Isolation transformers

[EngNate]

These are toroidal transformers and have a more efficient core which reduces size and weight. Wiring is same as other isolation transformers

 

[Steve DAntonio]

I am familiar with these transformers, and they are intriguing. They are also not ABYC compliant, as they do not use a metallic enclosure, and I don't believe they meet the primary to secondary shield or requirements. ABYC Standards require encapsulation.

Beyond that, I would strongly recommend against non-boosting transformer. With a non-boosting transformer, if you plug into 208 VAC service, which is common, you will end up with 104 or less at your outlets and 120 VAC bus, and that's less than ideal for things like refrigerators and HVAC.

This subject is covered here https://stevedmarineconsulting.com/wp-content/uploads/2019/12/ShorePowerTransformers181-04.pdf

 

[EngNate]

Yes, do look for ABYC approval, and definitely get 208/240 inputs.

 

[Bmarler]

I am familiar with these transformers, and they are intriguing. They are also not ABYC compliant, as they do not use a metallic enclosure, and I don't believe they meet the primary to secondary shield or requirements. ABYC Standards require encapsulation.

Beyond that, I would strongly recommend against non-boosting transformer. With a non-boosting transformer, if you plug into 208 VAC service, which is common, you will end up with 104 or less at your outlets and 120 VAC bus, and that's less than ideal for things like refrigerators and HVAC.

This subject is covered here https://stevedmarineconsulting.com/wp-content/uploads/2019/12/ShorePowerTransformers181-04.pdf

geez, this time of year it's common to get 104 volts at the dock pedestal anyway. the victron transformers i'm putting in have a slight boost. at 120 volt input i'm getting 127 at the output terminals. hopefully at 104-106 volt input i'll be close to 110-112 volts output. we'll see. these are toriodal transformers too, and don't exactly comply with abyc guidelines. (yet anyway)

 

[tiltrider1]

I am familiar with these transformers, and they are intriguing. They are also not ABYC compliant, as they do not use a metallic enclosure, and I don't believe they meet the primary to secondary shield or requirements. ABYC Standards require encapsulation.

Beyond that, I would strongly recommend against non-boosting transformer. With a non-boosting transformer, if you plug into 208 VAC service, which is common, you will end up with 104 or less at your outlets and 120 VAC bus, and that's less than ideal for things like refrigerators and HVAC.

This subject is covered here https://stevedmarineconsulting.com/wp-content/uploads/2019/12/ShorePowerTransformers181-04.pdf

Steve, how do you end up with 104v? A 208v circuit is because you have two 120v circuits 120 out of phase and not 180 out of phase. If you pick up just L1 you will have 120v. If you pick up just L2 you will have 120v. Granted if you try to use L1 and L2 to get 220v you will end up with 208v. IF the boat uses only 120v or if it steps 120v to 240v onboard then I'm not seeing an issue with using non boosting transformers.

 

[Bmarler]

Steve, how do you end up with 104v? A 208v circuit is because you have two 120v circuits 120 out of phase and not 180 out of phase. If you pick up just L1 you will have 120v. If you pick up just L2 you will have 120v. Granted if you try to use L1 and L2 to get 220v you will end up with 208v. IF the boat uses only 120v or if it steps 120v to 240v onboard then I'm not seeing an issue with using non boosting transformers.

i have to second that. many industrial facilities have 208 three phase power, depending on what style of transformer was installed. it's very common to see those installed for running the 120 volt loads for lighting and whatnot.
maybe his issue is when you take the 208 and run it through the transformer to make 120. i'd need to see this for myself to see if the 120 degree phasing remains.

 

[twistedtree]

i have to second that. many industrial facilities have 208 three phase power, depending on what style of transformer was installed. it's very common to see those installed for running the 120 volt loads for lighting and whatnot.
maybe his issue is when you take the 208 and run it through the transformer to make 120. i'd need to see this for myself to see if the 120 degree phasing remains.

It's a consequence of the isolation transformer, which is normally 1:1. So 208 L-L on the primary will result in 208 L-L on the secondary. But the secondary neutral is derived by the transformer and is split phase, not 2 legs of 3-phase Y. So on the secondary, the L-N voltages are 1/2 of the L-L, nominally 104V. Now add in any voltage sag out at the end of the dock and that 208 input turns into 190-100V, and now you are down to 95-100V on the L-N circuits. That's pretty low for many nominally 120V devices.

 

[Bmarler]

it's interesting to me how many folks that frequent this forum have strong electrical backgrounds.

