Service Manual

28
CAUTION
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment
damage or improper operation.
If ANY refrigerant tubing is buried, provide a 6 in.
vertical rise at service valve. Refrigerant tubing lengths
up to 36 in. may be buried without further special
consideration. Do not bury lines longer than 36 in.
THERMOSTATIC
EXPANSION
VALVE
EQUALIZER
TUBE
SENSING
BULB
COIL
A91277
Fig. 24 – Typical TXV Installation
REFRIGERATION SYSTEM REPAIR
Leak Detection
New installations should be checked for leaks prior to
complete charging. If a system has lost all or most of its
charge, system must be pressurized again to approximately
150 psi minimum and 375 psi maximum. This can be done
by adding refrigerant using normal charging procedures or
by pressurizing system with nitrogen (less expensive than
refrigerant). Nitrogen also leaks faster than refrigerants.
Nitrogen cannot, however, be detected by an electronic leak
detector. (See Fig. 25.)
BEEP
BEEP
A95422
Fig. 25 – Electronic Leak Detection
PERSONAL INJURY AND UNIT DAMAGE HAZARD
Failure to follow this warning could result in personal
injury or death.
Due to the high pressure of nitrogen, it should never
be used without a pressure regulator on the tank.
!
WARNING
Assuming that a system is pressurized with either all
refrigerant or a mixture of nitrogen and refrigerant, leaks in
the system can be found with an electronic leak detector
that is capable of detecting specific refrigerants.
If system has been operating for some time, first check for a
leak visually. Since refrigerant carries a small quantity of oil,
traces of oil at any joint or connection is an indication that
refrigerant is leaking at that point.
A simple and inexpensive method of testing for leaks is to
use soap bubbles. (See Fig. 26.) Any solution of water and
soap may be used. Soap solution is applied to all joints and
connections in system. A small pinhole leak is located by
tracing bubbles in soap solution around leak. If the leak is
very small, several minutes may pass before a bubble will
form. Popular commercial leak detection solutions give
better, longer- lasting bubbles and more accurate results
than plain soapy water. The bubble solution must be
removed from the tubing and fittings after checking for leaks
as some solutions may corrode the metal.
LEAK
DETECTOR
SOLUTION
A95423
Fig. 26 – Bubble Leak Detection
You may use an electronic leak detector designed for
specific refrigerant to check for leaks. (See Fig. 25.) This
unquestionably is the most efficient and easiest method for
checking leaks. There are various types of electronic leak
detectors. Check with manufacturer of equipment for
suitability. Generally speaking, they are portable, lightweight,
and consist of a box with several switches and a probe or
sniffer. Detector is turned on and probe is passed around all
fittings and connections in system. Leak is detected by
either the movement of a pointer on detector dial, a buzzing
sound, or a light.
In all instances when a leak is found, system charge must
be recovered and leak repaired before final charging and
operation. After leak testing or leak is repaired, replace
liquid line filter drier, evacuate system, and recharge with
correct refrigerant quantity.
Coil Removal
Coils are easy to remove if required for compressor
removal, or to replace coil.
1. Shut off all power to unit.
2. Recover refrigerant from system through service
valves.
3. Break vacuum with nitrogen.
4. Remove top cover. (See Remove Top Cover in
Cabinet section of the manual.)
5. Remove screws in base pan to coil grille.
6. Remove coil grille from unit.
7. Remove screws on corner post holding coil tube
sheet.