Can 9kbtu minisplit cool a 2k non-sealed grow room?

[tact1]

so theoretically, a 9k mini split could house a 2k room without any active air over the lights at all right? that seems to be my understanding as a 4k btu per 1k is the estimate for sealed rooms using co2, so surely 9k btus could cool a 2k flower room with no active air over the lights, but active air exchange for the room itself to replenish the co2 as it is not a sealed room.

I am having a 9k mr slim mitsu installed this week in a room i used to have a 2k light with active air taking a lot of heat directly out of my house. I want to eliminate the active air over the lights as it dumped in my driveway, and just continue to use the active air exchange for the room itself but not active air over the lights, just let the heat dump in the room if i understand correctly that the mini-split can compensate enough for that buildup of heat?

thanks guys..

 

[olekingkole]

Yup, a 9k mini should work, but why not put in a 12k so that you can expand? Or perhaps you are just trying to keep electrical use down.

 

[resinryder]

NO. I had one and hated it from the day I began using it. Just wasn't enough. And it was a small room with 2 ducted 1K's(air from out side the room through the lights, then out to another room). The 12 maybe but go with the 18500btu and you shouldn't need to worry about it.
That's my experience, that's my opinion.

 

[tact1]

Literally the 9k is sitting on the floor next to me from acwholesale, sooo, can't go up at this point. The room is not going to expand, when I move it will but it just can't here.


olekingkole:

I was trying to keep the electricity low, something I did not understand until after the fact is you don't plug these (except the breeze diy) into a wall outlet. The outside and inside units will connect to a AC disconnect box, and that box directly to your fuse box. So part of my decision was the assumption (from formulas posted on this website) that 9k should about cover 2k lights (even if that just means not in the dead of summer and I would have to turn one off). So the 9k I thought given the seer rating, would only be drawing 540w or some such, essentially being able to fit on my grow rooms electrical load. Well good and bad news, it won't use my growrooms electrical footprint load so thats not an issue, but having known that I should of indeed gone up to at least 12k.

So yeah.

So resinryder:

I have this one, hXXps://www.acwholesalers.com/Mitsubishi-Air-Conditioners/MZ-FH09NA-9000-BTU-30-5-SEER-Ductless-Mini-Split-Heat-Pump/42698.ac?catId=cat1028&mainCat=&subCat=&trail=1004:Mitsubishi

or,

Mitsubishi MZ-FH09NA 9,000 BTU 30.5 SEER Ductless Mini Split Heat Pump

So yeah. Even when 1k off, just running a 1k (@60% on knob) aircooled hood and I was getting 88f+ in the summer, at night. So maybe if not 2k, this will allow me a 1k full function in the summer, and then help the rest of the year...

 

[tact1]

Now my mind is truly caught in a bunch:

Homeboy HVAC guy can't get to it till next week sometimes he said.

It appears these use the same linesets, I could call and ask them to ship a 12k-18.5kbtu and see if I can get this shit back to them but I imagine you get punished for it. My whole goal is to run a 2k room at 70f for 9/12 months at least. Say the other 3 months are dead middle summer and I cut one light, that is fine for one grow/year.

Thoughts? I thought I had my shit covered by getting a 33 seer 9kbtu @ 4000btu/1k, WITH a room with air flow (though no lights, but COULD add flow to lights), would allow me to control the electrical footprint without an electrician adding juice. But with the AC disconnect understanding now, it is totally irrelevant to my grow rooms electrical load capability. Now I just feel like a dick.

 

[tact1]

I guess I will just have to make it a 1k room in the summer, just shipping it back costs $200, which is not what bothers me, as the 17,200btu mr.slim is actually $250 cheaper than the one I got due to mine being such a high seer rating, I just don't want to wait any longer to get the room back up. Order another one today, it won't ship till Weds, get it the week after. Hvac guy puts me back at the bottom of the list in the busiest time of year etc.

