All installations and services must be performed by qualified service personnel.
Modifications to ECM blower speed settings are done using the S3 and S4 dip switch controls. Thermo
Pride two-stage furnaces are factory shipped at the CFM settings listed below in Table 4C.
2-Stage Blower Settings (from factory)
Table 4C
Unit
Control Board
Dip Switch
Settings
Heating
CFM
(low fire)
Heating
CFM
(high fire)
Constant Fan
CFM
Cooling
CFM
CDX3-75
SW3 1-4 Off
SW4 1-3 Off
SW4 4 On
885 1012 500 1000
CHX3-75
SW3 1-4 Off
SW4 1-4 Off
760 931 500 1000
CDX3-100
SW3 1-4 Off
SW4 1-3 Off
SW4 4 On
1094 1340 600 1200
CHX3-100
SW3 1-4 Off
SW4 1-4 Off
1015 1243 600 1200
CDX3-125
SW3 1-4 Off
SW4 1-3 Off
SW4 4 On
1366 1673 700 1400
CHX3-125
SW3 1-4 Off
SW4 1-4 Off
1270 1556 700 1400
For adjustments to the Cooling CFM settings, as well as all additional CFM changes, please reference
the dip switch tables listed in the ECM operation manual. (Included with every furnace.)
5.
DE-HUMIDIFICATION
The ECM motor in conjunction with the W/R 50V51-843 has a feature to enhance de-humidification in the
cooling mode. In the dehumidify mode the indoor blower motor (ECM) reduces CFM. By reducing airflow
the indoor coil runs colder and thus extracts more moisture from the air.
The W/R 50V51-843 is shipped from the factory with dipswitch S5-2 set to on for system that do not have
a dehumidification connection from the thermostat. For systems using a thermostat that provides
dehumidification option move dip switch S5-2 to “OFF”. With the S5-2 switch in the “OFF” position the air
conditioning fan speed will be reduced 30% from the normal CFM setting when the humidity in the home
is higher than the set point of the dehumidistat.
6.
FIELD WIRING AND REPLACING WIRING
Field wiring between the furnace and devices not attached to the furnace shall conform with the
temperature limitation for Type T wire[63°F rise (35°C)] when installed in accordance with the
manufacturer’s instructions. If any of the original factory supplied furnace wiring is replaced or a separate
device other than the thermostat is wired internal to the unit 105
°
C thermoplastic or equivalent wire must
be used.
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