Air-to-Air Heat Exchanger FAQ

Specifiers and buyers ask the same handful of questions before they commit to a recovery core. Here are clear, numbers-backed answers drawn from the technology guide and our field experience. The short version: a recovery core is a passive device that moves energy between two airstreams and pays for itself by shrinking the heating and cooling plant, provided it is sized, controlled and maintained to the duty it actually sees rather than the catalogue headline.

What does an air-to-air heat exchanger actually do?

It transfers heat between two airstreams that never mix. In a ventilation system the warm, stale exhaust pre-conditions the cold incoming outdoor air in winter (and vice versa in summer), cutting the heating or cooling load without sharing contaminants. A 10,000 m3/h core at 80% effectiveness recovers roughly 26 kW of heating at a 30 degrees C lift, every hour the system runs.

Plate, rotary or heat pipe — which should I choose?

It depends on the duty and the separation rule. The plate vs rotary guide compares them: plates give 60% to 70% (crossflow) or 80% to 90% (counterflow) with zero carryover, ideal for healthcare and labs where supply must not meet exhaust; wheels add 60% to 70% latent recovery for humid commercial loads but carry 0.5% to 5% exhaust into supply; heat pipes are fully separated and frost-tolerant at 55% to 65%. Match the type to the airstream, then to the code.

How much energy can recovery really save?

For a DOAS or make-up air unit above about 2,000 m3/h, recovery typically cuts conditioning energy 50% to 80% on the ventilation portion, which is often 30% to 50% of the whole HVAC load. The payback calculator turns that into a number: a 17-point effectiveness gain on a 10,000 m3/h core is worth about $3,300 a year in a cold climate, usually paying back in one to three heating seasons. The economics guide scales this to whole buildings.

Do I need a summer bypass?

Almost always. In free-cooling season, forcing air through a core only adds fan resistance for no recovery benefit. A motorised bypass opens when outdoor air is within a degree or two of the return, letting the building free-cool. The bypass also doubles as the frost-protection path in winter, so it earns its cost twice.

How often must it be cleaned?

Plate cores in normal commercial air need an annual wash; greasy or dusty streams (kitchens, industrial) need two to four washes a year and a coated plate per the maintenance guide. A fouled core loses 15% to 30% effectiveness and raises pressure drop 20% to 40%, quietly wasting the saving. Start any project with the selection checklist, and when you are ready, use how to request a quote to send us the duty.

Will it raise my fan power?

Yes, by the core's pressure drop, which is why that number belongs in the selection, not just the effectiveness. A plate core typically adds 150 to 300 Pa per side; at 10,000 m3/h that is 0.4 to 0.8 kW of extra fan power per airstream. Weigh it against the 20 to 30 kW of recovered heating, and the fan penalty is 2% to 4% of the saving, so recovery still wins by a wide margin. Keep face velocity in the 1.8 to 2.5 m/s band where the drop stays modest, and the pressure-drop and fan-energy model will show the net saving honestly before you buy. The core does not filter or treat air, so pair it with proper filtration upstream and treat it as an energy device, not an air-quality device.

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