VS8420C,M MILLIVOLT GAS VALVE
7
69-1304
Checking Gas Input With Manometer
NOTE:
Both the inlet and outlet pressure taps have a
captive screw.
1.
Be sure the gas control knob is in the OFF posi-
tion.
2.
Loosen, but do not remove the outlet tap captive
screw.
3.
Attach a plastic tube with a 9 mm OD and 1/4
in.(6.4 mm) shell ID and connect the manometer.
4.
Check the outlet tap pressure.
5.
Turn the gas control knob to the OFF position.
6.
Shut off the gas supply at the manual valve in the
gas piping to the appliance or, for LP, at the tank.
7.
Loosen, but do not remove the inlet tap captive
screw.
8.
Attach a plastic tube with a 9 mm OD and 1/4
in.(6.4 mm) shell ID and connect the manometer.
9.
Check the inlet tap pressure.
10.
Turn the gas control knob to the OFF position.
11.
Repeat the Gas Leak Test at the pressure tap
with the main burner operating.
Check Safety Shutdown Performance
WARNING
Fire or Explosion Hazard.
Can cause property damage, severe injury or
death.
Perform the safety shutdown test any time work
is done on a gas system.
1.
Place gas control knob in PILOT position. Main
burner should go off and pilot should remain lit.
2.
Extinguish pilot flame. The VS8420 pilot gas flow
stops within thirty seconds. Pilot gas safety shut-
off proves complete shutdown because the safety
shutoff valve prohibits main burner and pilot gas
flow.
3.
Relight pilot burner and operate the system
through one complete cycle to ensure all controls
operate properly.
MAINTENANCE
WARNING
Fire or Explosion Hazard.
Can cause property damage, severe injury or
death.
Do not attempt to take apart the gas valve or
clean it. Improper assembly and cleaning can
cause unreliable operation.
Regular preventive maintenance is important in applica-
tions that place a heavy load on system controls such
as those used in the commercial cooking and agricul-
tural and industrial industries because:
•
In applications such as commercial cooking, the
equipment operates 100,000 to 200,000 cycles per
year. This heavy cycling can wear out the gas valve
in one to two years.
•
Exposure to water, dirt, chemicals and heat can
damage the gas valve and shut down the control
system.
The maintenance program should include regular
system checkout as outlined in the Checkout section,
and checkout of the control system as described in the
appliance manufacturer literature.
Maintenance frequency must be determined individually
for each application:
•
Cycling frequency—Appliances that cycle 20,000
times annually should be checked monthly.
•
Intermittent use—Appliances that are used
seasonally should be checked before shutdown and
again before the next use.
•
Consequence of unexpected shutdown—Where the
cost of an unexpected shutdown would be high, the
system should be checked more often.
•
Dusty, wet, or corrosive environment—Because
these environments can cause the gas valve to
deteriorate more rapidly, the system should be
checked more often.
Any valve should be replaced if it does not perform
properly on checkout or service. In addition, replace any
module if it is wet or looks like it has ever been wet.
SERVICE
WARNING
Fire or Explosion Hazard.
Attempted disassembly or repair can cause
property damage, severe injury or death.
Do not disassemble the gas valve; it contains no
replaceable components.
CAUTION
Equipment Damage Hazard.
Can burn out heat anticipator in thermostat.
Do not apply a jumper across (or short) the
valve coil terminals even temporarily.
If Main Burner Does Not Come On With
Call For Heat
1.
Confirm that the gas control knob is in the ON
position.
2.
Adjust the thermostat several degrees above the
room temperature.
3.
Use a dc voltmeter to measure the voltage across
the THTP and TP terminals.
4.
If no voltage is present, check the control circuit
for proper operation.
5.
If proper control system voltage is present,
replace the gas valve.
Warning To The Appliance Owner. For
Your Safety, Read Before Lighting
Appliance.
WARNING
Fire or Explosion Hazard.
Can cause property damage, severe injury or
death.
Follow exactly the instructions for Pre-Lighting
Checks.