Product Overview

V800 COMBINATION GAS CONTROLS FOR HEATING APPLIANCES
60-2019—09 12
Loss of Pilot Flame
The Pilotstat safety shutoff mechanism shuts down the
combination gas control if the pilot flame becomes
extinguished or too small for satisfactory burner ignition.
As the pilot burns, it constantly heats the thermocouple or
Powerpile generator, providing current for the Pilotstat power
unit in the gas control. A properly burning pilot supplies the
power unit with enough current to keep the safety valve open
and allow pilot gas flow. If the pilot goes out or decreases
current to the power unit, the power unit will "drop out",
closing the safety valve and preventing pilot gas flow and
main burner gas flow. To restart the system, the pilot flame
must be manually relit and the Pilotstat must be manually
reset.
The VS820 and VS821 Powerpile models generate current
independent of the line voltage and continue regulating pilot
and main burner gas flow. Therefore, in a power outage, the
gas control continues operating.
Servo Pressure Regulators
When the pilot flame is burning properly and the thermostat
calls for heat, the servo pressure regulator senses and varies
the outlet pressure to the main burner. When the thermostat
calls for heat, the valve operator ON-OFF lever opens the
left-hand gas supply port, lifting the servo regulator valve off
it's seat and allowing gas flow into the working gas channel
and evacuation channel. The working gas channel gas flow
increases the pressure in the working gas pressure chamber
which raises the main valve diaphragm and lifts the main
valve off it's seat, allowing main burner gas flow.
Outlet gas pressure variations are instantly reflected through
the evacuation channel to reposition the servo regulator
diaphragm. Repositioning the diaphragm adjusts the outlet
pressure by altering the flow rate through the servo regulator
valve.
When the outlet pressure rises, the servo regulator valve
opens and allows more evacuation channel gas flow. This
decreases the pressure in the working gas pressure chamber
and lowers the main valve toward its seat, lowering the outlet
pressure.
The opposite occurs when the outlet pressure falls. The servo
regulator valve closes and allows less evacuation gas channel
gas flow. This increases the pressure in the working gas
pressure chamber and raises the main valve from its seat,
raising outlet pressure.
Fig. 14. Gas Flow through the V800 Combination Gas Control Family.
M23303
GAS CONTROL
(ON-PILOT-OFF) KNOB
GAS
INLET
GAS
OUTLET
WORKING GAS
CHANNEL
PILOT
GAS
MAIN VALVE
MAIN VALVE
DIAPHRAGM
WORKING GAS
PRESSURE CHAMBER
SERVO PRESSURE
REGULATOR
OUTLET PRESSURE
ADJUSTING SPRING
SERVO REGULATOR
DIAPHRAGM
SERVO REGULATOR
VALVE
SERVO REGULATOR
PRESSURE CHAMBER
VALVE OPERATOR
ON-OFF LEVER
(SOLENOID OPERATED)
VALVE OPERATOR
EVACUATION
CHANNEL
POWER
UNIT
SAFETY
VALVE