Water under furnace [pics inside]

pringle12345July 7, 2011

I noticed a small amount of water around the front/side of the furnace, so I opened the bottom panel and found rusty water pooled in the bottom. I opened the panel right above that and found the gas burners. I tried to open the panel right above that (right behind the exhaust flue) but I wasn't able to pull it out. I was able to get all the screws off, but the panel wouldn't slide to the side or forward. The lip of the flue, from the furnace, was blocking the panel from coming forward. In any case, is this the panel I should be trying to open in an attempt to check for a drain problem?

Should I be investigating the pvc drain pipe instead?

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The typical and simplest answer to this would be the condensate may not be draining or not draining fast enough. The tray the evaporator coil sits in could have gunk blocking the drain hole or, the drain tube itself could be clogged. Maybe not fully, but enough that the condensate does not drain as fast as it is produced.
From there, it gets a little more complex. The pan can have a hole through it. The coil could be icing up due to low charge or restricted air flow from dust or the wrong type filter and, as it melts, pieces drop off outside the pan and melts in undesirable places. If the coil is dusty, the condensate may not drain down quickly enough, it builds up and the fan could be blowing condensate along the inside walls of the plenum and it runs down inside. Insulation may be needed because of a sweating plenum although yours does not show those signs since there would be more rust on the outside. The list goes on.
I personally feel yours is a simple issue and it is the most common. If you take the drain tube loose and run a small round brush into the drain hole at the pan, you'll likely get a rush of water and gunk so, have some towels or a shallow pan of some sort under the outlet. Blowing through the tube will give you a good indication if there is gunk in there, usually at the trap (bend in tubing). The gunk is dust that builds up over time, you can't avoid it even if you keep clean filters. This will solve the problem most times and, if this is the case, you'll need to get into the plenum and carefully clean loose material out of the pan. This would be a good time also to check the evaporator coil and give it a cleaning. As a DIY project, just do the best you can and that will do the trick for some years most times. A trained person with the right equipment might do a bit better.

That looks like an inspection panel behind the flue and should come off, giving you pretty good access to the coil, the drain pan and the drain outlet.

    Bookmark   July 7, 2011 at 9:43AM
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