Welded steel cabinet with powder coat paint 2. Access door to internal components with Duro-Dyne type handles for air tight seal. Aluminum pre-filter for sparks and larger particles. Main cartridge for finer dusts and smoke 5. Polyester charcoal filter to reduce odors 6. Cabinet grab handle 7. Push button for pulse cleaning 8.
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Back to Contents Page Home Energy Index About Home Energy Home Energy Home Page Back Issues of Home Energy Home Energy Magazine Online May/June 1993Integrated Heating and Ventilation: Double Duty for Ductsby Mark A. JacksonNorthwest building codes require mechanical ventilation in new homes. Combining heating and ventilation can fit the bill if the builder considers the whole system carefully.Building codes in Washington state and Bonneville Power Administration's specifications for new residential construction require mechanical ventilation systems. Since the majority of new houses built in the Northwest have forced-air heating systems, using the heating system ducts to supply fresh air as part of the ventilation system has become a popular option for home builders.When properly designed, installed, tested, and operated, integrated heating and ventilating systems can be effective, and relatively inexpensive to install. However, there are inherent inefficiencies in these systems, and the overall cost for ventilation using an integrated system is higher than for any other ventilation system commonly used. Worse, poorly designed systems can function like a rather large uncontrolled leak in the heating system, with unacceptable energy consequences and little to offer in the way of effective ventilation.The Basic SystemUntil recently, the typical approach to integrate the heating and ventilating systems required that mechanical components plus an electric control system be fabricated on site.
In the last year or so, several manufacturers have responded to the need for an all-in-one mechanical and electrical control unit. There are still many possible variations using a diverse array of air inlet and exhaust strategies, but the essential elements are pretty straightforward (see Figure 1):.
A fresh air duct which brings outside air to the return side of the air handler of a forced air heating system (gas, electric resistance, or heat pump). The fresh air duct must be tight and well-sealed to the return plenum to prevent the introduction of unwanted combustion gasses from combustion appliances. A balancing damper or other device that limits the flow rate of fresh air into the system. The volume of fresh air required has to be calculated, and the damper needs to be set using an accurate air flow measuring instrument. An electrically operated damper controls the flow of air into the system to prevent fresh air flow when it is not needed or wanted.
A clock timer is used to periodically cycle the system. A bypass or twist timer allows manual control to provide additional ventilation as needed. These controls open the electrically operated damper, and turn on the air handler and exhaust fan. An exhaust fan removes stale air from the house. A centrally located fan dedicated to the system or one of the bathroom fans can be used. The air handler blower provides the fan power to pull fresh air from outside into the system and to distribute the fresh air through the supply ducts. A two-speed blower is preferrable, so that the system can operate at low speed during ventilation mode.
The fan-motor sets in residential forced air heating systems are typically inefficient, requiring 400-600W for shaded pole blower motors. Better motors are available, one of which is the permanent-split capacitor motor.
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New adjustable speed drives may be somewhat more efficient at low speeds, but these are not yet common in residential applications.House-System InteractionsOne of the first questions that arose when integrated systems became popular was: What kind of damper do houses need to control fresh air entry into the system-are barometric dampers acceptable, or should electrically activated dampers be required? To answer this question, several types of dampers were evaluated in 25 single-family homes as part of the Residential Standards Demonstration Project, sponsored by the Bonneville Power Administration.