I am installing a new base board heater - 1000 watts. I have run a new 12/2 line to a 15 amp breaker that is the only thing on it. The room is 50 sq/ft and remains very cold. If I feel the top of the basebord heater it never get hot, it will get a little warm but that is about it. What am I doing wrong?

Did you hook it up to the correct voltage. Some are 120 volt others are 240 volt.

The heater is a 240 volt.

Again we must ask, did you hook it to a double pole 240 volt breaker?

Two wires must go to the same breaker, but sometimes that doesn't work either. Verify two wires to the same breaker.

If your heater is 240 volt like you say it is you will need a 240 volt breaker. They are usually two 120 volt breakers attached together at the factory with a tie bar so that both breakers will activate at the same time or trip at the same time in case of a short. They are sometimes called two pole common trip breakers. When all is said and done you should show 220/240 volts on your meter at the heater feed terminals. MAKE SURE the bare copper or green wire is grounded to the heater and at the grounding bar in the house service panel.