How much can I safely put on a circuit?


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Old 05-09-10, 05:24 PM
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How much can I safely put on a circuit?

Howdy howdy, y'all!

I have some track light fixtures in my kitchen that, as far as I can tell, are not hooked up to any power source. Since I'm about to replace the recessed lighting in the kitchen (have non-IC, need IC so I can insulate before the AZ summer starts!), I want to fix the track lights at the same time. (And by "fix" I mean replace the track lights with 3 recessed spots and have them controlled separately from the main recessed lighting.)

Should be easy, but... I can't figure out onto which circuit I should add the spots. The original plan was to add them to the circuit that is powering the two other switches in the box I was going to add this switch too. However, upon investigation, I found that those devices (a ceiling fan/lights combo & a set of 2 floodlights) - and potentially 6 other plugged in devices on 3 outlets - were hung off the 20A kitchen circuit that has my microwave & fridge. With 14AWG.

So not only can I not put my 3 new spotlights on that circuit, but I have disconnected the 14AWG from the 20A, and need a home for all of that as well. Total orphaned Amperage ~ 1.6.

Here are my options:

1) A 15A circuit that runs lights & fans throughout the downstairs. If - and this is a huge if - I were to turn all the devices on on this circuit at one time, it would pull 11.5A. (It is a huge 'if' because doing this would require me to leave the lights & fans running in 4 rooms and a hallway while having the lights and range exhaust hood on in the kitchen. I'm cheap - it's been in the upper 90s here in AZ I haven't turned on the AC yet - so I turn lights off, and live by myself, so I can't see this ever happening.)

2) A 15A circuit that has a bedroom (lights & ceiling fan), 2 bathrooms (yes, the GFCIs are on this circuit ), and the recessed kitchen lights. Total load, excluding any hair dryers, approximately 5A if everything were running. Of the easily accessible circuits, this one has the most available capacity, but... It's already wrong, and I don't particularly want to make it worse.

3) A 20A circuit in my laundry area - gas dryer, front load washer. Also on it 2 outlets and 180W of lighting. Total load on laundry night, maybe 2A. Personally, I think this is the best option for my orphaned devices, but have absolutely no idea where the wiring is for this one.

4) Oh, on other I hadn't thought about: I have the garbage disposal & dishwasher on a 20A that I could tap in to, although - to my knowledge - it isn't the right thing to do.

Any insights folks could offer would be greatly appreciative. Can I put my stuff on the 1st 15A circuit, knowing that - in reality - I probably use, at most 8A worth of devices at a given time? Or would hunting down the laundry wiring be best?

Thanks in advance for any advice y'all can offer. I want to do things as right as possible, and this is one of those things that has me wondering if I shouldn't just pull down all the drywall in the house and start from scratch... (unfortunately, I just don't have the fortitude to do that)

-Shalie
 
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Old 05-09-10, 06:34 PM
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You are correct that you had some problems with the way your wiring was installed. You were smart to correct it.

Unless you run a new circuit option 1 is the only feasible option. Others have code issues or are potentially overloaded already.
 
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Old 05-09-10, 06:59 PM
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PCBoss is correct. Your options 2-4 would be code violations. #1 is your best bet.
 
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Old 05-10-10, 09:57 AM
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Thanks, gents, for the input. I really appreciate it!

On option #1, putting the ~2A on that circuit wil bump it over 80%. Is that terrible, or would I be better off finding another circuit? Wire is cheap; replacing a burned-down house isn't.

I would run another circuit, but the box is full. But - considering I've mapped 70% of the house's wiring onto ~6 breakers - I'm pretty sure I'll find capacity elsewhere (if I can just find the actual wires).

When calculating load, is it just a straight addition of all the wattage on the circuit, even if the chance of it all being utilized at the same time is slight? Or is there wiggle room to put disparate things on the same circuit, knowing that they're not going to be used at the same time? (I assume it is the first, because even though I may not use everything at the same time, the next owners might - if I were to ever sell.)

Thanks again, all! I really really appreciate your help!

Oooh, PS: as it sits now, circuit #2 is a code violation, yes? The GFCIs are supposed to be on a 20A line with nothing else, correct? If I moved (somehow) the GFCIs off of this circuit and onto their own 20A, that would bring these up to code & free up this 15A line, correct? Thanks!
 
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Old 05-10-10, 10:08 AM
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Lighting loads are not considered continuous in a residential setting as the chance of them being on over 3 hours is not that great. This removes the limitation of 80% loading.

Under more recent codes bathroom receptacles are supposed to be on 20 amp circuits.
 
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Old 05-10-10, 11:17 AM
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Originally Posted by shalihe74
On option #1, putting the ~2A on that circuit wil bump it over 80%.
General-purpose circuits may be loaded to 100%.

When calculating load, is it just a straight addition of all the wattage on the circuit, even if the chance of it all being utilized at the same time is slight?
For known loads, add 100% of the general load (lighting/appliances), plus 125% of the continuous load (space heaters). For receptacle and lighting circuits which do not have known loads you may use an approximation such as 3 watts per square foot of area served by that circuit.

Oooh, PS: as it sits now, circuit #2 is a code violation, yes?
If left as-is the circuit is grandfathered under the code from the year the house was built. If you were to redo it, you would need to put the bathroom receptacles on a 20A circuit separate from the other loads.
 
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Old 05-14-10, 09:44 AM
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Thanks, all!! With your input, I've been able to plan out the changes I need to make.

Now I just need to get up the motivation to go up in the hot, nasty, filthy attic and do the work. :}
 
 

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