 

[Granger2]

Get what you need regardless of anything to do with price, shipping, etc. But you're going to try to cool the room with AC, AND pump outside air thru the room constantly? Unworkable. Get a CO2 set up, seal the room and use AC, dehum. Either that or just ventilate all the time and save your AC money. With a mini-split you're not necessarily going to use more electricity with a larger unit. They only cool as needed to do the job [thermostat setting]. They only run full blast when needed. Of course, if you're pumping warm air into the room and AC'd air out of the room constantly, full blast will probably be needed. Cheaper to seal the room and add CO2. Good luck. -granger

 

[tact1]

Get what you need regardless of anything to do with price, shipping, etc. But you're going to try to cool the room with AC, AND pump outside air thru the room constantly? Unworkable. Get a CO2 set up, seal the room and use AC, dehum. Either that or just ventilate all the time and save your AC money. With a mini-split you're not necessarily going to use more electricity with a larger unit. They only cool as needed to do the job [thermostat setting]. They only run full blast when needed. Of course, if you're pumping warm air into the room and AC'd air out of the room constantly, full blast will probably be needed. Cheaper to seal the room and add CO2. Good luck. -granger

I thought if you only want to replace depleted levels of co2 then one room change per five minutes (divide room size by 5) will be adequate for air exchange, as opposed to the function of cooling which would be the turnover of air in the room would be faster/unsustainable to cool. My basement is only about 70f, and the basement itself is cooled by ducting vents from my main homes hvac.

 

[resinryder]

Get what you need regardless of anything to do with price, shipping, etc. But you're going to try to cool the room with AC, AND pump outside air thru the room constantly? Unworkable. Get a CO2 set up, seal the room and use AC, dehum. Either that or just ventilate all the time and save your AC money. With a mini-split you're not necessarily going to use more electricity with a larger unit. They only cool as needed to do the job [thermostat setting]. They only run full blast when needed. Of course, if you're pumping warm air into the room and AC'd air out of the room constantly, full blast will probably be needed. Cheaper to seal the room and add CO2. Good luck. -granger

I agree with this.^^^
You could probably have no problem using the ac you have for 1 1K but I would go bigger. Last thing you want is to be kicking your own ass over not sizing your ac right to begin with.Go with the biggest unit you can go with. The 18500 would work for 2 1K's but if you ever want to add a light, say like for a smaller test table for new strains you've never run before, over power your room always instead of under powering it.
I would recommend a co2 burner over bottles. Propane is available everywhere and seems to last longer, last longer for me at least, and is cheaper and less conspicuous than buying bottles.
I would recommend the room setup Granger 2 has suggested. Been running my sealed room like this for 15/16 years and have been more than happy with it.

 

[queequeg152]

if your room has zero heat gain from outside then yea, it should work provided it performs as claimed.

if your room shares external walls, than the heat gain could easily exceed 9kbtuh.

 

[tact1]

Noooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo.

Man. Why ya'll gotta hit me with reality. Appreciate it, I am gonna look to the 17,200+ mr.slims. I have a 30amp spot free on my fusebox atm.

Uses 1/2 lineset stuff though, mine 3/8, there is a mr slim12000 that uses 3/8 but its out of stock until October. So I need to get all that shit again, lineset, etc. Anyways.

May just get another unit, and fuck with returning this other one within the 30 day window, or hold onto it for when I move to use in a 1k separate room partitioned out.

 

[queequeg152]

its possible 9kbtuh will work... just not real likely unless you are in a heating climate.

im in houston... we design to 99 degrees 70% humidity.

given the above... the vaulted ceiling alone in my living room gains like 2200 btuh with r-19 bats.


if you live in Minnesota or what ever... perhaps, but i would send it back if possible. 12kbtuh should be plenty unless your wall and ceiling construction is dog shit.

might be worth your time to investigate the insulation situation inside the walls and ceiling and air seal a bit.

 

[Granger2]

With window units and thru the wall units, you don't want to oversize the units too much or they will short cycle, etc. But with mini-splits, most of which use inverter technology, oversizing within reason is OK, because the compressor will run continuously with the output needed to maintain the thermostat setting. It will increase/decrease output as needed. Buying a unit that will allow for later expansion can be a money saver in the longrun. Good luck. -granger

 

[tact1]

Daaaamn they hit you like a bitch. 15% restocking fee, $300 to ship it back, im just gonna have them install the 9kbtu, shipping it back and getting the other one (which is actually cheaper than the this one) costs me almost a $1000 just to get it here. I am tempted to just buy a second 9k btu for fuck sake.

 

[queequeg152]

1000 bucks would buy a lot of insulation... tell me more about this room.

you might be able to blow in insulation above it( very cheap). and furr out the walls some to accomidate some better insulation.

if you can swing a hammer and run a taping knife you could do it all yourself.

 

[tact1]

1000 bucks would buy a lot of insulation... tell me more about this room.

you might be able to blow in insulation above it( very cheap). and furr out the walls some to accomidate some better insulation.

if you can swing a hammer and run a taping knife you could do it all yourself.

Zero insulation, it is a studs with drywall/door on one side, cinder block (basement corner) walls on two sides, and one the other grow rool wall is a the back of a slide closet that you access on the other wall. The closet back wall that makes up one of my grow room walls is boards horizontally nailed in. The ceiling is dry walled.

