Shorty after getting deep in refrigeration, I was asked to fix a de-humidification kiln. I know this isn’t food service, but I though it would help for others to think outside the box. Looking over the system so that I could understand what was the problem, I found a R12 system with a 12 HP R22 compressor feeding a coated evaporator with a ten ton expansion valve and 8 tube distributor. with a damper that diverted air flow either thru the evaporator or around it to the 15 hp blower and the condenser. Evaporator gas went back to a accumulator with temperature sensing set at 70F then to compressor. Condenser discharge came back to a horizontal receiver about 3 ft long and 6 inches in diameter. It then was piped with a 5/8 liquid line to a Sporland bolt on top filter and sight glass. Sight glass was full of foaming refrigerant to TXV. First thing I see is bubbles in the sight glass. I’m thinking low charge. Wrong, bubbles are normal on this unit due to the sheer volume of refrigerant moving. After looking at the manual, pertly much useless. Ok, let’s measure what is going on. Compressor discharge is a whopping 210F. Suction 76F but load is only 12 amps. Full load would be 19 to 20. So now I’m still thinking undercharge or maybe metering. But why the high head temp. Let’s look farther. Is the condenser clean? Is there a airflow problem? Being I’ve never seen anything like this, Let’s call the manufacturer. All they could tell me was that it was made to make 2 liters of water per minuet. Bubbles where normal as was the high temp discharge. This was in 1992 and we didn’t yet have digital temp equipment like today. So I tried adding 5 pounds of R12. No real change on output, but less bubbles. Ok, let back up. Could it be air flow. I check the damper controller and dampers that vary the air over the evaporator or around it. Doesnt close down all the way. Maybe a problem, Lets look at the blowers. 15 HP motor with 3 B belts. Belts are glazed and slightly loose. Lubricate the bearings and tighten the belts. Note the belt numbers to order replacements for the glazing. That improved the output, but not to full spec. OK, thermostat on the tail coil line set at 70, but the compressor suction is 78. Not supposed to be above 76. Tells me the dampers are allowing to much 140F air to go threw the evaporator. So I go through the extensive adjustment of the Honeywell damper control so they close all the way. Bingo, Now making just under a gallon milk jug in one minuet. Three problems in one call.
I later consulted with the Kiln company when we tried to find a replacement for R12. I also suggested changes that they incorporated in later designs. But it took a lot of time and studying. I had this account till the parent company went bankrupt in 2016. It was a awesome ride for sure.