how do i figure out capacity of a circuit?

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Old 11-26-11, 03:38 PM
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how do i figure out capacity of a circuit?

and how much of it is used?

my breakers arent marked very well but I want to possibly add more outdoor lighting. (possibly running new lines off the outlets) I have no idea how the outlets outdoor are wired to the main box (crawlspace is very difficult access so thats not an option to follow any wires). I'm assuming just find one outdoor breaker , mark it, and plug lights in each outlet outside to see if they are all on the same breaker?

goal here is to find low energy continuously on lighting for under my soffits, possibly LED, but not necessarily.
 
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Old 11-26-11, 04:40 PM
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You are going to need to develop a circuit directory to identify what breaker controls everything in your house. This should already have been done so that power can be shut off safely and quickly should you need to.

I would think it would be unusual for only the outside receptacles to be the only things on a circuit. Many times the outside is on the same circuit as the bathroom or garage in older hoses.
 
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Old 11-26-11, 05:35 PM
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You need to use a device to map out your receptacles. They have various names and prices range from about $20 and up.

Circuit Breaker Finders / Locators / Identifiers | Circuit Detective | Hitech Circuit Detective
 
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Old 11-26-11, 06:19 PM
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You can also do the "vacuum cleaner test" (you will not find this test anywhere because I just thought of it! )

Anyway turn everything on in your house, then plug your vacuum cleaner into the outlet you are thinking of tapping into for the lighting. If it can run for 5 minutes or so, then there is plenty of excess capacity on that outlet/breaker.

If you want to know how much extra capacity, look at the vacuum cleaner labeling. These usually say the amperage. My vacuum is 11 amps.

Note: The reason I thought of this is I used to live in an apartment which had many rooms on the same breaker. I had difficulty finding any outlets which would allow the vacuum to operate without tripping a breaker.
 
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Old 11-26-11, 06:26 PM
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Of course if you vacuum with the lights on you might have issues.
 
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Old 11-27-11, 08:01 AM
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And whether the circuit has extra capacity or not, there are some which legally cannot be extended beyond their designated areas. The circuits which cannot be extended include those that serve bathroom receptacles, kitchen receptacles, laundry receptacles, and most built-in or dedicated-use appliances.
 
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Old 11-27-11, 01:34 PM
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funny about the vac test...and i think i do have some kind of tester somewhere, just cleaned up the utility room over summer..have to check for sure..i know i never used

i think on most runs i have extra capacity because i have the microwave and geo foreman grill running at the same time, no issues..in bathroom have the ceramic heater and the hair drying running and not a blink. but without mapping everything i guess i dont know for sure what's going on outside with the outlets

i also was peeking around outside and forgot i have an outlet up near the soffit so i'm betting i can tap into that,put a photo sensor on it, run conduit, and run at least that corner of the house from there...i've started looking at out)door fixtures and most that i want are 20 watts or less. so even if i put in 10 of them (made up number) something tells me that just adding 200 watts should be safe.

i do have at least 7 spots around the house (rarely used because of the $$$ ) but i dont want to fool with that wiring and want to leave all those lights as is in case i ever need them

now if i could just isolate my neighbors central air from dimming my entire house all summer, i'd be golden lol.
 
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