Minisplit Efficiency
Hello, we have 2 minisplits one upstairs ,one down. We use them steady on the heat setting in the fall/ winter. In the summer we are mostly at the cottage and come back into town about once a week to look things over and do lawn care. My question is… for energy savings for the 3months of the summer what should we put our units on Cool, dry or auto? We dont want to burn energy for no reason. Also help keep the power costs down. One more thing, when we switched from heat to cooling the units eventually blow out debris like dirty flakes? I just cleaned everything last fall? So I want to know what the most cost efficient setting for our house would be? Why the flakes? Temps in the summer are around 27-35 C for a couple of months.
Thank you!
Ian
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Don't use auto or dry!
Dry = run the compressor all the time. (at least on mine - great for drying out the house though)
Auto = you may be switching back and forth between AC and heat. Just cool with a high set point is typically best. If you can increase your dead band that will cut your costs.
Leaving wall mounts cooling unattended for a long time is aking for trouble. The drain eventually clogs (seems to be about 5 years) and they will leak water. So the best setting for them is off while away. There are many smart options for these to be able to turn them on remotely so you don't come home to a hot house.
The flakes are probably dirt buildup on the coil. When you start cooling, the condensate will dislodge them which is probably what you are seeing.
In the summer, I'd turn off the mini-splits and leave a dehumidifier running. Probably on a timer - since 24x7 low humidity isn't needed to prevent mold.
Jon, how many hours/day do you want to dehumidify?
It's really only however many hours it takes to bring the RH to under 60% with some margin. In a tight house with very low ventilation rates when unoccupied that won't be very many hours at all- often zero hours, for many days on end in most locations.
In some locations/climates modest amounts of ventilation would do it, without any use of compressors.
Yeah, I'm in Coastal RI. Right now the DP is over 65, 90% humidity outside. It takes a while to get it below 60% inside.
Unless well shaded, houses in the summer time can get a bit hotter than outdoors. Even with a 65 outdoor dewpoint, you only need the house to get to 80F to have less than 60%RH indoors.
So the best is not to condition the house, let it get hot and run a dehumidifier. The extra heat from the dehumidifier is a good thing in this case.
Conditioning the house is wasting energy. Most likely it will not reduce the RH low enough if the thermostat is set to typical away settings. This is especially problematic with finished basements.