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Why Your Heater Keeps Shutting Off Early

Why Your Heater Keeps Shutting Off Early

We advise customers to have their heating systems repaired as soon as they notice anything wrong with them. This applies any time of the year, even during early spring when warmer days are just around the corner (or at least we hope so).

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If you notice your heater keeps shutting off early, we recommend calling for professional home heating services as soon as you can—even in April!

What Might Cause a Heater to Turn Off Prematurely

A heater that doesn’t run as long as necessary will heat a house unevenly. The rooms farthest along the ventilation system won’t receive as much heating as they should because the heater hasn’t stayed on long enough to generate enough heated air. When you notice uneven heating in your home, perform an inspection to confirm if your heater keeps turning on and off. If the run-time sounds shorter than normal, the heater may have a problem called ­short-cycling.

Short-cycling is when a heater doesn’t complete its regular heating cycle and turns off early. A full heating cycle for a furnace or heat pump is usually around 15 minutes or more. If your heater keeps turning off after only five minutes, that’s too short—no matter how low you’ve set the thermostat.

Causes of Short-Cycling

Clogged Air FilterClogged Air Filter

This is one of the most frequent causes of trouble in an HVAC system. If the filter is heavily clogged with dust and debris, it may cause the furnace to shut off as a safety precaution. Fortunately, this is a basic problem to solve—just put in a clean filter. We recommend changing the HVAC system filter every 1 to 3 months depending on how often you run the heater and the strength of the filter.

Malfunctioning Thermostat

If the thermostat in your home is sending incorrect signals, it may be be the reason your heater keeps turning on and off. The thermostat might be reading temperatures incorrectly or have a bad connection to the heater’s control board. Technicians can recalibrate the thermostat or take care of other repairs so it operates the heater correctly.

Corroded Flame Sensor

This applies to gas furnaces, which are the most common type of heating system. The flame sensor determines if the burners are on when the gas valve is open. The sensor will shut off the gas if it doesn’t sense flames—this prevents a buildup of unburned gas in the combustion chamber. Since the flame sensor is not able to detect fire when it’s covered in dirt or debris, it will continuously close the gas valve and cause the furnace to keep shutting off.

Oversized HeaterOversized Heater

This is the most serious issue that will cause a furnace to keep shutting off is an improper installation. When a heater is too powerful for a home, it will heat up the living spaces so fast that the thermostat will shut the heater off prematurely.

All you can do in this case is arrange for a new heating system installation—this time from a qualified professional who will make sure the heater is the right size.

Heating Repair & Install Services Near You

Wm. Henderson has provided heating services throughout Delaware County, Chester County, and the Main Line for over 42 years. We offer HVAC solutions for boilers, furnaces, heat pumps, and other types of systems. If you have a problem with your air conditioner, our team also provides air conditioning repair and replacement services. Give us a call by phone at (484) 206-8594 or book an appointment online to receive assistance. We offer heating options in areas of Pennsylvania such as West Chester, Broomall, Coatesville, and Conshohocken.

Related Article: Heat Pump Sizing Tips