How to wire and test an isolation transformer

[scherzoja]

Originally Posted by goboatingnow

Give me a few days and I will under a separate thread

Oh, Bless Your Heart. What a splendid idea to make a new thread for your concept. It's a shame you did not do that 4 days ago, rather than derailing this thread and alienating a very helpful member.

Happy fishing.

[s/v Jedi]

Originally Posted by scherzoja

Oh, Bless Your Heart. What a splendid idea to make a new thread for your concept. It's a shame you did not do that 4 days ago, rather than derailing this thread and alienating a very helpful member.

Happy fishing.

Thank you for your support. I know many appreciate my efforts so I will grab my stuff from here and find a better place for it, then keep adding new content there.

Anyway, you were right: anyone can look at the diagram and see that there is no underwater bonding plate, plus it was clearly stated in my notes. If there’s nothing to argue about then things are made up so that arguing can be done.

[RaymondR]

Originally Posted by s/v Jedi

Thank you for your support. I know many appreciate my efforts so I will grab my stuff from here and find a better place for it, then keep adding new content there.

Anyway, you were right: anyone can look at the diagram and see that there is no underwater bonding plate, plus it was clearly stated in my notes. If there’s nothing to argue about then things are made up so that arguing can be done.

Hang in here mate, your contributions are appreciated.

Confusion might be avoided by changing "Ships Ground" to "AC Case Grounding Bussbar" or something similar (Assuming neutral is not commoned to case ground in any of the attached gadgets)

[s/v Jedi]

Originally Posted by RaymondR

Hang in here mate, your contributions are appreciated.

Confusion might be avoided by changing "Ships Ground" to "AC Case Grounding Bussbar" or something similar (Assuming neutral is not commoned to case ground in any of the attached gadgets)

I’m afraid that won’t help, but I will go over everything before I post it elsewhere which will probably be in something like a PDF so it’s easy to download and I can publish them on my blog.

[goboatingnow]

Originally Posted by scherzoja

Oh, Bless Your Heart. What a splendid idea to make a new thread for your concept. It's a shame you did not do that 4 days ago, rather than derailing this thread and alienating a very helpful member.



Happy fishing.

My point was to step through the various circuits and avoid take it or leave it reference diagrams rather to explain the trade offs and options advantages and benefits of each approach.

It’s clear a lot of people don’t understand the point of earthing and the trade offs between different strategies with or without RCBOS etc.

But I’ll leave some time pass first as I don’t want it conflated together

[rgleason]

Listen you guys. You all have valuable contributions, and while I have not read this thread recently, please keep in mind that to uninitiated this is a complex subject and there are different approaches. and thus strong opinions...

Jedi and GBN, I have learned a lot from both of you, and respect your knowledge. Please try to be more gentle and accepting of the other person's "style", we would all learn so much more.

Peace.

[goboatingnow]

Originally Posted by rgleason

Listen you guys. You all have valuable contributions, and while I have not read this thread recently, please keep in mind that to uninitiated this is a complex subject and there are different approaches. and thus strong opinions...

Jedi and GBN, I have learned a lot from both of you, and respect your knowledge. Please try to be more gentle and accepting of the other person's "style", we would all learn so much more.

Peace.

It’s not that my approach is to try and discuss the technicalities so people understand the trade offs and what’s at stake. I don’t like this “ here’s the one way approach « for example

But again I’m in hospital right now so not a good time to try and draw electrical diagrams !!

[rgleason]

GBN Very sorry to hear that. Hope its temporary!

[goboatingnow]

Originally Posted by rgleason

GBN Very sorry to hear that. Hope its temporary!

Naw it’s a biggie. We shall see tomorrow after the big op

[s/v Jedi]

Originally Posted by goboatingnow

Naw it’s a biggie. We shall see tomorrow after the big op

I hope you will be okay GBN! I’m not finished grilling you yet so you better show back up here

[team karst]

Originally Posted by goboatingnow

Naw it’s a biggie. We shall see tomorrow after the big op

I am sure there is some stress with this. We all wish you the best.

[RaymondR]

The arbitrary designation of one side of the output of one side of the secondary winding of an isolation transformer does not make sense to me. Also connecting the case earth to the arbitrarily chosen "neutral", thereby making it live also appears contra-intuitive.

The use of double pole breakers appear to be in response to the realization that both sides of the output from the secondary windings are live?

[team karst]

Originally Posted by RaymondR

….

The use of double pole breakers appear to be in response to the realization that both sides of the output from the secondary windings are live?

One could argue that only a SP breaker is needed out of the iso xfmr.
Since each leg current must be equal in this balanced topography no matter what happens downstream.
A good iso xfmr will have a low probability of a L to core short.

[s/v Jedi]

Originally Posted by RaymondR

The arbitrary designation of one side of the output of one side of the secondary winding of an isolation transformer does not make sense to me. Also connecting the case earth to the arbitrarily chosen "neutral", thereby making it live also appears contra-intuitive.

The use of double pole breakers appear to be in response to the realization that both sides of the output from the secondary windings are live?

What is “live”? When you have a power source presented on two live conductors, calling one of them “neutral” and safe to touch is remarkable. Next step on that path is connecting that “neutral” to earth and to a DC “negative” (remember that the metal hull of boats was used for DC negative just like the chassis of a car still is today… and our engine blocks are still used as DC negative conductor!

Still, for shore based power distribution I have read reasoning that kind of makes sense, but remember that this was all devised a long time ago before breakers and RCD safeties. To replicate this setup aboard our sailboats doesn’t make sense, because we can afford to build the same levels of reliability and safety for our power as an operating room in a hospital or a clean room in a factory.

Looking at an isolation transformer aboard, you have to view this as a power source that is fueled by shore power but not galvanically connected to it, similar to a genset or a battery with inverter.

Out of any of those you get two conductors presenting the power source. You can safely touch one of the conductors as long as you don’t touch the other. When you connect one of them to ground, you can still touch that one safely, but not the other one anymore because we make a connection to ground just by standing on it, floating in water that connects to ground or touching anything else that connects to ground. By connecting one of the conductors to ground, we have made the other one more dangerous and we call it “live” or “hot”.

Luckily, we can use an isolation transformer and start over. Take the two grounding jumpers that come with a Victron isolation transformer and hide them so they won’t be found again. If someone tells you that you can’t use your shore power that way when hauled out, then use an extension cord instead. I always like to have a separate battery charger that can connect to every shore power in use in the world regardless of voltage or frequency so I can connect it to that extension cord and then simply use the inverter when hauled out.

Double pole breakers: when one pole triggers the breaker, the other pole is interrupted as well, i.e. they are mechanically linked. Even though it is safe to touch one conductor in a floating power system, it’s still safer not to touch any. When you have connected one of them to ground even before getting to the breakers, there is little use for double pole breakers because you created a path around the breakers that is almost unavoidable to touch, namely everything connected to ground and even the ground itself.

But for our isolated and floating system we have eliminated that alternate return path and we can and we do install double pole breakers.

Note that in the US a 240V circuit is floating too (both conductors are “hot” but unlike aboard a boat with isolation transformer, each of those conductors also has a 120V potential to ground and are much more dangerous than the power behind an isolation transformer) and you will find double pole breakers for those branch circuits. I think many new boats use double pole breakers even when they use a grounded neutral. Makes it easier to convert when installing an isolation transformer.

[rwidman]

If you cannot follow the manufacturer's wiring instructions and have to ask for advice on a boating forum, my advice is to have a licensed, ABY certified marine electrician install it.

An isolation transformer will do you no good if it's wired incorrectly and could be deadly.