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Old 01-16-2012, 12:21 PM   #1
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Sub Panel GND and mixed 240/120 VAC branch


Hi newb here.

I just installed a 8 slot sub panel next to my main 40 slot 200A panel in my home. I had used tandem breakers for a few circuits in the main panel before. I later learned about the CTL and 40 branch limit of a single 200A cabinet and the tandems had me at 44 circuits. Hence the change.

I have a couple questions:

1) Grounding sub panel. I didn't ground the subpanel per se. It is 3" from the main panel and I used a 3" long 1 1/4" rigid conduit nipple with lock nuts to join the cabinets. I am thinking this satisfies the grounding requirements for the cabinet. I did NOT install the bonding wire/screw on the neutral bus of the sub cabinet. The neutral bus is wired back to the main panel neutral bar. I have a 60A breaker feeding the sub panel with 6AWG wire for each phase and a white one for the neutral. I am in IL so everything is EMT here. Consequently I don't have Romex cables in cabinet with grounds going to ground bar. The EMT is considered the ground. Does this sound OK or should I bond the cabinet case with a bare 6AWG wire from ground bar of main panel to case of sub panel?

2) Running wires across panels. Since I live I IL with EMT mandate I already have several home run lines of EMT to my main panel. I need to run another branch circuit to my garage from the new sub panel I just installed. I can get most of the way to where I need to go using existing EMT and just add a short length to the last box in the garage. That means at the panel the wires will enter the panel on the main panel and then I will route them to the sub panel via the 1 1/4:” stub I have between the panels before terminating on the neutral bus and breaker. Is it with NEC to run wires through one panel enroute to the final destination in an adjacent panel (assuming I don't violate EMT fill limits)?

3) Mixed 120/240 branch circuit. I have run a 3 wire dual pole (locked tab breaker) to my garage for some plugs (split duplex) and a 240 V outlet for my compressor and MIG welder. I have split the top and bottom half of the six 120V outlets and run alternative phase to hot of each duplex half. They share a common neutral. The 240 V outlet is both hot phases and ground. Is it OK to mix a 240 outlet with several 120V split phase receptacles or does the 240 need to be a dedicated branch by itself? The breaker is dual pole 15A with the poles joined. The wire is three conductors 14 AWG in EMT. I am only interested in a NEC compliance perspective not what might be better.
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Old 01-16-2012, 12:28 PM   #2
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Sub Panel GND and mixed 240/120 VAC branch


First two answers are not a problem

The last answer would seem also ok 210.4 (c) exception 2
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Old 01-16-2012, 12:29 PM   #3
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Sub Panel GND and mixed 240/120 VAC branch


Doesn't Chicago require permits to be pulled for this stuff? Anyone.

I really do not know where to start on this one, so I am going to let the full-time sparkies tear it apart, while I munch on popcorn.
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Old 01-16-2012, 01:14 PM   #4
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Sub Panel GND and mixed 240/120 VAC branch


You do need 2 pole breaker on the split receptacles.

It is fine to run the 240 v circuit with the 120v circuits.

Is the emt the only grounds you have to any circuit?
Sounds like you did a good job.
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Old 01-16-2012, 01:43 PM   #5
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Sub Panel GND and mixed 240/120 VAC branch


Yes, the only ground on branch circuits is the EMT throughout the house. It seemed strange when I first moved to IL and to not see a ground bus with many ground wires. The only ground wire in the cabinet is the main one (1/0 or something quite large) going between the outside ground rods and the bonding point of the main panel (where neutral and ground are joined).

I have wondered if EMT conduit is as good as a continuous ground wire, point to point, as in Romex. It seems conduit connections offer an "opportunity" for corrosion or a loose connector to jeopardize ground integrity. I imagine this has been studied to death by the NEC authors though.
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Old 01-16-2012, 02:08 PM   #6
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Sub Panel GND and mixed 240/120 VAC branch


Can you please clarify what the last question is? Do you want to have a 120 and a 240 in the same conduit or have some outlets 120 and some 240 on the same breaker

Also 14 AWG seems quite small for 6 outlets and a welder
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Old 01-16-2012, 02:35 PM   #7
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Sub Panel GND and mixed 240/120 VAC branch


CuriousB, code office opens on Tuesday. Worst thing that they could do, is red tag if they decide to inspect, if no permits were pulled. But it is amazing if you accidentally drop an envelope of cash in their car up there in Chicago, that they help you out in getting it code compliant.
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Old 01-16-2012, 03:12 PM   #8
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Sub Panel GND and mixed 240/120 VAC branch


gregzoll.

haha a million laughs. I'll be sure to notify you first once I schedule the inspection. Be sure to wait by the phone for me.

