Make up air system 2

[nightrider]

I would greatly appreciate if someone can provide me clarification on the right system for a make-up air for a laboratory fumehood, current a fresh air make up had some condensation on fume hood surfaces where fresh make up air comes in contact first, especially when outside temperature is at maximum. Does it need to be air conditioned?

 

[quark]

Condensation occurs when fresh air(high humid) when comes into contact with metal surfaces.(generally at lower temperatures)

As you don't require cool air for laboratory fuming hoods, you can use desiccant dehumidifiers to remove moisture from air. Thus you can reduce wastage of energy.

Regards,
Repetition is the foundation of technology

 

[nightrider]

Thanks for your reply Quark, I think I did not explained clearly my problem, the existing fumehood was originally designed with fresh make up air unit and an exhaust electrically interlocked. The fumehood right now getting some condensation especially on warm days, any codes or standards that would clasify what kind of makeup air is to be installed on a fumehood?

 

[ChasBean1]

Nightrider -

No. If you condition the make-up air to the hood, you eliminate the purpose of having the make-up air system. The purpose of the auxiliary make-up hood is so fume hoods throughout the building don't exhaust excessive quantities of conditioned building air. This is an energy savings item. The unconditioned make-up air washes down the face of the hood and is removed (preferably with laminar characteristics) in lieu of conditioned room air. As a side note, typically hood performance deteriorates if auxiliary flow exceeds 70 percent of the volume exhausted.

If you experience condensation on the auxiliary air duct, or hood, start by insulating the duct and hood assembly. I think condensation might also be less of a problem with the system operating at steady state than if the system continually starts and stops during a workday. I would look into the controls of the system also.

Good luck, -CB

 

[VEEKRISH]

Nightrider - No the Make Up Air is not be conditioned. This defeats the very purpose of using Make Up Air.One uses Make Up Aitr to prevent loss of conditioned air through exhaust. The problem you are facing may be seasonal(when humidity of outside air is very high). Using a dessicant dehumidifier also will add to your capital and running costs. Simple solution is to insulate the area where condensation is occuring and be done with it.

 

[nightrider]

To you both Chasbean1 & VEEKRISH I greatly appreciate for the informations you have provided, that was such a great help to the doubts I have on such issue, Regards & HAPPY THANKSGIVING.