In many applications it is important to limit the cross contamination (leakage) from the exhaust to the supply side of an energy recovery wheel. In some applications, like laboratories, it’s critical. In other applications, like schools, it’s not a big concern.
There are two ways that air can leak from the exhaust side to the supply side of a wheel:
Cross-Flow Leakage occurs when air leaks from the exhaust side to the supply side through the seals or any gaps in the construction.
- Select the right equipment.
- Use high quality Custom Air Handling Units with Leakage at no more than 1% of the design volume at 1-1/2 times the design operating pressure.
- Use high quality Energy Recovery Wheels with high quality, properly adjusted, seals.
- Limit Cross Flow Leakage by Proper Fan Arrangement: Position the Supply Fan in a blow-thru and the Exhaust Fan in a draw-thru position for the safest fan orientation.
Carryover Leakage – occurs in rotary recovery wheels as the wheel rotates from the exhaust to supply air stream. A small amount of exhaust air can be carried over in the flutes of the wheel as it passes by the center-line seal.
- Limit Carryover Leakage with use of a Purge section. The purge section uses the pressure differential between supply and return to “purge” the media with clean outside air before its rotation into the supply air stream.
Note: The purge comes with a penalty. Fans typically need to be sized for an additional 5% of air flow.
Cross-Flow and Carryover leakage are two ways air can leak from the exhaust to supply side of an energy recovery wheel section. It can also leak through other sections or components in the Air Handling Unit. Choose a high quality Custom Air Handling Unit to avoid this.
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