 

[queequeg152]

basement walls do not flow much heat at all... walls that are exposed to hotter ambient air and walls exposed to direct sunlight are responsible for probably... 90% of heat gain.

presumably the ceiling above this basement is air conditoned to a temp below your target grow room temp so you can ignore that too.

what is the ambient temp in the basement during and immediatly after the hottest parts of the day? if its not more than 5 or so degrees above the your target temperature id say you are in decent shape.

you might run a test here... assuming you intall this ac unit. run both of your light fixtures, with both ballasts in the conditioned space. also plug in a pair of 60 watt incandesants, their heat gain would represent additional heat gain loads from stuff like electronics, blowers, computers or what ever else.

then put a fan in there to keep the air from stratifying.

at the worst parts of the day if your system cant keep up than you are fucked to some extent and will have to take additional measures to reduce the heat gain. if the room gets very hot, 80+... then there is likely no amount of insulation that will fix the issue as your heat gain from the lighting alone is far more than the ac unit can handle.

you might also take measures to minimise the latent heat gain from your set up... as water vapor in the air increases air enthalpy, and reduces the sensible cooling of the unit.

its important that you install this unit as well as you possibly can... even a minute over charge or under charge can reduce the total capacity of the unit. you dont have much of a margin built into the equipment in other words.

get some proper r3+ half inch + closed cell urethane foam insulation for your lineset along with a lineset protector ( reccomend the rectorseal pvc stuff).

the white protectors will save you like... maby 100btuh of heat gain if its in direct sunlight. the insulation soaks up sunlight, and the sweating of the pipe adds heat to the refrigerant as well.

 

[Subcooled]

Very interesting.
1hp=0.746kW=2544Btu/hr
1kW lighting=3413Btu/hr
manual J, really?? Isn't that above the scope of 99% of readers here?
I am a newbie to this site, so forgive me if I'm underestimating user knowledge of heat transfer.

 

[tact1]

Queequeg,

thanks for the extra time with your thoughts, I appreciate it. I am going to call up to acwholesaler (same as goductless), and ask if I get a another unit cross-shipped while I return this one will they waive, or partially waive the restocking fee.

Really though, even if its a $1000, I should get a 22k btu inverter in that bitch, the hard part is an hvac guy IS installing it, and I don't want him back in my room. The whole room has been shutdown for 3 weeks now while this 9k btu got here, while I waited I scrubbed the room, hid all my shit, have a tent in my bedroom that annoys the absolute shit out of me of GG4 and GSC, and im just DIEING to get my room back together. So I really need to take a step back and ask if 1-2 more weeks will affect me (no), but could it drastically affect the future of my grow room environmental controls (yes). Reading abotu people with 12k btus (granted in sealed rooms), but with 95f temps outside (though im in midwest the 4 month summer is brutal and humid), co2 burner, 2k lights, dehum, and he maintains 81+f which is fine if you are feeding co2, which I am not as my room is not sealed, nor insulated, nor have a burner.

One last note on my hesitation to seal, we have a new kid about to turn one and this is a hard sell to my wife, the co2 burner thing.

The krux of all of this was a failrue on my part to understand that these ACs do not plug into walloutlets (except maybe that breeze DIY?). And I tried to ride the edge witht he 9k thinking I wouldn't need an electrician that way, in truth I never needed one as I have an open 30 fuse on my breaker box, and that can take well into the 20k+ btus, and has zero footprint on my room itself.

As for the lineset its JMF SL line set with flare fitting connections, and fortress drain hose with a condenser pump to be used with the mini split as well. So I am totally counting on mr hvac guy to do all that shit right, he is a legit guy with a legit company doing it all cash on the side in a future weekend or evening most likely.

Average temp highs in August for where I live (STL) is 89 with average lows being 69, and in September those numbers drop to 77 high and 67 lows or something. The RH is an absolute bitch with all the rivers and perhaps that contributes to the relatively warm "lows", compared to daytime highs. There was over 10 days in July where it was over 100 (feel likes), and a few where I shit you not it was 'feels like' 112 @ midnight. It was like a sauna, truly disgusting. Enough to make you question why you live here, some Jamestown shit.

 

[tact1]

Very interesting.
1hp=0.746kW=2544Btu/hr
1kW lighting=3413Btu/hr
manual J, really?? Isn't that above the scope of 99% of readers here?
I am a newbie to this site, so forgive me if I'm underestimating user knowledge of heat transfer.

Say what?