Furnace Pressure Switches

Though you may not give much thought to the furnace in your Hudson home, knowing a bit about it and how it works can come in handy. At Chaves Heating & Air Conditioning, our heating, ventilation, and air conditioning (HVAC) professionals are always here to help and to answer any furnace questions you may have.

What Is a Furnace Pressure Switch?

Your furnace has a number of mechanisms allowing it to run safely and efficiently. One important component is the pressure switch. 

The pressure switch is triggered when it senses what is called backdrafting. Backdrafting is when exhaust fumes reenter your system. 

Your pressure switch can also sense other failures, such as a gas leak or a mechanical problem. When the switch senses the hazard, it automatically shuts off your furnace to prevent further damage. 

Gas leaks are nothing to mess with, so be sure to add one or more carbon monoxide (CO) detectors in your Massachusetts home. The Centers for Disease Control and Prevention (CDC) recommends installing one detector near every sleeping area for the highest level of safety.

What Does the Furnace Pressure Switch Look Like?

Typically, the switch is a disc-shaped metal component connected to a hose. Standard furnaces operate with a single pressure switch. 

Depending on your furnace, you may have more than one switch. Condensing furnaces will have two hoses on the pressure switch, while two-stage furnaces have two entirely separate pressure switches. Modulating furnaces can even contain up to three.

What Are Some Common Problems With Furnace Pressure Switches?

Furnace pressure switches are an important feature for keeping you safe in your Hudson home. However, malfunctions with the pressure switch can incur false positives, which cause your furnace to shut down.

Here are four commonplace pressure-switch errors you may experience:

1. The pressure switch is jammed shut.

This can be caused by moisture buildup, among other issues. If the furnace detects the switch is shut, it will not run. Typically, our HVAC Chaves Heating & Air Conditioning expert will have to replace the pressure switch if this is the case.

2. The inducer motor fails.

The inducer motor’s role is to blow harmful exhaust out of the furnace. When this does not work, the pressure switch can’t properly expel the fumes, so your furnace will stop operating. Our heating and cooling pro will test the voltage to see if the inducer motor is working, and if it is not will replace it.

3. The furnace does not ignite.

In some cases, the ignition mechanism can fail due to a bad pressure switch. If the mechanism gets stuck open, the furnace is blocked from igniting the pilot light, as well as turning on the blowers. While this could also be a sign of an internal error unrelated to the switch, we are trained to provide the proper diagnosis.

4. There is frost buildup.

Frost can develop when moisture from the exhaust mixes with cool air. Over time, the inside of the intake pipe becomes constricted, causing your furnace to shut down. Our Chaves Heating & Air Conditioning professional will clear out the frost—we may also extend the exhaust vent and remove obstructions to prevent the issue from happening again.

We Are Your Furnace Experts

Remember, your pressure switch is there to protect you! Ensuring it is in good shape will help safeguard you from harmful gases and keep your furnace running efficiently. Call Chaves Heating & Air Conditioning today at 978-562-5309 or request service online if you need to schedule a repair for any make or model of heating system. In addition to repairs, we offer installations and replacements as well as maintenance for the residents of Hudson, MA, and surrounding regions.