I have discovered that my recently installed mini-split is still consuming electric power when it is turned off. This is a 12k btu cooling only TGM mini-split inverter. I noticed that it seemed to be using more electricity than the similar mini-split that it replaced, and I thought that was strange given that both units have the same SEER rating of 21. So I started measuring loads on the circuit with my amprobe. What I discovered is a constant 24/7 load of 0.27 amps on each leg when the unit is off. This is with the remote set to off, air deflection vane in the closed position, no evaporator fan, no condenser fan, and of course no compressor load. I was measuring the load at the breaker and although it is a dedicated circuit, I thought perhaps there might be something else that I don't know about tapping into the circuit. So then I measured the load at the condensing unit and got exactly the same reading – 0.27 amps on each leg with everything off. In my opinion this 24/7 load is not an insignificant parasitic load that would normally be necessary to await a signal from the remote. And by the way, the other mini-split in my apartment is an older single speed unit that draws 0.0 amps when I select the OFF button on the remote. Yet it still responds instantly when I send a signal from the remote to turn on. Any new theories as to what is going on here with my new mini split? I have had this new unit for less than a month, and I am wondering if there is a defect.
Mini-spit AC unit consuming electric power when off
mini-split
Related Solutions
I can't speak to this specific unit, but in general forced air HVAC systems have two modes for fan:
Auto = Fan runs whenever the heat or air conditioning is running - i.e., to circulate the hot or cold air
On = Fan runs all the time.
Most often I see "Auto". Occasionally people prefer "On", especially in the current pandemic as constantly circulating air means it passes through air filters more frequently. (On the other hand, most HVAC air filters aren't all that great and it also means you circulate the germs...so who knows what is best. As with so many other current "recommendations". But I digress.)
Arguably, fan "On" in cooling mode makes sense as circulating air, even if it is not "cold", helps you feel cooler. Same idea as ceiling fans, though less forceful.
Anecdote time:
I had a commercial customer (computer hardware/software, not HVAC). They got a new HVAC system with a fancy thermostat. They ran a nearly 24/7 operation, at least from 4:00am Monday to 6:00pm Friday - sales & accounting during the day, order processing/shipping through the night. They wanted the fan "On" all the time. The HVAC people tried but couldn't figure it out even though that was their job.
I read through the Chinglish manual and figured it out. The thermostat wanted to divide every day into "occupied" and "unoccupied" times. During the occupied times, fan On vs. Auto worked as desired. During the unoccupied times, the fan would always be in Auto mode. That actually made sense for a typical user - if you have substantial time where a building is unoccupied, it makes sense not to run the fan since nobody is there to appreciate the cooling effects (in the cooling season) and/or just not have the air feel "stale".
The solution: Set the unoccupied times to 2 15-minute intervals (e.g., 7:00pm - 7:15pm and 8:00pm - 8:15pm) and the rest of the time (23-1/2 hours a day) the fan would stay on as desired.
Those two 50A single breakers need to be handle-tied, or replaced with a 50A 2-pole breaker. You can't have two singles on a 240V load like that.
The empty breaker space at bottom left should be filled with a proper UL-listed thing. They make blank filler plates, but I find them flimsy and expensive. I just use actual breakers, a CH120 is around $5.
(1) reusing the existing (6 AWG aluminum) wires from the 30-amp circuit to service a new heat pump with a dedicated 25-amp replacement double-pole breaker
Yeah, that plan is fine. Use "MAC Block connectors" to splice from the #6 aluminum to whatever other wires (Al or Cu) you'd continue with.
Note that since the #6 aluminum run does not have a neutral, they must be 240V-only heat pumps. Cannot use bare as a neutral.
You may find it challenging to land #6 wire on a 25A breaker.
(2) reusing the wires from the two 50-amp circuit to service a 100-amp subpanel to serve future wiring projects
Waii--what???
OK, you see that dual 30A and you immediately get "This is a 30A 240V circuit".
But then you see those two 50A singles and for some reason you think that isn't the same exact thing. It is the same exact thing, but somebody left off the mandatory handle tie so it looks weird.
So think of it as a 50A 2-pole breaker.
The problem is, the existing #4Al cable has only 3 wires and cannot supply a 120/240V subpanel.
- You need the bare wire for safety ground. This isn't 1963, you need a ground wire.
- Because it's #4 or larger, you can get neutral by re-marking one of the black wires white with tape.
- That leaves you 1 wire left to use for "hot", and that means the far panel can only be 120V.
The good news is, the SE/XHHW cable is allowed 75C temperature, so it can be provisioned to 65A and use a 70A feed breaker. There is no such thing as a 70A/1-pole breaker, so you will need to either re-use a 50A, or obtain a 70A/2-pole and use only one pole of it.
Best Answer
Your old system did draw current but your measurement equipment was probably not sensitive enough to measure it. If there is a remote to control and activate the system it has to have some power to do this.
Your new system being an inverter based system is also always drawing power the control buss is usually powered up to maintain the charge on the capacitors if it is powered down it will take an average of 30 seconds up to 3 minutes to deplete this charge and to wake the system up takes longer than when in standby and is harder on the electronics.
Where your new system will out preform a single speed system is it can maintain the coolant/ heating levels without starting and stopping all the time but running at a slower rate using less energy overall.
So yes your inverter based system is probably drawing 270ma but this is how that technology works just the elimination of a few hard startups a day will more than compensate for the small draw when not in use. And your equipment was not sensitive enough to measure the 15-20 ma of Curren draw in your old system if the remote can turn it on there is current being consumed.