Gas furnace sequence of operation

Heat call from the thermostat. Control Board internalexternal check pressure switch open 3.

Pressure switch must close to go to the next step.

Gas furnace sequence of operation. But for the most part manufacturers have all gone to a hot surface or direct spark ignition the sequence of operation is as follows. Heat call from the thermostat. Control board does a safety check limit switches roll out switches.

Inducer motor comes on. Pressure switch must close to go to the next step. Hot surface ignitor begins getting hot direct spark ignitor begins to spark.

The proper sequence of operation is. The thermostat calls for heat by the homeowner you turning the thermostat up. The thermostat provides 24 volts to the W terminal on the control board.

When you check with a voltmeter you should have 24 volts AC alternating current between W and C com on the control board. Gas Furnaces Sequence of Operation - The Standing Pilot Gas Furnace The standing pilot gas furnace is the most basic of all modern gas furnaces. They are being replaced with newer electronic ignition gas furnaces.

The standing pilot gas furnace remains in use. So it is necessary to troubleshoot a standing pilot gas furnace from time to time. With most standing pilot gas furnaces you will have two major.

In the standing pilot gas furnace sequence of operation there are many things going on. A good technician will follow the sequence through to determine where the furnace has a fault and make the repair. Gas Furnaces Sequence of Operation - There are many different types of electronic ignition high-efficiency gas furnaces in use today.

There some that are proprietary to various manufacturers. There should be a blue light in the burner box. If the burners fail to ignite the furnace shuts off the gas supply goes through a purge cycle and attempts to light the burners again.

The furnace tries a total of 3 times then if flame is not established goes into hard lockout. The flame sensor rod by sending a small electric currant through the flame it can tell or prove that there is ignition and not raw gas going in the furnace. Now the flame is heating up the fire box.

The Fan thermostat in the burner box will heat up and. Sequence of Operation Gas Furnaces. 24 vollts is always present to the thermostat R terminal.

When the thermostat closes its switch to call for heat 24 volts is sent out of the thermostat on the W terminal. This 24 volts goes back into the furnace then typically through 1 or 2 safety devices. The gas is ignited by the pilot light and provides heat to the plenum of the furnace.

When the air in the plenum reaches 120 degrees F the fan switch closes and the fan starts. The fan switch provides the necessary 120 volts to the fan motor for it to operate. Thermostat calls for heat.

Inducer motor turns on. Pressure and limit switches check for problems. Hot-surface ignitor turns on and glows or the electronic spark ignitor sparks.

Power is sent to the gas valve the gas valve opens with a click gas is. Furnace control begins the blower-ON delay period and continues to hold the gas valve GV pin 5 open. If the burner flame is not proved within two seconds the furnace control will close the gas valve GV pin 5 Furnace control will repeat the ignition sequence for up to three more Trials-For-Ignition before going to Ignition-Lockout.

In this episode Bryan talks to Justin Skinner about the standard gas furnace sequence of operation. Regardless of the furnace type it all begins with a heat call on W Then the furnace checks the safeties to make sure ignition is possible and safe. If all systems are a go the inducer motor comes on and clears a path for the exhaust.

Gas valve for the pilot opens 2. A spark igniter or HSI ignites the flame for the pilot 3. Flame is rectified 4.

Gas valve for the burners opens 5. Pilot flame ignites the flame for the burners 6. 90 gas furnace sequence of operation.

On a call for heat thermostat closes a signal is sent to the IFC and sequencing begins. The IFC electronically looks at the pressure switch. If the pressure switch is open power cannot pass through the IFC starts the inducer.

If the pressure switch is closed power passes through sequencing. Modulating Furnace Sequence of Operation 1. Thermostat - calls for heat 2.

Control Board internalexternal check pressure switch open 3. Inducer motor - ON 4. Control Board - proves pressure switch closed limits switches rollout closed 5.

Servo Valve on Gas Valve is energized-millamp current NO GAS FLOW 6. DSI Direct Spark Ignition. Sequence of Operation.

4 operation of furnace in cooling mode for 10 minutes. 14 furnace control to the gas valve GV is not making a good connection. The gas valve should open allowing the gas to flow the gas flame should crossover to the other burners in line and a signal should be received at the flame sensor telling the board everything is good to go.

As with many components in furnace troubleshooting if the part is getting power but not operating its likely failed. Normal Sequence of Operation Furnace lockout results when a furnace is unable to achieve ignition after three 3 attempts during a single call for heat. GMEC96 will display a one- flash diagnostic LED code.

GMVC96 will display an E0 code on the dual 7-segment display. What is the sequence of operation of my gas furnace. Gas furnaces a thorough understanding of the units sequence of operation is essential.

This publication is based on White-Rogers controls and provides the narrative and schematic drawingsnecessary to provide this understanding for thesefurnaces. Also included is a description of operating principles of different ignition systems. Gas Furnace Direct Spark Ignition Sequence Of Operation Furnace Sequence Of Operation Spark Ignition With Proven Pilot For York Model ZF Units York ZF036 York ZF048 York ZF060 York ZF078 York ZF090 York ZF120 York ZF180 York ZF240 Hot Surface Ignition HSI If your furnace was manufactured.

Standing Pilot Gas Furnace Sequence of Operation How Gas Furnace Thermocouples Work. With a lit pilot light the thermostat calls for heat and the heating contacts in the thermostat close. The main valve opens and introduces gas to the main burners.