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Flower case retrofit problem
Hello,
I just converted a flower cooler to R448a from R22 and it isn't going as planned. I'm looking for some insight from someone who has done this.
OLD Condensing Unit: Techumseh AK9446EC (BOM 2C208-9) w/ receiver, pressure control, and service valves (compressor AK165AT-035)
NEW Condensing Unit: Emerson M6GP-H064-CAA-177 w/ receiver, and services valves - I added a pressure control (compressor RST45C1E-CAA-102)
Evap is a Bohn LO-0400C (unchanged)
TXV is a Parker CE-AA-VW (unchanged)
TXV was just replaced about a year ago. Old unit had a suction service valve rust through yesterday which made the replacement more urgent.
I blew out the coil with nitrogen - no flush. I did install a suction filter drier. I charged as a liquid
Condenser Ambient - 73f
Box Temp - 53f
LP: 61.6psi EVAP SAT: 32.3f
VAPOR LINE: 52.6f (at suction service valve) SH 20.3f
HP: 234.1psi COND SAT: 97.0f
LIQUID LINE: 91.0f SC: 6.0f
DISCHARGE: 181f
Condensing unit amps: 8.89a (includes 1x 35W 1.4 FLA fan) The junction box for the compressor is on the other side and hard to get to - I will get a measurement for the fan tomorrow and subtract)
I see the evaporator is starving but I have opened the TXV wide open with no noticeable change. Do I need a larger TXV? I thought R22 and R448a were pretty close.
If someone could give me a little guidance, I would appreciate it.
Thank you!
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My experience with this 448 retrofit is that you need to charge lower than the 22 was.
Sometimes these systems like a few bubbles running in the sight glass. Try backing the charge off a bit
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What's the size of the box and how many glass doors ?
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Originally Posted by
Restaurant mech
My experience with this 448 retrofit is that you need to charge lower than the 22 was.
Sometimes these systems like a few bubbles running in the sight glass. Try backing the charge off a bit
When I had less charge my superheat was in the 30s.... that's why I pushed it to where it is now...
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Originally Posted by
VTP99
What's the size of the box and how many glass doors ?
6x8x7. 3 display doors 1 walk in door.
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System seems a little small not including the door load.
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Originally Posted by
VTP99
System seems a little small not including the door load.
It is not a high volume application - it is a small shop.
It may be undersized, but capacity hasn't been an issue before and it has worked at that rating since 1993.
Old unit was 5150 btu @ 25f evap and 90f ambient (R22)
New unit is 5290 btu @ 25f evap and 90f ambient (R448a)
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Door gaskets in good condition ?
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The compressor capacities are too close to matter so if there is no temperature drop in the liquid line I think I'd replace the TXV and the drier first.
With the logic: if you have liquid to the valve at adequate pressure and volume and the suction pressure is sufficiently lower - the only bottle-neck would be the TXV.
I'm not at all familiar with R-408 and so cannot say if a R-22 TXV plays nice with R-408. But in your case it sure seems like it either doesn't or is obstructed in some way.
Is the drier at the receiver or at the TXV?
PHM
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Originally Posted by
mjohnson2981
Hello,
I just converted a flower cooler to R448a from R22 and it isn't going as planned. I'm looking for some insight from someone who has done this.
OLD Condensing Unit: Techumseh AK9446EC (BOM 2C208-9) w/ receiver, pressure control, and service valves (compressor AK165AT-035)
NEW Condensing Unit: Emerson M6GP-H064-CAA-177 w/ receiver, and services valves - I added a pressure control (compressor RST45C1E-CAA-102)
Evap is a Bohn LO-0400C (unchanged)
TXV is a Parker CE-AA-VW (unchanged)
TXV was just replaced about a year ago. Old unit had a suction service valve rust through yesterday which made the replacement more urgent.
I blew out the coil with nitrogen - no flush. I did install a suction filter drier. I charged as a liquid
Condenser Ambient - 73f
Box Temp - 53f
LP: 61.6psi EVAP SAT: 32.3f
VAPOR LINE: 52.6f (at suction service valve) SH 20.3f
HP: 234.1psi COND SAT: 97.0f
LIQUID LINE: 91.0f SC: 6.0f
DISCHARGE: 181f
Condensing unit amps: 8.89a (includes 1x 35W 1.4 FLA fan) The junction box for the compressor is on the other side and hard to get to - I will get a measurement for the fan tomorrow and subtract)
I see the evaporator is starving but I have opened the TXV wide open with no noticeable change. Do I need a larger TXV? I thought R22 and R448a were pretty close.
