[JandC]

So the little white plastic vent on the basement wall, that comes out under the steps on a 3400, is a return air flow? When the temps dipped into the low 20's a couple weeks ago I taped mine up because so much cold air seemed to be coming in under the steps. Furnace seemed to run fine. Temperature gauge in basement never dropped below 31-35 degrees. So I need to leave that vent open when using furnace?