Thermo Pride Gas/Propane Furnace Induced Draft Highboy/Counterflow/Horizontal MHA1 - Manual (Page 31)

All installations and services must be performed by qualified service personnel.
28
Anticipators for the cooling operation are generally pre-set by the thermostat
manufacturer and require no adjustment.
5. Blower Motor Speed Wiring
:
• TURN OFF THE ELECTRICAL POWER to the furnace before
attempting to change blower speed wiring.
The blower motor is factory wired to the ignition control with standard heating
and cooling speeds pre-selected.
When changing motor speeds, simply switch the wire from the needed speed to
either the heating or cooling terminal as applicable on the module to obtain the
desired airflow. The wires for the unused speeds should then be reconnected to
the module in the “park” positions.
Figure 8: Blower and Control Panel
The option switches on the W/R integrated control are used to determine the
length of the heat delay-to-fan-on and delay –to-fan-off periods. The following
tables show the time periods that will result from the various switch positions.
SPEEDS
PARK TERMINALS
FOR UNUSED
234
1
ON
GREEN
12
0v
24
v
GREEN CAPACITOR
TERMINAL HEATING SPEED
TERMINAL COOLING SPEED
TRANSFORMER
NOTE:
MHA1-50,75,100,125
MDA1-50,100
USE LOW SPEED FOR HEATING
MDA1-75,125
USE MED-LOW SPEED FOR HEATING
MHA/MDA1-50 HAS A
3 SPEED MOTOR
HIGH SPEED (BLACK)
LOW SPEED (RED)
MED-LOW SPEED (BLUE)
MED-HIGH SPEED (YELLOW)
COMMON (WHITE)
OPTIONAL FAN
DELAY SWITCHES
EAC
HUMIDIFIER
EAC - COMMON
HUMIDIFIER - COMMON