The homeowner in our story lives in southern Ontario, Canada, and recently had a new air conditioner and high-efficiency, variable-speed gas furnace installed.

The homeowner’s letter started with the word “help.”

It seems he was told by a salesman that “furnaces run at high speed during the cooling cycle; but we purchased [our] furnace only to find out that this model runs at its lowest speed (600 cfm) when the air conditioner is on.”

They discovered that the air conditioner never shuts off, “because the cold air isn’t forced to rise above floor level and the thermostat temperature doesn’t lower.” After many visits from a technician, these homeowners were finally told that the furnace is doing what it’s supposed to do.

“The ducting is also brand new, the filter is cleaned regularly, our home is 950 square feet, and we live in southern Ontario, so cooling the house shouldn’t be difficult. I have been told by other sources that this will only work in homes that have ceiling air intake vents which we were never told were necessary.”

In a nutshell

Location:950-sq-ft home in OntarioEquipment:
  • Brand-new, noninsulated ductwork in good condition per visual inspection (replaced existing ductwork from older gas system);
  • 60,000-Btu gas-fired furnace;
  • 1.5-ton, split-system air conditioner;
  • Electronic air cleaner and bypass humidifier.
Repairs:Within one week of installation, the furnace’s inducer motor had to be replaced.Maintenance:Homeowner states that they have cleaned the filter every two months since the system was installed. Also, “We make sure that outside coils do not get dirty.”Fan setting:Installation contractor recommended to keep the fan on at all times, in order to ensure that the electronic air cleaner is working.Temp measurements:With the outside temperature 75°F and the thermostat set at 63°, the inside temperature was 73°. According to the homeowner, “Two hours later there was no change in the inside temperature.”In summation:“The contractor now repeats over and over that the air conditioner should have an output at 600 cfm, which is the same output as fan mode,” says the homeowner. “However, when we were sold the furnace and air conditioner, we were told it would output at a high speed.”

OK, Tech Heads: Is this a communication problem between the tech, the contractor, and the homeowner? Does the contractor and/or homeowner not fully understand the system’s operation? Are there problems with the t-stat or wiring? Or could it be the equipment itself?

How would you handle this service call?

Let’s start talking. Please send your replies to Troubleshooting/ Maintenance Editor Barb Checket-Hanks, no later than March 27, by e-mail ( or fax (248-362-0317). Answers will be published in an upcoming issue of The News.