ACHRNEWS

Troubleshooting Challenge: A Furnace That's Not Heating the Whole House

November 9, 2009
Figure 1. (Click on the image for an enlarged view.)

In our troubleshooting situation this time around, we have a customer who is complaining about one of the bedrooms in their home, specifically that the gas furnace doesn’t warm the room properly. When you arrive, you find that the bedroom in question is the furthest from the furnace, and that the duct system being employed is an extended plenum system like the one shown in Figure 1.

In your overall survey of this situation, you find that the customer has been trying to force more air into the back bedroom (shown at the top right of our duct system) by closing off other registers with cardboard and duct tape, which didn’t help the diminished airflow into the problem room. You also note in your evaluation that the return air system that employs a return grille in each room is operating properly without restriction in this ranch style home on a concrete slab.

Figure 2. (Click on the image for an enlarged view.)

As you begin your detailed evaluation of the equipment, you note that the manufacturer has specified a temperature rise of 55 degrees, and your temperature rise test shows a difference of 60 degrees. You decide next to check the operation of the blower motor, and note (as shown in Figure 2) the wiring connections.

Your troubleshooting question: What is the next step you need to take in solving this problem?

Compare your answer with ours by clicking here.

Publication date: 11/09/2009