Putting spiral duct right down the middle sounds interesting. However, the fans sure are handy and I am afraid spiral duct might cost more than I expect. It would be good to know what the cost of spiral duct is, though. Do you have an online supplier you can recommend?
I am located south of Shreveport, but if you are ever in the area definitely look me up.
In that large of a space... I would have 4 ceiling fans. Moving air feels cooler than stagnant air... adds to the comfort experience of the customer. Be sure to wire them so you can reverse them in the winter without using a ladder. This is something you or your 'handy guy' could do.
As to the Spiral... price varies based on location. It is high in the Atlanta area, because they can get it... Ask your HVAC guy, he will know.
The ceiling fans have high pitch blades so they move a lot of air. They will literally blow papers off your desk.
Unfortunately the direction switch is under the trim cap so I will have to get up on a ladder. I guess I could have the switch wired remotely. Will look into that.
The fans are strategically mounted at the peak of the building higher than any of the lights. I learned never mount fans below the lights after experiencing extreme "flicker effect" in a friend's store.
Will see if spiral duct is available through any of the local supply houses.
One thing that I did not mention about running spiral duct down the center of the building is that there is a 14" beam there so the duct would have to be run lower than the beam or run only half way, which is about 20' feet of the 40' depth.
With well insulated glass, it is not as critical that the windows have air on them as it used to be. Used to be in schools you pretty much had to run sill line radiation to take the chill off the windows. Nowadays, if the windows are insulated with no thru metal, the classrooms get by with just the main unit. I'm pretty sure the principle is the same for your store, especially in a Southern climate where the winters aren't as severe as they are up NJ, DE where I work. You could add strip electric heat under the windows. Cheap first cost and if you don't need them you just keep them off. Won't help in the summer months though.
I think the windows work pretty well in terms of rejecting heat. As well as one could expect anyway. They are double paned, and both panes are tinted with the outside pane having a solar reflective material. They are also laminated with 6 mil laminate I believe. These windows were originally designed for a city hall down in South Louisiana. The are designed to withstand the hurricanes they face down there.
I put my thermometer in the window a few days ago. I set the thermometer right on the security bars and left it all day. Should be as much heat there as anywhere on the window. The office was at 82 °F and the window was about 4 °F warmer on a day where it was 92 °F outside. In my mind that was not extreme.
I've been busy as a bee this morning taking measurements and working in Google SketchUp.
I want to use a media air cleaner and I looked at Carrier FILCAB (I have two of these in my home), the AprilAire 2210, and Goodman GMU2025. I was reading that the larger cabinets are good for up to 2000 CFM. The specs on the AprilAire at 2000 CFM the pressure loss was around 0.200 while at 1000CFM the pressure loss is around 0.06. That got me to thinking these media filters are really too small for a 5 ton unit.
I did a little Google research and came up with this thread here on HVAC Talk. Check out Post #6 by Mark Beiser. Thank you for the good idea and illustration, Mark
So, I got two of the Goodman GMU2025 cabinets (based on price, size, and construction) and worked this up in SketchUp.
Obviously I will have to tie these together and seal them in the center but that will be no problem.
The doors are on top so filter replacement will be easy and the return air plenum will attach to the dual filter cabinet.
Here are a few shots of the plenums tied to the air handler.
Something like the AprilAire units may allow you to reduce or eliminate adding outside air to the unit (check with your sheetmetal engineer about local requirements). You may still want some outside air added to reduce infiltration air from openings around the doors or exhaust fans running, but you should most likely be able to reduce the amount required by code.
Here are some drawings of the new supply plenum design.
Looking at the original design I thought it looked too skinny. The engineer explained that to be 0.06" WC/100' it should be 22.75" by 15" not 22.75" by 10.125". The previous design was 0.168" WC/100'! A quick check of duct calculator was enough to show my original design was a poor one.