Tech Challenge – May 2013
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A draft beer cooler in Orlando utilizing R-134a with a TXV metering device (and receiver) has a customer complaint of “warm beer.” The symptoms at the pub confirm warm product and the condensing unit appears to be running 100% of the time, with the low pressure control not being satisfied. What are the “possible causes” (Note: There is only one problem intended) with the following measured conditions on this field service check sheet?
Field Service Check Sheet
| Compressor Discharge Temp. | 200 deg. F.* |
| Condensing Press./Temp. | 174 psig / 121 deg. F. |
| Condensing Outlet Temp. | 111 deg. F. |
| Condenser Sub cooling | 10 deg. F. |
| Condenser Split | 41 deg. F.** |
| Entering Feed Device Temp. | 86 deg. F.*** |
| Evaporator Press./Temp. | 19 psig / 18 deg. F. |
| Evaporator Outlet Temp. | 28 deg. F. |
| Evaporator Superheat | 10 deg. F. |
| Compressor Inlet Temp. | 40 deg. F. |
| Total S. H. | 22 Deg. F. |
| Ambient Temp. | 80 deg. F. |
| Room/Box Temp. | 45 deg. F. |
| Compressor Volts | 240 V. |
| Compressor Amp. Draw | High |
*High Comp ratio & discharge Temp. **Very High ***Normal
And the answer is:
The problem is a dirty/insufficient air flow over the condenser. The condensing pressure/temp. is high to expel the heat gained in the evaporator, suction line and compressor, causing a high compression ratio, a high amp draw and high discharge temperature. The Subcooling and superheat are high to near normal because the TXV is attempting to maintain a constant S.H. with a lower refrigerant flow rate caused by the higher compression ratio.
Posted In: ACCA Now, Tech Challenge