 

[ksanders]

It's a consequence of the isolation transformer, which is normally 1:1. So 208 L-L on the primary will result in 208 L-L on the secondary. But the secondary neutral is derived by the transformer and is split phase, not 2 legs of 3-phase Y. So on the secondary, the L-N voltages are 1/2 of the L-L, nominally 104V. Now add in any voltage sag out at the end of the dock and that 208 input turns into 190-100V, and now you are down to 95-100V on the L-N circuits. That's pretty low for many nominally 120V devices.

Yes, but that is only if you use a 240 volt isolation transformer and think you are plugging into 240 volt single phase power.

Most of our boats are 120 volt, 30 or 50 amp.

 

[stevemitchell]

I ended up purchasing one of these a couple of years ago, tested it, and removed it from my boat after finding it was not ABYC compliant at the time.

I wrote an article about it at the time, and ended up taking down most of the text and left just the comments and a note.

Since then, I've been contacted by the manufacturer, ABYC, other electricians, and other people who have been curious or have installed it.

There was a comment posted recently:

From the Bridgeport Magnetics website:
“Our Marine-Puck family recently acquired UL Marine certification for the US and Canada. (E509703)”
“Marine-Puck complies with ABYC Standard E11.17.3.5, Polarization Transformers, except for the enclosure being non-metallic.”

However, as far as I know it is still not 100% compliant, but that could have changed.

 

[Bmarler]

I ended up purchasing one of these a couple of years ago, tested it, and removed it from my boat after finding it was not ABYC compliant at the time.

I wrote an article about it at the time, and ended up taking down most of the text and left just the comments and a note.

Since then, I've been contacted by the manufacturer, ABYC, other electricians, and other people who have been curious or have installed it.

There was a comment posted recently:

From the Bridgeport Magnetics website:
“Our Marine-Puck family recently acquired UL Marine certification for the US and Canada. (E509703)”
“Marine-Puck complies with ABYC Standard E11.17.3.5, Polarization Transformers, except for the enclosure being non-metallic.”

However, as far as I know it is still not 100% compliant, but that could have changed.

i saw that removed article a couple of days ago. i would have liked to see it before it was taken down.
those are still not 100% compliant. but i heard there was going to be some review of the toroidal transformers by the abyc in the near future. the manufacturer is sticking with their beliefs that it's a better product when installed as recommended. i have to say, it is a good unit, it works just fine, and i believe it's perfectly safe if installed correctly. i don't think the lack of a metal case is a bad thing. it sure eliminates any possibility of a short to case. creating a neutral/ground connection in the wiring cavity establishes a safety path back to the transformer.
if the abyc still doesn't accept them i'll sure be wondering what the reasoning might be.

 

[twistedtree]

Yes, but that is only if you use a 240 volt isolation transformer and think you are plugging into 240 volt single phase power.

Most of our boats are 120 volt, 30 or 50 amp.

Agreed, but someone was asking how 208V turns into 104V on a boat where at the dock 208V L-N is 120V.

 

[Steve DAntonio]

Steve, how do you end up with 104v? A 208v circuit is because you have two 120v circuits 120 out of phase and not 180 out of phase. If you pick up just L1 you will have 120v. If you pick up just L2 you will have 120v. Granted if you try to use L1 and L2 to get 220v you will end up with 208v. IF the boat uses only 120v or if it steps 120v to 240v onboard then I'm not seeing an issue with using non boosting transformers.

I'm referencing docks that provide 208/120 split phase service, this is very common on older infrastructure, I encounter it routinely. I'm also referencing vessels that normally accept 50 amp, 120/240 service.

If the vessel uses only 120, and you use a transformer, this issue is also not relevant.

208 service provides 208/120, however, once you use a transformer, the 120 portion of that split phase service is no longer used, the transformer's primary is fed with only 208, and if it is a standard non-boosting transformer, the secondary will provide 104/208. This is why boosting transformers are made, specifically for 208 (and lower) service applications.

 

[Steve DAntonio]

“Marine-Puck complies with ABYC Standard E11.17.3.5, Polarization Transformers, except for the enclosure being non-metallic.”

Polarization, but not isolation... That's very relevant.

Do they meet UL1561?

What standard is E509703? I'm unable to find it other than in reference to this transformer (and Carvers, which seem to have used them).

And...there is no such thing as E-11.17.3.5. Assume that's a typo as this section has nothing to do with shore power transformers. Here's E-11.18.3.5 "The secondary of the polarization transformer is grounded (polarized) on the boat (see E-11.5.3.2.2 and E-11.5.3.2.3 EXCEPTION)." If that's what they are referencing it has nothing to do with the transformer itself, it's related to installation.

Here is section E-11.17.3 in its entirety.

