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tomgoe, HVAC Technician
Category: HVAC
Satisfied Customers: 1645
Experience:  32 years servicing HVAC equipment
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I have a Trane high efficiency furnce model XE-90. Im getting

Customer Question

I have a Trane high efficiency furnce model XE-90. I'm getting condesate from the combustion blow backing-up and leaking out of the furnace. I cleaned out the condensate drain all the way from the furnance to the floor drain. It is clear and drains well. I removed the seal leg trap that collects the condensate from both the blower and the furnace heat exchanger. I cleaned this out as well. I did not reinstall this yet. In the interim, I connected the blower and heat exchanger drain tubes directly into the drain pipe, but there still is water back-up from just the tubing going into the drain tube. Water still is backing up and leaking. Can there be another problem other than the plugged or restricted drain tube?
Submitted: 8 years ago.
Category: HVAC
Expert:  tomgoe replied 8 years ago.


If I understand you correctly you have bypassed the trap. This condensate water is in the "negative pressure" side of draft blower. In other words with draft inducer running it is pulling air up this tube and keeping the water from running down it, that is why there is a trap . Water in the trap prevents air being sucked upwards and lets water drip downward. Reinstall the trap and see if you still get a leak

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Customer: replied 8 years ago.


I have a seal leg using the tubing coming off of the draft blower before it dumps in the drain. This seal leg is about 1-2 inches. How much of a seal leg do think is required to seal overcome the negative draft pressure? I do not have a seal leg on the condensate draining off the heat exchanger. How much of a seal leg is required for that one? I will resinstall the factory supplied trap, but I would like to know the above answwers in case it fails. I would then build my own seal legs from 3/4 inch plastic pipe.

Expert:  tomgoe replied 8 years ago.
It only has to be large enough to hold water. For instance if you are using 3/4 pipe - use two 90's and two street 90's to make a small trap