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Old 04-03-2013, 09:41 PM   #1
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NEMA #L14-30P generator connection to fuse box?


I recently got a generator that uses a L14-30P connection, I know that 12-10 AWG wire is recommended. However, I already have 33ft of 8 AWG.
Problem #1 is that I have 3 strands and I need 4. Don't want to buy all new wire (4 strands) so ......CAN I just buy a single strand of 8 AWG and use that as the fourth wire? It will all be in a conduit anyway.

#2 question....my generator is NOT back-up cause I'm OFF GRID. So I think I don't need a transfer switch. Can I connect the 8 AWG (4 wires) to a fuse box directly? IF so, What kind of fuse box do I need?

This is ONLY to run lights and a few small appliances, I got propane for stove, fridge, hot water heater and heater.

Any help would be much appreciated!

Thanks....Buckslugger.

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Old 04-04-2013, 02:17 AM   #2
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NEMA #L14-30P generator connection to fuse box?


Quote:
Originally Posted by Buckslugger View Post
?.. However, I already have 33ft of 8 AWG...
Even better. But NM is not allowed outdoors, even in conduit.
Quote:
Originally Posted by Buckslugger View Post
......CAN I just buy a single strand of 8 AWG and use that as the fourth wire? *
In conduit, I think yes. But if the gen receptacle is GFCI protected it will pop every time. The problem is the neutral and ground is bonded at the gen and at the service entrance of the building.
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Originally Posted by Buckslugger View Post
It will all be in a conduit anyway.
Best practice is not to run cable inside conduit.
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Originally Posted by Buckslugger View Post
#2 question....my generator is NOT back-up cause I'm OFF GRID. So I think I don't need a transfer switch. *
If the gen is the only electric supply, no transfer switch.
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Originally Posted by Buckslugger View Post
Can I connect the 8 AWG (4 wires) to a fuse box directly? * *
Yes, but I think you're better off with three wires. If the receptacle is not GFCI and you keep the bonds at the gen and the structure.
Quote:
Originally Posted by Buckslugger View Post
*IF so, What kind of fuse box do I need? *
Any that is service equipment rated.

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Last edited by Glennsparky; 04-04-2013 at 02:23 AM.
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Old 04-04-2013, 12:06 PM   #3
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NEMA #L14-30P generator connection to fuse box?


Glennsparky thanks for your input!

However still a bit confused. The generator has a built in 30 amp circuit breaker. I need to use a NEMA #L14-30P to connect to the genset. Because this is a 4 wire plug, I think I have to use 4 wires. I don't understand what it means that the neeutral and ground are "bonded" at the gen? Doesn't that mean I HAVE to use 4 wires?

Finally, Can I use 8 AWG with the L14-30P or do I have to use # 10 or #12?

Sorry, I'm such an idiot!
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Old 04-04-2013, 12:15 PM   #4
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NEMA #L14-30P generator connection to fuse box?


Quote:
Originally Posted by Buckslugger View Post
Glennsparky thanks for your input!

However still a bit confused. The generator has a built in 30 amp circuit breaker. I need to use a NEMA #L14-30P to connect to the genset. Because this is a 4 wire plug, I think I have to use 4 wires. I don't understand what it means that the neeutral and ground are "bonded" at the gen? Doesn't that mean I HAVE to use 4 wires?

Finally, Can I use 8 AWG with the L14-30P or do I have to use # 10 or #12?

Sorry, I'm such an idiot!
You do need four wires. This is not a service.

You cannot pull an extra wire with a cable. You can pull 4 separate wires. Or a cable with 4 conductors in it.
In your case THHN/THWN individual wires would be the best bet.
What type of wire is the #8?

You are required to use #10 wire minimum. You can go bigger like using the #8 you already have. But you cannot go down to #12.
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Old 04-04-2013, 01:04 PM   #5
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NEMA #L14-30P generator connection to fuse box?


OK, got it...but curious about why I can't pull an extra wire with a cable?
Is this a REAL safety issue or a code issue?
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Old 04-04-2013, 10:34 PM   #6
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NEMA #L14-30P generator connection to fuse box?


Curious, since you are off grid, is there existing wiring in your structure or will you be putting in new wiring, receptacles, switches, etc? Or more just like one or two receptacles to plug into when needed?
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Old 04-04-2013, 10:34 PM   #7
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NEMA #L14-30P generator connection to fuse box?