11.17.3 DC Grounding Bus
11.17.3.1 The DC grounding bus shall be connected directly to the engine negative terminal or the DC main negative bus.
11.17.3.2 The DC grounding bus serving more than one electrical device shall comply with E-11.17.2 for the largest device, and shall be manufactured and installed in accordance with the following:
11.17.3.2.1 If the DC grounding bus is fabricated from copper or bronze strip, it shall have a thickness not less than 1/32 in (0.8 mm) and a width of not less than 0.5 in (13 mm); and
11.17.3.2.1.1 shall be drilled and tapped providing its thickness ensures no less than three full threads of engagement for the terminal screws; or
11.17.3.2.1.2 shall be through-drilled, and the connections made with machine screws and lock nuts.
NOTE: Copper pipe may be used providing its wall thickness is sufficient for the pipe to be drilled and tapped as required above.
11.17.3.2.2 Copper braid shall not be used.

Polarization transformers are covered under E-11.18.3, see below.

These are the isolation transformer requirements from ABYC

11.7.1 Shore Power Transformers
11.7.1.1 ISOLATION TRANSFORMERS - Devices used as isolation transformers shall be either encapsulated, dry type or high frequency/switch mode.
11.7.1.1.1 Encapsulated, dry type transformers shall meet the requirements of UL 1561, Dry Type General Purpose and Power Transformer (see E-11.18, DIAGRAM 6, and DIAGRAM 7).
11.7.1.1.1.1 Encapsulated, dry type transformers shall have a metallic shield located between the primary and secondary winding and be electrically insulated from all other portions of the transformer. It shall be designed to withstand, without breakdown, a high potential test of 4000 VAC, 60 Hz, for one minute, applied between the shield and all other components such as windings, core, and outside the enclosure.
NOTE: Breakdown is considered to have occurred when the current which flows as a result of the application of the test voltage rapidly increases in an uncontrolled manner.
11.7.1.1.1.2 Encapsulated, dry type transformers shall have a separate, insulated wire lead or terminal identified as the shield connection that shall be solidly connected only to the shield, and brought out for external connection and shall be equal to or greater than the aggregate circular mil area of the largest transformer phase conductor(s).
11.7.1.1.1.3 The shield and its connection shall be of sufficient ampacity to provide a sustained fault current path for either the primary or secondary windings to ensure operation of the main shore power disconnect circuit breaker when subjected to a fault current level in accordance with TABLE 3A.
11.7.1.1.2 Isolation transformer cases shall be metallic with a grounding terminal provided.
11.7.1.1.3 Isolation transformers shall be tested and labeled by an independent laboratory.
11.7.1.1.4 High frequency/switch mode transformers shall:
11.7.1.1.4.1 meet the safety requirements of IEC/UL 62368, Audio/video, information and communication technology equipment, and
11.7.1.1.4.2 the environmental requirements of IEC 60945, Maritime Navigation and Radio Communication Equipment and Systems: Methods of Testing and Required Results.
11.7.1.2 POLARIZATION TRANSFORMERS - Devices used as a polarization transformer shall be of the encapsulated type and meet the requirements of UL 1561, Dry Type General Purpose and Power Transformers.
EXCEPTION: High-frequency switch mode isolation transformers connected as polarization transformers.
11.7.2 If installed, a galvanic isolator shall meet the requirements of ABYC A-28, Galvanic Isolators.

And requirements for polarization transformers...

11.18.3.1 Each ungrounded shore current carrying conductor is connected from the shore power inlet to the primary winding of the polarization transformer through an ELCI (see E-11.11.1) and overcurrent protection device that simultaneously opens both ungrounded current carrying shore conductors. Fuses shall not be used instead of simultaneous trip devices (see E-11.10.2.5.2).
11.18.3.2 The shore grounded (white) terminal of the shore power inlet is not connected on the boat.
11.18.3.3 The shore grounding (green) conductor is connected, without interposing switches or overcurrent protection devices (see E-11.5.3.5), from the shore power inlet to:
11.18.3.3.1 an optional galvanic isolator, and then to
11.18.3.3.2 the transformer grounded neutral secondary terminal, and
11.18.3.3.3 the transformer metal case, and
11.18.3.3.4 to all noncurrent carrying parts of the boat’s AC electrical system, including
11.18.3.3.5 the engine negative terminal or its bus.
11.18.3.4 If an optional galvanic isolator is used, the shell of a metallic shore power inlet shall be electrically insulated from the boat.
11.18.3.5 The secondary of the polarization transformer is grounded (polarized) on the boat (see E-11.5.3.2.2 and E-11.5.3.2.3 EXCEPTION).
11.18.3.6 If the boat's AC electrical system includes branch circuit breakers, the branch circuit breakers shall simultaneously open both current carrying conductors unless a polarity indicating device is provided (see E-11.10.2.3.2 EXCEPTION).
11.18.3.7 240 V branch circuit breakers shall simultaneously open all current carrying conductors (see E-11.10.2.3.3).
11.18.3.8 Polarization of conductors shall be observed in all circuits.

