Types of Gas Furnaces with Electronic Ignition

Plumber posing beside a gas furnace

Over the years, boilers, gas furnaces, and water heaters have improved from having the basic ignition system to having innovative electronic ignition. The former, standing pilot ignition systems relied on a lit pilot flame for the heater or boiler to function. The new models make it possible for the systems to work without maintaining the flame lit throughout the day and night.

Their uniqueness extends further in that when conducting your furnace repair in Utah, you need to have an expert who also understands electronic gadgets. You should know that these systems typically have a circuit board from the manufacturer or a control module added later located close to the gas valve. This circuit controls the valve using a thermostat. Although they differ in design, these types serve the same function, which is to heat your property.

Here are the popular options for ignition systems:

Direct Spark Ignition System

This version is designed to need no pilot. The main burners light up when heat is necessary. There is a sensor in the system that will detect a flame. When there is no flame, the gas valve will close. After a short period, usually a few seconds, the ignition module tries again and the sensor will act as before. The direct spark ignition module ideally tries three times before going into lockout mode. The lockout mode lasts for an hour and works as a safety measure so that gas does not build up and cause explosions.

Intermittent Pilot Ignition

Technician checking a gas furnaceIn this case, the pilot light is placed near the main burner and lights up when heat is needed. When it does, the ignition module opens the pilot valve that is housed in the gas valve. The process initiates a spark that lights up the pilot light. There is usually a flame sensor in the assembly that detects the flame and causes the circuit board to open the main valve.

Consequently, the main burners light up. When the thermostat detects adequate heat, it shuts off all the control components until the next time heat is needed. In case the sensor detects no flame, the process repeats itself for up to four tries before initiating a lockout.

Hot Surface Ignition

This version can have either an indirect fire or direct fire ignition. In the indirect fire, the igniter is a carbon element that glows when a certain amount of power is applied. The glow causes the main valve to open and when gas strikes the element, ignition happens. A flame sensor notes the flame and lights the burners. Meanwhile, power is removed from the element.

Mercury Bulb Ignition

This system relies on a mercury switch to detect the flame in the pilot light. The pilot is lit using spark ignition so that the mercury switch only confirms the flame. Once the flame is detected, the valve opens and the main burners light up. Note that current laws ban mercury products in HVAC equipment.

It is important to remember that these systems work in a sequence determined by the controller. If the safety controls find a problem anywhere, including the sensor, the sequence is disrupted and a lockout is initiated. Knowing how the sequence works for each system helps the professionals during furnace repair.

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