Ductless splits in Gymnasium

[emalsyd]

I was looking at a school gymnasium which currently has an air handler w/hot water coil serving the gym. The existing duct is sized to handle about 5000 cfm.
The supply duct is located above the ceiling with ceiling diffusers. The return drops down to the floor level.
The cooling load for the space is approximately 22 tons at 8400 cfm.
I was thinking of replacing the existing air handler with a new Trane climate changer (existing AHU is from 1959) w/hot water and dx coil. There would be a 12.5 ton condenser located on the roof.
Could the remaining load be handled by a few ceiling mounted ductless splits. The ceiling is 20 ft. high. I'm only thinking ceiling mounted as opposed to wall so i don't have to worry about the occasional stray basketball.
I was thinking the low returns would help pull the ductless air to the floor level.

 

[KiwiMace]

This concept sounds kind of scrappy and vulgar, if you don't mind me saying.

 

[emalsyd]

i don't mind you saying. they are working with a tight budget so i was trying to come up with something that would use as much of what they have existing as possible. there is no place to put pad mounted units outside. the roof has asbestos and the school would rather not spend the money, at this time, to get it abated so i'm kind of short on options. if you have any suggestions, i'd be glad to hear them.

 

[willard3]

Ductless splits will come with one or two-row coils which will do little to the latent load.

Latent loads are high in gymnasia.

The pressure drop and velocity may be unacceptably high using the same ductwork for the air handler with increased volume..

Perhaps, rather than taking professional risk, you should tell the owner he can't afford to do this with the current budget. Nobody will thank you if it works poorly.

 

[KiwiMace]

So this existing AHU is above the ceiling? How come you can change this out without disturbing the asbestos? How come you can't fit a new 22ton unit in the same space?

If you can mount a condenser unit on the roof, why not two 10 or 12ton package units?

Displacement ventilating pommel horse?

 

[ChrisConley]

Any source of chilled water nearby? A radiant ceiling panel would pick up load fairly well.

Possible to reduce the cooling load? White roof, better lighting, better glazing, more insulation?

What is your design wetbulb? Evaporative cooling is cheap (when it is appropriate).

Probably the easiest would be to add a 12 ton RTU.