L.B. White AD250(Spark Ignition) - Manual (Page 18)

TESTING THE MANUAL RESET HIGH LIMIT SWITCH
WARNING
Fire Hazard
■
Do not operate the heater with the high limit switch
bypassed.
■
Operating the heater a bypass high limit switch may
lead to overheating, possibly resulting in a fire, with
subsequent damage to the heater, building damage, or
loss of livestock.
The high limit switches should be tested a minimum of once
per year when the heater is given a thorough cleaning.
1. Disconnect the heater from its electrical supply.
2. Remove the high limit switch.
3. Holding the switch by one of its mounting legs, apply
a small flame only to the sensing portion on the back
of the switch. Be careful not to melt the plastic
housing of the switch when conducting this test.
4. Within a minute, you should hear a pop coming from
the switch, which indicates the contacts of the switch
have opened. Check for lack of electrical continuity
across the switch terminals to verify contacts have
opened.
5. Allow the switch cool down for about a minute before
firmly pressing the reset button on the switch.
6. Check for electrical continuity across the switch
terminals to make sure the contacts have closed.
7. Reinstall the switch back into the heater. Reconnect
the heater to its electrical supply. Start the heater
and check for proper operation.
FIG. 15
17
RESET BUTTON
SENSING
SURFACE
TERMINAL
FLAME
MOUNTING
LEG