Electrical question

[DWBOX2000]

I got a heater for garage. Runs ion 220 and says 20 amps. I installed and it works fine. Question, friend told me to use 30 amp breaker. That seem right?
Thanks.

[dad911]

The breaker protects the wire not the heater. What size wire did you run?

12awg=20A, 10awg =30A

[DWBOX2000]

10 awg

[schwarz633]

While 12AWG is rated at 20A, you are only allowed to use 80% of that (16A). Your 10AWG is rated at 30A, 80% is 24A. Protecting the 10AWG wire with a 20A CB is allowed, you can always put in a 30A CB if it starts tripping.

[DWBOX2000]

Perfect thanks everyone. It will be nice to finally have heat at the hit of a switch.

[rockfan4]

Originally Posted by schwarz633

While 12AWG is rated at 20A, you are only allowed to use 80% of that (16A). Your 10AWG is rated at 30A, 80% is 24A. Protecting the 10AWG wire with a 20A CB is allowed, you can always put in a 30A CB if it starts tripping.

Expanding on this a little. I found out from our electricians at work is you should only run the breaker at 80% as well. Running higher than that shortens the life of the breaker, worst case it won't trip when it needs to.

We had a 100a 3 phase running in the low 90's. Running a row of racks in a data center. We had to get creative and feed a couple of the racks from another source.

TL;DR, if you have 10g wire, and the heater does consistently draw 20a when running, use a 30a breaker. Just because it says 20a on the label doesn't mean it actually pulls 20a.

[Bill Douglas]

80%, that sounds like a good game plan.

There are breakers designed for things like compressors which require a big current for a moment when they fire up, then not much after that. These can be handy for situations where it trips too often. Electrician said I needed one for my compressor + plasma cutter but I said no thanks as it has never tripped.

but it could work in your situation if it's tripping often.