Here’s a scenario that will sound all too familiar to many homeowners in the Princeton area: Your home feels slightly chilly, so you adjust your thermostat to get the heating system running. Your heating system turns on and operates just fine, but then your furnace turns off after a few minutes. Soon after, it turns back on and begins to warm your home again, only to shut off once more.
This frequent on-and-off of your furnace is called short cycling. What causes a furnace to short cycle? From the perspective of the furnace troubleshooting experts here at Princeton, the problem can be traced back to an overheating heat exchanger, a dirty flame sensor rod, or an oversized furnace.
Overheating Heat Exchanger
A heat exchanger is the part of a furnace that heats the air. If there is low airflow in your furnace, the heat exchanger will get too hot. This, in turn, will trip the high limit switch, which shuts off the furnace to protect it from damage.
A low airflow issue in your furnace can have a few different causes. The air filter in your furnace may be dirty and clogged, causing the blower to struggle to pull air in over the heat exchanger. In this case, you would need to clean or replace your furnace’s air filter.
Your furnace may also have a dirty blower wheel, causing it to slow down and deliver less air over the heat exchanger. In this case, you should hire a technician to clean the blower.
You also might have too many air supply vents closed, slowing down the blower and reducing air flow. Whatever the cause of low airflow, if it makes your heat exchanger overheat, you’re not going to have a well-functioning furnace.
Dirty Flame Sensor Rod
If you are looking for the reason why your furnace shuts off and on again repeatedly after just a few seconds, this could be due to a dirty flame sensor rod. The flame sensor rod is a safety device in your furnace that shuts the gas valve when it does not detect a flame in the burners. If that rod has collected soot and become dirty over time, it may not detect a flame in the burner right away. When this is the case, it will signal the gas valve to shut, cutting off the supply of gas to the burner and putting out the flame. Cleaning or replacing the flame sensor rod will typically get your furnace running normally once again.
Oversized Furnace
If you recently replaced your furnace, or if short cycling has been a problem with your furnace for years, it could be due to an oversized furnace. An oversized furnace will heat your home up to temperature too quickly, causing it to turn off and on often. If you recently replaced your furnace and are dealing with oversized furnace problems, you should definitely contact the installer to have them address the issue. If you have an older furnace, now may be a good time to consider investing in a new, energy efficient, and properly sized furnace.
Call The Furnace Maintenance and Repair Experts at Princeton Air
As you can see, it isn’t always easy to determine why a furnace keeps shutting off, and HVAC system troubleshooting is often best left to the pros. At Princeton Air, we have the skills and expertise necessary to accurately diagnose what’s going on with your furnace. We can also maintain your furnace to make sure none of these issues arise, and if short cycling is undermining your home’s comfort, we’ll help you solve the problem!
If it's determined that replacing your furnace is the best option after diagnosis, we offer convenient on-bill repayment plans. These plans provide zero-interest financing for up to 84 or 120 months, with the monthly payments added directly to your existing utility bill—eliminating the need for extra statements or accounts. The specific terms and repayment lengths may vary depending on your utility provider, the energy efficiency upgrades you choose, and other factors, but we’ll help you navigate the process to find the best option for your home.
JS Needham-Master HVACR Lic. # 3980 | M Burt-Plumbing Lic. # 8389 | NJHIC # 13VH00255200 | PAHIC # PA001066
