In the wake of mold and moisture problems across the country, many HVACR design and installation professionals — people from associations such as the Air Conditioning Contractors of America and the American Society of Heating, Refrigerating, and Air-Conditioning Engineers — have mentioned the fact that the first air conditioning systems were designed to control humidity; lowering the temperature was a secondary benefit. Why, then, do we use thermostats that measure temperature alone?

This is starting to change.

It’s The Humidity

Tom Overs, IAQ product manager, Lennox International (Dallas), discussed the company’s SignatureStats, part of the Signature™ Integrated Comfort Solution. The product was in development approximately 12 months, he said, in response to comfort needs.

“We looked at it from the standpoint of, you don’t always need air conditioning, but you may need humidity removal.” Can it help prevent mold growth? There are too many variables involved in mold growth, Overs said, but this thermostat can help the air conditioning system control indoor relative humidity.

During high latent conditions, the SignatureStat will sense that humidity levels have exceeded a setpoint; the thermostat then sends out a demand to remove humidity. At this point, Overs explained, the air conditioning system’s compressor goes to “high” operation and the fan turns on “low.” To remove humidity, the system cools to 3 degrees F below the setpoint if needed; Overs said it typically satisfies humidity removal within 1 degree or 2 degrees. Then it shuts off and waits for the home to return to setpoint conditions. If the relative humidity measured is still above setpoint conditions, the unit may cycle again.

“The first and foremost need is to size the system properly for the home,” Overs said. However, if a system reaches its temperature demand before enough moisture is removed, “SignatureStat will come on.” In that sense, it has been applicable for very humid climates, such as those in Houston, New Orleans, and throughout South Florida, Overs said. It can also work in climates that experience more humidity than heat.

“We’ve sold a lot already,” he said. “There’s a huge demand.”

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Integrated Solution

White-Rodgers, a division of Emerson (St. Louis) and part of the Emerson Climate Technologies Business Group, recently introduced its ComfortPlus system, a home environment system that brings together the company’s technologies and support tools to provide “a completely integrated solution that helps contractors sell home comfort solutions,” the company says.

The system brings together White-Rodgers’ thermostats, air cleaners, and humidifiers to maintain a consistent temperature, improve air quality, and control the amount of moisture.

The Comfort-Set thermostat, “the core component of the ComfortPlus system,” is said to eliminate noticeable temperature swings and maintain temperature to within 1 degree of its setting. The custom programmable thermostat allows homeowners to tailor heating and cooling choices for comfort and efficiency. Using the thermostat’s programmable features, homeowners can save as much as 33 percent on their energy bill, the company said.

The company also announced plans to introduce its next advancement in its line of premium thermostats later this year: a new thermostat designed to control temperature as well as humidity. These thermostats will be available for single-stage, multi-stage, and heat pump applications.

The new humidity-control thermostat could be available as early as this summer, the company said. The first one will control humidification through a humidifier. Later this will be combined with dehumidification.

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Striving For Perfection

Honeywell’s (Morris Township, N.J.) Automation and Control Solutions unit offers the Perfect Climate Comfort Center for dehumidification, humidification, zoning, and airflow control, all in one unit.

The PC8900A1007 is the Perfect Climate Center control system panel, the company explains; this panel for the living space is used in conjunction with the W8900 remote module. The W8900C1000 model is for 24-VAC systems with cooling. This model features a humidity reheat algorithm to dehumidify the house, “and will not allow the temperature to drop below your cooling temperature setpoint,” the company says.

The thermostat can control the temperature to within 1 degree of the setting, the company states. It also offers the ability to change the thermostat’s settings and receive system alerts via phone.

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Publication date: 03/31/2003