Circuit capacities

Old 06-17-17, 01:22 PM
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Circuit capacities

Hi everyone,
Just wondering what the general rules or good ideas there are for loading each circuit in a house.

For instance, I read that you should count each duplex outlet as 1.5A and keep the total under the breaker rating for that circuit.

When does an outlet or fixture need a dedicated circuit? As in, my dishwasher outlet has a dedicated 15A circuit which makes sense because I wouldn't want to trip the breaker every time I turn on the vacuum while the dishes are running.

I ask because I want to use a 3.4A attic fan but there's no room for a dedicated circuit. Am I asking for problems wiring this into a circuit with 6 outlets, for example?

Should I use the operating amperage with a safety factor for these calculations or is there another spec I can refer to for a given fixture?

Thanks for all your input!
Old 06-17-17, 01:51 PM
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General rule is if a fixed in place device uses more than 50% of circuit capacity the circuit needs to be dedicated. A 3.4 amp load can share a circuit.
Old 06-17-17, 02:24 PM
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Code only required the circuit to be able to handle the load to be served. When calculating unknown loads, such as general receptacles in a house, you figure 180va per outlet.

I see no reason you can't add the fan to your existing circuit as long as it is not a dedicated circuit, or a circuit that is required to serve specific locations, such as the bathroom or kitchen circuits.
Old 06-17-17, 02:58 PM
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The 1.5A load is more for sizing the service, not circuits. Residential loads are typically transient and also lightly loaded.
Old 06-18-17, 07:48 AM
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You can have a workbench with 10 outlets spread out on a power strip and would typically only use one or two at a time. (Single circuit OK.)

Or outside outlets around a house. Might only use one at a time for say an electric lawn mower. (Single circuit OK.)

But the outlets in a kitchen might have many in use at the same time. (Multiple circuits better.)

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