If someone could give me a little guidance, I would appreciate it.
Thank you!
PHM
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When faced with the choice between changing one's mind, and proving that there is no need to do so, most tend to get busy on the proof.
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Originally Posted by
VTP99
Door gaskets in good condition ?
Yes. The glass doors rarely get opened.
The walk in door has some wear, but not horrible.
The unit hasn't had a capacity issue.
I believe I am looking at a TXV issue. My return gas is at box temp... I don't know if the TXV is defective or is the wrong size due to refrigerant change....
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Originally Posted by
Poodle Head Mikey
The compressor capacities are too close to matter so if there is no temperature drop in the liquid line I think I'd replace the TXV and the drier first.
With the logic: if you have liquid to the valve at adequate pressure and volume and the suction pressure is sufficiently lower - the only bottle-neck would be the TXV.
I'm not at all familiar with R-408 and so cannot say if a R-22 TXV plays nice with R-408. But in your case it sure seems like it either doesn't or is obstructed in some way.
Is the drier at the receiver or at the TXV?
PHM
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Drier is just after the receiver.
Half of the liquid line is new (whole line isn't but 8 feet)
The condensing unit and driers are brand new. I will check for temp drops this morning to verify.
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Suction pressure is too high , superheat is too low. Tev is flooding a bit. Just replace the valve all will be fine.
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Where did you add the liquid to? Damaged suction reeds & overcharged? On the original comp, the one w/ the rusted suction service valve? What caused the rust, low SH?
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When R-22 was sky high, where I work started doing conversions. Seems like there were a lot more problematic units. Owner finally said enough is enough, said if the unit came with 22, it's gonna get 22.
I do a triple evac with nitro to remove non condensables.
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I cannot remember a TXV that I did not have to adjust the SH when changing from the "The Three Amigos(movie)"(r12-r22-r502).
I see zero problems w/ a 20*SH @ the comp(Total SH). W/ an 8' lineset the evap SH will be higher than the "typical" 6*-8*-10* SH.
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There is something very important that has not been discussed yet. Which is . . . This not your run of the mill cooler. It's a flower box. Which means the TD of the evap is critical. Can't remember the exact number, but your TD should be in the range of 5*F. If you treat your temps and pressures like a normal cooler, you will ruin the flowers. Why, you may ask?
First let's discuss what TD actually is. It stands for Temp Difference. The difference between the air temp entering the evap and the saturated suction pressure (taken from your gauge) converted to temp.
A normal cooler will run 10-20*F TD, which will suck too much moisture out of the flowers and ruin the product. A flower box needs to run somewhere in the range of 5*F TD to maintain a higher humidity. If you don't understand this, the store owner will be very upset with you.
Probably bone up on what the TD should be for this flower box. You can run a higher superheat as long as you have cooling back to the compressor, but you cannot run a high TD like in 'normal' refrigeration.
I do a triple evac with nitro to remove non condensables.
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Originally Posted by
BBeerme
There is something very important that has not been discussed yet. Which is . . . This not your run of the mill cooler. It's a flower box. Which means the TD of the evap is critical. Can't remember the exact number, but your TD should be in the range of 5*F. If you treat your temps and pressures like a normal cooler, you will ruin the flowers. Why, you may ask?
First let's discuss what TD actually is. It stands for Temp Difference. The difference between the air temp entering the evap and the saturated suction pressure (taken from your gauge) converted to temp.
A normal cooler will run 10-20*F TD, which will suck too much moisture out of the flowers and ruin the product. A flower box needs to run somewhere in the range of 5*F TD to maintain a higher humidity. If you don't understand this, the store owner will be very upset with you.
Probably bone up on what the TD should be for this flower box. You can run a higher superheat as long as you have cooling back to the compressor, but you cannot run a high TD like in 'normal' refrigeration.
X2 & oh yeah, X3.
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Originally Posted by
TechmanTerry
X2 & oh yeah, X3.
X4. And 6. (I won’t be greedy and hog x5)
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I can't fix it if it won't stay broke..