Install Instructions

VS820 AND VS821 MILLIVOLTAGE COMBINATION GAS CONTROLS
5 95-6994EF—03
Turn on Main Burner
Follow instructions provided by appliance manufacturer
or turn up thermostat to call for heat.
Check and Adjust Gas Input to Main
Burner
CAUTION
1. Do not exceed input rating stamped on
appliance nameplate, or manufacturer’s
recommended burner orifice pressure for size
orifice(s) used. Make certain primary air supply
to main burner is properly adjusted for
complete combustion. Follow appliance
manufacturer’s instructions.
2. IF CHECKING GAS INPUT BY CLOCKING GAS
METER: Make certain there is no gas flow
through the meter other than to the appliance
being checked. Other appliances must remain
off with their pilots extinguished (or their
consumption must be deducted from the meter
reading). Convert flow rate to Btuh as
described in form 70- 2602, Gas Controls
Handbook, and compare to the Btuh input
rating on appliance nameplate.
3. IF CHECKING GAS INPUT WITH MANOMETER:
Make certain gas control is in PILOT position
before removing outlet pressure tap plug to
connect manometer (pressure gauge). Also
turn gas control knob back to PILOT when
removing gauge and replacing plug. Before
removing inlet pressure tap plug, shut off gas
supply at the manual valve in the gas piping to
the appliance or, for LP, at the tank. Also shut
off gas supply before disconnecting
manometer and replacing plug. Repeat Gas
Leak Test at plug with main burner operating.
VS820A; VS821A (Standard Pressure
Regulator)
1. Check the manifold rating listed on the appliance
nameplate. Gas control outlet pressure should
match the nameplate.
2. With main burner operating, check gas control out-
let gas flow using the meter clocking method or
pressure using a manometer connected to the out-
let pressure tap on the gas control. Refer to Fig. 2
or 3.
3. If necessary, adjust pressure regulator to match
appliance rating. Refer to Table 5 for factory set
nominal outlet pressure and adjustment range.
a. Remove pressure regulator adjustment cap
screw.
b. Using screwdriver, turn inner adjustment screw
clockwise to increase or counterclockwise
to decrease gas pressure to burner.
c. Always replace cap screw and tighten firmly to
ensure system functions properly.
4. If desired outlet pressure or flow rate cannot be
achieved by adjusting the gas control, check gas
control inlet pressure using a manometer at inlet
pressure tap. If inlet pressure is in the nominal
range (refer to Table 5), replace gas control. Other-
wise, take the necessary steps to provide proper
gas pressure to the control.
VS820C,P; VS821C (Step-Opening
Pressure Regulator)
1. Check the full rate manifold pressure listed on the
appliance nameplate. Gas control full rate
outlet
pressure should match this rating.
2. With main burner operating, check gas control out-
let flow rate using the meter clocking method or
outlet pressure using a manometer connected to
the outlet pressure tap on the control. Refer to
Fig. 3 or 4.
3. If necessary, adjust pressure regulator to match
appliance rating. Refer to Table 5 for factory set
nominal outlet pressure and adjustment range.
a. Remove pressure regulator adjustment cap
screw.
b. Using screwdriver, turn inner adjustment screw
clockwise to increase or counterclockwise
to decrease gas pressure to burner.
c. Always replace cap screw and tighten firmly to
ensure system functions properly.
4. If desired outlet pressure or flow rate cannot be
achieved by adjusting the gas control, check gas
control inlet pressure using a manometer upstream
of the gas control. If inlet pressure is in the nominal
range (refer to Tables 5 and 6), replace gas control.
Otherwise, take the necessary steps to provide
proper gas pressure to the control.
5. Carefully check burner lightoff at step pressure.
Make sure burner lights smoothly and without
flashback to orifice. Make sure all ports remain lit.
Cycle burner several times, allowing at least 30
sec. between cycles for regulator to resume step
function. Repeat after allowing burner to cool.
Readjust full rate outlet pressure if necessary to
improve lightoff characteristics.
Table 5. Pressure Regulator Specification Pressures in in. wc.
Model Type of Gas
Nominal Inlet
Pressure Range
Factory Set Nominal Outlet
Pressure Setting Range
Step Full Rate Step Range
VS820A,H,M NAT 5.0-7.0 — 3.5 — 3-5
VS821A LP 12.0-14.0 — 11.0 — 8-12
VS820C,P NAT 5.0-7.0 0.9 3.5 None 3-5
VS821C LP 12.0-14.0 2.2 11.0 None 8-12