BTU Calculation for AC + Mini Split Thoughts

Growroom Design
#1

Room Size: 10’ x 10’ x 8’

Likely Equipment (That will contribute to heat):

-Lighting; LEDs/Drivers - ~2000W
-CO2; 2-10 burner CO2 generator - ~5000 BTU/hr
-Dehumidifier; 28 L/day - 650W (5.4A x 120V = ~650W)
-Oscillating Fans; ~120W
-Inline Fans; ~75W

I don’t think I forgot anything.

[Oh, just found this site, and it’s ‘sponsored’ by OG. Cool. LINK]

So, with the ~5000 BTU of CO2 gen heat, the total I’m coming up with is around ~15500 BTU (I’m always rounding up).

This has been an off and on consideration for years (An AC). I have a 14000 BTU inverter ac, it’s a window unit though. I was playing with a CO2 gen for a bit just recently, and it doesn’t add as much heat as I thought, using two burners, and aiming for 800ppm co2. So now I’m reconsidering using ac (seems feasible), but would prefer a mini split. I would likely have to install the mini split myself, which isn’t unimaginable, it’s just the specific tools cost is high for a one time job. So I might see if I can do the install up to the vacuum part and all that, and just pay for that part to be done.

I am seeing some people using what seems to be an average of 5000-6000 BTU of ac for 1000-1200 watts of LED lighting (just saying, that’s usually what they’re running for lightings). So now I’m wondering if I should bother trying the 14000 BTU window ac for this “2000W led” room.

(This is related to an older post of mine: Air Conditioning - Sealed Room, so if I should merge or post this there, a mod can tell me, or just go ahead and do it. Thanks).

Also, anyone DIY install a minisplit - to any degree? I know there are many videos on it (from the diy/precharged units, to the standard units), I’ve seen most of them.

Thank you.

5 Likes
Air Conditioning - Sealed Room
#2

Depending on the cost of tools (I have no clue). The total cost to having my 2 ton mini split installed is $1200 right now. This does not include the cost of the unit which was around $1600 itself. I did not opt for the DIY version. My system has to be loaded. It’s being installed literally right now as I’m typing this and I wish I would have just grabbed a DIY to have saved the damn near same cost of the unit. I was trying to save time more so than money since I’m taking on about 75% of the rest of this converted garages construction in my new space… coulda woulda shoulda at this point but learn from me! haha

4 Likes
#3

Hmm. And that’s usd right? Must be a nice system; mitsu, fujitsu?

The “DIY” systems are acutally different (the lines are charged with refridgerant and pre-vacuumed, I think) so you don’t need the “tools” (vacuum pump and gauges). Whereas the standard systems require that equipment, but they can be “done yourself” as well - if you have the equipment. The actual “DIY” systems are often more money, for the “convenience”. I’ve heard they don’t work quite as well…

How much BTU/heat are you cooling, what size room, and how much/what type of lighting?

1 Like
#4

Yes USD. and it’s a Mr. Cool. 24k BTU 22 seer.

I converted my oversized 2 car garage into my space. It’s roughly. 24x23ft little over 500sqft.

For now I’m only going to be running 2 - 600w leds as well as a 300w and a 200w led light for veg/ breeding projects.

And yeah that’s why I went with a Non- DIY because they’re more efficient as far as I’ve seen with rating and have been told.
I’ll tell you right now this thing just made my garage into a winter wonder land haha unbelievably cool in here right now.

20230503_121322
20230503_1213224032×2268 219 KB

4 Likes
#5

As far as vacuuming the system a lot of auto parts store will rent vacuum pumps and gauges for free with a deposit of like $200. A small adapter for $10 on Amazon will make the gauges work with r410. You’ll also need a torque wrench for tightening the lines and tubing flaring/cutting tools if you do your own lines. And tools to do electrical work.

Also how are the lines getting into the building? I had to bore through brick and that required a hammer drill and carbide hole saws. And make sure you plan for where your condensate drain goes.

It does take some work and some good general tool knowledge but it’s very doable if you have the time.

I installed two 2-ton daikin mini splits (non-diy type) in my grow room. I choose them for the reasonable price, good reputation and 12 year warranty. I did all the work myself including cutting and flaring the lineset, running the electric and vacuuming the system.

I do have a background in automotive repair and was certified in automotive hvac so that helped a lot.

