Walk In Freezer Woes

[ar_hvac_man]

Brand new condenser and evap. 404a. Fired up and ran great. Hot box. Opened txv up a few turns... SH was way high.

Leave and go back next morning to set SH and check everything out. Box was at 8 degrees, 10 deg SC, 25 deg Sh at the bulb and around 40 at the compressor. Cool, I need to open the txv. Half a turn and no change in SH. Another half a turn and so on. Before I know it stem is back seated. Still 20 deg SH. WTF.

Call the "expert" who sized and sold me the equipment. He said for the box size and load and equipment btu rating I should have to be squeezing the txv closed, not opening. I tell him that goes against logic, to get my superheat down I need to open it. He says if I went to far I could be overfeeding the evap and he agrees with my logic but it is "one of those refrigeration phenoms". Tells me to take it back to mid point, leave and let it settle down, and come back and check. Im about to head that way and see how its doing.

Would love to hear thoughts from you experts

[ar_hvac_man]

To add. The loops are all nicely frosted except the top couple. Everything, IMO, points to the fact that the evap isnt flooded. Am I wrong in my thinking?

[Dad]

Just a thought if you want to concentrate on the TXV... are you sure you opened the valve?

Some valves turn CW while others turn CCW to open it up.

Another thing... are there aeroquip fittings on the condenser and or evap coil?

[ar_hvac_man]

Well to find my midpoint i closed the txv all the way down and my suction went to almost 0. Counted turns to get it all the way open then half as many turns clockwise to get it in the middle. So i do believe clockwise closes it down.

Not sure what aeroquip fittings are? It was all brazed in

[ar_hvac_man]

gotta run heres the numbers.

condenser - fjal-b301-tfc-o15-copc

evap - lce6-94bb-lark

txv- sqe body-spoe

head - kt-43-sz-spop

cartridge - qc-3-spop

[ar_hvac_man]

One more thing before I run. After finding the midpoint my suction temp at the evap suction line was lower than when the valve was fully open. Maybe the "phenom" he mentions has merit?

[Jonnyb]

With25sh it's sure you are not flooding evap. I hope to have the explication of that phenom!

[crymtide]

Is the system going through the fan delay cycle to prechill evaporator.

[crymtide]

Also, if you're starting with a hot box it could take a couple of days to cool off the floor and the box, and you might need a defrost on arrival to start checking superheat. I've had freezers that took three days to cool things off enough to adjust the txv correctly.

[hvac wiz 79]

Also, if you're starting with a hot box it could take a couple of days to cool off the floor and the box, and you might need a defrost on arrival to start checking superheat. I've had freezers that took three days to cool things off enough to adjust the txv correctly.

I agree about waiting to adjust the txv. 3 days sucks lol but I've waited out overnight. Constantly reading threads here will lead me never to forget that waiting time. I've chased my own a$$ a few times in my early days with hot pull down n attempting to fine tune

[ar_hvac_man]

Wasnt a complete hot pull down. Food was still frozen when we started the new one up.

Got there this morning and box was at 5 deg with 25 deg SH. The txv is not feeding correctly. Half a turn...no change. Another half a turn...no change. 3 full turns and i get a couple degrees movement. Evap will not flood.

I realize a hot pull down requires some time but Ive never had a new TXV that was so unresponsive, even with a warm box. With the matchup I have I should be having to squeeze the valve down, not opening it up.

Fan delay works fine. Defrost works fine. Evap is clear.

Picked up a new valve today and will start digging in the morning starting with pulling the bulb and warming it. Didnt bother today.... would have been useless since I didnt have the parts to do anything with it.

[crackertech]

Just a thought I once had coil we ordered fore R-22 but it was shipped with a 404 orifice in it drove us crazy.

[crymtide]

Is your txv bulb vertical or at 4 or 8 o'clock and is it insulated?

[thermofridge]

Pump it down and clean the TXV screen.

[hvac wiz 79]

Pump it down and clean the TXV screen.

i would hope it's not full of trash that fast lol

[Phase Loss]

whats your

SCT at?

SST at?

Are you maintaining a solid column of liquid?

[76olds]

Have you checked to see if a coil or pan heater is energized?

[ar_hvac_man]

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

[icemeister]

Just a thought I once had coil we ordered fore R-22 but it was shipped with a 404 orifice in it drove us crazy.

This is a good point. The distributor nozzle sizing for R22 and R404A are vastly different.

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):
http://www.heatcraftrpd.com/products...5CH-IM-64L.pdf

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.

[ar_hvac_man]

Thanks all Im off to the races Ill let you know what I find.