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HVAC122 - GasHVAC122 - Gas

Gas ValvesGas Valves

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Solenoid Gas ValvesSolenoid Gas Valves

• The solenoid gas valve is the simplest of all valves.

• This valve has an electrical magnetic coil which opens the valve when energized.

• This valve is designed with a seat and a valve disc.

• The solenoid gas valve is the simplest of all valves.

• This valve has an electrical magnetic coil which opens the valve when energized.

• This valve is designed with a seat and a valve disc.

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Solenoid Gas ValvesSolenoid Gas Valves

• The valve is designed with a seat and a valve disc. This disk lifts off the seat when the coil is energized.

• The solenoid valve is directional.– There is a definite inlet– The gas pressure helps hold the valve

closed.– If installed backwards the gas pressure will

tend to open the valve.

• The valve is designed with a seat and a valve disc. This disk lifts off the seat when the coil is energized.

• The solenoid valve is directional.– There is a definite inlet– The gas pressure helps hold the valve

closed.– If installed backwards the gas pressure will

tend to open the valve.

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Solenoid ValveSolenoid Valve

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Solenoid ValveSolenoid Valve

• The solenoid valve can be operated with a heat motor.

• A heat motor is constructed of bimetal wrapped with a heat wire.

• When voltage is applied to the heat wire the bimetal warps and changes the position of the valve.

• The solenoid valve can be operated with a heat motor.

• A heat motor is constructed of bimetal wrapped with a heat wire.

• When voltage is applied to the heat wire the bimetal warps and changes the position of the valve.

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Solenoid Valve OpenSolenoid Valve Open

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Diaphragm Gas ValveDiaphragm Gas Valve

• Used when the large solenoid type would be an additional load.

• Used when a quieter type valve is needed.

• Used when the large solenoid type would be an additional load.

• Used when a quieter type valve is needed.

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Diaphragm Gas ValveDiaphragm Gas Valve

• The diaphragm valve is pilot operated. A small pilot solenoid valve opens and controls the gas flow through the valve.

• A diaphragm separates the inlet from the outlet of the valve.

• The de-energized pilot coil keeps a bleed valve closed.

• The diaphragm valve is pilot operated. A small pilot solenoid valve opens and controls the gas flow through the valve.

• A diaphragm separates the inlet from the outlet of the valve.

• The de-energized pilot coil keeps a bleed valve closed.

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Diaphragm Gas ValveDiaphragm Gas Valve

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Diaphragm Gas ValveDiaphragm Gas Valve

• Inlet gas pressure is allowed to build pressure on the top of the diaphragm and keeps the valve closed.

• When the pilot coil energizes, the position of the bleed valve changes.

• The bleed port is then opened and the gas flow to the top of the diaphragm is stopped.

• Inlet gas pressure is allowed to build pressure on the top of the diaphragm and keeps the valve closed.

• When the pilot coil energizes, the position of the bleed valve changes.

• The bleed port is then opened and the gas flow to the top of the diaphragm is stopped.

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Diaphragm Gas ValveDiaphragm Gas Valve

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Diaphragm Gas ValveDiaphragm Gas Valve

• The gas is bled to the pilot flame.• The gas pressure now builds under the

diaphragm and opens the main valve.• When the call for heat stops the pilot

valve returns to its normal position.• The bleed port is closed.• Gas pressure starts building on the top

of the diaphragm and the valve closes.

• The gas is bled to the pilot flame.• The gas pressure now builds under the

diaphragm and opens the main valve.• When the call for heat stops the pilot

valve returns to its normal position.• The bleed port is closed.• Gas pressure starts building on the top

of the diaphragm and the valve closes.

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Diaphragm Gas ValveDiaphragm Gas Valve

• The pilot valve can be operated with a heat motor.

• The pilot valve can be operated with a heat motor.

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Heat MotorHeat Motor

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Types of valvesTypes of valves

• Different applications have different types of valves based on speed of operation and pressures.

• Multi-stage units and direct ignition may use different valves than standing pilot valves.

• Different applications have different types of valves based on speed of operation and pressures.

• Multi-stage units and direct ignition may use different valves than standing pilot valves.

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InstantaneousInstantaneous

• Instantaneous valves open immediately when energized. There is no delay.

• Used in direct hot surface ignition.

• Instantaneous valves open immediately when energized. There is no delay.

• Used in direct hot surface ignition.

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Slow OpeningSlow Opening

• Opens after a lapse of one to thirty seconds after being energized.

• Used in larger spark ignition systems.

• Opens after a lapse of one to thirty seconds after being energized.

• Used in larger spark ignition systems.

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Step OpeningStep Opening

• Opens at a reduced pressure and then steps up to a full manifold pressure.

• Used in gas fireplaces and some boilers.

• Sometimes seen in unit heaters.

• Opens at a reduced pressure and then steps up to a full manifold pressure.

• Used in gas fireplaces and some boilers.

• Sometimes seen in unit heaters.

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CombinationCombination

• Combines other gas burner assemblies such as a pilot valve and pilot safety.

• These are used in most older standing pilot systems and water heaters.

• Also available in a redundant style (next page)

• Combines other gas burner assemblies such as a pilot valve and pilot safety.

• These are used in most older standing pilot systems and water heaters.

• Also available in a redundant style (next page)

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RedundantRedundant

• A valve with two main gas valves in one body so that both valves open and close on every call for heat to assure shutdown in the event of a pilot or ignition failure.

• This is code in most areas.

• A valve with two main gas valves in one body so that both valves open and close on every call for heat to assure shutdown in the event of a pilot or ignition failure.

• This is code in most areas.

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ComponentsComponents

• The components of an electric gas valve:– Pilot shut off valve and safety reset / lighting

button– Main Gas Line Shutoff– Pilot gas adjustment– Gas pressure regulator adjustment– Pilot gas connection

• The components of an electric gas valve:– Pilot shut off valve and safety reset / lighting

button– Main Gas Line Shutoff– Pilot gas adjustment– Gas pressure regulator adjustment– Pilot gas connection

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ComponentsComponents

– Thermocouple connection (with built-in electromagnetic pilot safety control)

– Electrical terminals (to control circuit)– Inlet and outlet pressure taps

– Thermocouple connection (with built-in electromagnetic pilot safety control)

– Electrical terminals (to control circuit)– Inlet and outlet pressure taps

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