Isolation Transformer Installation

[quality time]

I'm most likely going to install an isolation transformer and am unsure whether there needs to be a breaker installed inline before the transformer? My 480DB had a breaker but I see some installation manuals online showing one and others that do not. Hubbel seems to be the only choice for 15kVA anymore and their manual isn't clear either IMO.

 

[dtfeld]

I've been going through this with an inverter upgrade. The issue is if you want to comply with the ELCI breaker requirement in the ABYC electric specs. You have to read carefully and look at your installation to tell if you need this or not.

Turns out Blue Sea Systems make such a beast specifically for this application. Its Blue Sea Systems SMS panel Part #3120. Its about $625 retail.

My bitch is it doesn't really fit anywhere I would logically like to put it.

 

[Skybolt]

The problem with all of this is this, if you have a problem and actually need the isolation transformer to fix an issue then the right thing to do is fix the issue causing the need. I went through this and now have zero issues with any GFCI powered dock.

An isolation transformer is a good thing to have but only after the real issue is fixed.

But to answer your question, yes you need a breaker system before the transformer. The one Dave mentioned is the right one to get.

 

[ttmott]

First - there is no need nor a requirement for a ground fault device (ELCI) on the main power coming on the boat.
Second - as the isolation transformer and wiring to it does require circuit protection and a disconnect consequently a circuit breaker between shore power and the device. This is a code requirement.
The isolation transformer is classified as a power source. Consequently, your boat's systems on the load side of the transformer (secondary windings) must bond the neutral and ground conductors (center tap of the secondary windings) at the power source (isolation transformer or primary ground buss). That bond must be one place only which is typically the main ground buss on the boat.
The shore power ground conductor must bond to the isolation transformer iron core yet be completely isolated from the boat's systems - all the systems. This is to ensure is if there is a fault in the primary windings (the shore power windings on the isolation transformer) it is grounded to the shore power system. This makes marine isolation transformers rather unique.
Assuming your boat is a split phase system 240 / 120 volt AC then the shore power neutral will not be used and needs to be capped off in that circuit breaker location. The isolation transformer primary is split phase 240 volt (hot - hot) windings with the shore power ground bonded to the iron core. The secondary is also split phase 240 volt on each end of the windings with a center tap. The center tap is the neutral and ground for the 120 volt services. It is important to balance to the best extent possible the 120 volt loads across both sides of that tap.

 

[ttmott]

Additionally- with the addition of an isolation transformer the boat becomes it's own power source consequently, there is no need for the galvanic isolators. Also, your boat will become rather immune to power surges and sags. The isolation transformer becomes a great buffer to shore power issues. Since the boat will be isolated from the shore power neutral and ground things get really simple in switching.
The down side is if you should slip where there is 120 volt AC shore power and it is not split phase providing that 240 volt differential then you will get zero volts from shore power.
Here is a graphic of a typical arrangement for an isolation transformer (disregard the inverters).

 

[Pgeee]

I’m no expert at all, the info above is so comprehensive. but as a layman just adding , my transformer (very different system but still an isolating transformer) , has an inbuilt breaker. Just an McB, I know this as I tripped it a couple of weeks back trying to run too many appliances at once.

 

[Skybolt]

First - there is no need nor a requirement for a ground fault device (ELCI) on the main power coming on the boat. ...

While the ELCI breaker is not required, ABYC does recommend having one. The other part of that standard is to a breaker with in 10' of the power entering the boat. One of the reasons Sea Ray put the power receptacle(s) on the side of the boat way back when.

Short version - https://shop.pkys.com/ABYC-standard-for-ELCIs-explained_b_50.html

 

[dtfeld]

First - there is no need nor a requirement for a ground fault device (ELCI) on the main power coming on the boat.

Tom trying to get into your thought process a little deeper on this subject. I'm assuming for quality time 's application, this is an EXISTING shore power installation, and there is already a breaker installed. Therefore the addition of an isolation transformer would not need or require any additional breakers or the ELCI breaker? Basically he's going top install it exactly as you've drawn above using existing SR breakers.

For my application I'm installing a NEW shore power system. In my thinking, using an ELCI breaker comes down to a 2 part question. First do I want to/need to comply with the ELCI requirement, and secondly, should I comply with it. I'm not a manufacturer, so I don't think I need need to, but as Orlando point out it might be a good idea. The difference between a basic breaker and the ELCI is $250. My issue with it the ELCI breaker is there not a great way to make a clean install (cosmetics).

