chweber
30-06-2007, 05:44 AM
Hello all,
I am new to this forum, but have enoyed reading the knowledgable back and forth for quite a while. I would appreciate some help with a refrigeration problem I am having.
It is an R22 supermarket walk-in cooler. Problem is that the system has not been reaching setpoint. Temperatures are erratic between 36-39+ for a setpoint of 34. ***** level is full. Low side fluctuates or drifts. When I first arrived it fluctuated between less than 15 to 20+ psi. Evaporator was iced due to unit not reaching setpoint. Deiced the unit but the low side pressure fluctuations persisted, though at a higher value. Hide side pressure has consistently been about 180 psi (depending on ambient conditions) and is steady. I initially thought that it was the TXV that was having problems, so I replaced it. And for about a week the system worked perfectly. However, then the initial symptoms started to recur. I did not replace the R22 at the time of the TXV change.
On the return visit the heaviest (frosty) icing was confined to the distributor tubes/header. Low side pressures again too low and fluctuating between 15 and 20 psi. High side as before. After deicing and taking care to warm the TXV/distributor header pressures initially normalized to a low side of 38 psi (after the unit got close to setpoint). The low side pressure was at first stable but after about 20 minutes it started drifting again, albeit to a lesser amounts at a higher pressure range of 28-35 psi. Again heated the TXV/distributor and again the pressures normalized for 20 minutes at about 38 psi before starting to drift again.
My suspicion now is that there is some moisture in the system, possibly supported by the fact that the low-pressure cutout on this pumpdown system was set too low on initial installation causing the system to go into a slight vacuum prior to shutting off the compressor. The lack of cooling capacity would also, obviously, be consistent with a liquid line/TXV restriction. It seems reasonable (now!) that suction line pressure changes of the type I am seeing would most likely be caused by restriction in a small tube, such as the TXV or distributor.
Other details: Evap fans OK; compressor amp draw stable for each phase; condenser fans OK. System is about 2 years old. Though I have not tested the compressor by front-seating the suction line access valve and disconnecting the high side, since it is has no problem reaching normal high side pressures my reasoning is that it is functioning normally.:confused:
I am now going to suggest recovering the *****, giving the system a good evacuation and replacing the liquid line and suction line filter driers before recharging with virgin *****. Should possibly have done this first. :(
Are there any other system defects I am missing that could lead to the same syptoms?
Thanks in advance for you help.:)
Chris W.
Redwood City, California
I am new to this forum, but have enoyed reading the knowledgable back and forth for quite a while. I would appreciate some help with a refrigeration problem I am having.
It is an R22 supermarket walk-in cooler. Problem is that the system has not been reaching setpoint. Temperatures are erratic between 36-39+ for a setpoint of 34. ***** level is full. Low side fluctuates or drifts. When I first arrived it fluctuated between less than 15 to 20+ psi. Evaporator was iced due to unit not reaching setpoint. Deiced the unit but the low side pressure fluctuations persisted, though at a higher value. Hide side pressure has consistently been about 180 psi (depending on ambient conditions) and is steady. I initially thought that it was the TXV that was having problems, so I replaced it. And for about a week the system worked perfectly. However, then the initial symptoms started to recur. I did not replace the R22 at the time of the TXV change.
On the return visit the heaviest (frosty) icing was confined to the distributor tubes/header. Low side pressures again too low and fluctuating between 15 and 20 psi. High side as before. After deicing and taking care to warm the TXV/distributor header pressures initially normalized to a low side of 38 psi (after the unit got close to setpoint). The low side pressure was at first stable but after about 20 minutes it started drifting again, albeit to a lesser amounts at a higher pressure range of 28-35 psi. Again heated the TXV/distributor and again the pressures normalized for 20 minutes at about 38 psi before starting to drift again.
My suspicion now is that there is some moisture in the system, possibly supported by the fact that the low-pressure cutout on this pumpdown system was set too low on initial installation causing the system to go into a slight vacuum prior to shutting off the compressor. The lack of cooling capacity would also, obviously, be consistent with a liquid line/TXV restriction. It seems reasonable (now!) that suction line pressure changes of the type I am seeing would most likely be caused by restriction in a small tube, such as the TXV or distributor.
Other details: Evap fans OK; compressor amp draw stable for each phase; condenser fans OK. System is about 2 years old. Though I have not tested the compressor by front-seating the suction line access valve and disconnecting the high side, since it is has no problem reaching normal high side pressures my reasoning is that it is functioning normally.:confused:
I am now going to suggest recovering the *****, giving the system a good evacuation and replacing the liquid line and suction line filter driers before recharging with virgin *****. Should possibly have done this first. :(
Are there any other system defects I am missing that could lead to the same syptoms?
Thanks in advance for you help.:)
Chris W.
Redwood City, California