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TABLE 9
Outdoor
Coil
Entering
CIRCUIT 1 CIRCUIT 1
Dis-
charge
+10 psig
Suction
Dis-
charge
+10 psig
Suction
112
128 293 124
337 130 130
382 134 381 133
430 136 427
139 476 137
B-Charging - Subcooling
1 - Attach gauge manifolds to discharge and suction
lines. With the economizer disabled, operate the unit
in cooling mode at high speed using the following
-
2 - Use the liquid line pressure and a PT chart to
determine the saturated liquid temperature.
3 - Measure the liquid line temperature at the condenser
outlet.
Subcooling Temperature = Liquid Saturated Temperature
Minus Liquid Temperature.
4 - Refer to TABLE 10 for subcooling temperatures.
A subcooling temperature greater than this value
indicates an overcharge. A subcooling temperature
less than this value indicates an undercharge.
TABLE 10
SUBCOOLING TEMPERATURE
Unit
Liquid Temp. Minus Ambient Temp.
1st Stage 2nd Stage
078 ++ ++
092, 102 ++ ++
++ ++
C-Heating System Service Checks
-
Before checking piping, check with gas company or au-
thorities having jurisdiction for local code requirements.
Refer to the LDT Installation instruction for more informa-
tion.
1-Gas Piping
the unit. Supply gas pipe must not be smaller than the
unit gas connection. Refer to installation instructions for
details.
UNIT
GROUND
JOINT UNION
MANUAL MAIN
SHUT-OFF VALVE
(REFER TO LOCAL CODES)
GAS PIPING
SUPPORT
DRIP LEG
ROOF
MOUNTING
FRAME
GAS PIPING COMPONENTS
REFER TO INSTALLATION INSTRUCTIONS
VALVE
CAP HERE
TO ISOLATE
VALVE WHEN
PRESSURE
TESTING
LINE
FIGURE 20
2-Testing Gas Piping
NOTE-In case emergency shutdown is required, turn o
the main manual shut-o valve and disconnect the main
power to the unit. These controls should be properly la-
beled by the installer.
When pressure testing gas lines, the gas valve must be
disconnected and isolated. Gas valves can be damaged
if subjected to more than 0.5 psig [14”W.C. (3481 Pa)].
See FIGURE 20.
When checking piping connection for gas leaks, use the
preferred means. Common kitchen detergents can cause
harmful corrosion on various metals used in gas piping.
The use of specialty Gas Leak Detector is strongly rec-
ommended.
Do not use matches, candles, ame or any other
source of ignition to check for gas leaks.
3-Testing Gas Supply Pressure
When testing gas supply pressure, connect test gauge to
the inlet pressure tap located on unit gas valve GV1. Test
range of the following values.
High pressure can result in permanent damage to the gas
For natural gas units, operating pressure at the unit gas
pressure at the unit gas connection must be between
On multiple unit installations, each unit should be checked
separately while operating at maximum rate, beginning
with the one closest to the supply gas main and progress-
ing to the one furthest from the main. Multiple units should
also be tested with and without the other units operating.
Supply pressure must fall within the range listed in the
previous paragraph.
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