Question about absolute minimum AC requirements

[ganjourno]

I am running an air-cooled setup now, but want to add a few more lights and switch to a split-cylce (half lights running during the day and the other half at night, in two separate rooms of course). Especially for the day cycle, temps will be an issue, so I was thinking about just switching the whole shebang over to sealed + A/C and CO2. The problem is, I will really be nearing the limit of what my power circuit can support if I go with a generously sized A/C -- so I was wondering what the absolute minimum would need to be keeping in mind I never need to get the room below 80 degrees when supplementing CO2.

Here's my design parameters:

Room 1: 1100 cubic feet, 8KW bare bulb, 12/12 day cycle

Room 2: 1100cubic feet, 8KW bare bulb, 12/12 night cycle

Only heat sources inside the rooms are the bulbs and some low power circulation fans - everything else (ballasts, pumps, etc) is outside the rooms. I would say additional heat load from fans is no more than 200W per room.

Outside Ambient Day temp (maximum, a few days per year): 82 degrees F.
Outside Ambient Day temp (typical, 95% of the year): 60-70 degrees F.

Target indoor temp: 84 degrees.

I calculated somewhere around 32000 BTU per 8kw room to be "ideal," but I really do not ever need to get the rooms down to 70 with the lights on. If I only need to get down to 82, would a 24000 btu per 8kw room do the job?

Thanks for any advice!

 

[Green Supreme]

Going with the absolute minimum will cause you issues a few times a year at crucial times. Better over prepped than under, especially when looking at the problems you could have avoided. Good luck. Peace GS

 

[ganjourno]

Thanks GS... Yeah that's sort of how I feel too - I'll be missing those extra 8000btu on the random 90 degree day and kicking myself.

With that in mind, what does the load profile look like on a mini split? Say it's daytime, one 8kw room is full on with the AC cranking away, I would guess that the compressor is drawing its rated continuous current. But what about the other compressor for the dark room during this time? I'm sure it will kick on every now an again as the temp slowly rises, but the load will be much less because there's no heat source expect for ambient. So does the compressor in this case draw the full amp load in a series of spikes, or does it run at reduced current in keeping with the cooling load?

I'm trying to get my head around this before dropping 10 grand on something I may not have the power for!

 

[Green Supreme]

What I am saying is; its better to say cool 6 lights efficiently rather than 8 inefficiently. Peac GS