Heat Recovery Ventilator (HRV)

Overview

A heat recovery ventilator gives a tight, well-insulated building the fresh air it needs without throwing away the energy used to heat or cool it. It runs two airflows at once: it pulls stale, humid air out of kitchens and bathrooms and pushes an equal amount of filtered outdoor air into living spaces. The two streams cross inside a heat-exchanger core, where the outgoing air warms the incoming air in winter (and the reverse in summer) without the two ever mixing.

Everything is packaged in an insulated Insulated Cabinet usually hung in a basement or mechanical room. Four ducts connect through the Duct Collar fittings: two to the outdoors and two to the house. Inside, the Supply Blower and Exhaust Blower move the matched airstreams, the Filter Set keeps dust out of the core and the home, and the Control Module sets the ventilation rate and runs the defrost cycle.

How it works

The recovery happens in the Counterflow Heat-Exchanger Core. Supply and exhaust air thread through alternating channels in a stack of thin aluminum plates, running in opposite directions so that every part of the cold incoming stream meets a slightly warmer part of the outgoing stream. This counterflow arrangement is what lets a good core hand over 80 percent or more of the sensible heat. Because the plates are solid, odors and pollutants leave with the exhaust rather than recirculating.

Two balanced blowers drive the system. The Supply Blower and Exhaust Blower use EC motors so the controller can trim each one until intake and exhaust flows match, keeping the house neither pressurized nor starved. The Sensor Set reads stream temperatures and indoor humidity; when a bathroom call or high humidity is detected, the controller boosts both fans together.

In cold climates the moisture in the exhaust air can freeze on the core's exhaust side. The Defrost Damper handles this: its motorized blade periodically blocks the cold intake and recirculates warm house air through the core to melt any frost, then returns to normal ventilation. Water that condenses out of the exhaust drips into the Condensate Drain and leaves through a trapped line. The whole unit answers to the Control Module board and its wall display, which lets the occupant pick a continuous low rate or scheduled boost.