Built Right Heat Pump Run at Variable Wattage?

[athflying]

When the heat pump kicked on today, it was running at a slightly lower wattage than yesterday. I just recently started monitoring energy consumption of it via an Emporia Vue. It usually is right around 5.7 kwh but today slightly lower at 5.4ish but then it did something I haven't seen it do before....it dropped down to 4.7ish for a few minutes before essentially turning off. The fan is still running and the pool is not to temp, however it seems to not be heating at the moment. Putting my hand over it, the air exiting seems to be about the same as ambient temps, not the cool air I would expect.

The only thing I changed today from prior days is to run my pool pump at 2200 instead of 1200. Not sure if this is some type of cycle it does or it's a bigger issue. I was always under impression it was either on or off, no in between or variable state.

 

[athflying]

Called Built Right and it is either on or off, so for fan to run and not generate heat, something wrong. They coming out Wednesday to look at it.

Nice thing, because of the Emporia I knew an issue immediately.

 

[athflying]

Turned breaker off Monday to heat pump since it wasn't working. Turned back on this AM in preparation for service call and it kicks on and it's heating. Let it run for 2 hours and heating as expected. Only thing I noticed, it's still running at a slightly lower wattage. Here are 3 screenshots. First shows running at about 5.8 kwh, then the middle it's running slightly lower then stops heating and just fan running, last one what it's running today around 5.4 kwh. This is a dedicated circuit with just the heat pump on it.

Any thoughts on the difference in the amount of power it's using? I cancelled the service call since it's a $95 charge if no issues are found a d it appears to be running as expected now.

 

[athflying]

So today confirmed that my heat pump runs at a lower wattage when the pool pump runs at a higher speed. See attached but when pool pump slowed down to 1200, the wattage used went up? Is that expected??

The first is the pool pump slowing down and dropping it's wattage used, second is the pool pump increasing wattage used.

Only other thing I can think of is how Emporia is reporting the usage but they are 100% on different circuits.

 

[ajw22]

With lower flow rate the water stays in the heat exchnager longer and absorbs more heat and has a higher exit temperature.

I think the HP has some internal heat sensors and is varying the speed of the compressor or fan based on the internal heat it senses. When you change the flow rate you change the internal temperatures the HP controls.