A different kind of compressor

 "Anyone can build a bridge that will stay up.  But it takes an engineer to build a cheap bridge that just barely stays up." - Unknown

 In 2017, we had a new heat pump installed, after the previous one had suffered several different types of failures - Start Capacitor Failure, Refrigerant Leak and compressor overheat, capacitor melt-down, which also ruined a control board.  The refrigerant was an older type that cost three times what newer refrigerants cost.

At the same time the heat pump was replaced, we also had the backup heat source replaced.  The original 240 volt, 80 Amp (19 Kilowatts!!!) electric furnace was replaced by a propane furnace.  In the coldest months, the heat pump wasn't usable, and we would rely solely on 19 Kilowatts of electric resistance heating in the central air duct for home heating.  The electric bills were astronomical, so it was time to revamp the system.

When we switched over to propane for back-up heat, I had to purchase and fill a 500 gallon propane tank, and then dig a trench for a line to carry LP gas from the tank to the house.  Housing code called for 15 ft minimum distance between the house and the tank, and I set it out about 50 feet.

Below:  New propane tank, new heat pump unit against the house, and a freshly filled in trench where the underground propane line runs over to the house.  That's a wasp trap hanging from the tree above and right of the heat pump.

The trouble with the replacement heat pump began last November, when the refrigerant compressor died.  It froze up and would not turn.  When started, the motor drew full start current, but the compressor never moved, so it was locked up.

I wasn't terribly concerned about getting it repaired immediately.  The outside temperature had already fallen enough that we were mainly using backup heat.  The heating system operates by using the heat pump when the outdoor temperature is above 40 degrees F.  Below that temperature, the heat pump wastes electricity and does a poor job of warming the house, so the system locks it out.  At that point the system switches over to back-up heat - the propane furnace.

Below:  The box with the "Daikin" label is the propane furnace section of the heating system

 Throughout winter we heated with propane, and then in May I called the installers to see about getting that bound-up compressor replaced.  Replacement was mostly a drop-in operation.  The technician drew the old refrigerant out of the system, de-soldered the two refrigerant connections from the compressor, unplugged it, and removed it.  The new one went in, got plugged in and the two refrigerant lines were re-soldered to the new compressor.  

 Below:  A Daikin replacement refrigerant compressor.

HOWEVER... the technician struggled to get the larger vapor return line to seal to the compressor.  He soldered it three times before it would hold.  Next, he pulled a vacuum on the system and ensured that it was airtight, and then filled it with 15lbs of refrigerant.  The compressor was under warranty, but the labor and refrigerant were not, so the cost for this event to our household was $1500.  Big Ouch.

One of the ways we reduce expenses is to open the house each night in the summertime.  We use box fans upstairs in the windows to draw heat out of the house.  On the main floor, cold air flows in from outdoors, while the warmer air rises to the second floor, and is exhausted outdoors by the box fans.  It can get downright cold inside the house on a midsummer morning, depending on how much the weather cools off overnight,

What I'm getting to, is that we didn't use the heat pump very much until this week.  This week the weather turned hot and muggy, due to monsoon moisture making its way all the way here from the tropical latitudes of the Pacific.  No point opening up overnight if your house will just be a sauna in the morning.  So we ran the heat pump.  Or not.

I got home after shift this morning and the central air fan was circulating, but the house was warm and muggy, just like outdoors.  Called a service technician and sure enough, the refrigerant joint that had given the first technician so much trouble, had popped out of its socket on the compressor - and all the refrigerant had leaked out, causing the compressor's safety circuit to shut it off due to low pressure.

This time the joint was brazed instead of soldered, and once again, it took three tries to get it to seal up.  But at least this time it should be a far stronger bond.  Fingers crossed.  The house is once again cooling down, which is good as we have another hot and muggy night to deal with.  Happily, every bit of this was covered under warranty - diagnosis, repair, and (importantly!!!!) replacement refrigerant.  Odd weather for summer this far north.  Hopefully we don't spark any wildfires with this.

Unfortunately, I have now been awake quite a long time, and have to do another night shift, with a lot of plant stuff running in manual due to the excessive (for here) temperatures.  It's going to be a heavy Monster Energy and coffee kind of shift :)