isolation Transformer fan operation

We have an ITR3600 auto transformer.

Recently, the temperature light has illuminated, the unit is still passing power, but the fan is not operational.

Does anyone with experience with this unit know if the fan always runs at variable speed, or is it sometimes off during operation?

Have hooked up a replacement fan, which is behaving the same way, though I have been unable to reproduce the temperature light.

Should it be running during operation, energ without the temperature light?

Attempting to troubleshoot and rule out a thermostat or other internal error vs fan failure.

kelzamedic asked
mike4nl answered ·

1 Answer

Isolation transformer high output voltage

I have an automatic isolation transformer that I am supplying with 120VAC input.

I’ve set the output voltage to 230VAC via the jumper settings provided in the manual but I am seeing 260VAC output.

What am I missing?

rspott asked
Rod answered ·

3 Answers


88 Posts
86 Users
1 Follower

Topic Experts

Kevin Windrem
67 Points
12 Points
Franz Voelkl
0 Points