Carrier 26H - Manual (Page 25)

Carrier S E R V I C E 26H
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2. INSTALLING GAUGES
a. Backseat suction and discharge shutoff valves.
b. Remove gauge plugs and install 1/8" MPT
X
1/4" flare half union coupling.
c. Attach 1/4" OD copper gauge line, flared at
both ends, to the couplings.
d. Attach suction and discharge gauges to these
lines, leaving connection slightly loose.
e. Crack the valve off back seat, allow a small
amount of refrigerant to escape, and tighten
the flare nut.
To read line pressures, turn the shutoff valves
slightly from the backseat position. If the gauge
needle vibrates, backseat the valve until there is
no vibration but the gauge still reads line pressure.
NOTE: To conserve refrigerant, use short lengths
of small bore tubing when installing gauges. This
unit is sensitive to charge and repeated installa­
tion and removal of gauges with necessary purging
of air will result in an undercharge of refrigerant.
SUCTION LINE
PRESSURE GAUGE
DISCHARGE LINE
PRESSURE GAUGE-
CHARGING HOSE ATTACHED TO THE SUCTION
VALVE WITH A 1/4" HALF UNION COUPLING
"FREON-12 DRUM
FIG. 11 - CHARGING MANIFOLD ATTACHED
FOR CHARGING UNIT
3. PUMP DOWN OF COMPRESSOR
If the refrigeration system must be opened at the
compressor, first "Pump Down". Proceed as follows:
1. Install a pressure gauge to the suction shut­
off valve.
2. Front seat the suction shutoff valve.
3. Front seat the oil return line shutoff valve
(on 26H5).
4. Operate the compressor intermittently until
the suction pressure gauge indicates 0 to 2
PSIG pressure is being maintained in the
crankcase.
5. With the compressor stopped, front seat the
discharge shutoff valve.
6. Loosen the discharge shutoff valve gauge
plug slightly and bleed off any remaining pres­
sure. The compressor can then be opened or
removed.
7. After repairing the compressor, evacuate and
purge it to remove residual air. Remove the
pipe plug from the gauge connection of the
discharge shutoff valve. Operate the com­
pressor for about 10 minutes. Place your thumb
over the discharge valve gauge connection^ at
the some time stopping the compressor. Crack
open the SUCTION shutoff valve, momentarily,
allowing a small amount of gas to enter the
compressor. Front seat the suction shutoff
valve immediately. A slight gas pressure
should not be felt against your thumb. Re­
place the pipe plug. The suction, discharge
and oil return line shutoff valves can now be
backseated and the machine is ready for op­
eration.
25 26H-57PD