Tech Challenge – November 2018
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A frozen food case utilizing R-507A with a TXV metering device (and receiver) has a customer complaint of “warm product.” The symptoms at the convenience store confirm that the case is 20 degrees warmer than normal and the condensing unit appears to be cycling on the low pressure control. 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. | 92 deg. F |
| Condensing Press./Temp. | 203 psig / 88 deg. F. |
| Condensing Outlet | 81 deg. F. |
| Condenser Sub cooling | 7 deg. F. |
| Condenser Split | 13 deg. F. |
| Entering Feed Device Temp. | 77 deg. F. |
| Evaporator Press./Temp. | 29 psig / -6 deg. F. |
| Evaporator Outlet Temp. | -3 deg. F. |
| Evaporator Superheat | 3 deg. F. |
| Compressor Inlet Temp. | 2 deg. F. |
| Total S. H. | 8 deg. F. |
| Ambient Temp. | 75 deg. F. |
| Room/Box Temp.34 | 20 deg. F |
| Compressor Volts | 240 V. |
| Compressor Amp. Draw | Normal |
Looking for the Answer: Check hvac-blog.acca.org on December 31, 2018, for the answer to this issue’s Tech Challenge.
Posted In: ACCA Now, Tech Challenge
