Air handler in attic space
I live in a condo in Chester, Va. We have 139 units. Most are all 3 years old or less. The air handlers are in the attic. Last winter we had 35 homes with condensation lines that froze when the the temp dropped. I disconnected the condensation line and had the water draining in a bucket but had to empty the buckets ever 4 to 6 hours. We called the builder and the a/c installer. They were told to go to new properties in other new neighborhoods under construction and get the pieces off those air handlers to fix ours. The builder then parted ways with the installer. I’m concerned about the other community that was effected by this. Any suggestions.
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First of all, can you tell us your name? (I'm Martin.)
The obvious point here (which we often mention on GBA) is that HVAC equipment belongs inside your home's conditioned envelope, not outside.
For more information, see these previous Q&A threads:
"Frozen condensate overflow line"
"How to deal with condensation in a cold attic furnace?"
One possible solution to your problem -- one that isn't very satisfying from an energy use perspective -- is to wrap your condensate drain with electric heat tape.
A thermostat activated heat tape is probably the best solution, with insulation wrapped around the tape and the pipe. It shouldn't cost much in energy use, as the attic temps will rarely drop below freezing in your location. It's just those few days a year that get really cold when the heat tape turns on and warms the pipes.
You also need to be careful of the furnace trap. Most condensing furnaces have a condensate trap that keeps conditioned air from blowing down through the drain pipe. This trap is roughly rectangular, and in most furnaces I've seen it is gray plastic. It is located inside the furnace cabinet, but not in the heated section. I see these freezing and splitting more often than the drain lines, and it is more difficult to wrap them with heat tape. I haven't yet seen a good solution for keeping these warm.
I agree with the other comments about using a thermostatically controlled heat tape as being the best option. Insulating the line would also help, since the condensate is a little warm when it exits the furnace (it’s a combustion byproduct after all). Regular pipe insulation over the condensate line will help it to stay warmer so it will have to get colder outside before freezup is a concern.
A larger diameter line will also limit freezeup, but won’t prevent it and may be difficult to install. I’d try insulation and a heat tape.
You can move the trap into a warmer area. I have one mechanical contractor I work with that doesn’t install traps on outdoor equipment (which would include attic equipment in this case) due to the problem with the traps freezing. As long as your condensate line is airgapped somewhere the trap isn’t protecting you from sewer gases anyway (although the concern for conditioned air leaking back might remain).