I am installing an updraft 3 ton system with the evaporator on top of the furnace. They fit nicely, but I'm not sure which front-or-back orientation the top unit should be in.

In the attached picture, the copper refrigerant lines are up front, as is the condensate drain, and they're all on the left of the unit. The 1/2" iron pipe stub-out is also on that side, as are the electrical wires. So, everything is conveniently placed.

However, the flue vent is going to go up vertically, and will be just about 3/8" or less away from the coil access panel, as well as the paper product label, and the coil access panel will be difficult to remove.

On the other hand, if I flip the evaporator unit, There's closer to an inch of clearance between flue and evaporator unit (the lips match up differently but it's a tight fit), though now the copper and condensate lines are to the rear.

I really prefer the first setup with the panel accessible. Is that OK? Do I need to elbow the flue away from the unit before I go vertical? Or should the copper/condensate go to the rear as well as the panel? Appreciate your help!

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  • I am not following your question the low pressure and high pressure lines to the evaporator look fine to me, not sure what the yo issue is this looks like an old fashion gas flue not a modern closed combustion system so I am not sure why you are concerned.
    – Ed Beal
    Oct 18, 2018 at 0:57
  • My 26 year old Carrier has 2" of clearance between the flue and the access panel for the evaporator. Even if you would elbow the flue away, it might still interfere at the bottom. Oct 18, 2018 at 1:13

1 Answer 1


Your flue is going to be a metal flue screwed together at the joints so it should be fairly easy to remove. I don't know how the access panel is removed but it looks like just a few screws and it possibly can be slid out with the flue still in place. If that's the case then when you route the flue try not to block access to any of the panel screws. I would be more concerned about the routing of the refrigerant lines because those are somewhat permanent. If you have a concern as to how close the flue can to the refrigerant lines, the wall, the drain etc. then post that as a separate question.

  • 1
    OK, got it. I've decided to add 2 45degree elbows to outset the flue from the panel. But that said, it's not "backward" correct? i.e. there's no problem with the refrigerant lines being where they are? Oct 18, 2018 at 18:45
  • 2
    Refrigerant lines are fine, they're not combustible. Oct 18, 2018 at 19:50

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