Air Supply to OR

[NealFC]

I am working on a AHU(1) dedicated to supplying air to an Orhtopedic surgery room. This air handling unit supplies a mixture of return air and air coming from a second air handler(no OA). This second AHU(2) is a mixture of returns from other parts of the hospital and oa. I was wondering if anybody else has seen a system like this or if this breaks any NYS codes. As far as I can tell it is getting the 3 ACH of oa and exceeds the recommended 25 ACH. I need some insight on the subject because my AIA book is vague.

 

[tys90]

The only thing I can really help with is that according to the latest AIA Guidelines, you need 4 ACH of outdoor air for operating rooms.

Can you explain the system more? Existing or new? Why are they using AHUs in series?

 

[NealFC]

The system is existing and I am still not sure why they are in series my only guess is they under sized the coil. AHU(2) had originally served the orthopedic room along with 15 other rooms, they added this new AHU(1) a couple years ago to solely serve the ortho trying to get the air changes up to 300(which they did not reach). AHU(2) is rated at 9120 CFM and supplies 15 rooms along with AHU(1), it is suppling 1810 CFM to the AHU(1). AHU(1) is rated at 7100 CFM.

 

[Ziggypump]

This kind of thing is similar to how they do it for tropical conditions (not return to AHU2 though). Try looking up tropical conditions design. If you find something, then it may give you some insight into your problem

When I worked on something like this (it's been awhile), it was for the government, and all of the information was given.