36C21 Series
Main Gas Valves
WHITE-RODGERS
INSTALLATION INSTRUCTIONS
Operator: Save these instructions for future use!
FAILURE TO READ AND FOLLOW ALL INSTRUCTIONS CAREFULLY BEFORE
INSTALLING OR OPERATING THIS CONTROL COULD CAUSE PERSONAL INJURY
AND/OR PROPERTY DAMAGE.
DESCRIPTION
These Gas Valves control the flow of gas to the main
burner under command of a room thermostat. They are
suitable for use on all gases and may be used with all
types of gas heating equipment. They may be mounted in
any position except upside down.
NOTE
Some parts of this gas valve are also used to make more
complex combination gas controls. Disregard the nota-
tions “Pilot”, “Pilot Adj.” and “Vent ”. Although these
notations do appear on the valve, they are not functional
on model 36C21 Series controls.
SPECIFICATIONS
Electrical Rating:
CAUTION
!
Main Valve
Do not use this valve on indoor LP gas furnaces
except with 100% shut-off system.
Model No.
36C21U
36C21
Voltage
750 MV
24 volts
Current
D.C.
.23 Amp
Mounting: Any position except upside-down
36C21A
120 volts .035 Amp
MOUNTING POSITIONS:
Upright, 90° from upright or vertical
INLET BOSS
Maximum Pressure Rating:
14" W.C. (1⁄2 lb. per sq. in.)
Ambient Temperature: -40° to 175°F
UPRIGHT
UP OR DOWN
LEFT OR RIGHT
360°
PIPE SIZES/CAPACITIES
Capacity (BTU/hr) at
1” pressure drop across valve
Nat. Gas
LP Gas
Pipe Size (1000 BTU/cu. ft., (2500 BTU/cu. ft.,
(inches)
1⁄2” x 3⁄8”
1⁄2” x 1⁄2”
1⁄2” x 3⁄4”
3⁄4” x 3⁄4”
64 Sp. Gr.)
100,000
230,000
230,000
280,000
1.53 Sp. Gr.)
162,000
372,600
372,600
453,600
WHITE-RODGERS DIVISION
EMERSON ELECTRIC CO.
9797 REAVIS ROAD
PART NO. 37-4048B
Replaces 37-4048, 37-2570, 37-1972
Printed in U.S.A.
9615
ST. LOUIS, MISSOURI 63123-5398
INSTALLATION
SYSTEM WIRING
CAUTION
MAIN PIPING CONNECTIONS
WARNING
!
!
Failure to turn off electric or main gas supply to
heating system could cause personal injury and/
or property damage by shock, gas suffocation,
fire, and/or explosion.
To prevent electrical shock and/or equipment
damage,disconnectelectricalpowertosystemat
main fuse or circuit breaker box until installation
is complete.
1. Turn off electrical power to the system at the fuse box
or circuit breaker. Also turn off the main gas supply.
NOTE
Allwiringshouldbeinstalledinaccordancewithlocal
and national electrical codes and ordinances.
2. If replacing an existing valve, disconnect all plumbing
and electrical connections from the old control.
3. Thecontrolmaybeinstalledinanyorientationexcept
upside down. The arrow on the valve indicates the
direction of gas flow through the control.
Always check that the electrical power supply used
agrees with the voltage and frequency shown on the
gas control.
4. You should use new pipe that is properly chamfered,
reamed, and free of burrs and chips. If you are using
old pipe, be sure it is clean and free of rust, scale,
burrs, chips, and old pipe joint compound.
Thesetypicalwiringdiagrams(figs.2and3)showonlythe
terminal identification and wiring hook up. Always refer to
wiring instructions provided by equipment manufacturer
for system hook-up and operation.
5. Apply pipe joint compound (pipe dope) or teflon tape
that is approved for all gases, only to the male
threads of the pipe joints. DO NOT apply com-
pound or teflon tape to the first two threads (see fig. 1
for typical piping connections).
High
Limit Thermostat
Gas Valve
Terminal Panel
6. If you are using a vise or open-end wrench to hold the
valve while installing piping, do not tighten exces-
sively, as this may damage the valve.
TR
ALL WIRING
MUST BE
To Pilot
Generator
TH
TH-TR
N.E.C. CLASS 1
7. See SYSTEM WIRING when making electrical con-
nections. After all gas and electrical connections are
completed, turn gas on and check for gas leaks with
leakdetectionsolutionorsoapsuds.Bubblesforming
indicate a leak. SHUT OFF GAS AND FIX ALL
LEAKS IMMEDIATELY.
Figure 2. Wiring for 36C21U
High
Limit
Automatic
Pilot
Thermostat
NOTE
36C21
Valve
24 VAC
All piping must comply with local codes, ordinances,
and/or national fuel gas codes.
Gas
Valve
NOTE: ALWAYS INCLUDE A
DRIP LEG IN PIPING
Figure 3. Wiring for 36C21 and 36C21A Models
Drop
Drop
Gas Valve
Horizontal
Riser
Horizontal
Gas Valve
3 in.
minimum
Gas Valve
3 in.
minimum
3 in.
minimum
Riser
Piped Gas
Supply
Tubing Gas
Supply
Piped Gas
Supply
Figure 1. Typical gas valve piping
3
ADJUSTMENT
PILOT GAS ADJUSTMENT
Pilot Adjust
Cover Screw
If the pilot flame is low and does not engulf the bulb of the
mercury flame sensor, the system will not energize the
mainvalve.Ifpilotgaspressureistoohigh,gaswillsputter
past the ignition electrode, and may not ignite. High pilot
gas pressure may also cause the flame to lift off the
burner,causingtheflamesensorbulbtosense"low"heat.
Gasket
Pilot
Adjust
Screw
To adjust the pilot gas pressure:
Remove the cover screw (see fig. 4).
To REDUCE pilot pressure, turn the pilot adjust screw
(beneath the cover screw) clockwise.
To INCREASE pilot pressure, turn the pilot adjust
Figure 4. Pilot gas adjustment
screw counterclockwise.
Replace and tighten cover screw.
PILOT LIGHTING
Before lighting the pilot burner flame, remove one of pilot
generator leads from the valve. This will prevent main gas
valve from opening during the pilot lighting procedure,
even if thermostat should be calling for heat.
If you need further information about this product, please write to
White-Rodgers Division, Emerson Electric Co.
9797 Reavis Road
St. Louis, MO 63123-5398
Attention: Technical Service Department
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