Can 20 amp mini breakers be used on electric heaters

If heater calls for 20 amp breaker, yes.

A 20 amp breaker or mini 20 amp both operate the same, just gives u more room for circuits in panel box.

Chuck

Had 110 both sides and it wouldn't work! Put in standard size 20 dble and it worked!
I am stumped!

A "mini-breaker" that you describe isn't 2 pole... it's a single pole breaker with two switches. You can't get 240 volts from that. It's 2 120 volt circuits on the same leg.

Damn do I feel stupid!! Thank ypo.

If your breaker is similar to the one in the photo, a 2 pole half size breaker with the two handles tied together, this one difficlut to see the pin in between the handles, then it is the correct breaker, you just had in in the panel incorrectly, both poles on one leg of the panel.

A full size two pole breaker is fool proof, it will only install so that each pole connect to each leg of the panel.

The label on the half size breaker, if truly is correct, will state 120/240 volts, and somewhere on the breaker it will state "common trip".