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VS8420 MILLIVOLT GAS VALVE
4. With the main burner in operation, paint the pipe
joints (including adapters) and valve inlet and out-
let with a rich soap and water solution.
5. If another leak is detected, tighten the adapter
screws, joints, and pipe connections.
6. Replace the part if the leak cannot be stopped.
Turn on System
Rotate the gas control knob counterclockwise
ON.
Turn on Main Burner
Follow the instructions provided by the appliance
manufacturer or turn up the thermostat to call for heat.
Check and Adjust Gas Input and Burner
Ignition
IMPORTANT
Do not exceed the input rating stamped on the
appliance nameplate, or the manufacturer rec-
ommended burner orifice pressure for size ori-
fice(s) used.
IMPORTANT
For complete combustion, be sure the primary
air supply to the main burner is adjusted prop-
erly. Follow the instructions of the appliance
manufacturer.
Checking Gas Input By Clocking Gas
Meter
1. Be sure there is no gas flow through the meter
except to the appliance being checked.
NOTE: Other appliances must remain off with the pilots
extinguished, or the consumption must be
deducted from the meter reading.
2. Convert the flow rate to Btuh as described in the
Gas Controls Handbook, form 70-2602.
3. Compare to the Btuh input rating on the appliance
nameplate.
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 position.
2. Loosen, but do not remove the outlet tap captive
screw.
3. Attach a plastic tube with a 1/4 in. shell ID and con-
nect 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 1/4 in. shell ID and con-
nect 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.
69-1165—3
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
to
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 VS8410 pilot gas flow
should stop within three minutes; the VS8420 pilot
gas flow stops within thirty seconds. Pilot gas
safety shutoff 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
applications that place a heavy load on system controls
such as those used in the commercial cooking and
agricultural 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.
6
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