Quote:
I don't understand what it means that the neeutral and ground are "bonded" at the gen?
They are electrically connected. Somewhere in the gen there is a wire jumper that goes between the greens and the whites. Also in a home's first panel you'll see bare grounds and neutral whites landing on the same bus bar. A big green screw or a strap will connect the bus to the metal of the panel. Grounds and neutrals must not touch anywhere else in the house.
Quote:
Doesn't that mean I HAVE to use 4 wires?
Electrically, no. But J.V. may be right, the code may require it. In which case you must not bond at the panel or anywhere the gen powers. The bond must be kept at the gen only. (Or bond only at the first panel and remove the bond in the gen, but that's probably more complicated.)
Quote:
Can I use 8 AWG with the L14-30P or do I have to use # 10 or #12?
Bigger wire is always electrically fine and often better. The question is, will it fit? Do you have enough room in your outlet box? Is it written on the L14-30P(or R) that the lugs are rated for wire that large?
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Originally Posted by Buckslugger View Post
OK, got it...but curious about why I can't pull an extra wire with a cable?
Is this a REAL safety issue or a code issue?
If it's anything, it's a code issue. Maybe J.V. can provide chapter and verse, and enlighten us.

Last edited by Glennsparky; 04-05-2013 at 01:09 AM.
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Old 04-04-2013, 11:28 PM   #8
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NEMA #L14-30P generator connection to fuse box?


I would definitely run 4 wires. It is a code requirement if neutral and ground are bonded at the generator (they certainly are) and you can't unbond them (you might be able to). But it is also a bit f a safety issue. If you run 3 wires and the neutral connection become loose anywhere between the generator and the panel, the results will be really bad: 240V applied across 120V loads, and up to 120V between the generator's metal frame and the earth. I would not risk that outcome. Running 4 wires fixes this problem by keeping the N-G bond as close to the generator as possible (inside it).
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Old 04-05-2013, 12:15 AM   #9
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NEMA #L14-30P generator connection to fuse box?


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I would definitely run 4 wires. It is a code requirement if neutral and ground are bonded at the generator ...
I'd like to read that section of the code. It makes more sense to require 4 wires if the gen is not bonded.
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... 240V applied across 120V loads...Running 4 wires fixes this problem ...
A loose neutral in 4 wire homes can cause loads to get greater than 120V. A ground wire doesn't help there and it wont help here.
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If you run 3 wires and the neutral connection become loose anywhere between the generator and the panel, ...and up to 120V between the generator's metal frame and the earth.
That would be a hot short to ground to energize the frame. I can't imagine how just a loose neutral would energize the frame. But the danger is the same.

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Old 04-05-2013, 01:38 PM   #10
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NEMA #L14-30P generator connection to fuse box?


Quote:
Originally Posted by Glennsparky View Post
I'd like to read that section of the code. It makes more sense to require 4 wires if the gen is not bonded.
250.142(B) (NEC 2011). The generator has a breaker built in - that's the first disconnecting means and OCPD, so if it's bonded before that, it's not compliant to use the neutral conductor for bonding.

Quote:
A loose neutral in 4 wire homes can cause loads to get greater than 120V. A ground wire doesn't help there and it wont help here.
You're right.

Quote:
That would be a hot short to ground to energize the frame. I can't imagine how just a loose neutral would energize the frame. But the danger is the same.
Look at the entire 3-wire system and you'll see how it happens. The generator frame is bonded to the current carrying neutral conductor. The neutral is bonded to at least one grounding electrode at the house. Apply a 120V load on one leg of the service. Now cut the neutral somewhere between the generator and the house. The grounding electrodes at the house are now connected to a hot leg through the load, and there is no completed return path for the load current. So the potential between the earth (tied to one end of the alternator's winding through the load and grounding electrodes) and the generator frame (tied directly to the other end of the alternator's winding) will be 120V. The load will appear to have no power, until you go fiddle with the generator while standing on the ground and complete the circuit yourself...

This is the same reason a loose utility neutral can cause electrified plumbing, or that a loose neutral on a 3-wire dryer electrifies the frame. The difference is that with utility power, the neutral is very well grounded by the utility grid so the voltage appears between the metal parts and the earth. With a portable generator, the neutral is bonded to the generator frame but the only actual grounding of the neutral is at the structure. So the voltage appears between the generator's frame and the earth.
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Old 04-05-2013, 08:01 PM   #11
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NEMA #L14-30P generator connection to fuse box?


Thank you, mpoulton. That is a very clear and thorough explanation. I just need to read it a few more times to get it in my head.

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