L.B. White HW 120 Therma Grow - Manual (Page 15)

15
AIR PROVING SWITCH
SWITCH W/ PADDLE
LEADS
NUTS
PADDLE
OBLONG HOLE
HOUSING SIDE
PANEL
1. Remove two sheet metal screws holding air proving
switch blower housing. Remove assembly by turning
switch assembly 90 degrees so the switch paddle can
be pulled through oblong hole on side of fan housing.
See Fig. 11.
3. Disconnect the leads from the air proving switch.
4. When installing replacement switch, use care in not
bending the switch arm, otherwise ignition problems
may occur.
FIG. 11
The high limit switch should be tested a minimum of once
per year when the heater is given a thorough cleaning.
1. Remove the high limit switch from the heat
chamber.
2. Holding the switch by one of its mounting legs or
electrical terminals, apply a small flame only to the
sensing surface on the back of the switch. Be
careful not to melt the plastic housing of the switch
when conducting this test.
3. Within a minute, you should hear a pop coming from
the switch, which indicates the contacts of the
switch have opened.
4. Allow the switch cool down for about a minute before
firmly pressing the red reset button on the switch.
5. Check for electrical continuity across the switch
terminals to make sure the contacts have closed.
6. Reinstall the switch back into the heater.
FIG. 12
TESTING THE MANUAL RESET HIGH LIMIT SWITCH
RESET BUTTON
SENSING
SURFACE
TERMINAL
FLAME
MOUNTING
LEG
WARNING
Fire Hazard
■
Do not operate the heater with the high limit switch
bypassed.
■
Operating the heater with a bypassed high limit switch
may lead to overheating, possibly resulting in a fire, with
subsequent damage to the heater, building damage, or
loss of livestock.
1. Remove hose and sediment trap from inlet of gas
control valve.
2. Remove the following
-- Screws from bracket at inlet of gas control
-- Burner bolt from underside of base
-- Screws and spacers at burner.
3. Remove control valve with burner from heater. Pivot
the valve/manifold assembly as necessary so orifice
block on manifold clears the burner casting venturi
port. See Fig. 13.
4. Replace component as needed.
FIG. 13
BURNER ORIFICE and GAS CONTROL VALVE
ORIFICE BLOCK AND ORIFICE