No 15 amp circuits

70-year-old house, everything has been rewired. But there are no 15 amp circuits which I can’t recall ever having seen before. Is this a problem?

No, it is not a problem, Tim…if the wire are 12 gauge or equivalent to the breaker.

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Ok thanks! All wiring was appropriate gauge.

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So lamps and what not won’t be over-amped?

No, not that I can see, Tim…you’re good.

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To calculate the amperage of a device, one must divide the number of watts by the volts powering the circuit. So a lamp with a 100 watt light bulb will use (100 w/120v) = .833 amps

Increasing the size of the breaker has no effect on the current drawn by the device.

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For general purpose lighting and receptacle circuits 15 or 20 amp circuits are permitted with the appropriate size conductors.

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What about a dedicated circuit such as a small furnace that only needs a 15. The size of the wire is fine, but would they either need a fuse at the furnace or change the breaker.

A 15 amp fuse is often at the service shut off.

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You’re correct, if a unit had a maximum overcurrent protection device size of 15 amps then a 20 amp circuit could not be used.

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I hear ya on that. I was worried about overheating.

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