Pump it down and clean the TXV screen.
Never kick a lying dog.
i would hope it's not full of trash that fast lol
Originally Posted by thermofridge
Are you maintaining a solid column of liquid?
Have you checked to see if a coil or pan heater is energized?
cracker: it came with 4 orifices. two for r-22 and two for the various other reefers. the correct one was field installed
crymtide: its at 10 oclock and is horizontal. my bad there, the book shows 4 or 8 or 3 or 9 oclock. ill move it this morning after confirming its working. yes its insulated.
hvac and thermo: ill be checking the screen today. hard to believe i got trash in it since we bubbled n2 while brazing
phase: it was cool yesterday. sct was around 100 sst was -20 with a line temp of +5 deg. full column to the txv.
76: 0 amp draw from all heaters
This is a good point. The distributor nozzle sizing for R22 and R404A are vastly different.
Originally Posted by crackertech
The OP has stated that he has the correct one in there, but I've found in a few cases, the nozzle size was a tad small for the application...especially for freezer pulldown.
Heatcraft's Refigeration Systems I&O manual has a good section of nozzle sizing (starting on p.7):
I would also recommend going up one size on the Q-Valve orifice, to a QC-4. The FJAL-B301 has a capacity of 9470 Btuh at -20ºF SST/90ºF Ambient but it's 13,100 at -10ºF SST/90ºF. The system seems to match up OK for the -20ºF condition, but it's clear the TXV will be undersized for pulldown.
Thanks all Im off to the races Ill let you know what I find.
My money is on the power head being bad. Doubt it is a MOP valve but that could also explain why adjusting doesn't give him movement.
The possibility of MOP powerhead did come to to mind. There's no adjusting those if the suction pressure is above 30#-35#. It was stated however, that it's a KT43-SZ, which is the non-MOP, standard powerhead, so I think we can rule that out.
Originally Posted by Dad
The existing head may well be bad, but if it were, I would expect the valve to slam shut.
Another possible problem, now that the TXV has been cranked every whichaway, is that the adjustment stem has been FUBAR'd...in which case a new valve would be needed.
Showed up to a -10 degree box yesterday. Stem at midpoint, still 25 deg sh. Pulled bulb and warmed it. Suction rose and suction line temp plummeted.
Screen had zero debris in it.
Reattached bulb and insulated. One turn away from being fully open and cannot get superheat down. Im stumped
Ive got a new txv but would like to know if you think I should stick a #4 in it before pulling and replacing?
Also..what damage can be done by adjusting the stem?
Originally Posted by ar_hvac_man
None unless you went past the stop.
I would put a #4 in it first.
The fact that you got a huge surge of flow when the bulb was warmed up tends to lead me agree with what Dad was saying about the powerhead losing its charge.
Since you have to remove the powerhead to replace the orifice, I'd go ahead and replace the powerhead as well.
Then again, you may want to do the powerhead first, just to determine if it was indeed the problem all along.