Pretreating outside air

[WilliamTz]

Hello

Quesiton:

In an air handling system with outside air and return air is it cheaper to treat the outsdie air first (dehum) before mixing with the return air.
Or will the same dehum/reheat energy be used if you just mix and treat the mixed air?

Thanks!

 

[HVAC-Novice]

It depends.

If you first treat the more humid OA, you can cool that to lower temperatures (more water removed) and then blend with RA.

Analyze where water comes from. In many climates OA contains more water than RA. But in a desert, for example, RA may contain more water than Oa. but in a desert, dehumidification likely wouldn't be a big issue.