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How To Fix A Heating System With Low Flowing Heat

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If you have recently moved into a home with a forced air heating system, and warm air does not seem to blow strongly through your vents, then you may need to invest in a heating maintenance service like Custom Comfort. You can also try to resolve the problem yourself before you call in the professionals.

Change The Filter

If you have not had to deal with a forced air heating system before, then you may not be very familiar with the types of maintenance tasks that you need to complete as a homeowner. Changing the air filter that is attached to the plenum above your heater is one of these things. If the filter is old and congested with debris, then this will stop air from moving up and through the vents with a good deal of force and speed.

You can inspect the filter first for signs of debris by looking for the filter in the wide square compartment that sits just above the heater and below the main ductwork of the heating system. If you see visible signs of debris clinging to the filter, then replace it. If the filter appears clean, then look at the MERV rating on the cardboard or plastic edge that sits around the filter. If the rating is between 9 and 16, then the filter material is too dense or closely woven. While this will remove between 85% and 90% of all debris, it will slow down the flow of air. 

Replace the filter with a filter with a MERV rating below 9. If you notice that there is more debris in your home when you do this, then invest in an air purifier in the home.

Increase Blower Speed

If you change the filter and air flow does not increase or if the air filter was the correct type, then the issue may be that the blower inside the heater is set at a slow speed. The blower is the device within the furnace that controls the speed of the air moving through the unit. Air is first brought into the blower through the air return. The blower will be a squirrel cage or centrifugal type with a fan wheel on the inside that increases the velocity of air. The speed of the wheel or fan will determine the velocity of the air that releases from the blower, and speed is controlled by a motor.

Most blowers will have variable speeds, and you may be able to increase the speed of the blower to help force hot air through the ducts with greater speed. Remove the casing from the front or side of your furnace and look for the blower and the motor. Look for wires connected around both devices. You will typically see a small control panel in the region of the wiring and a switch or dial. There will be different speeds or percentage markings near the switch. Switch the speed to the setting that says high or 100% airflow. Replace the cover and turn on the heater to see if airflow increases.

Inspect Blower Belts

If airflow is low and you hear a whining or screeching noise when the furnace blower turns on, then this is a sign that the belt connected to the blower may be broken, stretched, or warped. Open the cover of the furnace and look for a belt on the motor that is attached to the blower. Use a flashlight to look for cracks or signs of wear. Also, investigate to see if the belt is angled to one side, extremely tight, or sagging in the middle. If so, then you will need to replace the belt.

If you want to replace the blower belt yourself, then remove the old belt and take it to your local heating supply store so an exact replacement can be found. Slip the new belt on the motor pulleys. The belt may be difficult to fit onto the pulleys, so contact a heating repair specialist for assistance if you cannot get the belt on. You should also do this if you do not feel comfortable replacing the belt yourself.