Condensate drain checks before startup

What is going on

A condensing furnace makes water, and that water has to leave the house, so before you fire it for the first time, go over the drain and trap. This is the checklist from the field install section, and it is worth doing every time. A kink or a flat spot in a hose can back water up into the collector box and trip the pressure switch, so you get a no-heat call in the first cold week. Take a few minutes now and save yourself the callback.

Likely causes

• New install on the 96V or 96MDV series, upflow, downflow or horizontal
• Replacement furnace using an old drain run
• Unit that does not have forward pitch
• Drain in an unheated area where freezing is possible

Check in this order

1. Make sure all drain hoses are secure and fully seated
2. Check that no drain hose has kinks
3. Confirm all hoses and drain parts slope in the direction of water flow
4. Confirm all clamps and couplings are tight, including both worm-drive clamps on the flue transition hose clamps
5. Confirm all drain ports not in use are plugged
6. Confirm the unit has forward pitch
7. Install heat tape on the drain if the site requires it
8. Run water through the trap before firing, and watch for leaks

More furnace guides

• Annual and start-of-season inspection
• Blower codes 66, 61 and 60 - what to look for
• Blower does not start after burners light
• Burners go out before the heat call ends / short cycling
• Canada only: derate high altitude by lowering manifold pressure
• Cement PVC vent joints