Ask Rick: Energy Recovery Wheels on Laboratory Fume Hood Exhaust?

Q.  I am working on a laboratory system.  I have several fume hoods and general lab exhaust.  I need to incorporate energy recovery.  Can I use an energy recovery wheel for this application?


Thermotech Energy Recovery WheelA.  We have done a significant number of laboratory fume hood exhaust systems using Energy Recovery Wheels.  Of all the air to air energy recovery devices,  the energy recovery wheel provides the highest performance (typically 70 to 80% effectiveness).  That’s because the energy recovery wheel is the only true enthalpy (water) transfer device.  If the application runs in the summer, like most labs, we prefer to use a wheel.

If you use a high quality energy recovery wheel and design the air handling unit correctly (supply fan in blow thru and exhaust fan in draw thru) then cross contamination is kept at a minimum.   In most cases the fume hood exhaust stream is significantly diluted by all combined exhaust.  If a spill were to occur in a hood it would be nearly impossible for contaminant to be carried back to the supply side.   We have done analysis on this and not seen contaminant carryover reach NIOSH threshold limit values (TLV).

Here are Key design elements that we include when specifying Energy Recovery Wheels in lab applications:

  • Heavy Duty Wheel Structural Frame and Casing – designed and manufactured to allow a maximum rotor deflection of 1/32 inch
  • Include a Purge Section to eliminate transfer of containment from exhaust air into the supply air.  Make it field adjustable.
  • Wheel Media must be Aluminum Construction
  • Include only 4Å or 3Å molecular sieve desiccant  (size depending on application)
  • Require a 10 Year Warranty for the Energy Recovery Wheel
  • Design AHU fan arrangement with supply fan in blow thru and exhaust fan in draw thru (this way any leakage flows to the negative,  exhaust side of the AHU)

There are other features that we incorporate into our Laboratory Air Handling Units that make them even more energy efficient.  Have questions,  askRick?

Other Resources:
Thermotech -Energy Recovery Wheel Specification  for Lab Quality Energy Recovery Wheel.
Related Post:  Ask Rick:  How much cross contamination occurs with an Energy Recovery Wheel?

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