L.B. White 300 Director - Manual (Page 15)

Mounted on the heat chamber near the burner head,
the high limit is a normally closed switch that opens
i f t h e b u r n c h a m b e r r e a c h e s a b n o r m a l l y h i g h
temperatures, cutting power to the gas solenoid valve.
The switch may be tested by applying a soft flame for
about 20 seconds to the sensing side of the switch
Check for continuity before and after flame application
to determine if the switch has opened. Allow the
switch to cool. Recheck continuity to ensure the switch
has closed.
FIG. 13
Removal
1. Disconnect fuel supply line from pump.
2. Using a 2.5 mm. allen key, loosen the three set screws
where pump slides to motor shell. See Fig. 10.
3. Pull pump assembly from motor. Ensure pump coupling is
in good condition.
4. Disconnect solenoid valve lead from pump.
FIG. 10
Checking Pressure
1. Remove pressure gauge plug from fuel pump port as
shown in Fig.11, located in the upper right hand corner of
the pump. Use a 4 mm allen wrench.
2. Install a pressure gauge that has 1/8-28 BSP (British
Straight Pipe) threads to the fuel port marked “P”. See
Fig. 12. ( If 1/8 in. NPT is used, apply some pipe thread
compund to the threads)
3. Start heater (See Start-Up). Allow motor to reach full
speed. Pump pressure must be that given on dataplate
or Pg. 4 of Owner’s Manual.
4. To adjust pressure use 4mm allen wrench at adjustment
screw, lower left of the pump, marked “-” and the “+” .
Turn the allen head clockwise towards the “+” to increase
the pressure. Turn counter clockwise towards the “-” to
decrease pressure. See Fig.11.
FIG. 11
Maintenance
-- Before use, remove the filter using a 4 mm. allen key
and check for debris. See Fig.12.
-- Rinse the filter with clean kerosene.
FIG. 12
14
SET SCREW
FUEL PUMP
COUPLING
PRESSURE GAUGE
ADJUST
PRESSURE
HIGH LIMIT SWITCH
HIGH LIMIT