Isolation Transformers

[Southern Star]

As Nigel Calder points out, isolation transformers completely isolate you from shore power and hence provide more protection that galvanic isolators. As I pointed out earlier (and as confirmed by gegroves), they are also extremely useful as 'step-down' transformers if sailing in areas with 240 volt. If you have the space, can afford the weight (and can install one in an area where the heat can be dissipated to the exterior) there are a valuable addition to any cruising boat; on a steel boat, I wouldn't leave home without one.

Brad

[RBEmerson]

See a recent topic about someone, in Europe and on a steel boat, who found out, the hard way (mercifully not the hardest way, though), that his marina had swapped the hot and neutral wires (reversed polarity). An isolation transformer will "cure" this problem, removing a literally life-threatening risk.

[fives5s]

Buck,
Go to www.defender.com they have isolation transformers. They have exactly what you need at a fairly reasonable price.

[Ike]

Here is a quote from my web site from the section on transformers. The links are to especially good references on using isolation or polarization transformers. Both Victron and Charles make good transformers

The benefit is that there is no physical connection between the two coils. So the second coil is effectively isolated from the rest of the power grid. This principle can be used to isolate the AC circuits on a boat from the AC circuits ashore. See Wikipedia on Isolation Transformers. Galvanic Corrosion and Isolation Transformers. The green wire on the boat is connected to the white wire on the boat side of the transformer, at the transformer terminal. This is the only exception to the rule about not connecting the green and white wire on the boat! Here is a link to a wiring diagram in Professional Boatbuilder Magazine . Figure 9 and 10 are taken from ABYC electrical standards and show how an Isolation Transformer is wired in the circuit. This stops DC current in the green wire, which prevents galvanic corrosion.
Professional Boatbuilder Number 103, Oct/Nov 2006 had an article by Ed Sherman, A Technical Case For Isolation Transformers
Here is another article that compares the Galvanic Isolator and the Isolation Transformer.

Another transformer used to isolate the AC System on the boat from the AC system ashore is a Polarization transformer. Obviously, from the name it is intended to maintain polarity in the circuit. Here is an article from Technical Information Exchange, Published by BOATUS, entitled Isolation or Polarization, Which is the Safest Transformer Installation? When reading this keep in mind that the author is stating his own beliefs, but I believe that both isolation and polarization transformers have advantages and disadvantages. Which you choose is up to you, but they both will give you a good level of safety. The big difference with a polarization transformer is the green wire on the boat is still connected to the green wire ashore. This article is pretty technical but it does have a good discussion of galvanic corrosion and the use of transformers to protect the boat

[Extemporaneous]

Originally Posted by Ike

Here is a quote from my web site from the section on transformers. The links are to especially good references on using isolation or polarization transformers. Both Victron and Charles make good transformers

Have you heard of Mastervolt and do you know if they are any good?
I live in Canada and think that I can source a Charles or Mastervolt here. Can't seam to find a supplier of Victron though. If you know of one, I'd be interested.

Let me know if you know.

Thanks,
Extemp.

[Ike]

Yes Mastervolt makes isolation transformers. I don't know anything other than what I have read online or seen at boat shows, but they appear to be a good product.

[hellosailor]

Isolation transformers are hundred-year-old technology, so it doesn't take much to build one. I'd suggest looking for what is in stock locally--because they are big chunks of heavy metal and shipping will be a killer. After that, judge what is local by the warranty and the fit and finish. If it looks like it was made by folks who gave a damn--it probably is. And a warranty shouldn't be a problem for a good vendor, transformers don't really have much that CAN fail.

[GordMay]

There’s a wealth of good technical information on Peter’s [Ike] website at:
New Boatbuilders Home Page - About This Web Site

[Extemporaneous]

One oddity through. The spec says it is "3600W | 115/230V | 32/16A".
Now see my emails below to and from the manufacture.

"Chris.

I have found a supplier and am ready to buy, however there are still a couple of questions that I need answered.
You have told me that it comes with 2 16amp breakers for use with 230volt input.
Do the 16amp breakers need to be changed to 32amp breakers when the input is 115 volt?
Does it come with loose 32amp breakers to use when connected to 115v input?
What type/make of breakers are these and can I buy 3rd party replacements?
Let me know.
Best Regards,"

"Dear Sir, this will work fine out of the box, no changes are needed.

Chris
-MOBILE-
Victron Energy"

So what am I missing?
First, these breakers seem small, are they not the main breakers?
I didn't think you could put together two 16amp breakers to make a 32amp breaker. Can you?

Nothing in the documentation says anything about changing the breakers.

Let me know.
Thanks,
Extemp.

[GordMay]

Watts (Volt-Amps) ÷ Volts = Amps
3600W @ 115V = 31 A
3600W @ 230V = 16A

With a 230V Input, you use a 16 A Fuse in EACH of the Line (hot “in”) wires.
With a 115 Input, you use a single 32 A fuse in the single Line (hot “in”) wire.
The Neutrals are unfused.

