ASHP drain pan control logic?
We have two Daiken Aurora one-to-one units recently installed, 12k and 18k btu. It seems that the Multizone Auroras come with drain pan heaters installed, but the single zone units do not. We are pushing the limit for our area the cold side of Zone 7 in AK, but confident that a good portion of our heat load will be handled by these units. New construction PGH. Redundant heat systems in place, so not counting on the heat from the Daikens below 0F. We have been running the units some, in temps from 0F-25F and I’m not seeing any alarming looking icing, but not experienced with these machines. A small amount of ice seems ever-present in the pan at the bottom of the coils, and some ice/water is draining out. Has stayed very consistent. Am tempted to install heaters to add robustness to the system, but wondering about the energy penalty. Haven’t been able to get an answer from our installer or distributor about how the drain pan heaters operate. Are the heaters always on below a set outside ambient temp? Only on in defrost mode? A more sophisticated approach?
Any insight appreciated!
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The logic varies. I have seen ones that are on continuously below freezing and ones that have a much more complicated algorithm with variable timing based on conditions and demand. You need to consult the documentation for your particular model. Since you already have the unit installed, I would just keep and eye on the pan and leave it as is if it never blocks up.
I've got a Daikin Aurora single-zone unit too, and in colder temps, a bit of ice in the pan is normal. The drain pan heaters usually come on during the defrost cycle to melt any ice. They don't run all the time, so energy use isn't a big concern. Just check the manual or reach out to Daikin for specific details on your model. Adding heaters for extra reliability isn't a bad idea, especially in Alaska!
Thank you for the input. Did a little more digging and still don’t have a definitive answer really. The Engineering manual is mum, so are the install and operation manuals. I see where the heater (wattage?) has a thermostat in its simple wiring. The blurb for one Daiken drain pan heater online says it’s on in defrost mode and when temps “approach freezing”. That sounds like it’ll be on a lot! Anybody else familiar with how these things work?
Adding durability to the units is paramount, but still interested in the trade offs with efficiency.