2 pole breaker - split wired duplex

[ramsy]

Each outdoor-parking stall has a 3Ø 100A 5-space sub-panel, divided between lights and four 1P Readily-Accessible GFCI breakers that feed non-indicating split-wired duplexes.

1) Each spit duplex with 15A loads on separate neutral draws 30A continuous on a 20A device, since no MWBC neutral is there to cancel current.
30A violates the 20A listing of each duplex, so you need separate duplexes for each dedicated 20 GFCI outlet.

2) Do they make a 3Ø 100A 5-space sub-panel, and how expensive is it?
Would it cost less to use 1Ø 100A sub-panels, and balance 3Ø feeders between parking stalls?

 

[kwired]

Each outdoor-parking stall has a 3Ø 100A 5-space sub-panel, divided between lights and four 1P Readily-Accessible GFCI breakers that feed non-indicating split-wired duplexes.

1) Each spit duplex with 15A loads on separate neutral draws 30A continuous on a 20A device, since no MWBC neutral is there to cancel current.
30A violates the 20A listing of each duplex, so you need separate duplexes for each dedicated 20 GFCI outlet.

2) Do they make a 3Ø 100A 5-space sub-panel, and how expensive is it?
Would it cost less to use 1Ø 100A sub-panels, and balance 3Ø feeders between parking stalls?

Three phase panel is likely to have equal number of connections to each phase. That makes the most practical to make assembly have three spaces - which is basically a single breaker (three pole) assembly or in a more conventional panel 6 spaces - with two connections on each phase. I can't recall ever seeing a 6 space three phase loadcenter, 12 spaces is the common thing to see for the smallest loadcenter outside of a single breaker enclosure.

You kind of run into art 225 issues if this is separate structures, though I guess if you keep it to under 6 breakers at each structure you might still be fine.

I have no idea what might be available for pedestal type equipment (like you often see in RV parks) in three phase - might be worth looking into though. Even with those type might still be advantage to just use single phase equipment and balance phases as well as possible.

 

[infinity]

1) Each spit duplex with 15A loads on separate neutral draws 30A continuous on a 20A device, since no MWBC neutral is there to cancel current.
30A violates the 20A listing of each duplex, so you need separate duplexes for each dedicated 20 GFCI outlet.

If the tabs are broken and the neutrals are separate how does any one receptacle end up with more than 15 amps on it?

 

[kwired]

If the tabs are broken and the neutrals are separate how does any one receptacle end up with more than 15 amps on it?

Good catch. One basically has to think of it as two devices on one yoke. If you didn't break the tabs on the neutral side you still have a MWBC, but with parallel conductors on the neutral.

 

[ramsy]

If the tabs are broken and the neutrals are separate how does any one receptacle end up with more than 15 amps on it?

Never seen the Receptacle NRTL listing(s) language, if there's more than one.
Can we add the heat from both receptacles to the same device yolk?
Or, is the entire device yolk limited to 20A combined?

Since access to these product standards (Books) are proprietary, and expensive, much less easy to read or locate what your looking for, to error on the side of caution with separate GFCI devices may be advised.

 

[infinity]

Never seen the listing language.
Can we add the heat from both receptacles to the same device yolk?
Or, is the entire device yolk limited to 20A combined?

A duplex is two receptacles even if they're on the same yoke. Each receptacle can carry it's rated current.

 

[kwired]

Though a 15 amp duplex should be rated to be able to "feed thru" 20 amps. But if you have broken the tabs off you aren't doing this.

 

[ramsy]

2GFI Backyard Power Outlet

2GFI Backyard Power Outlet

This is what I use.


Cost less than 2-GFCI Breakers, and lasts longer than inferior bubble covers on 2-gang boxes.

 

[deb4523]

Each outdoor-parking stall has a 3Ø 100A 5-space sub-panel, divided between lights and four 1P Readily-Accessible GFCI breakers that feed non-indicating split-wired duplexes.

FYI, no lights, just a micro heating element on the fifth breaker.

1) Each spit duplex with 15A loads on separate neutral draws 30A continuous on a 20A device, since no MWBC neutral is there to cancel current.
30A violates the 20A listing of each duplex, so you need separate duplexes for each dedicated 20 GFCI outlet.

Couldn't I use four single receptacles instead of two doubles?

I'm sorry guys, I'm going to need some help getting this sorted. I know, I am not an electrician and definitely don't feel qualified for planning these types of projects. This should be fairly simple, but I just keep getting more confused. I started with a gfci outlet and a 2-pole breaker, then switched because I thought you guys said I could cut the tab on the hot side of the duplexes and use a two pole GFCI breaker. Can I not do the same thing with separate single pole breakers?

I need a way to plug in four vehicles for their engine block heaters (20A each) on a single pedestal. I was adding in the heater because breakers don't trip as well at extremely low temperatures (we try to plan for -50F). I know we currently have problems where water will get into the 'weatherproof' outlet boxes and burn up the wiring without tripping the breakers at the main panel. I am trying to come up with a different design to prevent this problem by having the breakers more local to the location and to heat the box a little to make sure the protection devices work as intended. I was intending the terminal blocks to be in a different enclosure and run conductors to the breakers the other box. The box could contain the outlets and the breakers or just the breakers. I've spent a good portion of today looking to see what is available on that front.

I found this product that is almost right: https://www.geempower.com/ecatalog/ec/EN_MW/p/U614C , but it is for 30A outlets instead of 20A. They've got another one with 4 duplex outlets: https://www.geempower.com/ecatalog/ec/EN_MW/p/U014C010 , maybe I could use that... Eaton makes power pedestals with up to four outlets.

