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Standard Pressure Regulator
1. Check the manifold pressure listed on the appli-
ance nameplate. Gas valve outlet pressure should
match the nameplate.
2. With the main burner operating, check the gas
valve flow rate using the meter clocking method or
measure the pressure by attaching a plastic tube
with a 1/4 in. shell ID to the manometer and
connecting the manometer to the outlet pressure
tap on the gas valve. See Fig. 4.
3. If necessary, adjust the pressure regulator to
match the appliance rating. See Table 1 for
factory-set nominal outlet pressure and adjustment
range.
a. Remove the pressure regulator adjustment cap
screw.
b. Using a screwdriver, turn the inner adjustment
screw clockwise
counterclockwise
pressure to the burner.
c. Always replace the cap screw and tighten
firmly to prevent gas leakage.
4. If desired outlet pressure or flow rate cannot be
achieved by adjusting the gas valve, check the gas
valve inlet pressure using a manometer at the gas
valve inlet pressure tap. If inlet pressure is in the
normal range (see Table 1), replace the gas valve;
otherwise, take the necessary steps to provide
proper gas pressure on the valve.
Table 1. HI/LO and Standard Regulator
Pressures in in. wc (kPa).
HI/LO Regulator
Setting Ranges
Type of
Gas
HI
Natural
3.0 to 3.7
LP
9.0 to 12.0
CHECKOUT
WARNING
Fire or Explosion Hazard.
Can cause property damage, severe injury
or death.
Do not force the gas control knob on the
appliance. Use only your hand to turn the gas
control knob. If the knob does not operate by
hand, the valve should be replaced by a qualified
service technician.
Gas Control Knob Settings
Gas control knob settings are as follows:
OFF: Prevents main gas flow through the valve.
ON: Permits main burner and pilot gas flow. Gas valve
and thermostat control main burner gas flow.
PILOT: Opens pilot valve and allows gas flow to the
pilot burner.
HI/LO: Manually adjusts outlet pressure.
NOTE: Valves are shipped with the gas control knob in
the ON position.
to increase or
to decrease gas
Standard
Regulator
LO
Setting Ranges
1.2 to 2.5
3.0 to 5.0
3.5 to 6.5
8.0 to 12.0
VS8521 VENTFREE MILLIVOLT GAS VALVE
Perform Gas Leak Test
WARNING
Fire or Explosion Hazard.
Can cause property damage, severe injury
or death.
Stand away from the main burner while lighting.
Hidden gas leaks can cause flashbacks in the
appliance vestibule. Check for gas leaks with rich
soap and water solution any time work is done on
a gas system.
Gas Leak Test
1. Paint the pipe connections upstream of the gas
valve with a rich soap and water solution. Bubbles
indicate a gas leak.
2. If a leak is detected, tighten the pipe connections.
3. Light the main burner.
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
recommended burner orifice pressure for size
orifice(s) used.
IMPORTANT
For complete combustion, be sure the primary
air supply to the main burner is adjusted
properly. 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.
5
to
69-1223—1
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