Ventilation Control Systems

Today's energy efficient homes do a great job of keeping conditioned air in. The downside is that reduced ventilation and air exchange with the outside can result in poor indoor air quality and possible health problems. Even air systems that are designed with fresh air intake do not provide ventilation or exhaust when they are not running.

Economical and affordable ventilation control systems are ideal for use with exhaust or supply fans, air handlers, heat recovery ventilators, intermittent whole-house exhaust systems, or anywhere specific ventilation rates are desired. Mixing the house air with fresh outdoor air can increase energy efficiency, reduce moisture condensation problems, and increase indoor air quality.

There are many types of ventilation control systems. Most manufacturers of ventilation equipment will also offer a control unit. Controls can be as simple as a twist-timer that is operated manually. Or, some units provide automatic control and are adjustable for cycle duration and time between cycles. Two available options are described here. The Airetrak is typically used with a single-port or multi-port low-power fan that provides exhaust or supply ventilation to one or more locations in the home. The FanRecycler is specifically designed to control the central HVAC air handler. It offers a means of timed operation of the air handler independently of a call for space heating or cooling. The central air handler can facilitate circulation of air in the home and better distribution of ventilation air. When a FanRecycler is used, a duct is often run from the outdoors to the return side of the air handler. The FanRecycler can open a motorized damper in this duct to bring fresh air into the home.

Airetrak

Airetrak's microprocessor-based control system is designed to give ventilation designers and installers the versatility required to balance proper ventilation with energy conservation. The standard unit is designed for single speed equipment, while the PRV model is allows for dual speed operation. For instance, a multi-speed exhaust fan might be operated at low speed to provide ventilation, but boosted to high speed when local bath exhaust to remove moisture was specifically desired. The solid state speed control offers 16 different settings for optimized air flow rate from 40% to 100% of fan capacity based on home size, occupancy, and other field conditions. According to the manufacturer, on-site programming takes less than two minutes and requires no specialized tools or training. The built-in timer is programmed during installation to operate the ventilation equipment in 5-minute increments (5, 10, 15, etc.) during a 12- or 24-hour cycle. The front panel override option activates the boost feature which operates the fan at full speed for 20 minutes before automatically resuming its programmed cycle. The system eliminates user error by automatically controlling the fan speed and cycle time, while still allowing the occupant access to a full-speed boost cycle. For noise-sensitive applications, the system can be paired with a quiet, energy-efficient fan. The units come with a lithium battery backup that holds saved settings in case of power failure for 400 hours. Input: 120 VAC, 60hz, maximum power output: 400 watt.

FanRecycler

Central fan controllers like the FanRecycler can be used to periodically mix indoor air or to introduce outside air into the home with a fresh air intake. When used in the latter capacity, an outdoor air intake duct is run to the return side of the air handler. A motorized damper is often installed in this duct as well to provide better control of the introduction of outdoor air. The FanRecycler turns the air handler on only after a selected period of time during which the central fan has not operated, such as when heating or cooling is not needed. It can also be used to control the operation of the motorized damper. An advantage of the FanRecycler in hot, humid climates is that it recognizes when the compressor has just shut off and avoids cycling air until the compressor has dried somewhat, to avoid sending too much moisture into the ductwork.

Indoor air quality in most buildings is lower than it is outside of the building. These systems help bring in fresh air while removing stale air in addition to helping equalize pressure and temperature in homes.

The Airetrak unit costs about $100. The FanRecycler, developed under a U.S. DOE grant, retails for $50.

By offering greater specification and increased user-control over particular mechanical ventilation systems, these two controls can decrease the cost of mechanically introducing fresh air into the home. The operational costs of any mechanical ventilation strategy will be dependent upon the fan characteristics, operating schedule, and climate.

UL listed.

The exhaust control unit fits into a standard single gang electrical box with a standard cover. No special wiring is needed. The central air controller is wired directly to the air handler. To provide fresh air, a 6- to 8-inch duct must be connected from outside to the return plenum.

Airetrak is warranted for a period of one year.

The FanRecycler is warranted on a case-by-case basis, typically for about three years. However, there is no set warranty.

By increasing the fan speed gradually and running the fan at a lower final speed, the Airetrak exhaust controller keeps exhaust fans operating quietly and economically. By programming ventilation equipment to fit specific customer occupancy patterns, energy losses are minimized. The unit costs less than the 24-hour timer, variable speed control, and boost switch it replaces.

A central fan controller can save energy by "averaging" or mixing the air in a residence, allowing an even temperature distribution from room to room. Periodic ventilation helps keep humidity under control to increase indoor air quality and durability of the home and its HVAC system. Additionally, air will be filtered more frequently as it flows through the HVAC system filter.