Raetone Freezer

[apprentice3]

Today i was working on a freezer. I made some repairs to it due to the defrost not working properly.. Once i start it up, after it pulls down to about 40 degrees the compressor overheats and goes off on internal overload. I checked my pressures. The refrigerant is MP66. My pressures were about 17 psi and 325 psi.. My subcooling was high 37 degrees.. The sightglass was clear. The system used to be a R-12 system. When i looked at the chart for MP66 i noticed that the pressure could go in a vacuum once the freezer pulls down to -10 to 0 degrees. That doesn't seem right to me. I feel someone probably overcharged the system. My superheat at the compressor seems high. I will measure it at the evap. next week. I was wondering what i should do next. Should i charge it back with R-12 or will a refrigerant like HP80 work?

[codgy]

i guess this is cap tube fed, yes its overcharged. if you have r-12 this is what i would use, weight it in by nameplate. these are very easy to overcharge, ignore the sight glass as this did not come w/ one. make sure fan delay is working as this helps prevent compressor overloading out of defrost. if serviced properly these will last many more years.

[james122964]

Take all the gas out, and use 402a, start with 80 percent of the original R12 charge.


Jim

[VTP99]

A 2 door that i service has duel cap tubes and a accumulator at evaporator.

[powell]

with R-12 or will a refrigerant like HP80 work?

Just an FYI.

HP80 is a high pressure interim refrigerant for R502 replacement.

Not to be used for low pressure refrigerant R12 replacement. ;)

[pecmsg]

:tussor:
Today i was working on a freezer. I made some repairs to it due to the defrost not working properly.. Once i start it up, after it pulls down to about 40 degrees the compressor overheats and goes off on internal overload.

What were the defrost problems?
What is the amp draw on the compressor? (Compressor Mod # would help)


I checked my pressures. The refrigerant is MP66. My pressures were about 17 psi and 325 psi.. My subcooling was high 37 degrees.. The sightglass was clear.

17#’s at 40*f for R-12 / MP66 is in the ball park. 325# is a huge problem.


The system used to be a R-12 system. When i looked at the chart for MP66 i noticed that the pressure could go in a vacuum once the freezer pulls down to -10 to 0 degrees. That doesn't seem right to me.

R-12 freezers run in a vacuum.


I feel someone probably overcharged the system. My superheat at the compressor seems high. I will measure it at the evap. next week. I was wondering what i should do next. Should i charge it back with R-12 or will a refrigerant like HP80 work?

As Powell said HP80 is a replacement for R-502 much higher operating pressures.
Pull the charge, if it’s a cap tube system remove the sight glass, if there’s a receiver remove that to. Change the drier, pull a vacuum and weigh in MP66 starting with 80% of the R-12 charge. You may have to adjust the charge + or - after you get near operating temperatures. Make sure the condenser coil is clean!