Motor, Fan, And Air Proving Switch; Auto Reset Limit Switches - L.B. White Tradesman 400 Dual Fuel Owner's Manual And Instructions

7. For reassembly, reverse the respective service
procedure. Ensure gas connections are tightened
securely.
8. After servicing, start the heater to ensure proper
operation and check for gas leaks.
9. Clean the heater's orifi ce with compressed air or a
soft, dry rag. Do not use fi les, drills, broaches, etc.
to clean the orifi ce. Doing so may enlarge the hole,
causing combustion or ignition problems. Replace
the orifi ce if it cannot be cleaned properly.
Motor, Fan, and Air
Proving Switch
1. Remove fan guard and screws securing the motor
mount to the heater's barrel. See Fig 12.
2. Lift motor/fan assembly from heater.
FIG. 12
Motor
-- Remove both screws and strap securing the motor.
-- Position the motor between motor mount stops
when reinstalling.
Air Proving Switch (See Fig. 13)
(Not provided on Tradesman 170 standard heater)
-- Remove screw securing switch bracket to motor
mount.
-- On reassembly, ensure tab on switch bracket is
located in hole.
NOTE: The air proving switch contacts must be open
prior to motor start-up. If the switch contacts
do not close after the motor starts, or are
closed prior to motor starting, the igniter will
not spark nor will the gas control valve open.
Tradesman Construction Heaters
REMOVE
REMOVE
(BOTH SIDES)
Owner's Manual • Tradesman
Fan
-- Loosen set screw at hub.
-- Pull fan from shaft.
-- Ensure fan is fl ush on shaft end, and set screw is
positioned over fl at of motor shaft before tighten-
ing.
FIG. 13
FAN HUB FLUSH WITH SHAFT END
SET SCREW
STRAP
REMOVE
SCREWS
Auto Reset High Limit
Switches
The auto reset high limit switch is designed to cut off
power to the gas control valve if the heater should
overheat due to blockage at the air inlet or discharge
outlet.
Depending on heater model, there can be one or
two high limit heat switches. All Tradesman 170
and Tradesman 400 Dual Fuel heaters
have two limits. Tradesman 400LP
heaters have only one limit switch.
Regardless of model, ensure any mounting hardware
(screws, spacers, or washers) is installed when
replacing or testing the switch.
Locations of the limits are:
Tradesman 170 and Tradesman 400 Dual
Fuel:
■ One on the burner plate and one on the underside
of the combustion chamber. See Figs. 14 and 15.
■ The switch on the underside of the combustion
chamber is accessed by removing the base bottom
of the heater.
Tradesman 170 only:
- The combustion chamber is stamped with the let-
ters P (Propane) or N (Natural Gas) adjacent to the
screw holes to identify location for the appropriate
gas being used.
17
TAB IN HOLE
AIR PROVING
SWITCH