Ask Me Help Desk - Upstairs wiring

Oh the joys of old homes :)
I pulled off the walls in two of my upstairs rooms to find knob and tube tied to old nonground two plug recepticles. Even better yet, it looks like that is all tied to a single 15amp breaker that powers most of the receptacle in all four of the upstairs bedrooms. Fortunately, at some point there was a separate 20amp circuit pulled for each of the bedrooms too.
So my question is I'm thinking of just ditching the 15amp knob and tube and wiring each bedroom exclusively to the 20amp. I'll have 6 recessed lights, 6 receptacle, fan, AC windows unit and computer as a max on the circuit.
What's typical for a bedroom? Two 15amp, one 15amp, one 20amp etc? Thanks

You can add up how many watts everything uses (lights, computer, especially the A/C unit in the window) and divide by 120 (volts) to find out how many amps you'll be pulling. You don't want to load a breaker to more than 75% of its rating, so 15 amps for a 20 amp breaker, or 11.25 for a 15 amp breaker. Good luck!

Can't quite help yet. Need some idea of the loads in terms of amps and watts.

You'll need arc fault breakers for the bedroom.

Would suggest, not mandatory, is to combine the overhead lighting/ceiling fans of all BR's into a single circuit. Need wattages here. Reason: Lighting circuits don't usually pop because there are no accidental overloads. Best option is to use 2 lighting circuits for all BR's, so that there will always be light should one circuit die.

The AC should get a separate circuit.

It would be nice if the computer got a separate one too. Again, not mandatory. If it did get one, it should/could be wired with an orange receptacle which has an isolated ground.

You don't have to use metal boxes either.

While you have the walls out run low voltage flex conduit to the TV/Computer locations with a pull string. You can then fish Coax/fiber/ethernet/phone as required. I like to use double boxes.

There are boxes that have a Low and high voltage conpartment.

These are only ideas.

Any load that is on for more than 3 hrs a day must be multiplied by 1.25.
Amps = Watts/120V. VA = Watts for all intents and purposes.

15A or 20A. Your choice depending on your load calcs. You can run all 12/2 w gnd, but if you want to save money, use 15A receptacles and a 20 or 15 A breaker.

Sorry but I have to clarify several mistakes here.

- A circuit with a continuous load must not be loaded to more than 80%, not 75%. In the case of the OP this does NOT even apply. There are no continuous loads and there is very little to actually add up to get a load number anyway. Receptacles do NOT count as anything in a residence.

- You only need AFCI (arc fault) breakers IF your area requires them. Not nearly all do yet.

- Not a mistake, but a difference of opinion: I do not have a problem mixing lighting and receptacles, especially with 20A circuits. Breakers tripping is a very rare occurrence these days and the whole "you'll be in the dark" thing is just dramatics.

- The A/C does NOT need a separate circuit.
It must not be more than 50% of the circuit's rating, and in a small bedroom with a 6000btu unit drawing about 5 amps this is an easy thing to accomplish.

- You DO NOT want or need an IG (orange) receptacle! This is for commercial applications and is useless in a home. I will also say that I guarantee 99.9% of them installed in homes are installed improperly and are possibly doing more harm than good!

- Any load that is expected to be on more than 3 hours a day is a continuous load. VERY little in a home fits this description in the eyes of the code. There are something's that are by code required to be considered a continuous load, such as electric heat.

The last time I checked. 1/1.25 = 0.8. MommyLeah said 75%.

Thanks for the AC clarification.

Thanks all! Very helpful. For clarification here' is the absolute worse case scenerio in any given room.

450W - Computer
Lighting - 75Wx6 recessed + 1 closet 75W = 525W
AC = 1020W
Fan = 450W Max
Total = 2445W

If I just run one addition 20amp for the computer room that should do me (OK 83% of max load but I can live with that :)
Am I missing something?

I like the idea of the computer being on a separate circuit.

Missing something? Maybe? Now what happens when you plug the vacuum cleaner in? Or the TV? Just don't use the peak watts or peak HP values for vacuum cleaner calculations.

I'd place all the lighting, say 3 BR @ 525 W each on one circuit. That's just an opinion.

Sorry, I couldn't remember if it was 75% 0r 80%, so I went with the safer answer, in case no one else answered. He was so low anyway, didn't figure it mattered too much.

Quote:

Originally Posted by KeepItSimpleStupid

I like the idea of the computer being on a separate circuit.

Missing something? Maybe? Now what happens when you plug the vacuum cleaner in? or the TV? Just don't use the peak watts or peak HP values for vacuum cleaner calculations.

I'd place all the lighting, say 3 BR @ 525 W each on one circuit. That's just an opinion.

Your idea got me thinking. Since I'm doing the back two rooms then the front two rooms, what I can do is run a single 20amp put the two rooms fans and lights on that circuit. Use the existing 20amp in each room for the recepticles. That'll give me 1950 max possible on the lighting/fan circuit and 1470 on the computer/ac/recepticle with plenty room for a vacuum cleaner etc.
Sound kosher?