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Electronic Ignition Gas Furnaces Types

Gas Furnace Electronic Ignition Control Board

Electronic Ignition Gas Furnaces Types | Gas Heating Systems.  Gas furnaces, boilers, and water heaters have evolved from the basic standing pilot ignition system to the state of the art electronic ignition models. Standing pilot gas furnaces relied on keeping a pilot flame lit for the furnace, boiler, or water heater to function. The advent of electronic ignition has made it possible to prove a flame without keeping a pilot light lit 24/7. This saves money because electronic ignition only needs to have a flame when there is a call for heat. Lastly, no more worries about lighting a pilot light. There are different types of electronic ignition gas furnaces. Remember, this is a classification of gas furnaces. There are other classifications or types of gas furnaces.

Electronic Ignition Gas Furnaces Types

Typically, electronic ignition is comprised of a manufacturer’s OEM circuit board or an aftermarket ignition control module. It is located near the gas valve of the furnace, boiler, or water heater. The gas valve is controlled directly by this circuit board or ignition module. Whereas the old the standing pilot gas valve is usually controlled by the thermostat. There are different versions of gas furnace electronic ignition systems but they all serve the same purpose and function. It is to safely heat your dwelling. Among these types of gas furnace electronic ignition systems there are:

  • Direct Spark
  • Intermittent Pilot
  • Hot Surface Ignition
  • Mercury Bulb
Direct Spark Ignition | Electronic Ignition Gas Furnaces Types

This version has no pilot light at all. It lights the main burners on a call for heat. The state of the art flame sensor detects a flame. If no flame is detected on a try for ignition the gas valve closes. After a specified amount of time, usually seconds, the ignition module will try ignition again. Again, if the flame sensor detects no flame a delay before trying again will occur. Typically, there are three trials for ignition. If the flame sensor does not detect a flame the ignition module will go into a lock-out mode. It will lock-out for at least an hour (most models).

This is a safety measure to prevent a dangerous buildup of gas. If the module endlessly tried for ignition the un-ignited gas could build up to dangerous levels. An explosion could occur. Consequently, *the spark coming from the gas furnace circuit board can exceed 10,000 volts so caution is advised.

Intermittent Pilot Ignition | Electronic Ignition Gas Furnaces Types

This version has a pilot light which only lights on a call for heat. The pilot light is located near the main burner. On a call for heat the ignition module or gas furnace circuit board opens the pilot valve. The pilot valve is inside the gas valve. It initiates a spark at the head of the pilot assembly to light the pilot light. The flame sensor is also located at the pilot assembly. As soon as the flame is detected the gas furnace circuit board opens the main valve inside the gas valve. The pilot light then lights the main burners. When the thermostat is satisfied all gas control components & shuts off until the next call for heat.

If a flame is not sensed then a trial for ignition will repeat itself. It will repeat for up to four trials. Then the gas controls will be locked out for a specified period of time. A minimum of an hour depending the gas furnace or gas controls manufacturer. Then a new sequence will start over again. Consequently, *the spark coming from the gas furnace circuit board can exceed 10,000 volts so caution is advised.

Hot Surface Ignition | Electronic Ignition Gas Furnaces Types

Hot surface ignition can be either direct fire or indirect fire to a pilot. The Honeywell Smart Valve is an example of indirect fire to a pilot. The igniter is a silicon carbon element which glows red hot when the voltage is applied to it. On a call for heat, the gas furnace circuit board sends a specified amount of voltage to the igniter. After a small timed delay and after the igniter is glowing red hot, the main valve opens. The gas strikes the silicon carbon element and ignition occurs.

A flame sensor located near the burners detects the flame and the main burners remain lit and the voltage is taken away from the hot surface igniter. If a flame is not sensed then a trial for ignition will repeat itself for up to four trials and then the gas controls will& be locked out for a specified period of time (a minimum of an hour depending on the gas furnace or gas control manufacturer) when a new sequence will start over again.

Lastly, this can include the Honeywell SmartValve which uses a hot surface ignitor to light a pilot light. The pilot light then lights the main burners.

Use our handy calculator to see how many BTU's your natural gas appliances are producing:

Mercury Bulb | Electronic Ignition Gas Furnaces Types

This system uses a mercury switch to prove there is a flame on a pilot light. Mercury bulb systems usually use spark ignition to light a pilot and the mercury switch proves the flame. Once the switch proves the flame the main valve in the gas valve opens. Then the pilot lights the main burners. Furthermore, mercury are very hazardous to the environment and not many manufacturers use this type of electronic ignition. While mercury bulbs are installed in older systems, current law has banned mercury products in HVAC equipment.

Electronic Ignition Gas Furnaces Types - Conclusion

It is important to note that all these electronic ignition systems work in a furnace sequence of operation as determined by the electronic ignition controller. If the furnace safety controls detects a problem with any of the safeties, including the furnace flame sensor, the furnace sequence of operation will be interrupted on a lock-out. Furnace sequence of operation varies from gas furnace to gas furnace. It is important to know the gas furnace sequence of operation to troubleshoot the gas furnace. That is, if a problem exists and the furnace is locking out the ignition of the furnace. Lastly, the electronic ignition gas systems can also be used on boilers.

Electronic Ignition Gas Furnaces Types

High Performance HVAC

Electronic Ignition Gas Furnaces Types

 

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