Again, a lot to like about the Bridgeport product, but it is not ABYC compliant, and their incorrect ABYC citation makes me a little nervous. Perhaps someone can ask them to clarify.

 

[ksanders]

Agreed, but someone was asking how 208V turns into 104V on a boat where at the dock 208V L-N is 120V.

ahhh

 

[diver dave]

Some circuits/devices need to be enclosed in a fire resistant enclosure. If plastic, typically needs to be V0 rated material.

 

[stevemitchell]

i saw that removed article a couple of days ago. i would have liked to see it before it was taken down.
those are still not 100% compliant. but i heard there was going to be some review of the toroidal transformers by the abyc in the near future. the manufacturer is sticking with their beliefs that it's a better product when installed as recommended. i have to say, it is a good unit, it works just fine, and i believe it's perfectly safe if installed correctly. i don't think the lack of a metal case is a bad thing. it sure eliminates any possibility of a short to case. creating a neutral/ground connection in the wiring cavity establishes a safety path back to the transformer.
if the abyc still doesn't accept them i'll sure be wondering what the reasoning might be.

Yeah, I took it down literally 48 hours after I wrote it because I had so many people write me about the ABYC issues.

I do think the concept is a good one, and I like how it was lower weight and less noise than my previous Charles isolation transformers on previous boats, but....

 

[twistedtree]

Yeah, I took it down literally 48 hours after I wrote it because I had so many people write me about the ABYC issues.

I do think the concept is a good one, and I like how it was lower weight and less noise than my previous Charles isolation transformers on previous boats, but....

I think there is a discussion/proposal on Toroidal transformers for ABYC in January. I know it came up before that they really weren't addressed in the standard. I don't personally know what the issues are, nor have I had a chance to look at the proposed language.


Interesting you mention noise. I have Acme/Hubbell isolation transformers on Tanglewood, and they are as silent as I can detect. This is a big contrast from the Olsen transformers on the last Tanglewood. I believe the Acme transformer case is filled with sand. It doesn't help with weight, but sure makes it quiet.

 

[stevemitchell]

Interesting you mention noise. I have Acme/Hubbell isolation transformers on Tanglewood, and they are as silent as I can detect. This is a big contrast from the Olsen transformers on the last Tanglewood. I believe the Acme transformer case is filled with sand. It doesn't help with weight, but sure makes it quiet.

If I found the right ones (https://hubbellcdn.com/literature/Wiring_WLFM004_IsolationTransformers.pdf) then, yeah, they are heavy! 170 pounds for my size needs, but I bet you have the 250 pound one!

 

[twistedtree]

If I found the right ones (https://hubbellcdn.com/literature/Wiring_WLFM004_IsolationTransformers.pdf) then, yeah, they are heavy! 170 pounds for my size needs, but I bet you have the 250 pound one!

I've got the 170lb 15KVA 50/60hz model, but there are two of them, one for each shore cord. It's a very nice transformer, and is easily wired to switch between normal 1:1 and a 15% boost for 208V shore power.

 

[Steve DAntonio]

I think there is a discussion/proposal on Toroidal transformers for ABYC in January. I know it came up before that they really weren't addressed in the standard. I don't personally know what the issues are, nor have I had a chance to look at the proposed language.


Interesting you mention noise. I have Acme/Hubbell isolation transformers on Tanglewood, and they are as silent as I can detect. This is a big contrast from the Olsen transformers on the last Tanglewood. I believe the Acme transformer case is filled with sand. It doesn't help with weight, but sure makes it quiet.

Both are potted in an epoxy/sand mixture, encapsulation is part of the ABYC requirement to prevent absorbing moisture. If I recall correctly, the Acme on the first Tanglewood wasn't soft mounted and the Hubbell is.

 

[angus99]

A few years ago, I swallowed hard and ponied up for a Charles 50 amp (12KVA) Isoboost transformer which, I believe, is no longer manufactured. I’ve often wondered what I’d replace it with if it ever failed. Can anyone explain the difference between the Hubble 15 KVA that can be “wired to boost” and the Isoboost, which boosts automatically (I’m probably misstating this)? Also, what would account for the more than $3K difference in price—other than weight (the Charles is basically a 250-lb basketball)?

