Need to provide GFCI on a strange voltage

[oldsparky52]

I need to see if it is possible to provide GFCI protection (of course at a "reasonable" cost, lol ) on a circuit that will be fed from an existing NQOD panel that is 3-phase 240V, no neutral, and has a line to ground voltage of around 138V. (I know y'all will want to know how this voltage came about, so here goes. The building service is 208Y/120, there were some loads that required 240V, so what they did was to install a buck/boost transformer on each of the power legs feeding a panel to get 240V line to line, which of course brings the line to ground voltage up to about 138).

What SQ D has told me is that their GFCI breaker will not work because it requires the neutral connection for the electronics inside the breaker. They started to entertain the idea of just wiring the neutral wire to ground, but when they found out the line to ground voltage was 138, then said it would damage the breaker.

So, now I need to try to come up with a way to deal with this if possible. I found this product, and was curious if anyone has used these before, and does anyone know if this product uses a line to ground connection internally (sort of like what used to be done with some electronic dimmers)?

Short of coming up with a usable product, the only thing I can think to do is to feed a small transformer with 240V in and 240/120V out. I think that's going to be a bit more work than the customer will want, and I understand that is not my problem but his (but we are friends and I would like to offer the most cost effective, code compliant way to do this).

(A special thanks to Dennis for pointing out the possible problem in using this product).

 

[oldsparky52]

really?

really?

Whoever corrected my title, I meant no offense with the word I used, and here is a copy of the definition of it.

3.something irregular, inferior, spurious, or unusual.

 

[jumper]

Whoever corrected my title, I meant no offense with the word I used, and here is a copy of the definition of it.

I changed it.

No offense was taken and I know what the word actually means, however, some may not.

Many words today are erroneously used in ways that incorrect. Instead of maybe explaining to a member who might question the use of the word, I edited it.

 

[Coppersmith]

Whoever corrected my title, I meant no offense with the word I used, and here is a copy of the definition of it.

Ah, the Internet is a wonderous thing. I quick search of "something irregular, inferior, spurious, or unusual" revealed the word you used. (Inquiring minds wanted to know.)

I've only ever heard that word (with the above definition) used with "file", but I can see why the mods would be concerned since it has a "loaded" meaning otherwise. Probably would be censored on a Disney site too. Don't feel bad. They are just trying to keep up the forum's "PG" rating.

I've heard of a school principal who was fired for using a perfectly innocent (but lesser used) word in a speech that sounded similar to a racial slur. Vocabulary challenged audience members were offended.

 

[kwired]

Potential product that may be of some use

 

[Coppersmith]

Potential product that may be of some use

Interesting product. Looks like you would have to customise a cabinet to use that. It's pretty deep and with the larger conductors going through it, slapping an extension ring on a 4x4 j-box isn't going to cut it.

Does "Each Cat. No. 6895 and contactor or relay combination MUST be approved by UL" mean that as long as you use one of the specified relays you're good to go or that you have to have a UL inspection for your installation?

 

[kwired]

Interesting product. Looks like you would have to customise a cabinet to use that. It's pretty deep and with the larger conductors going through it, slapping an extension ring on a 4x4 j-box isn't going to cut it.

Does "Each Cat. No. 6895 and contactor or relay combination MUST be approved by UL" mean that as long as you use one of the specified relays you're good to go or that you have to have a UL inspection for your installation?

I didn't say it wouldn't have some complications in using it - especially if you need an inspector to give his blessing. I think most of them you will find in the wild will be a recognized component of a listed assembly.

With GFCI expansion requirements in 2017 NEC though I think you will be seeing more variety of GFCI breakers available or even devices similar in concept to this one at some point.

 

[jumper]

Interesting product. Looks like you would have to customise a cabinet to use that. It's pretty deep and with the larger conductors going through it, slapping an extension ring on a 4x4 j-box isn't going to cut it.

Does "Each Cat. No. 6895 and contactor or relay combination MUST be approved by UL" mean that as long as you use one of the specified relays you're good to go or that you have to have a UL inspection for your installation?

Usually I have seen them already mounted in spa or pump panel enclosure like this:

 

[kwired]

Usually I have seen them already mounted in spa or pump panel enclosure like this:

View attachment 19188

As a recognized component of a listed assembly, correct?

 

[gar]

171221-1997 EST

oldsparky52:

Apparently Sq-D is deriving power, 120 V, for the electronics from one line to neutral. You need to know which hot line this is, then you connect a small, extremely small possibly 1 VA, autotransformer between that line, and one of the other hot lines.

The mid point of the autotransformer provides the 120 V.

