Hi.

My brand new Goodman furnace blowing lukewarm air.
It works fine otherwise, but since day one I noticed that it blows longer than old one use to work, and always blows lukewarm air. Gas burns fine with typical noise, chimney pipe EXTREMELY HOT, but supply duct almost cold right after furnace. I have ho clue where the hot air disappears. As it all some how goes into chimney and only some return air somehow bypassing the furnace itself and being blown back to the house. Please anyone if you have any ideas. I should have pay attention earlier since it does it since the winter started. But I was just postponing taking care of it. Until I saw on the bill that it burns twice more gas as usually... Because it takes long time this way to satisfy thermostats request.
Thanks in advance.

The furnace needs professional On Site burner setup. Whoever did the install did not do all the setup necessary for a new furnace. Hopefully this person has all the special tools needed to do a proper job. Pay close attention when they check the gas pressure and also set the blower air over the heat exchanger for correct temp rise. You paid to have your job done correctly so call back the installer and tell them to do it correctly.