Need some advice on a 12x12 grow room with central ac setup

drudown420 · Sep 8, 2017

Hello everyone. Haven't posted in a while because I usually have all the answers :biggrin:

Not a newb been growing indoor for years without about every setup you can think of but this is my first legit sealed room in an actual house. 12x12 with vaulted ceilings and central ac. 4 1000w raptors and I actually plan on switching to de cooled hoods soon but that's for a later question. What I wanted to know is I have a 8 inch fan on top of my carbon filter exhausting into the attic and it doesn't seem to be cooling quick enough. Without lights on in mid day it runs at about 82 degrees. Too hot. Should I bump the ac down (thermostat is at 78) or do I need a way bigger fan. I am not currently cooling the lights, which I usually do. I was thinking about running my carbon filter before the lights with a 8 inch fan and a splitter, ducting through the lights into a split onto an 8 inch fan on the other side, and then up into the attic. 1. will this cause a problem with passive/active pressure with the 2 fans? And if not will this be enough? and 2. should I just got with like 10 or even 12 inch fan and leave use 1 for the whole system? Furthermore will I be able to run co2 with this setup? Id really appreciate any help. Right now money is an issue since I haven't had a harvest in about 6 months, but if 1 fan will work better ill sell all my current ones a get a big bad ass one.

OldPhart · Sep 8, 2017

drudown420 said:
Hello everyone. Haven't posted in a while because I usually have all the answers Not a newb been growing indoor for years without about every setup you can think of but this is my first legit sealed room in an actual house. 12x12 with vaulted ceilings and central ac. 4 1000w raptors and I actually plan on switching to de cooled hoods soon but that's for a later question. What I wanted to know is I have a 8 inch fan on top of my carbon filter exhausting into the attic and it doesn't seem to be cooling quick enough. Without lights on in mid day it runs at about 82 degrees. Too hot. Should I bump the ac down (thermostat is at 78) or do I need a way bigger fan. I am not currently cooling the lights, which I usually do. I was thinking about running my carbon filter before the lights with a 8 inch fan and a splitter, ducting through the lights into a split onto an 8 inch fan on the other side, and then up into the attic. 1. will this cause a problem with passive/active pressure with the 2 fans? And if not will this be enough? and 2. should I just got with like 10 or even 12 inch fan and leave use 1 for the whole system? Furthermore will I be able to run co2 with this setup? Id really appreciate any help. Right now money is an issue since I haven't had a harvest in about 6 months, but if 1 fan will work better ill sell all my current ones a get a big bad ass one.

OK, you mention sealed room and central AC, then talk about shoving hundreds of CFM of ventilation from the room into the attic. Those are sort of mutually exclusive to each other. If you are going for sealed, you will need a few things: 1) no ventilation from inside to outside. 2) Must have CO2. 3) Must have cooling to cool the room. 4) Depending on environment, will probably need a dehumidifier. 5) Last but not least, you must seal the room! With a central AC you will be blowing the smell/heat/CO2/humidity all over the house. I see a few other issues, like trying to light a 12x12 with 4K; where you should have closer to 6-8K in lights. On the plus side, 4K should be very easy to cool, but will not effectively light more than about 60-80 square feet. Need to rethink what you are trying to accomplish. Unless you are able to seal the room and bring enough cooling into the room in a sealed fashion (dedicated ac/mini split/window ac), I would abandon the sealed room idea. As far as venting is concerned, that would be decided by what temp the "make up" air is. If it is 95 degrees outside and you are blowing all your 'conditioned' air out of the house every 5 minutes... well that just isn't going to work. On limited funds, and assuming it is hot outside; I would not bother with sealing the room and quit venting to the outside (attic) or vent very little. Then I would just crank the central AC for the desired temps. I would then vent the room through the carbon scrubber into a return air duct for the central AC. Expect to need dehumidifier as well. Good luck man, it is all about tuning what you have to work with.

mushroombrew · Sep 8, 2017

How big is your AC unit?

drudown420 · Sep 8, 2017

OldPhart said:
OK, you mention sealed room and central AC, then talk about shoving hundreds of CFM of ventilation from the room into the attic. Those are sort of mutually exclusive to each other. If you are going for sealed, you will need a few things: 1) no ventilation from inside to outside. 2) Must have CO2. 3) Must have cooling to cool the room. 4) Depending on environment, will probably need a dehumidifier. 5) Last but not least, you must seal the room! With a central AC you will be blowing the smell/heat/CO2/humidity all over the house. I see a few other issues, like trying to light a 12x12 with 4K; where you should have closer to 6-8K in lights. On the plus side, 4K should be very easy to cool, but will not effectively light more than about 60-80 square feet. Need to rethink what you are trying to accomplish. Unless you are able to seal the room and bring enough cooling into the room in a sealed fashion (dedicated ac/mini split/window ac), I would abandon the sealed room idea. As far as venting is concerned, that would be decided by what temp the "make up" air is. If it is 95 degrees outside and you are blowing all your 'conditioned' air out of the house every 5 minutes... well that just isn't going to work. On limited funds, and assuming it is hot outside; I would not bother with sealing the room and quit venting to the outside (attic) or vent very little. Then I would just crank the central AC for the desired temps. I would then vent the room through the carbon scrubber into a return air duct for the central AC. Expect to need dehumidifier as well. Good luck man, it is all about tuning what you have to work with.

