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A smart switch enables a bath fan to meet ventilation needs

Posted on Jan 27 2009 by Martin Holladay

This switch keeps track of fan run time

MARSHFIELD, Mass. — Lipidex Corporation, the manufacturer of the AirCycler control for supply ventilation systems, has developed a sophisticated switch for bathroom exhaust fans. Retailing for about $47, the SmartExhaust switch has the same features as — plus additional features that really make the switch stand out.

Unlike the EFI switch, the SmartExhaust switch keeps track of total fan run time and operates the fan when necessary to meet mechanical ventilation requirements. In most cases, the switch should be programmed to meet the requirements of ASHRAEAmerican Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). International organization dedicated to the advancement of heating, ventilation, air conditioning, and refrigeration through research, standards writing, publishing, and continuing education. Membership is open to anyone in the HVAC&R field; the organization has about 50,000 members. Standard 62.2.

Two parameters can be adjusted on the switch: the fan delay feature (0 to 60 minutes) and the ventilation feature (0 to 60 minutes per hour). To program the switch, it's necessary to know the effective airflow of the exhaust fan. Let's say you have a 100-cfm fan which, because of elbows in the fan's ductwork, has an effective airflow of 80 cfm. If your house needs 40 cfm of mechanical ventilation according to ASHRAE 62.2A standard for residential mechanical ventilation systems established by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. Among other requirements, the standard requires a home to have a mechanical ventilation system capable of ventilating at a rate of 1 cfm for every 100 square feet of occupiable space plus 7.5 cfm per occupant., the SmartExhaust switch should be programmed to run for 30 minutes each hour.

If the fan is programmed for a 15-minute delay, it will operate for 30 minutes if someone takes a 15-minute shower. In that case, no additional ventilation will be required for an hour. If no one enters the bathroom during the following hour, however, the switch will automatically turn on the fan for 30 minutes to meet ASHRAE 62.2 requirements.

The switch even includes a useful feature to override the programmed delay. If you are entering the bathroom for a short amount of time, and the fan delay feature is not needed, just "bounce" the switch on and off to override the fan delay.

Hats off to the Lipidex Corportation for developing this nifty little switch. For more information, contact AirCycler at 877-326-2668; .


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  1. AirCycler

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