 

[ttmott]

Tom trying to get into your thought process a little deeper on this subject. I'm assuming for quality time 's application, this is an EXISTING shore power installation, and there is already a breaker installed. Therefore the addition of an isolation transformer would not need or require any additional breakers or the ELCI breaker? Basically he's going top install it exactly as you've drawn above using existing SR breakers.

For my application I'm installing a NEW shore power system. In my thinking, using an ELCI breaker comes down to a 2 part question. First do I want to/need to comply with the ELCI requirement, and secondly, should I comply with it. I'm not a manufacturer, so I don't think I need need to, but as Orlando point out it might be a good idea. The difference between a basic breaker and the ELCI is $500. My issue with it the ELCI breaker is there not a great way to make a clean install (cosmetics).

Like a GFCI the ELCI provides current monitoring to ensure feed and return current is equal or within a limit and will disconnect the power if over the limit meaning current is leaking somewhere else. The difference is the ELCI provides current limiting features (traditional circuit breaker). With that said a basic configuration is the dock pedestal will have a circuit breaker of a given rating which protects the wiring to the boat up to the boat's first circuit breaker. (Note that retrofitted and new docks will have ELCI devices installed.) That means that the wiring between the the two circuit breakers must be at least rated to the amperage of the dock's circuit breaker. If, for example, someone should install a circuit breaker on the boat with a greater rating than the dock's circuit breaker then all wiring and devices must be rated at least to the dock circuit breaker.

Now, let's put an ELCI as the boat's first circuit breaker between the dock supply (circuit breaker) and an Isolation Transformer, for example. Obviously, the shore power cables and any wiring up to the ELCI will not be monitored nor protected by the ELCI installed on the boat. The ELCI will only monitor and protect that short run of wiring to the isolation transformer and any leakage to ground within the isolation transformer's primary windings. Is this avoiding an electrocution risk? Possibly but not to any reasonable extent due to the narrow scope of the installation - my opinion.

In a boat without an isolation transformer the dock circuits extend much deeper into the boat and should one desire to implement conversion from dual 30 amp feeds to a single 50 amp feed then, even though not required, the ELCI would bring an added measure protection to people.

 

[dtfeld]

For future reference, you can buy the Blue Sea ELCI breaker separately, but so far they don't make a standard panel mount and back cover for this this, like their other shore power breaker panels, so mounting become a custom job.

Like I said, I think it's a good idea, and if I can work it in I will. Retail is about $350, vs about $100 for a standard double pole breaker.

 

[ttmott]

I'm most likely going to install an isolation transformer and am unsure whether there needs to be a breaker installed inline before the transformer? My 480DB had a breaker but I see some installation manuals online showing one and others that do not. Hubbel seems to be the only choice for 15kVA anymore and their manual isn't clear either IMO.

The short answer is Yes.
You have no control over the dock circuit protection even though that installation is prescribed by NFPA. The boat must protect it's self.

 

[quality time]

The short answer is Yes.
You have no control over the dock circuit protection even though that installation is prescribed by NFPA. The boat must protect it's self.

Thanks Tom. So I can just use a regular 50A breaker in a mount like this?

 

[quality time]

The problem with all of this is this, if you have a problem and actually need the isolation transformer to fix an issue then the right thing to do is fix the issue causing the need. I went through this and now have zero issues with any GFCI powered dock.

An isolation transformer is a good thing to have but only after the real issue is fixed.

But to answer your question, yes you need a breaker system before the transformer. The one Dave mentioned is the right one to get.

Agreed, but after countless hours of chasing circuits we're having no luck finding the issue. The boat had a major refit in 2018 so the cross could be anywhere. I've been all through the boat doing other projects this winter and haven't seen anything out of the ordinary either.

I don't know of any good marine electricians in our area so we're just picking at it with limited knowledge and time at this point. It's no fun planning trips around which marinas have the new pedestals.

 

[dtfeld]

Thanks Tom. So I can just use a regular 50A breaker in a mount like this?

View attachment 162854

Yes, but that's just the enclosure. You'll need to add a 50A A-Series breaker #7242. There are a couple other options if you intend to surface mount, including the SMS panel above.

Good Marine electricians are pretty hard to find anywhere. I'm not overly familiar with where you are, but I've been using Peter Kennedy at PKYS out of Annapolis for a lot of the details on my project. He's all about helping a DIYer. Maybe point you the right direction if necessary. Pricing on almost everything is excellent as well.

PKYS INC is a specialty vendor of Marine Electrical Equipment based in Annapolis MD

 

[ttmott]

Agreed, but after countless hours of chasing circuits we're having no luck finding the issue. The boat had a major refit in 2018 so the cross could be anywhere. I've been all through the boat doing other projects this winter and haven't seen anything out of the ordinary either.

