177
To Use the Cooling Charging Chart
Use the outdoor air temperature, saturated suction temperature
and saturated condensing temperature (available on the Com-
fortLink display), and find the intersection point on the cooling
charging chart. If intersection point is above the line, carefully
recover some of the refrigerant. If intersection point is below
the line, carefully add refrigerant.
NOTE: Indoor-air cfm must be within normal operating range of
unit.
In order to determine which charging chart to use, the techni-
cian can verify the evaporator configuration of the unit (High
Cap or Std Cap) by counting the number of rows on the in-
stalled evaporator. Use Table 118 to identify the correct unit
configuration for refrigerant charging.
Table 118 — Unit Capacity Type
Units With Humidi-MiZer
®
Adaptive Dehumidification System
NOTE: All circuits must be running in normal cooling mode. In-
door airflow must be within specified air quantity limits for cool-
ing. All outdoor fans must be on and running at normal speed.
Use the following procedure to adjust charge on Circuit B of
Humidi-MiZer equipped units:
1. Start all compressors and outdoor fans. Allow unit to run
for 5 minutes.
2. Switch system to run in a Dehumidification mode for 5
minutes by switching RHV to ON through the Service Test
function (Service Test
COOL
RHV).
3. At the end of the 5-minute period, switch back into Cool-
ing mode through the Service Test function (Service
Test
COOL
RHV) by switching RHV to OFF.
4. Using the cooling charging charts provided (Fig. 55-92), add
or remove refrigerant until conditions of the chart are met. As
conditions get close to the point on the chart, add or remove
charge in
1
/
4
lb increments until complete. See paragraph “To
Use the Cooling Charging Chart” for additional instructions.
5. If a charge adjustment was necessary in Step 4, then repeat
the steps in this paragraph (starting with Step 2) until no
charge adjustment is necessary. When no more charge
adjustment is necessary after switching from a Dehumidi-
fication Mode to a Cooling Mode (Steps 2 and 3), then the
charge adjustment procedure is complete.
Gas System Adjustment (48P Only)
TWO-STAGE GAS VALVE ADJUSTMENT
The gas valve opens and closes in response to the unit control.
When power is supplied to valve terminals D1 and C2, the
main valve opens to its preset position.
The regular factory setting is stamped on the valve body
(3.3 in. wg).
To adjust regulator:
1. Set thermostat at setting for no call for heat.
2. Switch main gas valve to OFF position.
3. Remove
1
/
8
-in. pipe plug from manifold or gas valve pres-
sure tap connection. Install a suitable pressure-measuring
device.
4. Switch main gas valve to ON position.
5. Set thermostat at setting to call for heat.
6. Remove screw cap covering regulator adjustment screw
(see Fig. 93).
7. Turn adjustment screw clockwise to increase pressure or
counterclockwise to decrease pressure.
8. Once desired pressure is established, set thermostat setting
for no call for heat, turn off main gas valve, remove pres-
sure-measuring device, and replace
1
/
8
-in. pipe plug and
screw cap.
Fig. 93 — Two-Stage Gas Valve
MODULATING GAS VALVE ADJUSTMENT
The modulating gas valve is an electrically operated valve con-
trolled by a 0-20 vdc input directly to valve terminals or from
an external controller. The modulating gas valve is installed
downstream of a separate pressure regulator, such as a 2-stage
gas valve. See Fig 94.
Fig. 94 — Modulating Gas Valve Location
The modulating gas valve has both sides fitted for low fire ad-
justment. When 0 vdc is applied at the connect terminals, the
bypass provides a minimum outlet pressure of 0.3 in. wg for
2.0 in. wg at the gas regulator upstream the modulating valve
(factory setting).
For low fire adjustment (see Fig. 95):
1. Disconnect a wire from modulating valve connect terminals.
NOTE: Do not allow wire to come into contact with any other
part.
2. Remove the left bypass cap.
3. Turn adjustment screw using a small screwdriver to the
desired low fire adjustment.
NOTE: Clockwise screw rotation reduces flow rate. Do not over-
tighten.
UNIT SIZE
48/50P
NUMBER OF ROWS ON EVAPORATOR
High Capacity Std Capacity
030 43
035 N/A 4
040 63
050 64
055 64
060 64
070 64
075 64
090 64
100 64
INLET PRESSURE
TAP (ON SIDE)
1/8-IN. 27 NPT
OUTLET PRESSURE
TAP (ON SIDE)
1/8-IN. 27 NPT
HIGH-FIRE REGULATOR
ADJUSTMENT SCREW
LOW-FIRE REGULATOR
ADJUSTMENT SCREW
2-STAG E
GAS VALVE
MODULATING
GAS VALVE
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