8 Reasons Why Your Thermostat Drops Below Set Temperature

8 Reasons Why Your Thermostat Drops Below Set Temperature

Does your thermostat drop below its set temperature frequently? This can be a frustrating problem when your home’s temperature and your thermostat’s settings do not seem to match. No matter how much you adjust the thermostat, the temperature always falls short of the optimal level, resulting in a colder house than anticipated.

A functioning thermostat will regulate the right amounts of warmth and coolness in our homes. Quite understandably, we expect the thermostat to regulate at a consistent temperature that corresponds with our predetermined settings. If the thermostat drops below the set temperature, this brings into question whether the HVAC system works or not.

There could be numerous reasons why your thermostat drops below the set temperature. Some problems are simple to fix, while others will require more professional HVAC expertise to decipher. Below are eight common explanations about why the thermostat drops below a set temperature:

Reason #1: Your thermostat is improperly calibrated.

Your thermostat drops below set temperature because it is improperly calibrated.

As with any piece of technology, the thermostat may become faulty from time to time. This affects its ability to assess the temperature accurately. Due to these technical glitches, the thermostat could indicate a lower (or higher) number than the actual temperature.

To fix this problem, follow the instruction manual to ensure the thermostat is properly calibrated. The calibration process may vary between different thermostat models, but it should be simple and straightforward to perform. Every thermostat will require calibration, regardless of whether you have a manual model or a digital version.

Reason #2: Your thermostat is broken and needs to be replaced.

Your thermostat drops below set temperature because it is broken.

Sometimes, a thermostat is so completely broken that no amount of calibration will fix it. You will know your thermostat is malfunctioning if it causes your heater to turn on and off at inappropriate times. This is one of the most common warning signs that your thermostat could be broken. Other warning signs may include a non-responsive thermostat that won’t turn on or power off properly.

If you have a broken thermostat, the HVAC professional may be able to fix your device depending on the problem. Otherwise, you will have to replace the broken thermostat with a new version instead.

Reason #3: The outdoor unit is broken and not running properly.

The thermostat drops below set temperature because the outdoor unit is broken.

If the thermostat is working properly, then the problem may lie within your HVAC system. A broken outdoor unit could lead to less efficiency in your heating and cooling systems. Since the unit doesn’t operate at its full potential, you may get weaker power and lower temperatures as a result.

The prospective problems with HVAC units tend to be diverse and complex, ranging from a defective valve to a faulty run capacitor. Unless you have the technical expertise, you will need professional technicians to troubleshoot the HVAC system. Depending on the diagnosis, further repairs or a full system replacement may be necessary.

Reason #4: The temperature is too cold outside.

The thermostat drops below set temperature because it is too cold outside.

Winter can be an intensely cold season with plummeting temperatures. If the outdoor temperatures drop too much, your heat pump may experience a loss of efficiency under these extreme weather conditions.

Most heat pumps are built with a supplemental heating system that kicks in to give it extra power during the cold. However, the outdoor temperature could drop to a point where your heat pump is simply not powerful enough. In other words, the warmth that it generates cannot sustain against the coldness of winter.

Reason #5: The outdoor unit is frozen and covered in ice.

The thermostat drops below set temperature because the HVAC unit is frozen.

Along with the cold temperatures, snow and ice are quite prevalent during the winter season. During a snowstorm, the coil of your heat pump might be covered in a layer of ice. If these coils are completely blocked by ice, the heat transfer between the refrigerant and the outside air cannot occur. As soon as these coils are cleared, you can expect your desired temperature to come roaring in again.

Reason #6: Your furnace isn’t the right size.

The thermostat drops below set temperature because the furnace isn't the right size.

When a furnace is inappropriately sized, this could cause heating issues inside a home. A furnace that is too small may not have the power to reach high temperatures. Conversely, a furnace that is too large may warm the air so quickly that it overheats faster than the thermostat expects.

Reason #7: Your home isn’t adequately insulated.

The thermostat drops below set temperature because the home isn't adequately insulated.

Warm temperature has a way of escaping from poorly insulated homes. The easiest way to check your home insulation is to feel the interior ceilings, walls, and floors. If they are warm and dry during winter, this is a good signal. If they are damp or cold, you haven’t applied enough insulation.

Reason #8: There are leaking ducts in your home.

The thermostat drops below set temperature because there are leaking ducts in the home.

Your HVAC system is significantly impacted by the leaking ducts in your attics, crawlspaces, and basements. When there is a leak, the heated air will escape through these openings and never arrive at their intended destination. The leaky ducts will create cold spots, heat losses, and uneven temperatures throughout your home.

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