March 2015 Tech Challenge
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A frozen food case utilizing R-404A with a TXV metering device (and receiver) has a customer complaint of a “warm case.” The symptoms at the store confirm that the case is 25 degrees warmer than normal and the condensing unit is running continuously. 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. | 230 deg. F. |
| Condensing Press./Temp. | 181 psig / 82 deg. F. |
| Condensing Outlet Temp. | 80 deg. F. |
| Condenser Sub cooling | 2 deg. F. |
| Condenser Split | 12 deg. F. |
| Entering Feed Device Temp. | 78 deg. F. |
| Evaporator Press./Temp. | 15 psig / -22 deg. F. |
| Evaporator Outlet Temp. | 12 deg. F. |
| Evaporator Superheat | 32 deg. F. |
| Compressor Inlet Temp. | 48 deg. F. |
| Total S. H. | 54 Deg. F. |
| Ambient Temp. | 70 deg. F. |
| Room/Box Temp. | 20 deg. F. |
| Compressor Volts | 240 V. |
| Compressor Amp. Draw | Low |
Looking for the answer? Check hvac-blog.acca.org on April 30, 2015 for the answer to this issue’s Tech Challenge.
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