hmmm.

Well, you can't have a 30 amp breaker and 12 gauge wire. That clearly won't work. That is an immediate hazard.

I also question if you are drawing 29.5 amps on just the air handler. Pulling that much sustained current should have tripped the 30A breaker as well as caused other problems on an otherwise 20 amp circuit.

Do you know for sure that it's pulling 29.5 amps (you metered it). If so, check the rating plate on the AH and see if your metered reading is in line with the rating plate. It doesn't sound right.

A typical residential furnace is going to be on a 20 amp circuit. You would normally have 12/2 wire, a 20 amp breaker and a disconnect switch on the side of the unit (your codes may vary).

If your air handler really does pull 29.5 amps in normal service, then you need to beat up the installer who hooked it up to the 12/2. Did they also install the oversized breaker?

The sustained draw should not exceed 80% of the circuit rating - therefore you can't run a 29.5 amp load on even a 30 amp circuit (w/ 10/2 wire and 30 amp disconnect).

Like I said, the 29.5A number doesn't sound right. Get back with us once you have checked the rating plate and if possible, metered the load.

You aren't including the outdoor unit in this are you? On smaller residential AC units that will typically be a 30 amp circuit.