13
Maintenance and Repair
The occurrence of the manual reset limit control to trip is an
abnormal condition. Care should be taken to determine the
exact reason that the high limit control tripped before a man-
ual reset of the limit control. Possible problem areas could
be dirty heat exchanger, blocked air inlet or outlet, fan/motor
malfunction, too high operating ambient, incorrect operating
voltage, or leaking heat exchanger. In the event that the heat
exchanger is defective, it must be replaced.
1. The manual reset limit control is located in the heating
element hazardous location enclosure on the heat ex-
changer which is covered by the sheet metal housing at-
tached to the side of the unit. To gain access, remove the
four sheet metal screws holding the sheet metal cover in
place and unthread the cast aluminum enclosure lid. (See
Figure 11.) The manual reset limit control device has a
small reset button protruding from the center of its back
housing. Depress this button in to reset the control. Re-
place the aluminum enclosure lid and sheet metal cover.
146 mm
(5-3/4")
146 mm
(5-3/4")
Figure 11
III. FAN MOTOR AND BLADE
1. The motor is a sealed unit that requires no lubrication. If
the motor is defective, it must be replaced with an origi-
nal factory supplied motor. (See renewal parts section.)
2. To replace the motor, proceed as follows:
A. Disconnect the unit from power supply.
B.
Remove the motor terminal box cover.
C.
Note wire connections for future reference and dis-
connect all wires from the motor terminals.
D.
Remove 4 bolts in the motor base holding it to the rear
cabinet shelf.
E.
Remove 4 screws holding the fan guard to the cabinet.
F.
Carefully lift the motor, fan blade, and guard off of the
cabinet.
G. Note position of the fan blade hub on the motor shaft.
Loosen the two set screws to remove the fan blade
from the motor shaft.
Figure 12
Figure 13
H. Place guard and fan blade on replacement motor shaft
in same locations as original motor.
I. Reposition motor back on unit. Center fan blade in
opening and rotate to be sure that it clears housing
and guard.
J. Replace bolts in motor base and reattach fan guard to
back of housing in four places. Recheck blade rotation
and tighten all hardware.
K. Reinstall cable gland into motor terminal box and in-
stall cable.
L. Reconnect wires to motor. Verify correct motor wiring.
Attach ground wire to the connection inside the enclo-
sure. Replace cover and tighten securely.
M. Check fan rotation by momentarily energizing the unit.
Air must exit at cabinet front. Reverse any 2 leads at
contactor or line supply disconnect to reverse rotation
of three phase motor.
