Teledyne manual 6712FR Refrigerated Sampler Maintenance, Always recover the refrigerant

6712FR Refrigerated Sampler

Section 8 Maintenance

As the compressor runs, the temperature of the evaporator will fall below 32•F (0•C) and the evaporator temperature indicator, located on the circuit board, will go out. The internal temper- ature and the compressor run indicators will both be lit. The compressor will continue running until the internal air temper- ature of the refrigerator reaches the temperature set on the tem- perature control knob. Once this temperature is reached the internal temperature indicator will go off, the compressor run indicator will go off, and the compressor will shut off. After the compressor shuts off, the refrigerator melts the frost that accu- mulated on the evaporator while the compressor was running. Once the evaporator temperature has warmed to the calibrated temperature (approximately 2•C) the evaporator temperature LED indicator will turn on.

When the refrigerator's internal temperature gets warmer than the temperature setting, the internal temperature indicator will light. When both the evaporator temperature and the internal temperature indicators are lit, a signal is sent to the solid state relay. This activates the refrigerator's compressor and turns on the compressor run indicator. The compressor will continue to run until the internal temperature indicator goes out.

If a problem with the circuitry is suspected, remember that the compressor shuts off when the internal temperature sensor reaches the setting on the temperature control knob. But, to turn the compressor on, both the internal temperature sensor and the evaporator temperature sensor must be warm. The com- pressor/fan solid state relay may be replaced but do not attempt to replace any other components. Otherwise, the calibration of the circuitry will be disturbed. It is suggested that the entire board be replaced or the board be returned to the factory for repair.

8.11.2Refrigeration System The refrigeration system is shown schematically in Figure 8-9.The charge capacity of the system is 7.5 oz of R-134a refrigerant.

CAUTION

All refrigeration repair work must be performed by a qualified refrigeration technician.

Always purge the system with nitrogen. NEVER USE AIR to purge the system.

Always recover the refrigerant.

When recharging, do not leave a line tap in the refrigeration system because of possible corrosion or leakage problems.

8-20