Pumped Glycol Energy Recovery | Filtering Exhaust Air

Energy Recovery Filter Section

Energy Recovery Filter Section

Just skip the pre-filters in front of the exhaust side of the energy recovery device?   Is that wise?  We know that adding filters can impact costs:

  • cost to purchase pre-filters
  • labor to change
  • disposal costs
  • increased pressure drop

This question has been asked before and opinions have been offered by facility engineers.  Prefilters in Front of an Energy Recovery Device.  

Here is a look at the same question from the perspective of manufacturers of related equipment.    

This question was posed: 

We are recommending to an engineer that he leave filters off the face of a glycol coil on the exhaust side of a lab application.   He would like to hear the pro’s and con’s on why not to install filters.   How does your company answer this.


Rudolf Zaengerle, President of Konvekta USA Inc.  

It is not typical for engineers to recommend filtration in front of our coils.  With Konvekta coils, there are several reasons why filters are not mandatory:

  • Konvekta Pumped Glycol Coilfins are flat and wide spaced: coil can be power-washed easily (once in 5-15 Years) – certainly less frequent than exchanging filters
  • lab exhaust is usually not high in particulate load (more so vapors that don’t ‘plug’ the coil)
  • in labs, our coil normally is epoxy-coated which is better in terms of ‘no dust adherence’ than no coating or almost any other coating


Paul A Tetley, Vice President & General Manager, Strobic Air Corporation

Typically all labs have pre-filters (30/30).  This is the default, unless they know that the primary air stream will be constantly clean and particulate free.  

UNH Strobic Fans

I fully agree that a typical class room lab in a university is exhausting conditioned air that is very clean and should not need any filtration prior to the coil, but it has always been specified.   I have seen sites as mentioned that took them out and never used them to save the pressure drop.

NIH Filtration guidelines say that the Design Engineer shall review the specific Program of Requirements to establish specific filtration criteria.  That’s the best bet for all applications.

There you have it.  Two industry experts weighing in on the subject.  I would agree that it really depends on the application.  On an animal lab you will need filtration, on a chemistry lab – probably not.  Best to look at it in a case by case basis but to always look at it.  There could be a significant savings passed up by just defaulting to filtering the air.

Related Blog Posts:
Ask Rick: Prefilters In Front Of An Energy Recovery Device?
Ask Rick: Custom Air Handling Units | Recommendations On Merv Filters

For More Information - askRick







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