I don't know of any good marine electricians in our area so we're just picking at it with limited knowledge and time at this point. It's no fun planning trips around which marinas have the new pedestals.

My advice regarding this - An isolation transformer should not be a band-aid to a problem elsewhere. If the boat is tripping a dock ground fault device there there is a bonified ground fault issue on the boat. Air Conditioning units, refrigeration, and water heaters are usual suspects. However, if the re-wire of the boat bonded a neutral to the ground with the transfer switch in the shore power position then you have an issue that needs to be corrected. Besides the obvious hazard of current leakage you will begin to see metal erosion in your underwater gear and rapid anode consumption.

 

[quality time]

Good Marine electricians are pretty hard to find anywhere. I'm not overly familiar with where you are, but I've been using Peter Kennedy at PKYS out of Annapolis for a lot of the details on my project. He's all about helping a DIYer. Maybe point you the right direction if necessary. Pricing on almost everything is excellent as well.

PKYS INC is a specialty vendor of Marine Electrical Equipment based in Annapolis MD

Thanks, I keep coming across their page but never looked to see where they were located. Might be worth a call.

 

[dtfeld]

He's been a huge help to me.

 

[quality time]

My advice regarding this - An isolation transformer should not be a band-aid to a problem elsewhere. If the boat is tripping a dock ground fault device there there is a bonified ground fault issue on the boat. Air Conditioning units, refrigeration, and water heaters are usual suspects. However, if the re-wire of the boat bonded a neutral to the ground with the transfer switch in the shore power position then you have an issue that needs to be corrected. Besides the obvious hazard of current leakage you will begin to see metal erosion in your underwater gear and rapid anode consumption.

Understood and thank you all for your input. The rapid anode consumption was the first sign of an issue then tripping on a new pedestal on vacation last summer. Funny thing is, the next marina we visited also had ELCI pedestals and we were fine.

The PO had the bottom cleaned so I'm guessing they just replaced the anodes every 6 months...

 

[ttmott]

Tom trying to get into your thought process a little deeper on this subject. I'm assuming for quality time 's application, this is an EXISTING shore power installation, and there is already a breaker installed. Therefore the addition of an isolation transformer would not need or require any additional breakers or the ELCI breaker? Basically he's going top install it exactly as you've drawn above using existing SR breakers.

For my application I'm installing a NEW shore power system. In my thinking, using an ELCI breaker comes down to a 2 part question. First do I want to/need to comply with the ELCI requirement, and secondly, should I comply with it. I'm not a manufacturer, so I don't think I need need to, but as Orlando point out it might be a good idea. The difference between a basic breaker and the ELCI is $250. My issue with it the ELCI breaker is there not a great way to make a clean install (cosmetics).

Hey Dave - I wanted to follow up and clarify - These requirements ABYC, NFPA, etc are not retroactive unless specifically stated. So, if the ELCI requirement was adopted in 2015 for example then vessels built after that adoption would need to be compliant but nothing retroactive. There is an interpretation that if a retrofit is beyond XX percent then the latest code / standard is in effect but I've never seen that in print; maybe @Skybolt or @hughespat57 or someone else has.
So, to install or not to install to the latest code? These are your choices. I tend to bring things up to current standards if I'm replacing as you know - but in this case with an isolation xfmr the value just isn't there. Now if you were to install the ELCI device after the isolation xfmr or after the inverters/transfer devices then there may be some added safety value.

 

[dtfeld]

Hey Dave - I wanted to follow up and clarify - These requirements ABYC, NFPA, etc are not retroactive unless specifically stated. So, if the ELCI requirement was adopted in 2015 for example then vessels built after that adoption would need to be compliant but nothing retroactive. There is an interpretation that if a retrofit is beyond XX percent then the latest code / standard is in effect but I've never seen that in print; maybe @Skybolt or @hughespat57 or someone else has.
So, to install or not to install to the latest code? These are your choices. I tend to bring things up to current standards if I'm replacing as you know - but in this case with an isolation xfmr the value just isn't there. Now if you were to install the ELCI device after the isolation xfmr or after the inverters/transfer devices then there may be some added safety value.

Similar response from Peter @ PKYS. I would post up, but don't have his permission.

I'm paraphrasing, but basically The new standards are voluntary, but may become an issue for insurance or during survey/sales process. If making upgrades, its expected you will update to the latest standards. No mention of % system upgrade.

Insurance and resale are in my mind real and major issues. I think it's cheaper and easier to plan for and take care of it now. Its a couple hundred bucks...

I intend to add a ELCI for this reason alone. If its a little safer, all the better.

Of course the real issue is fitting in the new hardware were none was ever intended to be installed.