How to slope air intake tube on sidewall venting job??

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alanmuller
alanmuller Posts: 2
in THE MAIN WALL

It's usually given clearly that the exhaust should be sloped back to the appliance. I've done the same with intakes. But recently I encountered a job where a good bit of intake tube condensate was running into the furnace where it clearly did not belong—soaking the gas valve and wetting down wiring. The intake runs through about 4 feet of cool basement and

I'm thinking that warm humid outside air is getting drawn in via the house ventilation fans. This system has been in place for over ten years without this problem being observed before.

I could rework the intake tube to slope away from the furnace but should this be necessary? seems to me it should not be unless there is a defective heat exchanger.

Any advice?

Comments

  • pecmsg
    pecmsg Posts: 7,613

    how are you drawing in air in a sealed system?

    If the heater is not running no air should be moving between the intake and exhaust.

    Is the heat exchanger compromised?

    alanmuller
  • JUGHNE
    JUGHNE Posts: 11,644

    I usually put a wye clean out in the horizontal pipe near the furnace.

    The plug points towards the furnace and down. Then drill a couple of 1/4" holes in the plug. Any moisture flowing toward the furnace will collect there in the angle of the wye and drip out as an indicator.

    Also this plug is only finger tight and can be removed temporally to allow inside air for combustion if the inlet is closed up for any reason. Also to test the inlet pipe for blockage.

    mattmia2alanmuller
  • Mad Dog_2
    Mad Dog_2 Posts: 8,746

    Every manufacturer could have different requirements, but I prefer to keep air intakes pitched away from unit to keep the water from a down pour and even snow away from the unit. Mad Dog

    Consulting by Mad Dog & Matt Jr.
  • alanmuller
    alanmuller Posts: 2

    Thanks for the suggestions. I'm wondering if a dry (from evaporation) condensate trap might not create a cross-connection. I like the idea of pitching the intake piping away from the unit, thought in the case of this job, with low clearance, it might be difficult to implement. Sometimes people do turn a hose on the air inlet fitting. I can put a wye or combo in the intake lines as suggested. This has been an interesting experience and I'm still not convinced I understand what's going on…..

  • Kaos
    Kaos Posts: 989

    Some units require an intake trip leg. Should be easy to add.

    image.png
    PC7060

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