AC PLANT DESIGN

[jakked]

I'm somewhat a rookie, and I'm trying to develop the proper sizing for an AC plant. The space to be conditioned is an old movie theater, which is being converted to a church. The space dimensions are 5960 sq ft of floor space with a 44' ceiling(262240 cu ft). Anticipated occupancy is a maximum of 250 people.

Obviously many factors come into play when trying to size a system, but is there a general thumbrule that could be used to size this system? I have seen numbers of 4000 cu ft/ton and 1000 cu ft/ton.

Does anyone have any recommendations?

 

[KenRad]

jakked,

It's unlikely that anyone answering in this forum would suggest sizing a system like this based on thumbrules, and neither would I. That being said, the 1000 cu ft/ton is probably extremely on the high side, even in the far South. The 4000 cu ft/ton is probably closer to reality, although you still need to consider the details of the load (location, building construction, lights, bodies, etc).

Ventilation requirements will account for a significant portion of the tonnage, since you need 15 CFM of outside air per occupant to comply with the mechanical code.

Good Luck!

---KenRad

 

[IRstuff]

Most churches I've been in didn't seem to have sufficient A/C capacity

OR,

they didn't have sufficient dehumdification.

Whatever system you wind up with might need to be augmented with a humidity control system

TTFN

 

[Jonkatz]

For rough sizing purposes, 250-300 sq.ft/ton is probably safe for the application, BUT as others have said, a proper load calculation should be performed to ensure sufficienct cooling capacity and dehumidifcation.
J. KAtz

 

[PacificSteve]

I'll add my voice to the recommendation for a full-on load calc to be performed, preferably by a professional engineer.

That said, I can recommend the following: During church use, the load is way up, and I have often seen lack of capacity. During non-use, you may get away with no AC, but depending on your area, you may have to deal with humidity and molding problems. Molding problems are really coming in to the limelight, and will be the liability issue of this decade if you ask me.

I suggest a small system to handle the omnipresent office space for clergy and admin, and also control humidity. This system could be purchased with "heat pipe" system that shifts the capability to higher latent capacity (i.e. higher ability to remove moisture)

Then a larger system for during mass. Perhap both systems work during mass, to keep the overall tonnage present from getting out of hand.

250SF per ton is normally a worst case scenario, but I wouldn't recommend feeling safe with this ROT for this application.

PacificSteve