As far as sizing your your system I was taught to take the total actual wattage of all the equipment in the grow room and multiply it by 3.7 and this will give you the minimum btu requirements. Don’t do wattage equivalent or anything with leds, just total power draw no matter what light.

Total Wattage x 3.7 = minimum btu requirements

5 Likes
#6

No places around here will have that option.

The only things I don’t have are basically the hvac specific things; the gauges, the proper flaring tool, the vacuum pump, various adapters for gauges, etc.

Just siding and basic, wooden framing materials.

I have the general tools themselves (hand and power tools). And I’m familiar with general “diy”; some automotive, electrical, etc.

So, why’d you cut the lineset? For a cleaner installation (had extra length)? Or didn’t like the factory flares or something? And did you have to add refrigerant? I wouldn’t wanna mess with that realm - adding refrigerant. I’d just curl up any excess lineset, or run it/locate the condenser so that I didn’t need to alter anything. (Though I might want to cut and redo the flares if they didn’t look good).
I still need to find out options/“code” for installing a condenser. Probably can go on the ground, too much snow there in winter. On a wall bracket, off the ground, there’s a big double window in that space, so it might have to go what I would think is a “silly” height off of the ground.

Yea. I’m talking about actual watts.

2 Likes
#7

Nice. Good to hear it went well and you’re in the cold now.

So you’ve got a pretty big space at 24x24. I’ve got a 10x10. And you’re running ~1700W for light right now. With a 24K BTU.
How much more wattage in lighitng do you expect to add (or what total would you plan to use in there, max.)?
And what else is in there creating heat, though, and watts? Dehumidifier? Are you running it sealed, and if so are you running propane burner or just a gas tank?

Edit: $1200 for the installation; did that include the electrical too? Like a disconnect and running the wire, all that?

#8

I run a 24kbtu mitsubishi in a 10x10 room. It was sized for 4-5kw HID lighting (single ended bare bulbs), but have since switched over to LED. It was just enough to keep up with the HIDs, and now running ~2.5kw in LEDs that it cools with ease.

35 pint dehui, a handful of circ fans, bottle fed CO2 (no burner). Had it installed by a friend with HVAC experience as opposed to going the Mr. Cool route for the extra efficiency and lack of learning curve. Runs sealed during the day then dump with air exchange during lights off to handle CO2 and humidity

$3k total for unit plus install a couple years ago including electrical from the panel and exterior disconnect

2 Likes
#9

Sounds like you have most of it worked out. :+1:

I like the line sets to be cut to exact length I need because it makes for a cleaner install and I don’t have to mess with making loops or anything. The daikin units I used had a minimum line length of 8’ I think and you could up to 25’ without adding extra refrigerant. I cut both of mine at about 12 feet or so, just where everything ended up.

Also adding unnecessary loops to your lines can trap oil and actually starve the compressor. I paid to have a unit installed some years ago and that’s exactly what happened. The guy used 50’ lines sets for 30’ runs and put huge loops in the ceiling that we didn’t know about. Two compressors burned up in less than a year.

3 Likes
#10

Thanks for that tip on the line loops and trapped oil. That’s good to know about.

2 Likes
#11

I wonder what window ac’s can handle as far as cold outdoor temperature. What would happen if a good quality, inverter window unit was run in -10* to -15*C, I wonder?

#12

Trying/planning to cool a basic residential room to use in a “sealed” fashion is a pain in the ass, in many ‘residential’ scenarios. Fuck. Even if you think, well - I’ll just hang a window ac out the window, problem solved with the “least effort”, you realize it almost certainly won’t work in the winter like that.
I’m trapped! In a room that must remain ventillated!

Hmm. Anyone ever seen a mini split condenser on the front/street side of a house, up high on the wall/side of the house? I would have to assume it’s more common with homes where there’s high snow, or other scenarios… maybe.

Just venting (like the room is)…

#13

Don’t forget to add in the general Btu’s required to keep your room at desired temperature during the hot parts of the year when nothing else is contributing heat.

Wall mount mini splits condensers visible from the from are becoming more common, especially as more multi zone heat pump splits are being added for heat in the winter. Get the vanity line set covers and it will look a lot nicer.

You can also just buy the cheap 150$ vacuum pump/gague set from amazon and return it when you finished saying the quality isn’t good enough, because well it isn’t.

For a 10x10 I would just be running a bottle, not a burner.

1 Like