coolguy4
13-08-2021, 04:08 AM
Hello everyone, nearly 3 years ago I installed a Pioneer 12K BTU 22 SEER inverter driven mini split heat pump in my living room and overall the performance has been quite impressive for the price in both cooling and heating modes and it is extremely cheap to run. However, ever since I installed this unit, I noticed that it seems to perform better the hotter the outside temperature is.
Where I live, I see temps of up to nearly 100 degrees F with very high humidity. This unit has never had trouble keeping up during the hottest part of the day either, the temp in my living room rarely goes over 73 degrees F with the unit maxed out. Oddly enough, where the unit struggles is in the evening when the outside temperature starts to drop to below around 80 degrees F. The evaporator's delta T drops from up to around 26 degrees F in the afternoon heat down to around 16-17 degrees F when the outside temp drops and my living room sometimes gets up to around 78 degrees F- Not much cooler than outside temp, but certainly much drier.
So my question is what could cause the unit to perform well in hot weather and somewhat poorly in moderate-warm weather. As a test, one evening I tried partially blocking the condenser airflow with cardboard to raise head pressure, simulating hotter weather to see if the delta T would increase back to normal. Doing so lowered the delta T. I then wet the coil down with water, which slightly increased the delta T. This would seem to suggest that the issue isn't mechanical, but perhaps something with the controls.
I'm thinking the controls may have some type of issue or flaw that causes the compressor to slow down when the outside temp drops even when the inside temp is still much higher than the setpoint. I tried to test this theory by heating the ambient air temp sensor on the outdoor unit with a heat gun as an attempt to trick the unit into thinking it's hot outside to see if the compressor would speed up and start working better, but heating the sensor made no difference. However, since there are other sensors such as for compressor discharge temp and coil temp, my simulation wasn't perfect.
Anyways, I'm really looking forward to hearing your input on this one. Thanks in advance as always!
Where I live, I see temps of up to nearly 100 degrees F with very high humidity. This unit has never had trouble keeping up during the hottest part of the day either, the temp in my living room rarely goes over 73 degrees F with the unit maxed out. Oddly enough, where the unit struggles is in the evening when the outside temperature starts to drop to below around 80 degrees F. The evaporator's delta T drops from up to around 26 degrees F in the afternoon heat down to around 16-17 degrees F when the outside temp drops and my living room sometimes gets up to around 78 degrees F- Not much cooler than outside temp, but certainly much drier.
So my question is what could cause the unit to perform well in hot weather and somewhat poorly in moderate-warm weather. As a test, one evening I tried partially blocking the condenser airflow with cardboard to raise head pressure, simulating hotter weather to see if the delta T would increase back to normal. Doing so lowered the delta T. I then wet the coil down with water, which slightly increased the delta T. This would seem to suggest that the issue isn't mechanical, but perhaps something with the controls.
I'm thinking the controls may have some type of issue or flaw that causes the compressor to slow down when the outside temp drops even when the inside temp is still much higher than the setpoint. I tried to test this theory by heating the ambient air temp sensor on the outdoor unit with a heat gun as an attempt to trick the unit into thinking it's hot outside to see if the compressor would speed up and start working better, but heating the sensor made no difference. However, since there are other sensors such as for compressor discharge temp and coil temp, my simulation wasn't perfect.
Anyways, I'm really looking forward to hearing your input on this one. Thanks in advance as always!