[hellosailor]

ext-
If that board is "converted" from 110 to 220 by physically moving the input wire connections, then perhaps it uses the two 16A breakers in parallel (effectively making them into one 32-amp breaker) when it has been wired in the "110 V /32 A" configuration.

I'm not sure if that's kosher but it would be the only sensible way that the breakers could "convert" from 16 to 32 amp service.

You'd need to check with the maker about that, and ask some of the other folks if that's a safe way to play with breakers.

As the breakers being small...well, yes, even in household breaker panels there are "half sized" breakers these days. Breakers aren't all the same, some are thermal breakers (limited life cycles), some are magnetic breakers (more life cycles), some have larger contact areas than others. As long as they have a UL or similar certification on them, they should work safely enough.

[Extemporaneous]

Originally Posted by GordMay

Watts (Volt-Amps) ÷ Volts = Amps
3600W @ 115V = 31 A
3600W @ 230V = 16A

With a 230V Input, you use a 16 A Fuse in EACH of the Line (hot “in”) wires.
With a 115 Input, you use a single 32 A fuse in the single Line (hot “in”) wire.
The Neutrals are unfused.

Gord,
That is my exact understanding of how it works and hence my confusion regarding Victron's answer to my email and also the diagrams in the less than stellar documentation that came with the unit. Perhaps it's not less than stellar and they are JUST telling me what I need to know and NOT how it works (you know the Black Magic Voodoo stuff).
Also it is for the European 230v system and so it only has one line in (see attached). My understanding is (NORMALLY) that one would only need one 16amp breaker while the source is 230v and then if one changed to a 120v source you would have to take the 16amp breaker out and replace with one 32amp breaker. Once again, hence the confusion regarding the reply from the Victron Rep. (see red and violet below).
Oddly (to me) the Circuit wires don't connect to the breakers (TCB's in the Diagram). Perhaps that is where my confusion lies. Maybe only one of the 16amp breakers is used when the transformer is receiving 230v, but through some BLACK MAGIC it uses both 16amp breakers to make a 32amp breaker when receiving 120v????

Regards,
Extemp.

Originally Posted by hellosailor

ext-
If that board is "converted" from 110 to 220 by physically moving the input wire connections, then perhaps it uses the two 16A breakers in parallel (effectively making them into one 32-amp breaker) when it has been wired in the "110 V /32 A" configuration.

I'm not sure if that's kosher but it would be the only sensible way that the breakers could "convert" from 16 to 32 amp service.

You'd need to check with the maker about that, and ask some of the other folks if that's a safe way to play with breakers.

Ya something like that. I've never heard of paralleling Breakers, but perhaps it can be done. But I'm not sure and I don't like things I don't understand (sucks to be me). But I try.
Also note, I did try to check with the maker.

Originally Posted by Extemporaneous

One oddity through. The spec says it is "3600W | 115/230V | 32/16A".
Now see my emails below to and from the manufacture.

"Chris.

I have found a supplier and am ready to buy, however there are still a couple of questions that I need answered.
You have told me that it comes with 2 16amp breakers for use with 230volt input.
Do the 16amp breakers need to be changed to 32amp breakers when the input is 115 volt?
Does it come with loose 32amp breakers to use when connected to 115v input?
What type/make of breakers are these and can I buy 3rd party replacements?
Let me know.
Best Regards,"

"Dear Sir, this will work fine out of the box, no changes are needed.

Chris
-MOBILE-
Victron Energy"

So what am I missing?
First, these breakers seem small, are they not the main breakers?
I didn't think you could put together two 16amp breakers to make a 32amp breaker. Can you?

Nothing in the documentation says anything about changing the breakers.

[vacendak]

Extemporaneous

hey, you are a lucky guy ! receiving any answer from Victron
I once asked them a question - in reply they asked me to get lost

speaking seriously - yes, fuse paralleling is possible [IMHO]
and this unit may be not a "classical", but a fashionable "switch-mode"
transformer, providing different abilities with rather electronical, not
electrical means.

[Extemporaneous]

Originally Posted by vacendak

Extemporaneous

hey, you are a lucky guy ! receiving any answer from Victron

I once asked them a question - in reply they asked me to get lost

Well times have changed and they must have a new found value for customers, after all, look at the evidence. He wasted 14 whole words on me. Oh ya, and didn't really answer my question.

Extemp.

[Rodz]

Gord, I don't think your answer about the fuses is correct because Extem ... asked about EUROPEAN - 230V nor American 240V. The connections in Europe are totally different!! 230V is phase to ground voltage of a three phase transformer !! and transformers are STAR connected. You NEVER install a fuse in NEUTRAL, right?The European 230V comes through LIVE + NEUTRAL + GROUND. Neutral is connected to "ZERO" in transformer and grounded there. All the European transfomers at this voltage level are 3phase and single phase is distributed to homes from such transformer.