November 2014 Tech Challenge
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A Rooftop with R-438A retrofitted refrigerant and a fixed orifice-metering device has a customer complaint of “no cooling.” The symptoms at the business confirm that the thermostat is not satisfied and the blower is running continuously. What are the “possible causes” (there is only one problem intended) with the following measured conditions on this field service check sheet?
Field Service Check Sheet
| Compressor Discharge Temp. | 242 deg. F. |
| Condensing Press./Temp. | 287 psig / 122 deg. F. |
| Condensing Outlet Temp. | 102 deg. F. |
| Condenser Sub cooling | 20 deg. F. |
| Condenser Split | 42 deg. F. |
| Entering Feed Device Temp. | 90 deg. F. |
| Evaporator Press./Temp. | 100 psig / 55 deg. F. |
| Evaporator Outlet Temp. | 60 deg. F. |
| Evaporator Superheat | 5 deg. F. |
| Compressor Inlet Temp. | 70 deg. F. |
| Total S. H. | 15 Deg. F. |
| Ambient Temp. | 80 deg. F. |
| Room/Box Temp. | 82 deg. F. |
| Compressor Volts | 240 V. |
| Compressor Amp. Draw | High |
Looking for the answer? Check hvac-blog.acca.org on January 5, 2015 for the answer to this issue’s Tech Challenge.
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