Where Good Neighbors and Good Servicemen Meet

Continuous Fan Blower Operation

This article is in response to a question from a customer: "Under what circumstances would I run my fan continuously?" he asked.

The Split System

Vernon has what is called a split system. His home uses electricity for cooling and gas for heating. His thermostat has a fan switch that has two choices: "Auto" or "On." Normally his fan switch will be set at "Auto." When the thermostat calls for cooling, it sends two signals. One goes to the outdoor condenser where heat is extracted from the freon. The other signal engages the indoor fan blower that circulates air throughout the house.

Under special circumstances, he should set his fan switch to "On." When he does that, his fan blower will run continuously, but his compressor will cycle as needed to maintain temperature.

Hot Spots in the House

Cooking in the kitchen or even sitting in front of a hot computer are good reasons to temporarily run the fan blower continuously in the "On" position.

Poor Air Distribution (One room is especially hot or cold)

Occasionally the air duct distribution system is out of balance. Often the answer is simply opening air register shutters that have been closed. Sometimes your AC professional will need to modify the duct system. Continuous fan blower operation is a good temporary answer to the problem.

Upstairs and Downstairs on the Same System

It's not a good practice to cool or heat two floors using the same AC system, but sometimes it can't be avoided. If your thermostat is downstairs, that space will enjoy the best temperature control. Upstairs temperatures will vary, but those variations can be minimized by running the fan blower continuously. If your bedrooms are upstairs you might choose "On" during sleeping hours, and "Auto," during waking hours.

Humidity Control

An important part of the air conditioning process is the removal of humidity. Moisture condenses on the evaporator coil. Each evaporator coil has a drain pan, and the best pan is one that has a built-in slope for drainage. Some drain pans—especially horizontal ones, made for attic use—have a flat pan. When I install a horizontal coil, I tip the coil for drainage. Some have questioned the correctness of my installation because it looks funny, but there's a reason.

If moisture is allowed to pool in the drain pan, it could re-evaporate later, and be re-distributed throughout the house as humidity. That is most likely to happen if you run the fan blower continuously. If you sense an increase in humidity, you might want to have your AC professional check your installation.

The Koolness Continues,

Dr. Kool

p.s. See The Kool Konnection. Then Register as a Kool Kustomer.