HVAC guys I'm reaching out to you*** Multisplit flip flop setup***

Hey brothers,


I have a specific setup in mind and hear is my reasoning for it:

I have very little amperage to play with (40a @240v) and I need efficiency. I'm switching over to DIY Led and already have high efficiency fans on all my scrubbers (hyperfan) working in sealed environments with quest 105 dehumidifier.

So I will have a 3 room setup, 2 separate flower rooms one with 2400w of DIY led (cree 3590) in a 9x9x9ft room, 3200w led in a 12x10x9 room and 500w of cmh/ t5 for the mother/ clone room (9x9x9)

Now, ideally i'd just buy 3 separate minisplits and call it a day, but I can't have 3 separate compressors cycling 24/7, it'd put to much strain on my electrical service, so I was thinking of a single outdoor unit to do all three rooms, a Mitsubishi heavy industries 8kw multihead unit, so i'd only have a single unit drawing 2.1-2.8kw max to cool the setup. Now I will run the 3200w flower room at night and the other 2400w room during the day in a flipflop arrangement and the clone/mother room will be 18/6.

The outdoor unit will be within 5 meters of all three rooms for minimal pipe run. The rooms are mortar construction with an added small amount of insulation. Ambient temps get up to 100f a couple days a year but are typically 85-90f in summer. Each room will have approx 400w of fans for circulating/ scrubbing.

I like the idea of going for the 10kw model but it uses a considerable amount more in power 2.9-4kw
.
My calculations say 8kw will work but i'm not 100%, all 3 rooms together will draw 5.5kw (lights and fans) at any one time max (since running flipflop), but the room with lights off will still need cooling.

Can any experts chime in on this as I am losing hair on what to do next, no hvac guys hear have a clue so I'm left doing internet research and we all know how that go's...

You need to add an additional 20% to your numbers so you are in the safe zone in terms of electrical safety and what not. You were on 39.51 amps already and pushing it imo.

The numbers I gave out are loose, My actual power draw will be 35amp, and when I said 40 amps max to 'play with' I actually have 50, but like you say I need to have a safe buffer zone so using 35 out of the 50 available. A typical day the system should cycle from 30-35amp according to my calculations. Electrical safety is paramount so I appreciate your concern, I should have been more clear.

If you want to oversize your cooling needs then go with this formula, for every 1000W of heating you need 6000 BTU's of cooling. In that case you would need to go with the 10 KW unit. But it can work with the 8 KW unit as that means for every watt of heating you have allowed for 5 BTU's of cooling which is sufficient.
How much cooling does the lights off room need? I have found keeping the lights off rooms a few degrees only cooler gives optimum results and saves me on cooling .

I hear ya man, 10kw would be the go, it's not even much more expensive to buy, just the damn power draw, now if it didn't have to work too hard the 2.9-4kw input rating would hopefully only stay at the 3000w mark but I just don't know, and if the 8kw model is being 'overloaded' it will run at full tilt 2.8kw input.

To be honest I agree with you, even a lights off temp of around 72-75 would be fine, so from ambient temps of 90f with 900w of fan/dehumidifier I don't think it would take too much btu to cool it.

I don't even know if these a/c's can be configured to have 2x 5kw heads and a 2.5kw head (12.5kw total) all hooked up together (obviously you couldn't run them at max power at the same time with an 8kw outdoor unit).

Bolded is a big concern as i'm not 100% sure how these multisplit units work. I've seen a few videos were hvac tech explains you can hook up more indoor head kw than what the out door unit is spec'd for under the assumption that all of the indoor heads will not be on at the same time- where mine WILL be but wont require max cooling in every room. The whole zoning aspect confuses me. I need a cone.