R12 to R22 REPLACEMENT

[mrhvacmechanic]

Gentlemen,
We just replaced a R12 refrigerator system with a R22 condensing unit.We were told to replace the expansion valve and we did the usual drier replacement and evac and so on. This was not a burn out.The system had a leak so we replaced the condensor to r22. Its water cooled with a water reg valve, pump down via solenoid by stat.

Unit is 3/4 hp and was charged to clear sight glass. Reg valve set to 210LBS. This is a refrig, not freezer.The problem, the evap freezes up at the bottom, about 1/3 of the way up.So only the upper 2/3 passes air through coil.

Any reccomendations?????

[jeffcolledge]

Is the drain plugged?

[selfemployed]

Sounds like your starving the coil. Would help if you posted some P/T readings on system. Should watch for oversized piping using 22. Can cause oil return problems.

[mrhvacmechanic]

SELF
Box maintains around 40F. Pipe run very short, cond sits right on top of box lines right down to evap.. No signs of frost on comp or suction line. since this is a refrigerator and system has defrost timer, how often would you defrost a refrigerator like this per day?

[Dad]

Can you tell me the name brand and model of your TXV?

Can you tell me the name brand of the evap coil?

Did you check inside the coil distributor to see if it has an R-12 orifice spud?

Can you tell me what your subcooling is with this water cooled unit and did you take superheat calculations near the TXV bulb?

Are there any problems with the box with air infiltration or door closer problems?

Is this box located in a high RH area?

R-22 air-over defrost...fans running during defrost
4 X 30 minutes a day.

[selfemployed]

2-3 for 30 min. under heavy entering load or occupancy. Usually pump down in off cycle for better defrost on coolers with or without timer.

[refer dude 2479]

If the coil has a distributor that was originaly sized for R-12 you may need to resize and replace the distributor. Orfice sizes for r-22 are typically only 2/3 that of r-12. could be causing a flow problem to the coil circuits. Also your distributor tubes may bee slightly large. The distributor and tubes are the second half of the metering device after the TXV.

[selfemployed]

Well I missed that completly (nozzle). I'll blame it on the bump on my head.