Electrical question
 

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.

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

12awg=20A, 10awg =30A

10 awg

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.

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

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.

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.