Is it ok to have too little load on circuit?


Old 11-22-17, 05:04 PM
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Is it ok to have too little load on circuit?

I have a wire that was already run to my basement bathroom that is a 12-2 red wire(black and red conductor). I was going to install a heater and according to Stelpro(heater manufacturer) it takes 10w of heating per square foot of the room. So for my small bathroom, a 500w heater would be enough. Since the already run wire is a 12 gauge, I thought the breaker amperage had to match the wire size so I was thinking of installing a double pole 20amp breaker, but the heater will only draw 2.08amps(500watts/240Volts). Is it bad to have too little of a load on a circuit? Do I have too available current in case the device decides to malfunction, the breaker won' trip?
Old 11-22-17, 09:11 PM
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The minimum amperage branch circuit is 15 amps.

The appliance, etc. will draw just the amperes it wants. It is impossible to prevent all possible fire hazards that a 3 amp appliance could malfunction into if it had 20 amps at its disposal but not be a hazard if there could exist a 5 amp circuit to plug into. However all appliances, lights, etc. using less than 15 amps and with proper (usually Underwriters Labs) approval are designed to be plugged into a 20 amp circuit and it is not against code.

If you are sure that other things will not be plugged into the circuit at the same time you can installe a smaller rated breaker for example 15 amps on what was a 20 amp circuit.
Old 11-22-17, 11:09 PM
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Since that is a 240v circuit.... there is little chance of something getting plugged into it. Use a 2P15A breaker to protect the circuit.
Old 11-23-17, 05:31 AM
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Normally you match the breaker size to the wire size, but you can use a smaller breaker with no issues. A 2 pole 15 amp breaker as others suggest will be just fine.
Old 11-23-17, 04:54 PM
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thanks for the info. technically i knew it would of work with a bigger wire and smaller breaker but i was just wondering what the code says about that?
Old 11-23-17, 05:21 PM
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Code states the minimum conductor size for a breaker. You are allowed to go larger.

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