Most recovery underperformance is designed in, not manufactured in. The same handful of selection errors shows up project after project, and each one quietly costs energy or causes a freeze-up that a ten-minute review would have prevented. Here are the seven most common, and the fix for each.
1. Sizing on peak airflow
Designers often size the core at the absolute maximum airflow, which the system reaches only a few hours a year. At that flow the face velocity is high, effectiveness drops and condensation forms on the wrong side. Fix: size near the average duty and confirm the part-load curve, as in the sizing guide.
2. Ignoring pressure drop
A 30 Pa tighter core looks like a rounding error on the spec sheet but costs fan energy every operating hour for the life of the unit. Fix: include pressure drop in the fan-energy model before choosing, not after the fan is already specified and the budget is closed.
3. Forgetting frost in cold climates
A plate core exhausting below 0 degrees C freezes solid without protection, blocking the airstream and tearing the plate. Fix: add preheat, exhaust recirculation or an automatic bypass per the frost-control guide.
4. Using a wheel where separation is required
Rotary wheels carry 0.5% to 5% exhaust into the supply. Fine for an office, fatal for an OR or lab. Fix: specify a separated-stream plate or heat-pipe core for healthcare, cleanroom and lab duty, where codes forbid carryover and the consequence is a failed inspection.
5. No summer bypass
Running exhaust air through a core in summer free-cooling season just adds fan resistance for no gain. Fix: include a motorised bypass that opens when recovery is not useful, typically above the building neutral temperature, and confirm the actuator is commissioned.
6. Mixed or dirty airstreams without coating
Kitchen grease or corrosive exhaust fouls and eats a bare aluminium core in a single season. Fix: use epoxy-coated or polymer plates and a washable layout from the maintenance guide.
7. Reading effectiveness at the wrong velocity
Effectiveness is published at a nominal face velocity; read it at your actual velocity or you will over- or under-state recovery by several points. Fix: always read the datasheet at the operating point.
Close the loop with documentation
Every one of these mistakes is cheaper to prevent on paper than to fix in steel. Capture the chosen face velocity, pressure drop budget, frost strategy and separation requirement in the specification, and attach the selection checklist to the submittal so the reviewer can confirm each box before the core is built. A one-page duty sheet that travels with the project from design to commissioning is the cheapest insurance against a $6,000 core arriving with the wrong coating or the wrong rotation, and the sizing guide shows the exact inputs that sheet should carry so nothing slips between disciplines.
Specifying a unit for your project?
EN159 builds plate, rotary, heat-pipe and counterflow air-to-air exchangers for commercial, industrial and healthcare duty. Send airflow (m3/h), inlet temperatures and available space and we will size it.
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