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APPLICATION
The VS8421 Millivolt Gas Valve is compact and has a
60,000 Btuh capacity (1 in. pressure drop for
straight-through configuration). The design makes it ideal
for fireplace and space heating applications that are
ventfree (unvented). This valve is only for ventfree
(unvented) applications.
SPECIFICATIONS
Main Gas Connection: Valve: 3/8 in. NPT thread.
Pilot Gas Connection, Flow and Adjustment:
Connection Size: 7/16-24 UNS.
Flow: 1700 Btuh at 4.0 in. wc pressure drop.
Pilot is not adjustable.
Thermocouple Connection: M8 x 1.
Pilot Threads: Metric and UNS.
Ambient Temperature Range:
0°F to 175°F (-18°C to 79°C).
Option for -40°F (-40°C) and 225°F (107°C).
Pressure Regulation (Standard Regulator):
Servo regulator with adjustable outlet pressure.
Natural Gas: 3.5 in. wc, typical.
LP: 11 in. wc, typical.
Regulator Adjustments (Standard Regulator):
Natural Gas: 3 in. to 5 in. field adjustable.
LP: 8 in. to 12 in. field adjustable.
Voltage: VS8421: 750 mV operator, thermocouple in
ODS pilot burner.
Approvals:
International Approval Services (IAS) Certificate:
C2030022.
European Community (CE) Certificate: Applied for.
® U.S. Registered Trademark
Copyright © 2000 Honeywell • All Rights Reserved
Ventfree Millivolt Gas Valve
INSTALLATION
When Installing this Product...
1. Read these instructions carefully. Failure to follow
2. Check the ratings given in the instructions and on
3. Installer must be a trained, experienced service
4. After installation is complete, check out product
INSTALLATION INSTRUCTIONS
them could damage the product or cause a
hazardous condition.
the product to make sure the product is suitable for
your application.
technician.
Operation as provided in these instructions.
WARNING
Oxygen Depletion Hazard.
Can cause injury or death due to
asphyxiation.
Use only vented gas valve models on vented
appliances. Use only unvented gas valve models
on unvented appliances.
WARNING
Fire or Explosion Hazard.
Can cause property damage, severe injury
or death.
Follow these instructions exactly:
1. Turn off gas supply at the appliance service
valve before starting installation, and perform
a Gas Leak Test after the installation is
complete.
2. Always install the sediment trap in the gas
supply line to prevent contamination of the
gas valve.
3. Do not force the gas valve control knob. Use
only your hand to turn the control knob. If the
knob does not operate by hand, the valve
should be replaced by a qualified service
technician.
Place Bar Code Here
VS8421
69- 1219- 1
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Summary of Contents for Honeywell VS8421
- Page 1 Ventfree Millivolt Gas Valve INSTALLATION INSTRUCTIONS APPLICATION INSTALLATION The VS8421 Millivolt Gas Valve is compact and has a When Installing this Product... 60,000 Btuh capacity (1 in. pressure drop for straight-through configuration). The design makes it ideal 1. Read these instructions carefully. Failure to follow...
- Page 2 Gas valves are factory-set for HORIZONTAL 3 INCHES natural (and manufactured) or LP gas. (76 MM) TUBING VS8421 ventfree valves are not convertible. MINIMUM SUPPLY Location Locate the combination gas valve where it cannot be CONTROL affected by steam cleaning, high humidity, dripping water,...
- Page 3 VS8421 VENTFREE MILLIVOLT GAS VALVE INLET OUTLET PRESSURE TAP PRESSURE HI/LO WIRING REGULATOR CONTROL KNOB TERMINALS M12670 Fig. 3. Top view of gas valve with HI/LO regulator. INLET OUTLET PRESSURE TAP PRESSURE PRESSURE WIRING REGULATOR CONTROL KNOB TERMINALS ADJUSTMENT (UNDER CAP SCREW)
- Page 4 VS8421 VENTFREE MILLIVOLT GAS VALVE WIRING OPERATION Follow the wiring instructions furnished by the appliance The Ventfree Millivolt Gas Valve System is configured to wiring diagrams, see Fig. 6. include a gas valve, ODS pilot burner, and a millivolt thermostat. In the ODS pilot burner, the thermopile drives...
- Page 5 2. Push the plunger on the piezo until the pilot burner sequence can begin again. The VS8421 drops out is lit. Hold down the knob until a strong flame is within 30 seconds.
- Page 6 Follow the instructions of the appliance burner should go off and pilot should remain lit. manufacturer. 2. Extinguish pilot flame. The VS8421 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.
- Page 7 VS8421 VENTFREE MILLIVOLT GAS VALVE MAINTENANCE If Main Burner Does Not Come On With Call For Heat 1. Confirm that the gas control knob is in the ON WARNING position. 2. Adjust the thermostat several degrees above the Fire or Explosion Hazard.
- Page 8 VS8421 VENTFREE MILLIVOLT GAS VALVE 3. Test C (Thermocouple): Have thermostat contacts open and pilot lit with Pilotstat knob turned to PILOT. Reading should be a minimum of 12 mV in a new ODS pilot burner assembly. If the reading is less than 12 mV, replace the ODS pilot burner assembly.
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Questions and answers
What does it mean when the LED light on the VS8421 gas valve flashes once every 8-10 seconds?