Furnace short cycling at set temperature
I badly need help diagnosing a two year old split system that is causing me to lose sleep. And money.
I have a 850sf ranch house, insulated w r15 batt and foam insulation r36 in the attic rafters.
I have a 2ton outdoor scroll compressor w TXV and an indoor heat pump and blower.
I have recently noticed (since the compressor sits outside the window by my bed) that the compressor is making a loud noise when running at night (in the 30s and 40s here). Upon further study, I am realizing that it is bot short cycling (running less than ten minutes and restarting in less than a minute) and also running for twenty minutes or so, but also then stopping and restarting in less than a minute of compressor shutting off. Sometimes the blower has time to shut off first. Sometimes it starts again so fast it just stays on.
The compressor isn't always this noisy. But is more frequently so at night when it is colder out.
The entire time this phenomenon is occurring THE INDOOR TEMP MATCHES THE SET TEMP (tonight it is 68. Last night it was 70).
I mean if it is cycling 3 or for times in an hour, running for the entire hour with 60sec (or less) stops ... The entire time the set temperature = the indoor temperature.
The service tech has been out twice. Once in January. Once yesterday.
In January the tech removed 3.5 pounds of refrigerant after hooking up a dual gauge to the compressor and taking a reading of 600 (should have been 450 to 500). This company was actually called out by me after I realized the company that did the original install was incompetent and lying to me. Trusting them, and not sure what was wrong now, I called them back again. He came today. I was worried that they had removed too much refrigerant. This time he took static pressure and got the cfms and several other measurements using the thermocouple and duct attachment. He said the previous tech definitely got the refrigerant within range and that the original installers must have severely overcharged the system. He said the cfms were low but at threshold of acceptable. Think he said 358. Threshold was 350?
He persuaded me to leave it there since it would be less humid in summer if all else was okay. But looking in to other possible explanations for this phenomenon, it seems like the most plausible is cfms being too low.
Possibly exacerbated as of late by my switching air filter types to pleated, and it took me a while to notice?
Oh. And he replaced the thermostat today to rule that out as well.
But the noise. Sort cycling. And odd restarting nearly immediately continue.
All while the thermostat constantly reads that the indoor temperature is at the set temperature.
This last part I CANNOT understand.... If the thermostat is showing the indoor temp,to match the set temp WHY IS THE FURNACE RUNNING FOR NEARLY A SOLID HOUR?
This is what I noticed when I got in bed tonight around 12:56am
12:56 running loud
1:04 cycled off
1:04 (+30sec) Cycled on
1:14 cycled off set 68 at 68
1:14 and 40 sec cycled on
1:45 cycled off set 68 at 68
1:45 and 30 sec cycled on
AT 68 for entire 45 minutes of observation
Loud the whole time as well.
ANY THOUGHTS PLEASE???