Maybe next time you chime in on this you can actually add some value to the discussion rather than your permit and inspection rant...
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Old 01-16-2012, 03:21 PM   #9
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Sub Panel GND and mixed 240/120 VAC branch


The value is, you get the pleasure of straightening out someones mess. The rant will be you, once you find that this was unpermited work, and how bad the Chicago area inspectors are, when it comes to trying to get them to check off on stuff that you have gone and pulled the permits for. Catch is, they can make you rip everything out, if the previous person did not pull permits to do any of it. It is just the nature of the beast up there.

Down here, we only have to pull permits for new construction, and that is the only time the inspector shows up to sign off. Otherwise, homeowners can do all of their work, as the city defines "In a professional code compliant nature."
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Old 01-16-2012, 07:00 PM   #10
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Sub Panel GND and mixed 240/120 VAC branch


Are any of these receptacles in areas that require GFI protection?
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Old 01-17-2012, 08:14 AM   #11
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Sub Panel GND and mixed 240/120 VAC branch


I probably should have these outlets on GFCI but they presently are not except for the original outlet provided by the builder which has a GFCI in it.

I am not sure the best way to handle this. I guess I could:

1) Put two GFCI outlets on the first box in the branch and then slave all the downstream outlets from these GFCIs. This would be a problem for the 240VAC plug which is also downstream as it doesn't use the neutral the GFCI would see any 240 load as a ground fault (because there would be no matching neutral current). So everytime I used the 240 VAC outlet one of the GFCIs would trip.

2) I could separate the 240 VAC outlet and feed it before the GFCI outlets and claim it is a dedicated purpose outlet so excempt from the GFCI requirement? It seems the code excerpt below doesn't speak about 240 VAC is it by default excempt from the GFCI requirement?

3) I could get an fairly expensive two pole GFCI breaker (no neutral) for the 240VAC outlet only and run it as a separate branch from the panel.

4) I could buy one of these 240/120 GFCI breakers (two phases plus neutral) but they are really expensive (>$200 each) to feed the existing circuit of both 120 and 240 VAC.

5) Other ideas?


I am trying to honor the spirit of the NEC but I am sure there are a lot of 240 VAC outlets in garages with workshops and I doubt too many have GFCI protection. I wonder if all the people who put sub panels in the garage/workshop have fed their many plugs with GFCI protection?




NEC:
210-8(A) Dwelling units. All 125-volt, single-phase, 15-, and 20- ampere recepticles installed in locations specified in (1) through (8) shall have ground fault circuit interrupter protection for personnel.
(1) Bathrooms
(2) Garages and accessory buildings that have a floor at or below grade not intended as habitable rooms and limited to starage areas, work areas, and areas of similar use.
Exception No.1 to (2): Recepticles that are not readily accessable
Exception No.2 to (2): A single recepticle or a duplex recepticle for two appliances located within a dedicated space for each appliance that, in normal use, is not easily moved from one place to another and that is cord and plug connected.
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Old 01-17-2012, 08:19 AM   #12
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Sub Panel GND and mixed 240/120 VAC branch


240 volt circuits do not require gfci protection.
Put gfci receptacles at the first location, then install normal receptacles downstream.
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Old 01-17-2012, 10:49 AM   #13
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Sub Panel GND and mixed 240/120 VAC branch


Quote:
Originally Posted by curiousB
I probably should have these outlets on GFCI but they presently are not except for the original outlet provided by the builder which has a GFCI in it.

I am not sure the best way to handle this. I guess I could:

1) Put two GFCI outlets on the first box in the branch and then slave all the downstream outlets from these GFCIs. This would be a problem for the 240VAC plug which is also downstream as it doesn't use the neutral the GFCI would see any 240 load as a ground fault (because there would be no matching neutral current). So everytime I used the 240 VAC outlet one of the GFCIs would trip.

2) I could separate the 240 VAC outlet and feed it before the GFCI outlets and claim it is a dedicated purpose outlet so excempt from the GFCI requirement? It seems the code excerpt below doesn't speak about 240 VAC is it by default excempt from the GFCI requirement?

3) I could get an fairly expensive two pole GFCI breaker (no neutral) for the 240VAC outlet only and run it as a separate branch from the panel.

4) I could buy one of these 240/120 GFCI breakers (two phases plus neutral) but they are really expensive (>$200 each) to feed the existing circuit of both 120 and 240 VAC.

5) Other ideas?


.
As jbfan said 240v outlets don't need a gfi protection. Therefore put it first, then off that put 2 gfi's that will supply your other outlets.
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