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Discussion Starter #1
I'm new here and hoping to tap into some of the group wisdom. I've built a wedding venue in Alabama and need to install heat/AC and trying to figure out my best path forward. My intention is to self-install. To date, I've installed 2, 5-ton Goodman package units on my houses. I've also installed 1 mini-split. Here's my building


The main room is 90'X40' (3600 sq feet) which is 10' high at the sides, 16' high at the center. The roof is metal with thin bubble insulation underneath. The walls are wood outside and inside with R-19 insulation installed. The building is sealed up pretty well and temperature stays fairly consistent. I had my first wedding in February and was able to heat it easily with a couple of shop propane heaters.

I'm torn on how to design a system. Keep in mind, at this point I'm only concerned with AC for the main room. I'll put little mini-splits in the side rooms (bride/groom suites and bathrooms). Here is what I'm considering:

1) A single, 5-ton package system, run ducting in and up to the ceiling and tie off to the metal rafters around the 12ft mark. This would have a 90-foot run on the ducts.

2) 2, 3.5 ton units, coming from either end of the building. Could do package units or install splits with the air handler mounted up high. Each duct trunk would run 40 feet towards the center.

3) 5-zone mini-split system with cartridges installed about 15 feet apart.

On options #1 and #2, how big would you make the ductwork? 14"? I'm leaning away from option #3, as you'd have 5 remotes to deal with. I'd really prefer to have a single thermostat to adjust. Would appreciate any words of wisdom you'd care to share. Thanks in advance. Here's a pic of the inside:
 

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I am curious about whether your building had to pass a code inspection for that use. That would not pass as a public assembly space in NY or FL, the states I am familiar with. I am not familiar with your state, please fill me in.
 

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I had to same question that Old Thomas posted above regarding permits. As far as the type of system to install I would have a contractor come out and look at it. Have him thru the required calculations to see what he comes up with. Actually, the way things are right now you may get a really good price from a contractor to do the actual installation. It would certainly be worth having somebody come take a look at it and give you a quote.

I'm betting that a comment on the capacity of systems but I think the idea of having at least 2 separate units is a much better idea than one large one.
 

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I don't know about hvac. This is just basic thought I had over past years. I would go with your option 3 because:
1. smaller/separate units are easier to repair/replace
2. mini splits are part of life and accepted


I don't think there was another post that asked for a hvac design. I think you'd be better served searching for online hvac design service or such. There are hvac heat/cold loss calculators and I saved some money because of it. I had to insist on ac condenser (?) that is one ton less than the installer recommendation. I think you should get both calculation and a design service.
 

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Discussion Starter #6
I am curious about whether your building had to pass a code inspection for that use. That would not pass as a public assembly space in NY or FL, the states I am familiar with. I am not familiar with your state, please fill me in.
No, it does not. I'm in a rural area, no codes involvement. The State Fire Marshall has decided to start inspecting wedding venues and (lucky me) I got picked as one of the first ones. FM already came out, told me to install extinguishers, 36" out-swinging doors, exit signs and to submit an architectural drawing and life-safety plan (which I've already done).

Sorry I put this in the wrong area. Mods, would someone please move this to the HVAC forum?
 

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Discussion Starter #7
Mods, thanks for moving this thread. Wondering about another option, window units.

https://www.lowes.com/pd/GE-230-Volt-Electronic-Room-Air-Conditioner/1001780572

24k BTU, runs $669 each and just run 230-volt power. The 5-ton unit will run me $4k (with ducts) and only put out 57k BTUs. 4 of these units will run $2.8k and put out 96k BTUs. If one goes down, pop in another, easy, easy. Yes, it's not as cheap on power but I'm only going to be cooling this place on event days (10-20 during the summer). Is this idea crazy?
 

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What is the occupancy rating?
 
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You’ll have code dictating the need for outdoor air/fresh air exchange.
You’ll have to run a load calculation to determine the correct size equipment. Staged equipment will be ideal for the varying load from different amounts occupancy.
Packaged equipment would be best.
A 3600 square foot building in Alabama in the middle of summer with 200 occupants could require 15 tons or more to cool the space.
 

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Discussion Starter #11 (Edited)
You’ll have code dictating the need for outdoor air/fresh air exchange.
You’ll have to run a load calculation to determine the correct size equipment. Staged equipment will be ideal for the varying load from different amounts occupancy.
Packaged equipment would be best.
A 3600 square foot building in Alabama in the middle of summer with 200 occupants could require 15 tons or more to cool the space.
Thank you. I had a HVAC guy who told me the space needed 6 tons and was quoting $15k for mini-split systems installed. It seemed low (BTUs) to me. If I did 4 of these window units then I'm sitting at 8 tons (to start). At this point, my $$$ are very thin. I've put about $120k into the project and am stretched. Add to that, the pandemic obliterated weddings. I did 1 in February (went very well) and nothing else on the books. It's risky to keep pumping money but I'm committed now. Cheapest carries a lot of weight right now. I can re-tool after revenue starts flowing (fingers crossed).
 

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Discussion Starter #13 (Edited)
Keep your investment managed. Start off with a load calculation to see what size you actually need.
Here are numbers from an online load calculator. 12 foot ceiling, 3600 sq feet, 95 degrees outside.

Recommended equipment capacity - 48,000 BTU
Calculated Cooling Load: 120,800 BTU

That one didn't take into account the bodies involved. Another calculator that did take people into account said I needed 309,200, or about 15 tons (like you said). Still another approach might be start with 4 of these units, then add a 5-ton, package. This makes my noggin hurt.
 

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15 tons is only 180,000 BTUs total cooling capacity.

309,000 BTUs is just over 25 tons.
 
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Those are likely manual J calculations for residential systems. You need a manual N for commercial spaces, to take into consideration not only space loads but also occupancy load.
Multiple residential systems are not how you want to go about this. You need a minimum amount of outdoor air being brought into the space. To avoid sick building syndrome, and other stale air problems.
 

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Discussion Starter #18 (Edited)
Thought I'd share an update. I bought 2 of the 24k btu (2 tons) window units from Lowes (GE) and installed them. They're working much better than I ever dreamed. On Saturday it was high 80s outside and full sun and inside was a pleasant 73 degrees. Keep in mind, this entire structure is sealed and well insulated with R-19. Total spent, $1700. I'm planning to add 2 more on the other side of the building and likely will mount some oscillating fans (Northern Tool has an 7500cfm fan for $190) to help spread the cooling even more. What really surprised me is the coverage. In the pic you can see these are about 30 feet apart (building is 90 feet wide) and they kept the entire room cool. Very pleased with this decision. FYI.

 

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Thought I'd share an update. I bought 2 of the 24k btu (2 tons) window units from Lowes (GE) and installed them. They're working much better than I ever dreamed. On Saturday it was high 80s outside and full sun and inside was a pleasant 73 degrees. Keep in mind, this entire structure is sealed and well insulated with R-19. Total spent, $1700. I'm planning to add 2 more on the other side of the building and likely will mount some oscillating fans (Northern Tool has an 7500cfm fan for $190) to help spread the cooling even more. What really surprised me is the coverage. In the pic you can see these are about 30 feet apart (building is 90 feet wide) and they kept the entire room cool. Very pleased with this decision. FYI.

And that was with zero occupancy correct?
 

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And that was with zero occupancy correct?
Yes, that's correct. Before any more events I'm going to add 2 more units and probably some booster oscillating fans. Might end up adding 2 more after that, if needed. It's pretty unlikely that I'm going to pickup any hot weather weddings for 2020.
 
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