VR8200, VR4200
SERVICE
15
68-0046—4
Service
WARNING
FIRE OR EXPLOSION HAZARD,
CAN CAUSE PROPERTY DAMAGE,
SEVERE INJURY OR DEATH.
Do not disassemble the gas control; it contains no
replaceable components. Attempted disassembly
or repair may damage the gas control.
CAUTION
Do not apply a jumper across or short the valve coil
terminals. This may burn out the heat anticipator in
the thermostat or damage the DI module.
IMPORTANT: Allow 60 seconds after shutdown before re-
energizing step-opening model to assure lightoff at
step pressure.
IF THE PILOT BURNER FLAME WILL NOT LIGHT
1. Assure the main gas supply valve is open and the
pilot gas supply line is purged of air.
2. Attempt to light pilot burner flame following proce-
dures in the Light the Pilot Burner Flame section. If pilot
burner flame still will not light:
a. Check the pilot gas adjustment screw. If closed, read-
just the pilot flame. Refer to the Adjust the Pilot
Burner Flame section.
b. Perform the Gas Leak Test at the compression fit-
ting. If a gas leak is detected, replace the old com-
pression fitting or tighten the newly installed one.
Refer to Fig. 9.
c. Assure the pilot burner tubing or pilot burner orifice
is not clogged.
IF THE PILOT BURNER FLAME GOES OUT
WHEN THE GAS CONTROL KNOB IS RELEASED
1. Assure the gas control knob is held in at least one
minute to allow the thermocouple time to heat.
!
2. Check the pilot burner flame adjustment. Refer to the
Adjust the Pilot Burner Flame section.
3. Check the wiring between the thermocouple and the
gas control valve operator.
4. Assure thermocouple connection to the power unit is
tightened 1/4 turn beyond finger tight.
5. If pilot burner flame still goes out, measure the open
and closed thermocouple output voltage. Compare it to the
acceptable range charts in the thermocouple specifications or
in the Gas Controls Handbook. Replace the thermocouple if
voltages are outside the acceptable range.
6. Check the power unit resistance. If above 11 ohms,
replace the gas control.
IF THE MAIN BURNER WILL NOT COME ON
WITH A CALL FOR HEAT
1. Assure the gas control knob is in the ON position.
2. Adjust the thermostat several degrees above room
temperature.
3. Use an ac voltmeter to measure the voltage across
terminals TH and TR. If:
a. No voltage is present, check the control circuit for
proper operation.
b. Correct voltage (VR8200, 24 Vac; VR4200, 120 Vac)
is present, but first operator did not click open, check
for excessive inlet gas pressure. If inlet gas pressure
is correct, replace the gas control.
4. Measure the open and closed thermocouple output
voltages and compare to the acceptable range charts in the
thermocouple specifications or in the Gas Controls Hand-
book. Replace the thermocouple if voltages are outside the
acceptable range.
IF THE MAIN BURNER IS OVERFIRING
Adjust the gas control pressure regulator to the correct
pressure. If the regulator cannot be adjusted and supply
pressure is in the normal range, replace the gas control.
!