Do you guys have any suggestions on what to do here or should I just stick with the current set-up and not try to improve things?

Money is always a huge factor, but getting something safe that works is more important!

Is it just better to just have four GFCI duplex outlets with four breakers for the four parking spaces per pedestal? And cut the heater?

 

[ramsy]

Not aware of outdoor, NEMA 4, Temperature-Controlled Enclosures listed for temps below -20F.

I doubt NEMA 6 gaskets are listed to handle -50F below zero either.

You will need to investigate wiring methods, raceways, & conductor insulation at those temperatures.

If no equipment exists with listings rated at such temperatures, much less employees, you may need heated equipment rooms, or insulated garages, before starting this project.

 

[kwired]

started with a gfci outlet and a 2-pole breaker, then switched because I thought you guys said I could cut the tab on the hot side of the duplexes and use a two pole GFCI breaker. Can I not do the same thing with separate single pole breakers?

Two single pole GFCI's can not supply a MWBC, not because of code issues but because of how they work. If you tried to use two single pole GFCI's and share a neutral conductor they will never hold. What goes out the "hot" must come back on the white (within 4-6 mA) or it trips. With multipole breaker what goes out on one conductor, must come back on another conductor (including the neutral) or it trips.

 

[deb4523]

Two single pole GFCI's can not supply a MWBC, not because of code issues but because of how they work. If you tried to use two single pole GFCI's and share a neutral conductor they will never hold. What goes out the "hot" must come back on the white (within 4-6 mA) or it trips. With multipole breaker what goes out on one conductor, must come back on another conductor (including the neutral) or it trips.

By sharing a neutral conductor, you mean back at the terminal block on the 100A circuit? The last drawing I posted shows separate neutrals for each receptacle. I guess that would need to use single receptacles instead of duplex.. So I can use separate breakers if I have totally separate receptacles or use two pole breakers if I use 'split' duplex receptacles.

 

[deb4523]

View attachment B3101 HBH Sept 14.pdf
So I could do something like this with single gfci receptacles, right?

Or I could use two pole breakers with two single gfci receptacles and share a neutral?

 

[ramsy]

View attachment 21184
So I could do something like this..

Terminal block enclosure before sub-panel? Your employer should hire a qualified P.E. / or licensed electrcal consultant. Sending you internet fishing on the cheep is not working.

The internet will not provide the training or education you need to design this project, and without a clue about Code or Trade, anyone who encourages you risks legal liability for your attempted negligence.

While your plea for instruction gets an A+ for effort, there is no excuse for dirt-bag employers expectng draftsmen to design power or electrical projects.

There are electrical power engineers on this forum that consult to provide the qualified plans you need. Your task should be introducing them to your employer, not attempting the work yourself.

 

[DrSparks]

I'm sure this has been discussed somewhere on this forum, but I can't seem to find any previous threads.

I would like to use a 2 pole 20A breaker for a split wired duplex receptacle - one phase to one outlet, one phase to the other outlet & share the neutral and ground. Essentially, I need two separate 20A outlets, but would like to minimize expenditures, because I need to do this many times for head bolt heater outlets in parking lots.

Is there any code against doing this? I don't think it qualifies as paralleling...

Also, would I be able to have a 15A load on each of the outlets simultaneously, or would that trip the breaker? I'm not sure because each of the loads would be on a different phase, but it is still one breaker. :?

As always, thanks in advance for your expertise!

This not only allowed but done quite frequently.

No issues with shared neutral on line side of GFCIs. I do MWBCs for kitchen appliance circuits in all new construction.


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[DrSparks]

Another question: can this be done with GFCI outlets (they will be installed outdoors in weatherproof enclosures) or should it be done with GFCI breakers?

As long as the receptacles have WR rating. Receptacles would be cheaper


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[DrSparks]

Suggestions:

1. Don't forget to break the tabs between the terminals, but only on the hot side of the receptacles.

2. Use a flat-blade screwdriver to increase the distance between the terminal metal parts, just to be safe.

Well you wouldn’t break any tabs on a GFCI receptacle


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[DrSparks]

Um I don’t understand why you would want to install the panels outdoors in the elements. Why not install a sub panel inside where it’s warm and run each circuit outside to gfci receptacles? If you’re worried about voltage drop up the conductor size to 10 or 8.


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[DrSparks]

Terminal block enclosure before sub-panel? Your employer should hire a qualified P.E. / or licensed electrcal consultant. Sending you internet fishing on the cheep is not working.

The internet will not provide the training or education you need to design this project, and without a clue about Code or Trade, anyone who encourages you risks legal liability for your attempted negligence.

While your plea for instruction gets an A+ for effort, there is no excuse for dirt-bag employers expectng draftsmen to design power or electrical projects.

There are electrical power engineers on this forum that consult to provide the qualified plans you need. Your task should be introducing them to your employer, not attempting the work yourself.

While I tend to agree with you I think this project can be solved shy of a registered PE. I think a seasoned master electrician?


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[kwired]

By sharing a neutral conductor, you mean back at the terminal block on the 100A circuit? The last drawing I posted shows separate neutrals for each receptacle. I guess that would need to use single receptacles instead of duplex.. So I can use separate breakers if I have totally separate receptacles or use two pole breakers if I use 'split' duplex receptacles.

When I said MWBC I meant what NEC defines as a MWBC. In your case that means two "hots" and one neutral is a MWBC, two "hots" and two neutrals is not a MWBC.

You can not handle tie two single pole GFCI breakers to supply a MWBC, it would be code compliant, but it won't work, as current going out on "hot" needs to all return on corresponding neutral on the same GFCI, or it trips.