Repairing Leaks - Thermo Scientific XBF40-MD Series Installation, Operation And Service Manual

Appendix
Table 2: Troubleshooting Procedures
SYMPTOM
Unit runs continuously.

14.4 Repairing Leaks

36 Installation, Operation and Service Manual
POSSIBLE CAUSE
1. Poor gasket seal.
2. System undercharged.
3. System overcharged.
4. Non-condensable gas/air in system.
5. Worn or inefficient compressor.
6. Defective temperature sensor or control
settings.
Copper tubing joints are made using "Phos Copper" solder which is a high
temperature brazing needing no flux and with good working characteristics.
Leaks in these joints are usually caused by copper to copper or copper to
steel contact (rubbing) which can cause a hole in the copper tubing.
Leaks occurring in components such as pressure controls or valves usually
must be dealt with by replacing the offending component. Whenever a
system has been opened for repair, it must be evacuated to a very low
vacuum (50 microns or lower) and the drier must be replaced. Always
replace the drier with the same BRAND AND SIZE as originally supplied.
EVACUATION
A refrigeration system's worst enemy is air in the system, because all air
contains moisture. Moisture in a refrigeration system will mix with the oil
which has refrigerants in it, and with the added compressor heat, it will or
can cause an acid condition within the system. This acid will cause the
compressor to eventually to fail. It is quite simple to purge air from a system
but eliminating moisture is more difficult. There has always been a tendency
with technicians to open a system and not replace the drier after doing so.
Note The filter-drier must ALWAYS be replaced whenever the refrigeration
system has been opened to atmosphere.
TEST AND CORRECTION
1. Check and replace door gasket or
adjust door alignment.
2. Check operating pressures. If low,
shut down, warm up overnight and
check for refrigerant leak.
3. Check operating pressures.
4. Check operating
discharge will be high and suction
pressure low.
evacuate and recharge.
5. Replace Compressor.
6. Replace sensor or check control
programming.
Thermo Scientific XBF40-MD Series Blast Freezers
pressures,
Recover charge,