What could cause excessive condensation drainage from the heat pump

heat-pump

I have a one-year-old heat pump in my attic that is producing substantially more condensate this summer than it did last summer (and last summer was hotter!).

There is a drain pan that is often full of water, and very frequently drains right onto my front porch two stories down. We didn't have any problems like this at all last summer, or any time this summer until about a month ago.

The floor is dry underneath the heat pump and the drainage line, and it doesn't look like there are any leaks anywhere.

I would have thought a full drain pan would indicate a clogged drainage line, but the symptom that made me notice the problem at all is the excessive drainage from that drainage line, so it looks like that's not the case either.

Best Answer

first, if you have an air conditioner in your attic, then there should be TWO drip pans, and TWO drain lines.

  • one of the drip pans should be built in to the air handler/coil unit
  • the second drip pan should be at least as big as the entire air handler and coil unit, and positioned under the air handler to provide coverage for the entire unit
  • both pans should have INDEPENDENT drain lines
  • ideally, the second drip pan should have a float sensor unit it to shut off the system BEFORE it overflows.

either drain should be able to completely empty whatever amount of water you have in the pan within seconds. if it can't, then you have a clog somewhere.

also, the large drip pan below the air handler should typically be completely dry. it's there as a backup in case the drain line for the air handler clogs up. if you have any amount of water in there, then you have a problem somewhere else.

so, than being said, do the following:

  • verify that both the air handler and the external drip pan have independent drains
  • get a wet/dry shop vac and suck out both drain lines
  • pour bleach down both drain lines
    • if you don't have a way to pour bleach down the drain connected to the air handler, make one. a simple way is to cut the existing line at a vertical run, splice in a T, then make an L shaped piece out of some tubing and an elbow. leave the top part unglued so you can remove it. see drawing.

drain line with a T splice for cleanout

  • test your newly cleaned drain lines. remember, both drain lines should be able to quickly remove any water you pour in them. if they drain slower than your bathroom sink, you have a clog somewhere.
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