Some simple strategies can be used to ensure proper installation and operation and also keep homeowners happily humidified while avoiding costly callbacks.

Checking The Initial Installation

With the introduction of Aprilaire's newest version of its automatic humidifier control, a new diagnostic circuit and red LED indicator are utilized, he said. "It does a check of the components on the circuit board, and ensures that either the outdoor temperature sensor or plastic resistor case (for operation in manual mode) is attached to the outdoor temperature sensor terminals." If the circuit is not proper, the red LED lights, notifying the installer of a problem before leaving the jobsite. "This definitely prevents callbacks," noted Darkow.

Table 1. Recommended indoor humidity levels.

Achieving Optimum Humidity

1. A humidistat, used with a manually controlled humidifier, needs time to react to an increase or decrease in the call for humidity. "Make sure your customers clearly understand the reaction time difference between a thermostat and a humidistat," he emphasized. A call for a change in humidity takes much longer to fulfill than a call for a change in temperature. Therefore, it's best to make a humidistat adjustment in the morning for what the anticipated evening low temperature will be.

For example, if the low temperature is expected to be 20 degrees F, the relative humidity should be set for 35 percent. The humidifier should be adjusted for every major change in outdoor temperature, he said. See Table 1 for recommended settings.

To avoid making constant manual adjustments, the homeowner can opt for a new automatic humidifier control, which constantly monitors indoor humidity and outdoor temperature to respond immediately to a humidity call.

2. Run the furnace blower constantly. "Whole-house humidifiers work in conjunction with the furnace blower motor," related Darkow. "If the blower operates constantly, every time a humidity call is made, the call will be fulfilled immediately. In addition, if there is excess humidity in the home, the furnace blower will effectively dissipate excess moisture over time."

For newer, tighter homes, an energy recovery ventilator can also be used to remove excess moisture from the home. With this accessory, inside air can be circulated more effectively and efficiently, he said.

3. Explain the basics of humidification to the homeowner. "Common sense might lead the average customer to assume that as temperature decreases, the humidifier adjustment would need to increase," Darkow stated. "However, the exact opposite holds true. As air becomes cooler, its capacity to hold moisture decreases. Therefore when the temperature dips to below freezing, the recommended relative humidity will decrease and the homeowner will need to set the humidistat dial lower."

Although no one will ask you to predict the weather, he said, "It would be worthwhile to don your weatherman's hat and quickly explain relative humidity to the customer. The term is unfamiliar to many people, but it plays a critical role in comfortably humidifying a home."

Simply put, he explained, relative humidity is the amount of water vapor, in percent, that is actually in the air compared to the maximum amount the air could hold at the same temperature. For instance, air in a home heated to 70 degrees F can hold approximately eight grains of moisture per cubic foot, which would be 100 percent relative humidity (rh). If there are currently two grains of moisture per cubic foot in the home, then the air is holding one-fourth, or 25 percent, of its total capacity. The relative humidity is then 25 percent, because the air could hold four times as much moisture.

"Optimum humidity varies depending on whom you ask," he said, "but most people agree a comfortable range is between 40-60 percent."

4. Change the evaporative element annually. "Most homeowners don't realize how critical the evaporator is to humidification," commented Darkow. "It is the heart of the unit and must be in good condition to assure high capacity and trouble-free performance. Its importance can be illustrated in two ways: First, it is the means by which moisture is added to the air. Its many tiny surfaces allow water to be dispersed and then evaporated for distribution as moisture. Second, it traps minerals left behind from the water passing through it. As the mineral deposits build, the humidifier's evaporation rate could be affected. These two reasons make it important to change the evaporative element annually, ensuring maximum comfort in the home."

As a reminder for the homeowner, Aprilaire recently introduced a new humidifier control with a water panel change indicator light on the front of the control.

Table 2. Condensation on windows. With a constant indoor temperature of 70 degrees F, this table illustrates the outside temperature at which condensation is likely to occur.

How To Avoid Over-Humidification

To keep windows from fogging, decrease the humidistat before family gatherings, said Darkow. "Inform the homeowner that moisture from internal sources other than the humidifier will not immediately dissipate once the temperature drops and condensation appears."

Other humidity-causing household events include cooking, boiling water, taking showers, and watering plants. While none of these events can bring enough moisture into the home for comfortable, cold weather living, any one, given the proper circumstances, can elevate the humidity level high enough to cause condensation on windows.

"And this excess moisture can occur even when the humidifier is off or in homes without a humidifier," Darkow remarked, "so remind the homeowner that, on occasion, this is normal." See Table 2 for likely condensation points.

Homeowner's Humidifier Checklist