Below is background but the question is what is the correct TXV for a Grunert R12 based deep freeze system.
Installed when I bought boat
: Eaton 223 FA 1/2 9 degree superheat
"Borrowed" from fridge loop to limp along last year: FF-1/2-C with 26F superheat
Manual from later version suggests: FS-1/2-ZP for R409A for the freezer
Have located a FF-1/2-ZP which would be the R12 version of the R409A valve
My best guess is the FF-1/2-ZP is probably what was in there to begin with. Any other recommendations?
Backup Details for those so inclined:
Over the last 10 years I have had good success keeping my Grunert refrigerator
A few years back the fridge holding plate developed a leak between the refrigerant and the eutectic solution. After drying the system and removing the refrigerant loop I got it running well.
Last season the txv control became intermittent, i.e. could not move frost line around or adjust as expected. I swapped out the TXV from the fridge side to make a trip happen and it worked reasonably well getting the plates to about 20F. The fridge is running in spillover with a thermostatic fan.
This spring i decided to get the freezer working correctly (it used to go to 0F easily and would go to -15F if left running). I had known that somewhere along the way a second plate was added in series and that the txv was on the vertical line between the two circuits of the second plate. So I have cut away at the freezer box to access the suction line and moved the bulb onto the horizontal portion of the line.
At this point i see much better positive control with superheat and the second plate freezes first and completely before significant frost shows up on the first plate. The only issue is that with the refrigerator
txv i can control the frost line but when it gets to 20F it just stops. The repurposed fridge txv is:
Sporlan: Ff-1/2-C which notes its superheat mid range is 26 degrees.
Suction pressure at the compressor
case is 6-7psi (i.e. -4.4F to -6.6F at the txv). Temperature at the TXV bulb is 23F to 26F. So superheat is 23 - (-4.4) = about 27.5F which is near the stated value on the refrigerator TXV. I suspect measuring at the compressor
case and with 15 feet of 3/8" line the actual pressure is a bit higher in the plate.
The target according to the manual is 10F to 12F of superheat. I suspect the choice of a fridge txv with a large superheat value allowed the fridge and freezer to run peacefully in parallel.
The freezer TXV which came with the system (when I bought the boat
, does not look original):
Eaton 223 FA 1/2 9 degree superheat.
This valve worked well in the system before it started becoming "sticky" resulting in either an inability to get below 20F or significant frosting of the return line without control. Considered moisture intrusion from above event but new dryer, evacuation to 150 microns for 2 days, and site glass moisture monitor
This was when I swapped out the freezer txv with the one from the fridge and good good control but with a lowest temperature of about 20F. Pulls down from room temperature in 90 minutes, cycle time is 25 minutes and very repeatable. Frost line moves as expected with 1/8 turn.
This is consistent with sporlan's documentation
of the FF-1/2-C being useful from 50F to -10F.
Reading the 2002 version of the Grunert manual (which appears to be an R409A system) recommends:
FS-1/2-C - for fridge applications
FS-1/2-ZP - for freezer applications
With all that said, I need a new TXV for the freezer side. The question is which one.....
I have found old (unused)
FF-1/2-ZP - This should be R-12 version with maximum operating pressure. The difference of the Z and ZP from Sporlan's documentation
Type ZP charges have essentially the same characteristics as the Type Z charge with one exception: they produce a pressure limit Maximum Operating Pressure (MOP). ZP charges are not
intended as replacements
for Z charges. Each should be selected for its own unique purpose.
I have found FF-1/2-C which I don't know if they all have the 26F midrange for superheat?
So the long winded question is: what TXV should I be looking to use for freezer (targeting 0F) as that is what the plates are setup to use.
I suspect the original valve was the FF-1/2-ZP but the 1985 manual does not say what was used. Only the later 2002 manual.
BTW: I enjoy learning
on this system and putting a few dollars into is and having it work
is fun. I did get the proper license
, use a recovery pump
, and reload the system with the refrigerant I pull off.