Wiring and CB overkill

I am wiring an air-spa tub in the master bath. The instructions require a 120V/15 amp GFCI. I have some leftover 10-2 that has been sitting in the garage for three years that I would like to use. I know it is overkill but is there any problem with using 10-2 and a 20 amp GFCI breaker for this application just to avoid buying a new roll of 12-2?

Thanks
Kim

Nope, other than being harder to work with. Actually, you'll save power, but it won't be measurable .

I don't think you should use a larger breaker than specified. Breakers are sized to protect the component, and in your case,they should "pop" if 15 amps is exceeded. As pointed out, other than difficulty in working with the heavier wire, there is not reason not to use the 10 gauge.

You can use heavier gauge wire to make a connection than the minimum, you just can't use a lighter gauge for a heavier load than the requirements. I've heard some places require 12g for a 15A circuit...and it isn't a bad idea if the run is quite long.

So long as the wire is used for the entire circuit on that breaker and not mixed with other sizes of wire. (Breaker to outlet(s).)

There can be a potential safety problem if mixing wire sizes on the same circuit, especially if there is a hidden lower gauge segment of wire somewhere. Someone comes along and sees 12 ga. at the breaker and at the outlets then switches the breaker from 15 amp to 20 amp. Well that would not protect the "hidden" segment of 14 ga. wire he could not see!