New geo compressor, continued problems
I have a WaterFurnace geo unit, installed in 2004. I've had trouble with the unit ever since it was installed. Its original compressor would get stuck, drawing immense amount of power for a few seconds (browning out the rest of the house), tripping brown-out protection which forced it to rest for a few minutes then try to start again. At times it would quit running completely.
The service tech has been responsive and helpful. Yesterday he installed a new compressor, which I am told is WaterFurnace's solution to my problem. Apparently WF had reports of the same problem from multiple customers, and have addressed it by switching to a new compressor supplier.
Since the switch, I've noticed that the geo cycles on and off more frequently -- a sign that it might be working better. Before it was as if the unit would never shut off. The heat now seems a touch warmer out of the vent too.
Two problems remain. First, the new compressor has a harder start than the old one. Even with the hard start kit, we are seeing power surges in the house every time the unit starts up. This time of year, that's about every 20 minutes. VERY annoying. The geo has its own electrical panel, and my house is rural so it is the only user of the power company transformer, capable of serving several homes. Way back when we first had compressor problems, we verified adequate wiring, connector torque, utility power supply, breaker quality, meters, etc. All was fine.
For the second problem, the new compressor is louder and has an annoying loud thunk at the end of its cycle.
Does anyone have any advice on how to improve things?
What exactly are your "power surges?" Do your lights dim for a split second? You didn't say how big a system you have, but any motor, including a dishwasher or clothes dryer can cause a brief flicker at start up. How far from your main panel is your heat pump sub-panel? Even if your wiring is adequate, the distance will make a difference with in-rush current that can cause slight voltage changes. You had the wiring checked with the old compressor but it sounds like the new one may be bigger since the unit now cycles instead of running constanly, unless there were other changes made. As for the clunk when it shuts down, that could be a number of things that are not related to the compressor. Gotta hear that one.
The power surges are the typical power drops as a massive amount of current goes to the motor. It is clearly the type of drops that motors are known to cause. However -- the geo compressor is dropping power at least 100x the next major appliance. We don't notice any power issue with the washing machine, refrigerator, dishwasher, garage door openers, etc.
On my computer's UPS I can see the voltage drops to about 85V and then spikes up to 140V, all in about a quarter of a second.
The wiring length is 10 feet from the panel with #4 stranded copper.
As for the "thunk" at the end, it is something within the compressor returning to home position, probably related to hard start.
"Thunk at the end" is a common sound scroll compressors make when they shut off. Can also sound like a brief knock and the compressor can shakes a little, then stops.
If electrical issues are 100% normal, I as the tech on the scene would next look over the refrigeration cycle. There could be somewhat of a restriction on the discharge side of the compressor, the system could not (or does not) equalize during the off cycle, system is running a high head pressure in heat mode due to airflow problems, etc. No way to really tell without going through it.
Also, did the tech who changed the compressor sweep the lines with nitrogen while brazing and pull a 500 micron vacuum that held prior to adding back the refrigerant?
Building Physics Rule #1: Hot flows to cold.
Building Physics Rule #2: Higher air pressure moves toward lower air pressure
Building Physics Rule #3: Higher moisture concentration moves toward lower moisture concentration.