RDI low refrigerant flow

[Aaronn]

Got an RDI (manitowoc) PCL0127B indoor coil, PCL149M outdoor unit, CF04K6E-TF5-270 comp, Poe oil. Originally R22 but converted to r404 at some point. Walk in cooler supposed to be 34*. Customer called and said its warm. I get on site and its in 2 hour defrost supposed to be at 3am but its noon. Reset defrost timer, unit kicks on and pulls down from 55* to 34* in about 10 minutes. Pop doors open and let it warm up and pull back down, put a done stamp on it and roll out.

Call back this morning with same issue getting warm. I get on site and check it. Unit running, box at 60*, 9lbs sp, 170lbs hp. Sight glass has trickle going bye it. Try cycling unit, adjust txv in and out, check LL solenoid. Finally I turn off cond, call for cooling, let system equalize, turn cond on and system fires up 50ish lbs sp, 240ish lbs hp, unit cooling. Figured something getting stuck in txv so pump it down, change txv, LL solenoid, and filter drier. Pressure test, evac down to 500 microns, open up LL valve and fire it up. Unit starts up and pulls down to 5lbs sp, 170lbs hp, now it's cycling on lp switch. Try adjusting txv in and out with no success. Packed up and left cause it was getting late. So am I plugged up in the distributor or what? Headed back in the AM to keep pluggin away on it.

[DarkSunRider]

Quick question, were you cycling on your low pressure switch before you did all the changes? Might want to check and make sure your solenoid is not leaking by or your compressor may not be holding the pump down.

[Aaronn]

System would run continuously. Comp held pump down

[trippintl0]

Does the sightglass indicate that there is moisture in the system?

[Aaronn]

Does the sightglass indicate that there is moisture in the system?

No

[2sac]

. I get on site and check it. Unit running, box at 60*, 9lbs sp, 170lbs hp. Sight glass has trickle going bye it. .

Why a trickle?

[2sac]

Does this unit have a headmaster?

[Aaronn]

Does this unit have a headmaster?

Yes. When the issue is present there is no heat going into condenser. Pretty much all bypasses into receiver.

[2sac]

The headmasters job is to keep the head pressure at whatever rating it is stamped for. It's going to try and do this no matter what the ambient. It also has no idea how much refrigerant is in the system. So, you need to ask yourself why is there a trickle going thru the sight glass. Back to basics.

[Aaronn]

Headmaster is not going to restrict flow? It's bypassing condenser and dumping right into receiver?

[2sac]

If the unit is properly charged, during the summertime, and the headmaster was bypassing, your head would trip the HPS.

[2sac]

They fail open or closed. Yours sounds like its attempting to keep the head pressure up. They do not restrict flow, just redistribute it.

[Aaronn]

So where do I go from here. There doesn't seem to be any adjustment for headmaster. Sound like a low charge? Just strange that it was working and cooling intermittently.

[2sac]

Yes, sounds low on charge. If you're experiencing cool nights and warm days, it will cool intermittently. Also, sometimes if you pump it down, you've backed up the refrigerant and it may work normally for awhile until the ambient drops. If it were me, I'd add a little gas. Your sight glass will clear once the headmaster kicks in. Make sure it operates correctly. Find and repair the leak. Charge the unit properly. There is a Sporlan document floating around this site on proper headmaster charging.

[Aaronn]

Thanks. Drop a little over 1 lb in and it kicked right in and cooled.