Today I met an old time farmer who has a Bard water source split system heat pump. He told me his heat pump never has worked right since day one. He said he's had numerous service technicians work on the unit every year for the past 11 years trying to get it to work properly.
I immediately noticed that the txv was iced up and could tell it was starving for r-22. My suction pressure was 20 psi and the compressor was cycling on the low pressure switch. My inlet water temp was 50 degrees and the outlet temp was 49 degrees. (water was SCREAMING through the exchanger). I glanced to the TXV and noticed that it had been replaced less than a year ago (dated). Naturally my first thought was it was simply low on charge. To be thorough, I switched to cooling.
Initially the suction pressure stabilized at 40 psi and the high side was 125 psi. A quick glance to the indoor unit to see a piston style meetering device. I mumbled "well thats not too far off.." I decided to elevate the high side pressure by closing a valve on the water supply to see if the suction pressure would come up. I was suprised to see that while my suction pressure initially increased, eventually it FELL below 25 psi. "must be low on charge.." I said for my benefit. I wanted to add charge in the heating mode so I de-energized the RV, opened the water valve and went to get the refrigerant.
I got back to the unit, new 30 pounder and scales in hand. Low and behold the suction pressure was up around 45 psi. "What the..." I said under my breath. The old timer was looking at me with his hands on his hips. I looked into his face and I could see the impatience that so many others must have seen. "Do you know how many bottles I've seen out here?" as he hastily pointed around. I managed a small laugh as my eyes darted around the internal components. I decided to watch things for a few more minutes. Eventually the suction and discharge pressures began to fall and the txv began to ice up. "There it goes again.." I mumbled. The heat pump fell back into the cycling on the low pressure switch as 51 degree well water fed by a 2HP irrigation pump screamed through the exchanger at mach speed.
This is a very simple water source split system heat pump with a remote desuperheater serving the domestic HWH. The water source is an ungodly 2hp pump at 70 psi feeding the exchanger via 1 1/2" pvc. The inlet water temperature is 51 degrees. The system has the correct charge as per nameplate. Both the heating and cooling cycles operate at normal pressures for 10 min or so before the pressures go foul. There is no debris or moisture in the system causing meetering device failure.
The old timer is tired of hearing the heat pump run continuously, the massive water pump cycling every 10 seconds, the auxillary heat light on and paying the utility company his social security check every month.
Whoever can figure this out gets a new bottle of POE oil in there stocking.