Furnace Problems Caused by Thermostats

thermostat problemsWhen you’re experiencing issues with your furnace it makes sense to rule out the most common culprits: dirty furnace filters and broken hoses. If those are fine, then it’s time to take a closer look at your thermostat.

Common thermostat problems

If there is an issue with your thermostat, you will notice that your furnace is either not producing heat, puts out too much heat, or cycles on and off more frequently than needed. The most common problems with thermostats and furnaces are as follows:

  • Wire Issues
  • Dirty Thermostat Interior
  • Power Problems
  • Mismatched Thermostat and Heating System
  • Improper Thermostat Location
  • Wrong Heat Anticipator Settings

Wire Issues

Loose connections, disconnections, and faulty and aging wiring can cause your thermostat to lose its connection to your heating and cooling systems, thereby causing an interruption in service. If your furnace stops working properly, it’s a good idea to inspect your thermostat’s wiring. If you suspect faulty wiring, tighten and replace wires as necessary, or consult with a knowledgeable HVAC professional.

Dirty Thermostat Interior

Dust and debris is a common culprit for malfunctioning thermostats. Cleaning the interior of your thermostat is fairly simple. First, remove the cover from your thermostat (you may require a screwdriver to do so), then use a soft brush to lightly dust the interior of the thermostat, including the bimetallic coil and the 2 switch contact surfaces. Don’t touch any of the interior parts with the fingers

Power Problems

If there is no power on your thermostat, then the first step should be to check the power switch and to make sure nobody accidentally turned it off. It it’s not the power switch then you may need to replace the batteries of your system. AA lithium batteries are recommended.

If your system is running at inconsistent times then you should take a look at the batteries you currently have in the unit. Alkaline batteries run out fairly quickly, especially if the backlight is on, or if you’re frequently checking the readings, so you might want to switch to AA Lithium batteries.

If the power switch is on and new batteries don’t do the job then it could be a fuse or circuit breaker.

Mismatched Thermostat and Heating System

Your heating system and thermostat must be matched in order for your furnace to function properly. Private residences normally use low voltage thermostats. They run off a transformer that reduces line voltage from 120 volts to a lower lever somewhere between 12 volts and 24 volts.

Thermostats need to be matched to the heating system depending on the type, capability and capacity of your furnace. If you are unsure about the proper matching consult with an HVAC professional.

Bad Thermostat Location – Inaccurate temperature readings

The thermometer should react to the temperature of the air in the living space. Oftentimes issues are caused by thermometers that have been installed in the wrong places such as:

  • On a wall that has high heat gain or loss
    This will cause the heater or air conditioning to come on when the home’s temperature is too warm or too cold. Or trigger it when there is no need because the thermostat is reacting to the temperature of the wall.
  • Where direct sunlight hits the thermostat – this falsifies the temperature reading as the air surrounding the thermometer will be warmer than the rest of the area.
  • Near an outside door or window – the thermostat will be affected every time you open or close the door or window.
  • Near a heat source – think hot or cold water pipes, radiant heaters, fireplaces, electrical devices which produce heat etc.
  • Where larger holes in the wall behind the thermostat cause drafts – those will need filling with some insulation to reduce the airflow.

Wrong Heat Anticipator Settings

Mechanical, non-digital thermometers have a heat anticipator. The heat anticipator should be set by a qualified heating technician as it needs to be set according to the amp draw on the heating control circuit.

The heat anticipator’s job is to tell the thermostat when to turn off the burners. When not set properly it will cause your furnace to cycle on and off more frequently than needed. An amp meter is required to determine the proper setting.

Digital and programmable thermostats have built in heating and cooling anticipators which automatically set themselves without any manual adjustments.

If you’ve checked your furnace filters, hoses and the thermometer but your furnace is still causing you trouble then it’s time to call a qualified technician to take a look at your furnace.

Our HVAC experts at S&C Mechanical Systems have ample of experience with furnaces and will be able to diagnose the problem for you. With us, you will get a detailed fixed-price quote for any repairs that may be needed, and a 12-month hassle-free guarantee once the job is completed.

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