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Sub Panel Question

Posted by lwim (My Page) on
Tue, Nov 23, 10 at 17:06

I had to have a sub panel installed by a licensed electrician a couple of years ago for an outdoor patio project because I was out of space for more circuits in the main panel. From the sub panel he ran three circuits using a 12/3 run and a 12/2 run with three 20 amp breakers. I noticed the sub panel is connected to the main panel with a 50 amp circuit breaker. Is this OK, or should there have been a bigger feed? I also have a second and third question related to this.

Right now we only use the 12/3 line. On one circuit I have a warming drawer. The other circuit has three outlets on it which get occassional minor use. The 12/2 line is unused, but we're finally getting around to finishing up the project. So the second circuit on the 12/3 will have six can lights (600-900W), two fans, a pair of floodlights (300W total) and four outlets. I'll probably add an outlet or two to the circuit with the warming drawer since it pulls about 8.5 amps, although the specs say it should have its own circuit. The 12/2 line is going to be used for landscape lighting and should be fine. Finally my question. Since the feed to the sub panel goes through a 50 Amp circuit breaker will I need a larger feed? Also if I want to add another circuit, am I already at my limit and need another sub panel?

Thanks for aking the time to look at this.

Cheers,
Larry


Follow-Up Postings:

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RE: Sub Panel Question

Given the loads you describe, you should be well within the capacity of a 50-amp sub-panel and still have room (and ampacity) for another circuit or two.

This assumes that the electrician wired the panel with a 120/240V feed, which would be the usual practice. (It's a two-pole or "double" 50-amp breaker in your main panel, right? Also, the use of the 12/3 doesn't make any sense unless the panel has a two-pole feed.)

That being the case, keep in mind that each of the two legs provides 50 amps of current at 120V. If you have no 240V loads, you can think of that as like having two 50-amp feeds, or 100 amps of available power for 120V circuits.

IMHO, you'd be better off running a new circuit for additional receptacles than tapping the warmer drawer circuit because, technically speaking, there's a potential code violation lurking when you don't follow the manufacturer's specifications for a dedicated circuit.


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RE: Sub Panel Question

Thanks for the quick response terribletom. You're right, it is a double pole 50 amp breaker. I don't really have to add anything right now to the warming drawer circuit so I can keep it clean. I am curious about your code violation comment as it might apply to a refrigerator too, the manufacturers of which, usually recommend a dedicated circuit. I guess the key wording is "recommended" or "required". The warming drawer is hard wired as opposed to a plug in. I'll have to check the specs again to see if they say it's required or recommended.

Thanks again.


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RE: Sub Panel Question

I pretty much see it as you do, lwim. When the manufacturer of a plug-in appliance like a refrigerator "recommends" using a dedicated circuit, I wouldn't interpret that as a mandatory installation requirement potentially rising to the level of a code violation. On the other hand, where the instructions for installing a hardwired device specify a dedicated circuit, the appliance wiring becomes part of the residence's permanent wiring and failure to follow instructions can be interpreted as a code violation.

Just my take.


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RE: Sub Panel Question

"recommend" is not binding.

"require" IS binding.


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