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Air con - Need Info

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Hi all,

        So for many year, I have put Air - Con on the back burner. As it is another cost towards power. But this my new Solar System only few week away, I have been head down in my bills and running numbers. After many hours, I think finally I can run a Air - Con based only on the saving I will be getting from my Solar System. I have done a bit of reading on Air - con systems, but its all just website stuff and no personal experience reviews on it. Has or does any one use Air-Con?


I run a 3mx3mx2.8m room - insulated, run 4 x 600 watt 4 girls, atm I have in and out fans. However will go to a sealed room - no in/out. Only oso Fan. Sadly I do have access to a Co2 system after a close friend passed away after his battle with cancer, I bought it off his wife to help pay for funeral cost. But never have used it. I grow is coco, 4-5 week veg , 8 + week flower depend on strain.. atm I am growing the sweet blueberry. 


After few hours reading, the info it pointing towards a Inverted Reverse Cycle Split System is looking the way to go. If I am right the Inverted system turns on at 100% to cool the room to set temp say 27-30, then will drop down to 50 -30% to maintain that temp. The Reverse Cycle cools the room to set temp, then cools the out side air and pumps in into the room while taking air in the room out. So the need for in and out fans is not needed. The split system part is that it will cool the air if its hot and heat the air if its cold. If any of that is wrong please correct me.


So the air con sites work on btu but in auz systems are sold as KW. 1 kw = 3500 btu


I was reading on site that said that 1 watt of light power, makes 3.4 btu of heat. 

4 x 600 watt light x 3.4 = 8160 btu heat made from light 

To cool a room with out HID light, they say L x W ( H x 5 ) in feet - 10 x 10 (10 x 5) = 5000 btu

So adding 8160 + 5000 = 13160 btu needed to cool a room.

Taking 1kw is 3500btu - 13160 / 3500 =  3.76 kw system


So a 4kw with those numbers would cool my room. 


The thing I am trying and cant figure out is, will that system be running all the time. Even with the inverted system.

Or should I be looking at a larger system, like a 6kw system. As i am thinking if a had a 6 kw system it might have a easier job cooling, so it will run at 50% or less.


The other point is, if i do run a inverted reverse cycle system. Do you need Co2 system or is the air that the system brings in enough to keep a good Co2 level in the room

Also, if you do run air con, what $$ a day you look at.


Any info will help. I have always wanted to run a sealed room.


Thanks All 







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Hey Chopper

"....However will go to a sealed room - no in/out..." WTF. Don't do it. Plants need fresh air.

Here's an idea, stick your head in a plastic bag, see how long you last. By having your plants in a sealed room you are doing exactly the same thing. You can use a CO2 system if you want, personally its a lot of pissin around to set it all up properly, when decent air exchange will do the same thing.

YOU NEED AIR EXCHANGE!!! Otherwise you are just circulating the same crap around and around. I say 'crap' as the plant expels its own 'crap' out into the air, sure you are going to be adding CO2 but how does the plant get rid of its own crap if there is no air exchange.



Hope it helps


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Hi Chopper I install split systems for a living, they do not bring in fresh air from outside and as Merlin pointed out you will need fresh air. I f you get a good brand like Mitsubishi or any other Japanese brand name you can program it to come on at any time and go off anytime as you probably will not need it at night if your useing sola panels.to help pay for the power.

I have 4kw of panels and two 375w CMH lamps with extraction ect and run them in the day to take advantage of the panels and I dont pay anything for the grow I actualy get money back, my bill was cut from $350 to an average of $175 inclusive of rebates ect.

Depending on how many KW of panels you have will effect whether  you cover the a/c or not.

Your calculations are good if you use cool tubes it will enable you to use a smaller unit 3.5kw and it will not have too much to do.

I used a 2.6kw unit in a 1.2x1.2  tent with a 600w hps and precious little extraction so it got hot as you can imagine. However it easily cooled the tent and I could have gone to a 2kw mitsubishi if I wanted.

You will find you will need a cool tube and extractor fan but not to strong as you will loose the cooled air by it being sucked out. The lower temps useing a cool tube will help make the lost air less of an issue.

On the positive side mold be no problem as they dry the air, mine took out about 2 ltrs a day from the air I was amazed how much the plants transpired.



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Arrr so I was lead in thinking the air con will change the air enough.


So if I do run a sealed room, Co2 is a must.

I have been told Co2 is a stuff around. And can get really $$$ if you get it wrong or you have leaks in the room. Might just stay with in/out and put baffles on them, and have them on timers. So they just kick in to change the air, and when they shut off the baffles close to keep cool air in.


I have looked at jap brand system. They seem pretty good, on price and energy rating.


Well thanks for the info. I will do some more reading, might even have a go at Co2 first before investing in a air con system. If Co2 is the nightmare it can be, might sell it to pay for the air con.

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I do agree Louise, but if he's adding CO2 into a sealed room, there has to be exhaust somewhere. I've added CO2 to a room previously but for the pissin around it took, air exchange is much easier, cheaper and more efficient IMO. Although I have seen plants grown in a sealed chamber before, they weren't Canna. Even with an AC system there is no exchange involved and, again, I agree he could use a scrubber but still air exchange is much easier. IMO
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