W/I Clr Retro Guru's needed

[tbk]

Geesh ! I wish they would put this forum in the pro section! But anyway

Been fighting this W/i for awhile. Dont have Mod #'s but dont believe it is relavent at this time.

14 door convience store of course in BF egypt. I cond unit on roof, 2 evaps I think Larkin 180's. 1 Tmep contol and 1 liq line sol for both units.

Was orig R-12. found one bad flair at txv on dist side on one unit , unknow how long running like this.

Anyway cond unit had been changed to r-22 but could not verify the correct txv's were installed so replaced them change out c304 dryer on roof and pulled vac blah blah. unit pulls down to temp then after about 30 mins txv's freeze and low press drops and cuts unit out on low press switch. txv's thaw and cycle repats but only takes about 15 mins to freeze up each time.

Figured moisture still! change out c304 again after couple days due to time constraints and go thru process agian. SAME THING, txv's freeze.

open txv,s chech strainer both clogged, cleaned them out and replaced (Blackish grit). have replaced 3 or 4 c304 f/d and even added a small 052 or something like that right before the txv,s and this damn thing is doing the same thing again. it runs about 15 or 20 mins then freezes txv,s. it will keep the box around 45 or 50 but we know this is bull. The temp control was alos replaced (out of cal).

going back today and check the txv screens again. What am I missing guys!!!!! Oh and the refrig was replaced on the initial visit. This is killing me just in Gas alone!

Incase it matters replaced txv,s with Q body type valves at 1 1/2 tons each. which evaps are rated at.

[Slatts]

Was orig R-12. found one bad flair at txv on dist side on one unit , unknow how long running like this.

Figured moisture still! change out c304 again after couple days due to time constraints and go thru process agian. SAME THING, txv's freeze.

gedday tbk, do you know what the LP was set at? when the system was short of gas did it run down to a vacuum?
I'd suggest you decant the charge, change the oil in the compressor & perhaps fit a suction line drier, then vac the hell out of the whole system. check the vacuum with a micron gauge. If it seems to take forever to pull down, you might consider breaking the vac with dry nitro a couple of times to help dry the system out.
Don't you just hate low side leaks?

[tbk]

Did not pull into a vacumm, think it was set at 10psi. have, did, always use a micron gauge and yes have broke with nitro, and yes takes hours to pull down!

This first time I repaired and pulled down, so much crap in system, had to change vac pump oil in middle of vac, was milky, milky white!!

[smurphy]

Whats the suction, high side pressures? compressor and evap superheat? Evap coils clean? Get the horsepower of the condenser, 3 horse? Can be alot of things at this point. moisture can be the problem, but need more info.

[tbk]

All press align to PT chart until the valves freeze, unit has been there for some time, checked the sizing originally and all matched up, dont see where you are going with this.

[Slatts]

All press align to PT chart until the valves freeze, unit has been there for some time, checked the sizing originally and all matched up, dont see where you are going with this.

Mate, change the oil. It's full of moisture.

[forged alloy]

4HP Really marginal for a 14 door walk-in. When I sell them new they come with 5 ton system standard.

That blackish goo you see will probably be all throughout the valve, not just the screen. The push rods & needle will be contaminated.

[yotaman16]

why was the cooler converted to r22 from r12?? personally i would have used MP39 or 409a.. Sound like ur cooking the oil to me tho

[tbk]

unknow why coverted to 22, thats just whats there now, wasnt a blackish goo, more like oxidation particles from brazing.

Pumped down and removed the screens again, NO contamination, screens still clean.

So I started from scratch again, removed all refrig, nitro leak checked after reassembling and replacing the 304 dryer again. tripple vac with nitro breaks. pulled down really well and fast the last time.

Charged her up and startup. Bang everything looks great. 8-10 dg super heat at evaps 27 at comp. runing at 55 psi low side (box alitlle warm and FULL) high side 200ish depending on the fan pressure switches ( dual fans, both on switches).

Have no idea!!!!!!! Watched it for about 2 hours, will check back in tommorow!!!!! This is a herm comp. wrote down all the numbers and left them on site ( DA). Did an acid test and neg.

[Executioner]

I may be wrong but the R12 comp. just ain't gonna cut it for R22, 2 different animals.

Charge with R409 or atleast 134A which is more inline with 12
The radically difference between the make up between R12 and R22 may have stirred up or "scrubbed" the system loosening up a bunch of crap.

[ezone]

Sounds like you finally got it dried out, and cleaned out. That was a lot of moisture. The end result of a bunch of top offs. Not finding the low side leak and just adding gas,gas gas. Those kind of boxes are subject to high humidity hits. Loading up, customers standing there trying to make up there mind etc.
A lot of water sitting under that TX. Don't garuantee that compressor. Why are they always in B F?

[k-fridge]

You need to check the application of the compressor, if it's an R-12 pump you need to use a suitable refrigerant. I suggest R-409 or MP-39. You also need to change the oil and go back with AB.

[northstar1]

I've found that (after having water cooled cond. break open to systems) that using 1/2 in. hoses is the only way to go when evac. contaminated wystems.
I've ran pumps in tandem for days and have seen your sit.
Good Luck