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Old 12-14-2009, 06:34 AM   #1
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Adding a light to a 30 amp circuit?


I have a existing 110 VAC, 30 amp circuit (30 amp single pole breaker/10-2 wire) that goes to a shed I use to store my camper. Shed is a pole building with a roof and no side walls. It has a weather proof box with a TT-30 receptacle that the camper plugs into. There are no other boxes or connections to this circuit. I would like to add an overhead light in this shed. Just a bare bulb and a pull chain switch.

Is there any code compliant way to do this? Can I just tap off the TT-30 receptacle and go to an overhead fixture box? Do I need to run 10-2 wire? Can I pigtail the 10-2 in the fixture box to a smaller gauge to connect to the porcelain lamp holder?

Thanks for any help you can provide.

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Old 12-14-2009, 06:53 AM   #2
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Adding a light to a 30 amp circuit?


No big problem. Tie into existing box with, e.g., a 14-2 cable (15a) for the light. However, as I've done in similar jobs, I passed the 15a wiring through a fuse assembly which was mounted on a plate that installs into a utility box. Any variation of this senario is OK as long as the 15a line is correctly protected.

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Old 12-14-2009, 07:19 AM   #3
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Adding a light to a 30 amp circuit?


Any conventional light fixture itself (as well as any conventional 120 volt receptacles) must be protected at 20 amps or less. Any 14 gauge wires in the subcircuit must be protected at 15 amps or less.
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Old 12-14-2009, 07:24 AM   #4
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Adding a light to a 30 amp circuit?


So the 15a fuse would need to be connected with 10-2 to existing #10 (not #14)
Then after the fuse would be #14 wire
Sounds like...?
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Old 12-14-2009, 08:25 AM   #5
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Adding a light to a 30 amp circuit?


Please remember that the smallest wire aloud any where on a circuit is:

On 15a breaker/fuses #14copper
20a needs #12 copper
30a has to have #10

As required by 240.4(D)

Also it is not usually permitted to add another fuse/breaker on a branch circuit.

I hope I understand your question proberly.

And so it goes, R
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Old 12-14-2009, 09:30 AM   #6
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Adding a light to a 30 amp circuit?


You can't tap the 30A receptacle because those terminals are for one wire only. But you could install a larger box, add two pigtails onto the end of the 10/2 with one going to the receptacle and another going to a fused switch. From the fused switch you would go to the light. If you use 14ga, you must use a 15A fuse.
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Last edited by HouseHelper; 12-14-2009 at 09:32 AM.
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Old 12-14-2009, 05:05 PM   #7
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Adding a light to a 30 amp circuit?


Quote:
Originally Posted by Saturday Cowboy View Post

As required by 240.4(D)

Also it is not usually permitted to add another fuse/breaker on a branch circuit.
I guess I am confused. Are you saying there is no way to add a light by code? Is the fused switch suggested by HouseHelper not a valid way to protect the smaller gauge wire and the lamp holder? Do you know of a way that I can make this work?

Thanks to all who responded.
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Old 12-14-2009, 05:16 PM   #8
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Adding a light to a 30 amp circuit?


I don't know of any code that prohibits adding another fuse/breaker box off a run
But I don't know all the code
But basically a sub is doing the same thing....
Unless someone can quote a code reference that prohibits it ?
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Old 12-14-2009, 05:50 PM   #9
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Adding a light to a 30 amp circuit?


I think the best bet would be a weatherproof 2 space loadcenter with 2 breakers, one single 30 A for the trailer, and 1 single pole 15 or 20 A for the light. For a few dollars more, put yourself a standard receptacle too, on the same breaker as the light. I guess you'd need a grounding system too, being that there is overcurrent protection at the shed, and would now be feeder instead of a branch circuit.
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Old 12-14-2009, 09:51 PM   #10
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Adding a light to a 30 amp circuit?


Somewhere it was discussed that an in-line automotive style cartridge fuse in the box requiring unscrewing the switch yoke to get at was not allowed. I can't see any problem with the switch unit pictured above with a fuse that is readily accessible.
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Old 12-14-2009, 10:40 PM   #11
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Adding a light to a 30 amp circuit?


If you are not usuing this shed for yur camper anymore then change the 30 amp braker to a 20 amp and you are good to go
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Old 12-16-2009, 07:45 AM   #12
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Adding a light to a 30 amp circuit?


Quote:
Originally Posted by 300zx View Post
If you are not using this shed for your camper anymore then change the 30 amp breaker to a 20 amp and you are good to go
Still using the shed for the camper, so I need the TT-30 and the light. Since the AC only requires 20 amps and I am not using anything else when I am working on the camper, how about if I changed the breaker to 20 amps and added my light using 12-2 wire? I guess the question is can I leave the TT-30 receptacle on a 20 amp circuit and still be compliant? The idea of using the fused switch also sounds good but there is apparently some diagreement amongst you'all on whether it is compliant.
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Old 12-16-2009, 05:26 PM   #13
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Adding a light to a 30 amp circuit?


I opened the outside RV receptacle and noticed the electrician used 10-3 cable and since this is a 110 volt circuit, the red wire is capped. Can I make a MWBC? To do this I would need a two pole breaker (common trip) with a 30 and 20 amp combination. I do not know if that exists. I have a 200 amp GE panel with enough space to add a 2 pole breaker.
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Old 12-16-2009, 09:47 PM   #14
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Adding a light to a 30 amp circuit?


Quote:
Originally Posted by rjniles View Post
I opened the outside RV receptacle and noticed the electrician used 10-3 cable and since this is a 110 volt circuit, the red wire is capped. Can I make a MWBC? To do this I would need a two pole breaker (common trip) with a 30 and 20 amp combination. I do not know if that exists. I have a 200 amp GE panel with enough space to add a 2 pole breaker.

Since all you really need is a handle tie, and not a real double pole internal trip breaker such as for a 240 volt circuit, a 20 and a 30 handle tied would work, but I am not sure if you can get separate handle ties for GE. If you are under the 2005 code cycle or earlier, a handle tie on a circuit like this wouldn't be required, but a good idea.
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Old 12-17-2009, 01:23 AM   #15
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Adding a light to a 30 amp circuit?


Using a SSU as pictured above, Would be ok, at least I am unable to find where it would not. I was opposed to using the inline auto fuse. SSU's are usualy used to protect utilization equipment. An SSU is a proper way to transition from a #10/30A to a lesser amp circuit. Hope this helps.

R

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