Consider a 25 VA Signal transformer. Connect the two 120 V primaries in series to work from 240 V. The mid point is your 120 V. The secondaries are unused. So any one of the 25 VAs can be used.

One source is Digi-Key, another Mouser.

https://belfuse.com/resources/A41.pdf
https://www.digikey.com/product-detail/en/signal-transformer/A41-25-16/595-1278-ND/953148

Absolutely necessary that one of the hot lines is the correct one.

.

 

[MAC702]

Potential product that may be of some use

Since this still needs the neutral, what is its advantage over the breaker? I agree it will work, but maybe just because it's more advantageous to get a neutral somewhere other than where the breakers are?

 

[kwired]

Since this still needs the neutral, what is its advantage over the breaker? I agree it will work, but maybe just because it's more advantageous to get a neutral somewhere other than where the breakers are?

You could (not necessarily according to listing or instructions) protect any circuit at any voltage - as long as conuctors are small enough to fit through the CT, but do need a 120 volt "control circuit". OP would still need to come up with some other source for control voltage.

 

[jumper]

As a recognized component of a listed assembly, correct?

Yes. Never tried to fab one in myself, just replaced faulty ones.

 

[oldsparky52]

I went by the site and tested the voltage at the outlet that fed the saw and the voltage went from 124 to 119/220 (fluctuated). The amps were about 12.3 . Very close to nameplate ratings (I think the name plate was 13 amps). This was with them using the saw.

We checked some other things on the saw and put it back together and it started tripping the GFCI a second or so after turning it on. This is what they said it was doing to them. They said it would work for a while, then start the tripping the GFCI receptacle, then after they kept resetting the GFCI the circuit breaker for the circuit tripped. They also said the reset button on the motor would pop occasionally.

I told my buddy he didn't need it wired 240, he needed it repaired or replaced. He's a smart guy, he said he's replacing it. They've used it out there (outside under awnings) for about 4 years.

Thank you to all that offered help.

 

[Ingenieur]

what is the ckt v?
240/3
240/1
138/1
???

 

[oldsparky52]

what is the ckt v?
240/3
240/1
138/1
???

They were using the saw plugged into a 120V GFCI receptacle (which is fed from a 208Y/120 panel about 225' away).

They were having problems with the saw, and they thought if it was wired 240V the problems would dissipate.

The 240 would come from a panel (adjacent to the one feeding the 120V receptacle), and that's the panel that has the 3 phases boosted so the voltage phase to phase is 240V. The motor would be wired to just 2 of the phases. The 240V circuit to the motor does not yet exist.

 

[GoldDigger]

If you connect three boost transformers (equivalent to creating three autotransformer) to a three phase wye you will have an existing solid neutral present at that point, whether you use it at the equipment or not, and it will be bonded to ground at the original service disconnect.
The two pole GFCI breaker may not be designed for use with a two-of-three phase circuit, whether it is 208/120 or 240/138.
The idea of wiring a center tapped winding between the two hots to feed the breaker neutral (not used by the load) may be technically practical (work) but having the neutral at a high voltage (although less that 120V) to ground may not meet the specifications and testing conditions of the breaker.
And anybody who later tried to connect a load neutral to that point would be in for rude surprise.

Sent from my XT1585 using Tapatalk

 

[gar]

171222-1042 EST

GoldDigger:

From post #1

I need to see if it is possible to provide GFCI protection (of course at a "reasonable" cost, lol ) on a circuit that will be fed from an existing NQOD panel that is 3-phase 240V, no neutral, and has a line to ground voltage of around 138V. (I know y'all will want to know how this voltage came about, so here goes. The building service is 208Y/120, there were some loads that required 240V, so what they did was to install a buck/boost transformer on each of the power legs feeding a panel to get 240V line to line, which of course brings the line to ground voltage up to about 138).

What SQ D has told me is that their GFCI breaker will not work because it requires the neutral connection for the electronics inside the breaker. They started to entertain the idea of just wiring the neutral wire to ground, but when they found out the line to ground voltage was 138, then said it would damage the breaker.

This problem is an overvoltage problem, and one side of the supply to the breaker internal electronics is one of the hot legs of the breaker. The source already has a real neutral tied to EGC and earth.

The problem is how to get reduced voltage to the breaker internal electronics. There is no way the breaker wire that would go to neutral can ever be tied to any neutral of this source without an overvoltage to the electronics. Thus, that wire should not be called a neutral, rather it is simply a wire that when the breaker is used normally is wired to neutral. It is probably a very wimpy wire.

The electronics in the breaker is not likely to require any phase correlation with the source. Thus, almost any appropriate voltage source of the correct voltage could be used.

.