As the weather dips below freezing (and below zero here in Minnesota!), it’s the season for HVAC shops to start getting calls from homeowners about low air flow from their vents, making homes uncomfortably chilly and energy bills soar.
HVAC pros know there is rarely one cause for this situation. Sometimes, it requires a little detective work to diagnose the problem. Here are five troubleshooting tips to help you find the culprit.
- Check the air filter(s)
Always the first place to start, right? Many homeowners don’t know they’re supposed to change their air filters, or exactly how to do it. Over time, dust and dirt accumulate in the filters, which will restrict the airflow. Most HVAC techs know checking the filter is job one. It’s a short and sweet fix, the homeowner is happy and you can get on to the next call. While you’re checking out the filter, give the homeowner the info about how and when to change it.
But the filter problem might not be just dirt and dust. It might be a high MERV filter used on a system that’s too old to accommodate it. This incompatibility can reduce airflow, cause strain on the motor, and potentially damage components.
- Inspect the ductwork
A whole cornucopia of problems can come from the system’s ductwork. Critters can get in and cause obstructions. The ductwork itself can be poorly installed. It can have kinks or bends that can impede airflow. It can come loose, collapse or be crushed. Any and all of these problems can cause low airflow systemwide.
- Look at the blower motor or ECM (electronically commutated motor) blower
Many homeowners are choosing to upgrade their furnaces with an ECM blower fan because they’re higher efficiency (up to 75%) than traditional PSC motors, which usually reach about 45% efficiency. They adjust their speed instead of just turning on or off like PSC motors, and that means they use less electricity, resulting in lower utility bills and reduced strain on the HVAC system. All good, right?
Yes, except ECM blowers can lose efficiency quietly. With traditional PSC motors, you either hear them running or you don’t. No hum? The motor isn’t working. But ECMs can sound like they’re running and not be delivering the proper airflow.
When that happens, the system has to work harder to maintain the desired temperature in the home, raising energy bills and causing uneven airflow.
- Check for refrigerant leaks
For homes with heat pumps, a leak in the refrigerant line will cause significant problems. In addition to reduced airflow and heating, it could potentially damage the compressor and even freeze up the entire system. The tell-tale sign? Hissing or bubbling. You’ll need to find the source of the leak seal it — hopefully before too much damage sets in.
- The vent itself
This is one of those “doh!” solutions. If the homeowner is experiencing low airflow in just one room, it could be the vent itself. There could be a problem with the damper, it could be partially closed, or otherwise impeding airflow in a way you can’t initially see. Take the vent off and if you feel a whoosh of air, you’ve got your culprit.
With these tips, you can troubleshoot low airflow quickly and get the home comfy and cozy in no time. In our next blog, we’ll talk about common winter plumbing problems.
