MORTEX
PRODUCTS
INC
FORT
WORTH,
TX
76106
Page
10
white thermostat wire to the W” terminal on the furnace
terminal strip. This signal energizes the heater contactor(s)
closing the contacts to the heaters. The blower heating speed
wire is connected to the “W” terminal on the terminal block so
the blower is energized at the after the ON delay has expired.
The blower will continue to operate until the thermostat call
for heat has been satisfied. When the call for heat has been
satisfied the “W” terminal is de-energized and the heater
contactor opens turning off the heater. The blower motor will
continue to operate until the OFF delay has expired. The
furnace is now in standby mode waiting for the next heating
cycle.
The 12 kW, 15 kW and 20 kW models have a black wire that
is connected to the “W” terminal on the terminal block. For
two stage operation the black wire needs to be removed from
the “W” terminal and connected to the W2 wire from the
thermostat. Connect the wires using a wire nut. The other end
of the black wire is connected to the 24 VAC coil on the
second heater contactor. You must have a thermostat that has
the second stage heating feature “W2”. The second stage heat
cycle is enabled when the room temperature typically falls
more than 3 degrees below the thermostat set point. The
thermostat energizes the second heater to aid in heating the
room back to the thermostat set point. Once the room is within
1 degree of the thermostat set point the second stage heater is
de-energized until the thermostat calls for second stage heat
“W2” again.
SECTION V: TROUBLE SHOOTING
The following checks should be made before trouble shooting
the furnace controls for a no heat issue.
1.
Check all of the circuit breakers. Make sure they are
turned to the “ON” position and have not tripped.
2.
Check all fuses, especially the 3 amp fuse on the top right
side of the control box. If the fuse is blown, check the
wiring with an OHM meter for a short to ground. If
shorted, repair the short, and then replace the fuse.
3.
Check any electrical switches that are external to the
furnace to make sure they are turned on.
4.
Check all wiring connections, especially on any of the
components, to ensure they are securely fastened.
If you have 240 VAC coming out of the control box circuit
breakers and you have 24 VAC between the load side if the 3
amp fuse and ground, then continue on through the rest of the
checks.
CONSTANT TORQUE Motor Check – Heating Mode
1.
If the motor is not running, check for 240 VAC on the L1
and L2 terminals. Check 24 VAC at the motor terminals
connected to the “W” and “C” terminal on the terminal
block. If the 240 VAC and 24 VAC is present continue to
the steps below. Refer to Figure 10 and Table 1 for
terminal locations and definitions.
A.
If 240 VAC is not present at the motor check for a
broken wire between the circuit breaker and the
motor.
B.
If 240 VAC is present at the motor terminals continue
to the next check.
C.
If 24 VAC is not present at the motor check the fuse
or transformer.
D.
If 24 VAC is present at the terminal block “W” and
“C” terminals then check the motor connections.
E.
If the motor connections are ok then the motor is bad
and needs to be replaced.
CONSTANT TORQUE Motor Check – Cooling Mode
1. If the motor is not running, check for 240 VAC on the L1
and L2 terminals. Check 24 VAC at the motor terminals on
the “Y” and “C” terminals on the terminal block. If the 240
VAC and 24 VAC is present continue to the steps below.
Refer to Figure 10 and Table 1 for terminal locations and
definitions.
A.
If 240 VAC is not present at the motor check for a
broken wire between the circuit breaker and the
motor.
B
If 240 VAC is present at the motor terminals continue
to the next check.
C.
If 24 VAC is not present at the motor check the fuse
or transformer.
D.
If 24 VAC is present at the terminal block “Y” and
“C” terminals then check the motor connections.
E.
If the motor connections are ok then the motor is bad
and needs to be replaced.
Figure 10: Constant Torque Motor Terminals
For personal safety be sure to turn the electrical power
“OFF” at the main circuit panel (Circuit Breaker Box)
before attempting any service or maintenance operations.
Home owners should never attempt to perform any
maintenance which requires opening the furnace control box
door.
To avoid personal injury or property damage, make certain
that the motor leads cannot come into contact with non-
insulated metal components of the unit.
