Light Industrial
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Heat Exchangers


Heat exchangers recover energy in exhausted indoor air and use it to temper the outside air brought in to replace it. During winter, the heat of exhausted indoor air warms the outside air brought in to replace it. During the summer (in an air-conditioned building), the “cool” of exhausted indoor air is used to cool and dehumidify the outside air brought in to replace it.

Air-to-air heat exchangers also have the advantage of providing “balanced” ventilation. For every cubic foot of air exhausted, an equal volume is brought in to replace it. This avoids problems associated with exhaust fans that must draw air through holes in the building envelope: down-drafting chimneys, radon or sewer gas drawn in from the basement, etc.

Bypass core heat exchangers have closely-spaced air passages separated by thin walls. Heat is transferred across the thin wall surfaces.

Heat wheel systems use a rotating mass of material. Heat in one air stream warms the mass, which loses the heat as it rotates through the other air stream.

Glycol run-around systems use a fluid to transfer heat between coils in the two air streams.

The choice of a contractor is as important as the choice of equipment. Duct and other equipment must be installed to assure proper air flows, otherwise the benefits of the air-to-air heat exchanger are lost. Avoid long or twisting duct runs. Be wary of small-diameter duct runs. The intake and exhaust ducts — as well as duct runs through unheated spaces — should be insulated. The installer should test and adjust the system after installation to verify balanced air flows.

Air that is cooled will cause condensation within the heat exchanger core. In most units, condensate drain tubing needs to be routed to a sink or floor drain.

During frigid weather, condensing water can frost the chilled surfaces of the heat exchange core - and potentially block it. Each manufacturer takes a particular approach to defrost. Verify that design features to prevent defrost are effective.

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