Growroom cooling Minisplit

So starting to do my research on minisplits for next spring to install. I’m running 5-600watt hps currently MAY go to 3-1000s instead. Non cooled. Sealed room and c02. Grow area itself is 12x12, but entire room is 12x24. Everything for most part is INSIDE room. Last summer I ran a 12k window shaker and a 14k portable (each vented out of room into the garage the room is in heating the ambient temp pushing against room). I’ll be adding some more insulAtion for the room in the ceiling area and hopefully staying away from using my window unit unless things get bad. What size minisplit should I be looking at? Keep seeing people say they function MUCH better than windows or portables so I was thinking I could possibly get away with a. 12,000 BTU 1-Ton 21 SEER AHRI and Energy Star Certified... it covers up to 600 sq for DOUBLE what my room is. But with calculations idk if it’s be enough. Anyone with experience using these? Any advice would be grateful.

Mini-Splits are the way to go in sealed rooms.

I think the general consensus is about 4k to 5k btu's of cooling for each 1000 watt light in a sealed room. That figure accounts for the dehumidifier as well.

I've always gone by that, and it's never let me down.

Good Luck!

So your putting ~8000btu in the room with your lighting alone, and used 26000btu of cooling last year. Which I'm guessing didn't work? and now your asking if 12000 will be enough.

I'm obviously reading this wrongly. Could you go over it again?


There are some major issue's I can't see, such as the weather and insulation values, which seem to be playing a MUCH larger role than your lighting. What's the room like without lighting? Iceland? Jamaica?

I think if you used 26k before, then the result of that is your best guide. But you should know, that 26000btu of cooling, creates as much heat while operating, as 3k of hid lighting.

Something is terribly wrong here. I hope it's my grasp of what your saying

f-e said:

So your putting ~8000btu in the room with your lighting alone, and used 26000btu of cooling last year. Which I'm guessing didn't work? and now your asking if 12000 will be enough.

I'm obviously reading this wrongly. Could you go over it again?


There are some major issue's I can't see, such as the weather and insulation values, which seem to be playing a MUCH larger role than your lighting. What's the room like without lighting? Iceland? Jamaica?

I think if you used 26k before, then the result of that is your best guide. But you should know, that 26000btu of cooling, creates as much heat while operating, as 3k of hid lighting.

Something is terribly wrong here. I hope it's my grasp of what your saying

Click to expand...

From what I’ve read minisplit is far more efficient and effective at cooling than a portable or a window AC. Maybe I’m wrong but I’ve seen many people using 12000kbtu mini per 2-3 1000s without issue. So no you didn’t read that wrong. Also how is the minisplit creating heat? It’s creating zero heat inside the room?

To remove 12000btu, around 16000btu is ejected somewhere. If this is into a room surrounding your room, then the insulation is a big issue.

Did you say 26000btu was used before? Did it work?


I'm interested in your idea of portable. To me, a 12000btu mini split is a portable. It's in wheels, and plugs in. It's not fixed equipment. But it's 12000btu and that is that. Packaging makes no difference at all. But now you say that, I have to wonder what your idea of portable is. Because if it wasn't split, then your room wasn't sealed. It was getting air from somewhere, and the area around it was being heated by your lights+the same again from your 26000btu. Which is where the heat from the cooling comes into play.

I just don't know what your doing. But it does seem to hinge around 26000 not covering your 8000 for some unknown reason, that is your main issue

Connection fail..

Post something else quick..

I know..

As the day warms up here, it can be 23 indoors, and 30 outdoors, but just outside my window can be 35c as the sun beats on the building, warming it's skin above ambient, so the air rises up the building face at around 35, though it's 30 out, and 23 indoors. So.. it's 23c. British design temperature for lounging. Soon to get hotter. So.. I open up the window and toss out the aircon hose. My aircon now extracts 23c air from my room and kicks it out with a load of extra heat from cooling. This air that left my room, must be replaced, or I would end up in the vacuum of space. So, in the window comes 35c air to replace the 23c air that left. Coming in at a rate that my 12000btu unit can't cover. So, using my aircon makes my room hotter. Because it's not a split. It draws in hot air from outside.

My advice, 6-8k btu per 1k of lighting, depending on your climate. Zero exception. Go slightly bigger than what you need so your a/c isn't working under full load all the time.

Saves energy in the long run and save on wear and tear as well.



dank.Frank

about sizing i think the unit must not be undersized .. for obvious reasons
but an oversized unit can be problematic ..

can lead to difficulty to control humidity during day at the end of bloom..

because the compressor will work at low regimen so the refrigent is coming to the indoor unit at relatively higher temp .. more the unit is running at full power more it will dehumidify the air inside the growroom.. refrigerant can arrive in the indoor unit as low as 1 degree celsius(34f) on the best AC brands .. like mitsubishi or others

at the beginning of the cycle (vegetative) we want relatively higher temp and rh
then more the bloom progress more the temp/rh will decrease.. so the ac will run more intensively to bring down the temp and at the same time the RH
ex: veg 80f 70%rh
bloom 75 f 60%rh
ripening 70f 50rh or lower

a well sized AC will allow these manipulations .. and to stay in the vpd chart at each stage of growth .. without fancy controllers
just AC , dehumidifier(with integrated hygrostat) and timer

also, today every minisplit are INVERTER technology .. meaning if the unit is very oversized, the AC will do short cycles, leading to premature aging of the compressor, big electricity bills .. it will come on, cool the room in 5 minutes, then turn off for 5 min, then on again etc ..
BAD


for the size i would say it very dependant from the climate
if its summer with 90outside it will be harder to cool the room
more work for the outside unit to throw them calories with a hot air
and also heat irradiating by the walls
in this case ===>5000 btu per 1000w

in winter with 50f outside its different .. in these conditions i know 3600w can be run with a 3.5kw AC , 1 ton
which makes around 3000 btu per light

Here in Florida I have installed a 18k btu (20 seer) Mr Slim in a 10x 10 with 3x1000 watts in a garage and it keeps the room at set temp +/- 2 degrees 24/7/365. I can give you a dozen examples of room size/btu/wattage that I know of personally because I installed the AC units.
Look closely at the specs of whatever unit you zero in on; all inverter units have a min/max btu rating. The 18k btu I mentioned has a 3500 btu minimum, perfect for Florida winters when the only heat being produced is solely from your hips bulbs. And for night time

Rule is half ton of ac per light... if I were u with your room size being 12x12 I would get a 2 ton unit and have the ability to add 4th light... the price difference between the1 1.5 and 2 ton are not that much different and will give u a lot more control amd ability to add a 4th light if u want

Also the outside unit needs to be outside not just outside the room they produce a fuk ton of heat when installed inside ... it's possible but u will need to really insulate the room n vent the hot air produced from the outside unit outside

yeah like f-e said for 12 000 btu of heat generated by lights, fan etc ... 16 000 btu will be rejected outside, because there is imo the heat from the compressor and the outdoor fan
but in cold temp put the out unit in a room with just windows opened is better .. no bad wind, too cold temp, freeze ..

You can oversize successfully as log as it has inverter tech so it can run slower when needed.