 

[twistedtree]

Both are potted in an epoxy/sand mixture, encapsulation is part of the ABYC requirement to prevent absorbing moisture. If I recall correctly, the Acme on the first Tanglewood wasn't soft mounted and the Hubbell is.

That’s very possible. I would have to check pictures to be sure.

 

[twistedtree]

A few years ago, I swallowed hard and ponied up for a Charles 50 amp (12KVA) Isoboost transformer which, I believe, is no longer manufactured. I’ve often wondered what I’d replace it with if it ever failed. Can anyone explain the difference between the Hubble 15 KVA that can be “wired to boost” and the Isoboost, which boosts automatically (I’m probably misstating this)? Also, what would account for the more than $3K difference in price—other than weight (the Charles is basically a 250-lb basketball)?

Boosting transformers just have different connection points for the wiring for normal vs boost.

The isoboost also includes electronics to monitor the voltage and automatically control a switch that switches between normal and boost. Alternately, you can wire a manual switch to change between normal and boost, and set the switch according to the dock voltage wherever you are. BTW, a company called Nauti Boost makes a more generic version of the isoboost electronics that can control and transformer with taps/wiring points for normal/boost.

 

[angus99]

Boosting transformers just have different connection points for the wiring for normal vs boost.

The isoboost also includes electronics to monitor the voltage and automatically control a switch that switches between normal and boost. Alternately, you can wire a manual switch to change between normal and boost, and set the switch according to the dock voltage wherever you are. BTW, a company called Nauti Boost makes a more generic version of the isoboost electronics that can control and transformer with taps/wiring points for normal/boost.

Thanks for that. If mine ever goes TU, it’s good to know alternatives are out there for less than five boat units.

 

[catalinajack]

I have followed this discussion with interest. In 5,500 miles of cruising the Great Loop and a couple thousand more, and having stayed in perhaps different marinas, we never once encountered the 104V/208V problem so I am having difficulty understanding that a transformer is a critical need, at least for this reason. Low voltage in the odd marina or two or ten, I would just run the generator as needed in the evening and let alternators do ther job the next day. What am I missing especially since so few boats are so equipped and they seem to get along just fine.

 

[Steve DAntonio]

A few years ago, I swallowed hard and ponied up for a Charles 50 amp (12KVA) Isoboost transformer which, I believe, is no longer manufactured. I’ve often wondered what I’d replace it with if it ever failed. Can anyone explain the difference between the Hubble 15 KVA that can be “wired to boost” and the Isoboost, which boosts automatically (I’m probably misstating this)? Also, what would account for the more than $3K difference in price—other than weight (the Charles is basically a 250-lb basketball)?

Charles did stop making and supporting their range of IsoBoost products. The Charles xfmr should never fail irreparably, the winding itself is pretty much bulletproof. If the electronics fail, an aftermarket replacement is available. Capacitors can fail, and they too are replaceable.

The difference between a transformer that can be wired to boost, vs. one that boosts automatically is, well, the boosting function, which includes the electronics and relays.

Hubbell offers an automatic boosting transformer.

The weight is a function of both the windings, which should ultimately the same for the two units, and the potting, which may be different.

 

[angus99]

Thank you, Steve. I never want to mount anything that heavy on a bulkhead again.

 

[Steve DAntonio]

I have followed this discussion with interest. In 5,500 miles of cruising the Great Loop and a couple thousand more, and having stayed in perhaps different marinas, we never once encountered the 104V/208V problem so I am having difficulty understanding that a transformer is a critical need, at least for this reason. Low voltage in the odd marina or two or ten, I would just run the generator as needed in the evening and let alternators do ther job the next day. What am I missing especially since so few boats are so equipped and they seem to get along just fine.

If you don't have a transformer, you would never see 104. 104 VAC, or lower, only occurs when plugging a non-boosting transformer into 208 VAC (or lower) shore power. Otherwise, w/o a transformer you'd see 208/120.

Transformers are far from a necessity, however, they do offer a number of advantages, protecting against dockside reverse polarity, protecting those in the water from electric shock drowning especially in fresh water (never swim around docks energized with shore power), and completely isolating the vessel's underwater metals from those of other vessels, bulkheads, docks etc. and galvanic and stray current corrosion that can cause.

Many larger vessels have transformers, as do steel and aluminum vessels.

 

[Alaskan Sea-Duction]

Good subject matter.

Last year I have found in SEAK that marinas were replacing shore power with GFI (marine nomenclature???) When they were doing maintenance.

I have 2-50amp shore power receptacle for ASD. When I hooked both to shorepower it would trip both breakers. If I only hooked up one to shore power, no problems does not trip.

Other than spending 6k to install an isolated transformer, is there a work around?