I'm investigating installing a central air system and in doing so it was brought to my attention that my high efficiency furnace may not be installed properly. I'm in a narrow semi without much clearance and they vented the furnace out through the roof a couple of years before I moved in.

There's a pump off the furnace that pushes the condensation into my drain, but no drain line off of the pipe itself. Is this set up ok, is there something I can do to retrofit this, or am I looking at major work here?

vented out the roof

  • 3
    You need to find the model number of your furnace and consult the manual. It will tell you what the allowed installation conditions are.
    – longneck
    Jun 3, 2020 at 0:28
  • Yes, can you give us a make/model and/or nameplate photo for the furnace please? Jun 3, 2020 at 0:55

1 Answer 1


All of the units I have installed the condensate in the exhaust drains back to the firebox and drains with that condensate. The pipe if run horizontally is supposed to have a slope. So I do not see a problem. Adding an ac coil or evaporator should not affect the heat system exhaust unless it needs to be re routed you can add the ac drain to your condensate pump but I would install a sensor to alarm if the pump fails. So you know because both systems can make quite a mess when the pump fails and they do fail.

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