Most recovery projects do not need a custom core, but a few absolutely do. Knowing which camp your duty falls into saves weeks of lead time and a large premium, and prevents the frustration of forcing a standard part into a space it was never meant to fill or watching a project slip because the only option was bespoke.
When a standard core is right
Catalog plate cores are built in common footprints (500 x 500 mm, 600 x 600 mm and up) and standard airflow steps (500, 1,000, 2,000 m3/h and beyond). If your air handler matches one of those, an off-the-shelf core drops in with a 1 to 2 week lead time at the lowest cost. For the vast majority of offices, schools and retail units this is the answer, and a selector tool will find the match in minutes without a single engineering call or a custom drawing.
When to go custom
- Nonstandard footprint: a rectangular plenum or a retrofit where no catalog size fits the duct without a costly transition.
- High temperature: exhaust above 80 degrees C (ovens, kilns, some industrial processes) needs special seals and metals that standard cores lack.
- Corrosive or greasy streams: kitchen, lab or chemical exhaust needs epoxy-coated or polymer plates and a washable build.
- Very high effectiveness: a counterflow plate or a wheel tuned to a specific duty that catalog parts cannot hit at the required pressure drop.
- Integrated functions: bypass, frost control and filters built into one cassette to save field labour.
A worked custom scenario
Consider a retrofit where the only available plenum is 1,340 x 410 mm with 7,500 m3/h of greasy kitchen exhaust. No catalog plate fits that rectangle, and a bare aluminium core would foul in a season. The right answer is a custom 1,340 x 410 mm epoxy-coated counterflow core with an integrated drainable pre-filter, quoted at roughly 2.5x the standard price and a 6-week lead. The alternative, a transition duct plus a standard square core, costs more in sheet metal and floor space and still fouls, so the custom route is cheaper on true installed cost despite the premium.
| Factor | Off-the-shelf | Custom |
|---|---|---|
| Lead time | 1 to 2 weeks | 4 to 8 weeks |
| Cost multiplier | 1x | 2x to 4x |
| Fit certainty | High if standard | Exact |
| Performance ceiling | Good | Tuned to duty |
Making the call and costing the detour
Start with the selector and the sizing guide. If a standard unit meets effectiveness, pressure drop and footprint, stop there. Only escalate to custom when one of the five triggers above appears, and expect to share a duct drawing so the shop can match the connections. Remember that custom is not just a higher price tag; it is also engineering time, a drawing review, a longer hold on the critical path and a spare part unique to your site, so weigh that against a small compromise on footprint that buys a catalog lead time. Reserve the custom route for duties no standard core can meet, and review the broader technology guide before deciding which core type the custom build should even be, then give us the duty in the format in how to request a quote so the proposal is accurate on the first pass.
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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