I've got about 60A of 120v equipment to run in one room (at times, all of it simultaneously). Currently there's only one 20A circuit feeding the entire floor. So I was thinking of installing two 30A circuits and one 20A. I would have three ganged boxes, each holding two duplex receptacles, and each circuit would feed two of those receptacles (in adjacent boxes).
However, when reading my books on wiring, I see no mention of any 30A duplex receptacles...only the single receptacles you might see for an A/C. I could use all 20A circuits I suppose but would probably need four. Are 30A 120v duplex receptacles something that exists? Is it strange to do things this way?
If you were going to use 30 amp outlets, you'd need to use 30 amp plugs as well. It would be less expensive to use 15 or 20 amp plugs on the cords, and use more 20 amp receptacles
Do you mean I can hook multiple 20A outlets to a 30A circuit and as long as I don't draw more than 20A from any single outlet (and don't go over 30A cumulative) I'm ok? Wouldn't that have a danger of drawing more than the outlet can handle w/o the breaker tripping? Or perhaps nothing that draws more than 20A would ever be able to plug into a 20A receptacle?
This did occur to me. I have one subpanel off the main now. It uses a breaker that spreads across both sides of the box. Another subpanel would make things simpler in some ways. I guess I can add up to more than 200A total in breakers as long as I don't draw more than 200 at once?
no doubt. this is for my art studio. here's a partial list:
electric griddle 12A electric griddle 12A heat stripping gun 12A
1 or 2 space heaters 12A each A/C in summer 8A computers 4A or more tools 15A
this wouldn't all be on at the same time, but the griddles, stripping gun, computers, and an A/C or heater would be on any time i want to do encaustic (wax-based) painting
You may not put 15 or 20 amp outlets ("receptacles") on a 30 amp circuit. You may put 15 or 20 amp outlets on a 20 amp circuit (however if there is only outlet, it must be 20 amp)( NEC 210.21(B)(3) ).
I count at least 6 loads that you cannot put 2 of them at the same time on a 20 amp circuit. You are going to need at least 6 circuits.
It sounds like you have a lot of high current appliances. I personally would run a separate circuit for each of those.
Based on your list, I would install eight 20A circuits, using 12/2 cable, and regular 20A recepticles. Your computers could share the lighting circuit if you wish.
Depending on your usage patterns, you may be able to combine the stripping gun and "tools" on a single circuit too. For example, you probably wouldn't be using the stripping gun, a drill, and a dremel tool all at the same time. Those could share a circuit if you wish.
Basically, if you use an appliance that draws 10A or more and is on continously (i.e. the griddles), you should have a separate circuit for it. You could probably get by with 15A circuits for most of your appliances, but it wouldn't cost much more to run 20A and would give you greater capacity.
If you have balanced loads (i.e. two matching griddles), you could combine a couple of circuits with a single 12/3 cable, sharing the neutral line. Just make sure the two hot wires are on opposite legs of the incoming 240V supply. This would reduce your cable runs somewhat, and is frequently done for similar situations like kitchen wiring.
If your breaker panel is a long distance from your studio, it may make more sense to install a subpanel in the studio, then run each circuit from the subpanel. This would ease later additions too.
Thanks all for the advice---I really appreciate it. I'm now leaning towards a subpanel in the studio, as running 6-8 circuits from the basement to the 2nd floor attic is going to be difficult. I have a passage that will work for 2 or 3 cables, but 6-8 will require a lot more fishing.
I appreciate the 12/3 cable idea...I'll consider that. This would also be easier to accomplish with a subpanel (so I wouldnt' have to move current breakers to get on both sides of the incoming).
Just to clarify--when I originally proposed 30A outlets I was hoping that 30A outlets were available in the 'normal' blade style (e.g. it would look just like a 20A plug but would allow up to 30A to be drawn through it, say for two griddles). Clearly that's not the case.
You could run 14/3 to an outlet and break off the tab on a duplex receptacle. This would give you 15A to each plug. The loads on the two plugs do not need to be equal.
With 3 14/3 cables this would give you a minimum of three duplex receptacles with a total of 90A of potential current draw. You could also add more outlets on each circuit for convenience.
You could run #12 but it's going to be bigger and more expensive cable, and somewhat harder to work with. I did it in the garage, but I have some tools that draw 15A so they needed it.
One other thing to consider is that once you start bundling cables together you need to account for the heat. This starts to reduce the allowed cable ampacity.
Since you want to put Two duplex outlets into a box, put one on one
20A breaker and the other on another 20A breaker. Put several of these in the room on separate breakers. I'd run at least 6 breakers for that room. If your panel lacks spaces. run a sub panel in that room, off a 60A main from the house panel. You can easily buy 6 or 8 breaker sub boxes. I'd go for the 8 or even a 10 for expansion, and maybe put a 100A sub in the main panel. Of course you need thicker wire to feed the thing and you need enough power coming into the house to start with.
1 - 15A breaker (and you want this separated from other stuff except maybe room lights)
1 - 20A breaker w/ two duplex outs so you dont have to keep unplugging them.
Total 7 - 20A breakers and 1 - 15A breaker. I'd add one more breaker w/ an outlet for a spare.
This isn't rocket science, just a lot of wiring.
You can always plug a small hand tool like a drill into the same outlet as the griddles. Like I said, keep the computer on it's own breaker other than some lights. Power tools can cause issues with a computer.
Go with 20 amp circuits. Wiring is easier, cheaper and less explaining to do if and when you ever sell your property. Besides, if you split the loads over several circuits, if one circuit fails or blows, the others are still working.
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