Why Your Heater Keeps Shutting Off Early

heating-elementWe 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).

If you notice a problem like your heater turning 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, listen for the sounds of the heater 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 turns off after only around five minutes, that’s too short—no matter how low you’ve set the thermostat.

Some reasons for short-cycling include:

  • Clogged 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 can lead to overheating and the heater shutting down 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: A thermostat sending incorrect signals to the heater can create short-cycling. The thermostat might be reading temperatures incorrectly (a miscalibration) 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. Corrosion on the flame sensor will cause it to keep shutting off the gas valve because it can’t detect the flames when they are there.
  • Oversized heater: This is the most serious reason for short-cycling because it means the heating system was installed incorrectly in the first place. 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.

Wm. Henderson Plumbing, Heating & Cooling Inc. has provided heating services throughout Delaware County, Chester County, and the Main Line for over 42 years. Call us for those late season heating repairs.

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