r-22 med temp

[kamikaze126]

Picked up big hvac account with a cafe. I havent done much refrigeration. Right off A compressor for the walk in cooler is shorted. Minor burn I cant find cause. so I do New comp 3phase 41000 btu, new contactor (old one ok) no acid, still new dryer r11 flush, new r-22. Startup good amps volts SH all in range. Flooded condenser I charge 75 % and clear glass., 55F OAT I block condenser and build to 225psi. Unblocked im running 45 low 175 high (valve has a 180 psi rating.) pump down operating normally box down to 39F set for 35F. I have trouble accepting that the coil is not freezing? I would never leave an A/C unit like this. Suction line iced but coil perfect. It ran for 3 hours nonstop due to warm product but no changes. I am goin back soon what did I miss checking ? Are pressures normal? No problems claimed before the compressor shorted.

[Dchappa21]

This is how to add your winter charge http://sporlanonline.com/90-30-1_072012.pdf

Unless you have a microchannel condenser.

What is superheat in range mean?

45 psi is about a 22 degree coil so that looks good. Is this a really short run? I would not think you would have ice on the suction line unless your flooding or have a short run with good insulation.

Need to know the SH at the coils and compressor.

[kamikaze126]

Yes 10 ft up up roof and all insulated. I had 10F superheat @ compressor never got one @ coil exit but i do see refrigeration literature asking for it. Due to short run And 1 large long coil i didnt get it. I will next visit. Thanks for the info

[Dchappa21]

Copeland does not want anything lower than 20 degrees SH 6" from the compressor.. Between 20*f and 30*f would be ideal. There reasoning for this is a little wiggle room in case the coil does ice up or you lose a fan, ect.

I would just check and adjust SH at the evap coil till you get the sh in the 15 to 20 degrees range at the compressor. 10 to 15 degrees range at the evap coil should work and hopefully still get you down to setpoint with out a problem..

Or you could try and lose some armaflex, but that method won't be very effective in the winter time.

[Dchappa21]

Also check the crankcase heater when you go back. If it's got one, if not add one.

[Snapperhead]

How did you get all of that R 11 cleaner out ? ?

Maybe you didnt

Which is why I dont use flush anymore , been bitten too many times

[ryan1088]

Picked up big hvac account with a cafe. I havent done much refrigeration. Right off A compressor for the walk in cooler is shorted. Minor burn I cant find cause. so I do New comp 3phase 41000 btu, new contactor (old one ok) no acid, still new dryer r11 flush, new r-22. Startup good amps volts SH all in range. Flooded condenser I charge 75 % and clear glass., 55F OAT I block condenser and build to 225psi. Unblocked im running 45 low 175 high (valve has a 180 psi rating.) pump down operating normally box down to 39F set for 35F. I have trouble accepting that the coil is not freezing? I would never leave an A/C unit like this. Suction line iced but coil perfect. It ran for 3 hours nonstop due to warm product but no changes. I am goin back soon what did I miss checking ? Are pressures normal? No problems claimed before the compressor shorted.

If what you're asking is if we think your coil is below freezing? Yes it is, it has to be. Assuming even a 10 degree delta, to get 37 degrees in the box the coil would have to be 27 degrees. If this is an air defrost, you are relying on it cycling off on temperature and being off long enough to melt the ice. Some have defrost timers that hold out cooling for a period of time to make sure you don't build excess ice.

[2sac]

I have trouble accepting that the coil is not freezing?

Why?

This coil/system is designed to run this way. First off, you are dealing with, more than likely, a 10 degree drop across the coil. Idealy at 45psig, you are at a 22 degree coil which should reflect a 32 degree box if unit is sized properly. Once your t-stat reaches setpoint at 35 degrees unit pumps down. The coil will eventually warm to 39 degrees at the same time, or close, as the box, closing the t-stat to start over again. Remember, there is minimal to no refrigerant in your evap during a pumpdown. Any condensate that may have formed on the coil during running time should drip off during the off time. Med temp coils freeze because of air/moisture infiltration

[kamikaze126]

How did you get all of that R 11 cleaner out ? ?

Maybe you didnt

Which is why I dont use flush anymore , been bitten too many times

The burn was minor so after removing compressor I just flushed from open discharge line thru closed discharge service valve and from suction valve thru open suction line followed by nitrogen purge. I thought it evaporated ? how has it bitten u in the past?

[kamikaze126]

I definitely understand the coil below freezing. as an A/C guy I have to get used to it. Like stated lack of moisture in box makes it much harder to freeze coil. In an A/C application that same coil would freeze up quickly as shown by the ice on suction line outside the box. Thanks for the replys I am going back tommarrow

[craig1]

The burn was minor so after removing compressor I just flushed from open discharge line thru closed discharge service valve and from suction valve thru open suction line followed by nitrogen purge. I thought it evaporated ? how has it bitten u in the past?

If the burn is minor, I throw an oversized HH core liquid dryer on and call it a day. If its major I'll come back and replace it and do an acid test. I've never had a repeat burnout.

I used to put suction filters on on burnouts, but now I only do that on the worst ones.

I agree with others that flush does more harm than good

[jpsmith1cm]

How did you get all of that R 11 cleaner out ? ?

Maybe you didnt

Which is why I dont use flush anymore , been bitten too many times

Flush compounds that I've used are simply HFC fluids with a higher vapor pressure than commonly used refrigerants. Very similar to R-11 and R-123

I've heard this 'more harm than good' before and I'm dubious.

HFCs are compatible with the oils that we use and a proper evacuation will remove it just as surely as it removes non-condensibles and moisture.

[Snapperhead]

I've only used the flush a couple of times , and both were a total Hoe getting all of the flush out. I dont know how many times I blasted it with Nitro , but it was plenty , and seemed like each blast kept sending out flush. It was like never ending battle of getting it out.

Within couple months the compressors locked slam up.

Never again.

Since then I just add both liquid , and suction filters when needed. Im done with flush.