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Blog - Furnace not igniting or heating after the call for heat is given?

Furnace not igniting or heating after the call for heat is given

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Furnace not igniting or heating after the call for heat is given?

Is your furnace having trouble staying on once it fires up? Does it quickly shut off, after you start it? Does it do this a few times and then fully shuts down? Many homeowners have this problem every years, it is a dirty flame sensor.

Heating, Ventilation, and Air Conditioning is a complex industry, but this repair is simple enough, that you can perform it yourself.
Our example will be shown by using a gas-fired furnace, but you can find flame sensors in boilers and other gas-burning appliances.
Simple is the keyword in this process, but most furnace related service work is not very simple and show be performed by an HVAC professional.

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What Is A Flame Sensor and What Does It Do?

A flame sensor is a simple device, located at the burner assembly. The flame sensor is a thin, bent, metallic rod which sits in front of the flame stream, while the furnace is running. The purpose of the flame sensor is to confirm that fire is present, in your furnace, when the gas valve is opened. The flame sensor prevents your furnace from emitting gas that has not been ignited and prevent a dangerous build up of gas.
At the start up of your furnace, the burners are ignited and the flame sensor has a short amount of time to detect a flame; if a flame is not detected in this short period of time, your furnace will shut down automatically. The majority of units have a “safety lockout”, which means after 3 shutdowns, it will lockout a start up for approximately 1 hour.
For this time, you will be without heat but worse, the repetitive process of starting up and shutting down will wear certain parts of your furnace and will reduce the lifespan and the efficiency of the unit.

What Causes a Flame Sensor To Get Dirty?

A flame sensor gets dirty from a build up of carbon; it can become faulty but many times, the build up causes the problem. The flame sensor cannot tolerate many variations in reading the flame, so sometimes the slightest carbon can cause the misreading and the resulting shut down of your system. Many furnace units are located in basements, attics, and laundry areas, this can easily cause debris to build up on the sensor; this creates both carbon and dirt build up on the flame sensor.