I recently had a new Carrier furnace installed. I have propane for gas. I cannot tell if the installer converted the furnace to propane, as I cannot find a sticker saying the unit was converted. What would typical symptoms be if it was not converted (noise, etc.). Thank you.

To main things have to happen to change it over. Gas pressure regulator spring needs to be changed and adjusted from 3.5" W.C. to 14 "W.C.. The orifices that feed the burners will also have a smaller opening. If he did the gas valve spring right he should have changed the old chrome cap to the LP black cap. I don't know an easy way for you to find this out. But if he didn't do something right the furnace will light hard, possibly with a boom, or when the burners are on it will be very nosey and the temperature rise will be to great. Call the company back, tell them you want it double checked and the sticker signed, dated and put on the gas valve like he should have done.