Figure 6-16 High Pressure Switch Testing - Carrier 69NT40-511-300 Operation And Service

6.9 HIGH PRESSURE SWITCH
6.9.1 Replacing High Pressure Switch
a. Turn unit start-stop switch OFF. Frontseat both suc-
tion and discharge service valves to isolate compres-
sor. Remove the refrigerant from the compressor.
b. Disconnect wiring from defective switch. The high
pressure switch is located on the center head and is
removed by turning
Figure 2-3.)
c. Install a new high pressure switch after verifying
switch settings. (Refer to paragraph 6.9.2.)
d. Evacuate and dehydrate the compressor per para-
graph 6.6.
6.9.2 Checking High Pressure Switch
WARNING
Do not use a nitrogen cylinder without a
pressure regulator. Do not use oxygen in or
near a refrigeration system as an explosion
may occur.
NOTE
The high pressure switch is non-adjustable.
a. Remove switch as outlined in paragraph 6.9.1
b. Connect ohmmeter or continuity light across switch
terminals. Ohm meter will indicate no resistance or
continuity light will be illuminated if the switch closed
after relieving compressor pressure.
c. Connect hose to a cylinder of dry nitrogen. (See
Figure 6-16.)
1
4
5
2
3
6

Figure 6-16 High Pressure Switch Testing

d. Set nitrogen pressure regulator at 26.4 kg/cm@ (375
psig) with bleed-off valve closed.
e. Close valve on cylinder and open bleed-off valve.
f. Open cylinder valve. Slowly close bleed-off valve to
increase pressure on switch. The switch should open
at a static pressure up to 25 kg/cm@ (350 psig). If a
light is used, light will go out. If an ohmmeter is used,
the meter will indicate open circuit.
g. Slowly open bleed-off valve to decrease the pres-
sure. The switch should close at 18 kg/cm@ (250
psig).
T-285
counterclockwise. (See
1. Cylinder Valve
and Gauge
2. Pressure Regulator
3. Nitrogen Cylinder
4. Pressure Gauge
(0 to 36 kg/cm@ =
0 to 400 psig)
5. Bleed-Off Valve
6. 1/4 inch Connection
6.10 CONDENSER COIL
The condenser consists of a series of parallel copper
tubes expanded into copper fins. The condenser coil
must be cleaned with fresh water or steam so the air flow
is not restricted. To replace the coil, do the following:
Do not open the condenser fan grille before
turning power OFF and disconnecting
power plug.
a. Using a refrigerant reclaim system, remove the refrig-
erant charge.
b. Remove the condenser coil guard.
c. Unsolder discharge line and remove the line to the
receiver or water-cooled condenser.
d. Remove coil mounting hardware and remove the coil.
e. Install replacement coil and solder connections.
f. Leak-check the coil connections per paragraph para-
graph 6.5. Evacuate the unit per paragraph 6.6 then
charge the unit with refrigerant per paragraph 6.7.
6.11 CONDENSER FAN AND MOTOR ASSEMBLY
Do not open condenser fan grille before
turning power OFF and disconnecting
power plug.
The condenser fan rotates counter-clockwise (viewed
from front of unit), pulls air through the the condenser
coil, and discharges horizontally through the front of the
unit. To replace motor assembly:
a. Open condenser fan screen guard.
b. Loosen two square head set screws on fan. (Thread
sealer has been applied to set screws at installation.)
Disconnect wiring from motor junction box.
Take necessary steps (place plywood over
coil or use sling on motor) to prevent motor
from falling into condenser coil.
c. Remove motor mounting hardware and replace the
motor. It is recommended that new locknuts be used
when replacing motor. Connect wiring per wiring dia-
gram.
d. Install fan loosely on motor shaft (hub side in). DO
NOT USE FORCE. If necessary, tap the hub only, not
the hub nuts or bolts. Install venturi. Apply "Loctite H"
to fan set screws. Adjust fan within venturi so that the
outer edge of the fan projects 3.2 to 6.4 mm (3/16"
¦1/16") back from edge of the venturi. Spin fan by
hand to check clearance.
e. Close and secure condenser fan screen guard.
f. Apply power to unit and check fan rotation. If fan
motor rotates backward, reverse wire numbers 5 and
8.
6.12 WATER COOLED CONDENSER CLEANING
The water-cooled condenser is of the shell and coil type
with water circulating through the cupro-nickel coil. The
6-10
WARNING
WARNING
CAUTION