Hussman WIC R22 restriction? or...?

[Frosty_VA]

Hi folks! Been reading forum for 2 years, now I really need your help. I'm working on walk-in cooler, Hussman, R-22, 2 evaporators, single condensing unit. CU has receiver and headmaster, no fan cycle controls. First I got a call 'both evaps iced up'. So I removed/thawed ice, unit low on charge. Pressure tested w/ nitrogen to about 350-370psi, found VERY small leak right at receiver inlet at nut. Tightened nut, looks like leak is gone. Pulled deep stable vacuum(440psi) with LL solenoid open, charged unit with 8.5lbs of refrigerant(sight glass clear, added juuust a bit over for winter charge). What's weird is that right at compressor outlet pressure is over 360, but at LL past filter, solenoid and sight glass is about 220. So I checked if filter-dryer plugged - no, no temp drop across, no temp drop across solenoid either. Headmaster works, opens/bypasses below 180 like it should. So I decided to double check incondensibles, pulled deep vac again, all valves open, charged with 8 lbs of R22 again. Now discharge pressure 230, pressure at LL 170!, suction 20 psi, sight glass clear. WTH? Why there is ressure difference of 50-60 psi across condenser coil? Restriction at condenser? I also checked amps at compressor - 5.5A, they're lower than exact same neighbour unit has - 8.5. 3ph unit, proper voltage, no difference between legs. Superheat at TXV with 20psi is about 55 degrees. Could I damage TXV while pressure testing with nitrogen?
Any ideas?

[Frosty_VA]

UPDATE: I added just 1 lb of R22 and pressures went: suction - 51-52 psi with 12F of SH at both evaps(so looks like TXVs are fine) box is close to designed temp(not a hot pull down), liquid - 250, discharge - 350. So units somewhat works as of now but that 100psi difference is killing me guys!

[jpsmith1cm]

Didja maybe leave a valve part-way closed?

[Frosty_VA]

Didja maybe leave a valve part-way closed?

Nope. Unit got no suction service valve, just a shraeder @ suction filter and shraeder @ actual suction line. The only service valve is @ receiver outlet, and I triple checked it))) Out of ideas what is the problem. Thought compressor giving me a hard time because of wires(gauge too small) or discharge line too small, but exact same unit next to mine works fine. What would YOU do?

[Frostmonkey74]

Sounds like the headmaster is holding back...

[trippintl0]

Very common for headmasters to get filled with black oily sludge from compressor oil overheating. I'm almost to the point of just replacing them anytime I do a compressor, if they look old. I've had multiple times where I change the compressor and start it up, just to find that the headmaster is stuck in bypass because it's filled with black sludgy goo.

[Frosty_VA]

Thank you for your replies, I'll get new headmaster and update.

[Poodle Head Mikey]

Standard air cooled condenser piping design would have the PD through the coil at about 6-8 lbs max. Less being better of course - but hey; production costs do add up. <g> Although I have occasionally seen higher; I would consider a 20 lb. PD through a condenser coil to be really dirtball design or a blockage of some kind.

50 lb. PD? It just can't be right. I think I would want to add an access valve directly to the condenser coil outlet while I was replacing the LL drier.

PHM
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Hi folks! Been reading forum for 2 years, now I really need your help. I'm working on walk-in cooler, Hussman, R-22, 2 evaporators, single condensing unit. CU has receiver and headmaster, no fan cycle controls. First I got a call 'both evaps iced up'. So I removed/thawed ice, unit low on charge. Pressure tested w/ nitrogen to about 350-370psi, found VERY small leak right at receiver inlet at nut. Tightened nut, looks like leak is gone. Pulled deep stable vacuum(440psi) with LL solenoid open, charged unit with 8.5lbs of refrigerant(sight glass clear, added juuust a bit over for winter charge). What's weird is that right at compressor outlet pressure is over 360, but at LL past filter, solenoid and sight glass is about 220. So I checked if filter-dryer plugged - no, no temp drop across, no temp drop across solenoid either. Headmaster works, opens/bypasses below 180 like it should. So I decided to double check incondensibles, pulled deep vac again, all valves open, charged with 8 lbs of R22 again. Now discharge pressure 230, pressure at LL 170!, suction 20 psi, sight glass clear. WTH? Why there is ressure difference of 50-60 psi across condenser coil? Restriction at condenser? I also checked amps at compressor - 5.5A, they're lower than exact same neighbour unit has - 8.5. 3ph unit, proper voltage, no difference between legs. Superheat at TXV with 20psi is about 55 degrees. Could I damage TXV while pressure testing with nitrogen?
Any ideas?

[Frostmonkey74]

Anyone else Curious what the solution was??

[Abrnth3]

sure