I have a high efficiency furnace (tempstar) installed in an older (1972) ome and wonder if i can use the combustion air vent for the fesh air intake? Also, since installing the new furnace and finishing the basement the current fresh iar intake vent has been frosting and drippng into the basement rooms. If i need the fresh air intake how do i stop it from frosting and dripping??
You have 2 plastic pipes, 1 for combustion air and the other for exhaust and they MUST be left alone. You can insulate the combustion air pipe with pipe wrap if it sweats. The old 5-6" combustion air pipe may be needed for the gas water heater if you have one. If not you can convert it to a fresh air pipe to the return duct and put a damper in it. I recommend a motorized Hoyme damper to allow the air thru it only when the heat is on. Post some pics of what you have. Where do you live?