Mini Split Efficiency Test
 

Hey guys, long time lurker, very infrequent poster. Had a new Bryant (Midea best I can tell) 18k single high wall indoor unit minisplit installed a few weeks ago. Rated to heat down to -20F.

This is to take the place of electric baseboard heat which was the sole heating method of my 700sq ft single story home. So far we’ve had nights into single digits and no problem keeping at 68 inside.

My efficiency question comes with indoor fan speed. Can someone with an energy monitor see if running the fan at high speed results in less energy use than letting it run in auto? What I’m trying to figure out is if compressor speed stays the same and I end up with a lower delta T between evap and condensing temps.

Ive noticed my idu supply air temp does descreaae if I turn the fan from auto when it’s running at a low speed, to high, but I don’t have the equipment(power Monitor) to determine if there’s a bottom limit to that temp before the compressor ramps up to maintain a certain supply temp, or if it doesn’t care.

Side note can anyone reccomend a low cost 230vac power monitor? I’d like something with logging so I can see a graph of power use. Anyone built something like this themselves?

Mine are inverter Mini splits and they use less energy in auto.
The compressor is based off how far you are away from the set point not the fan speed.
I have 3 9K units and one 18K duel head unit.

Any idea why they use less in Auto? Do you think it’s just the extra fan power use on high or something to do with condensing temperatures being different?

Also what equipment do you use for current/temp logging? I’d love to do some of these tests on my own.

I use TED
TED The Energy Detective
but I have it to monitor solar power. It is to expensive for just a appliance.

Yes it is just the fan using more power.
Mine have a turbo mode that well turn the fan to high and make the mini split ramp the heat way up. It also uses lots of power so I really don't use it.
I use it for cool in my office once in a while my office gets full after noon sun.

If you have a quality unit - heating down to -20 seems to indicate that - the fan speed is gonna do much effeciency wise. The fans watts usage will be little difference.
Auto is just the units best guess to keep you comfortable with the amount of heat it has determined is needed.


For measurment, make sure you are measuring actual billable usage that is PF corrected. The compressor will be all over the place in PF, but residential users don't have to pay for that.