Thermo NESLAB HX 150, Service Manual

Page: 15 / 51

15
FILTER/DRYER REPLACEMENT
NOTE: The filter/dryer contains a desiccant which will absorb
moisture from the atmosphere. The filter/dryer should be
replaced whenever the refrigeration system has been opened
and allowed to go to atmospheric pressure. Unsealing and
installing the new filter/dryer should be left until the last pos-
sible minute to minimize contamination of its
desiccant.
Disconnect the unit from line voltage
1. Recover the system refrigerant.
2. Remove all Shrader valve cores.
3. Remove solenoid valve internal components (See “Solenoid
valve replacement procedure” for drawing) Wrap a damp rag
around the solenoid valve body.
4. Apply purge gas to the system.
5. Desolder and remove old filter/dryer.
6. Place new filter/dryer in position, with direction-of-flow arrow
pointing towards the liquid line solenoid valve.
7. Wrap the filter/dryer body in a damp rag.
8. Introduce nitrogen purge gas into the discharge service port.
9. Braze connections using BAg 28. Orient torch flame away
from the filter/dryer body. Any bubbling of the paint on the
filter/dryer indicates excessive temperature is being ap-
proached - stop and allow to cool if this occurs.
10. Remove the damp rags and the nitrogen supply.
11. Insert new schrader valve cores.
12. Assemble the solenoid valve (Do Not over tighten - Use two
wrenches).
11. Pressurize and leak check.
12. Evacuate system.
13. Charge system.
14. Test.
15. Install any access panels removed.