I'm renting so a wall unit isn't really an option as I can't modify the house anymore than I have. So best bet would be to set the exhaust on a timer? Or not vent at all and just use the ac, co2 and dehumidifier?

mushroombrew said:
How big is your AC unit?

Not sure a new unit was just installed in the house but it seems to blow pretty hard

mushroombrew · Sep 8, 2017

You need to figure out what you are working with. You can't seal a room with "blow pretty hard"

You need numbers. 1000W = 3412btu

So you need a minimum of 15KBTU to seal. 20Kbtu would be better if ambient temps get high.

Go check some labels and figure out what you got...

dansbuds · Sep 8, 2017

your sucking all that cool air out of the room by exhausting it into your attic ! just scrub the room ,don't exhaust it . if you don't want it completely sealed , have an intake from another room or from outside to get the CO2 the plants need .
you will need an exhaust to get rid of the carbon dioxide , but a small 6" fan on a timer that exhausts the room for 15 minutes twice a day should be fine .

drudown420 · Sep 8, 2017

mushroombrew said:
You need to figure out what you are working with. You can't seal a room with "blow pretty hard"

You need numbers. 1000W = 3412btu

So you need a minimum of 15KBTU to seal. 20Kbtu would be better if ambient temps get high.

Go check some labels and figure out what you got...

thanks I will

dansbuds said:
your sucking all that cool air out of the room by exhausting it into your attic ! just scrub the room ,don't exhaust it . if you don't want it completely sealed , have an intake from another room or from outside to get the CO2 the plants need .
you will need an exhaust to get rid of the carbon dioxide , but a small 6" fan on a timer that exhausts the room for 15 minutes twice a day should be fine .

Should I just cool the lights then since they are air cooled sealed hoods and run it out the attic or will I still be loosing the cool air.And I have a co2 tank and regulator with monitor.

Thanks everyone

mushroombrew · Sep 8, 2017

If you want to run air cooled just keep it separate. So pull air in from outside ground level go through the lights and up into attic. Just make sure it is truly sealed.

Then you can(If you got enough AC) seal and cool the room independently of the air cooled
system.

If you have enough AC and can afford it; running without aircooling/glass increases lumens about 12%.

drudown420 · Sep 8, 2017

mushroombrew said:
If you want to run air cooled just keep it separate. So pull air in from outside ground level go through the lights and up into attic. Just make sure it is truly sealed.

Then you can(If you got enough AC) seal and cool the room independently of the air cooled
system.

If you have enough AC and can afford it; running without aircooling/glass increases lumens about 12%.

thanks much appreciated. I'm gonna check on the cooling capacity first and make sure I have enough. Getting air into the room might be hard without cutting a hole so I think I might just scrub it or exhaust just a few times a day.

caljim · Sep 8, 2017

If you are using the homes central heating/cooling you need to keep a cold air return open to move air back to the air handler or it will have a hard time pushing air into a "sealed room". This is why minis are ideal for sealed rooms.

OldPhart · Sep 8, 2017

caljim said:
If you are using the homes central heating/cooling you need to keep a cold air return open to move air back to the air handler or it will have a hard time pushing air into a "sealed room". This is why minis are ideal for sealed rooms.

That is why I suggested hooking the carbon scrubber/fan to the return air duct. Will really boost the air turnover in the room, and control odor at the same time. Really just trying to use the house as the lung room for the grow room.

drudown420 · Sep 9, 2017

OldPhart said:
That is why I suggested hooking the carbon scrubber/fan to the return air duct. Will really boost the air turnover in the room, and control odor at the same time. Really just trying to use the house as the lung room for the grow room.

I'm kinda confused. How would I go about doing that? I need to get this figured out before I flip to flower. I lowered the thermostat and theres no problem during the day, but I just came back after the lights had only been on for an hour and it was 94. I took some of your advice and put the exhaust on a timer but it doesn't seem to really do much at all to cool so probably better I just scrub it.

Maybe I should have an hvac tech handle that?

I turned the house thermostat down and I'm going to check it in another hour. Ufortunately a mini is out of the question at this time until I get a few harvests to recoup costs and talk my landloard into it

drudown420 · Sep 9, 2017

By the way you guys are very helpful and I really appreciate all the feedback

drudown420 · Sep 9, 2017

I will put some pictures up of the room later its actually very nice with its own subpanel

drudown420 · Sep 9, 2017

If I'm able to talk my landloard into an external ac would a mini split be the best way to go? Ive always wanted to run completely sealed. It seems like that may be the best way to go rather than run the house ac thermostat low all the time.

0'dweeds · Sep 11, 2017

Yes, a mini split would 100% be your best (and most expensive) bet, if going the sealed route. Would definitely raise a red flag for your landlord though. Is he/she ok with the grow? If not, a window unit may work better for your situation. Just remember to be safe and calculate 4k btu's of cooling for every 1k lights you run. 4x 1000w lights will work for a room that size but as someone else already mentioned, 6x 1000's would be even better. just really depends on what you're allowed to get away with. If only doing 4k of lights, possibly border off a couple walls, making the grow space smaller (you want a 10x10 space for 4k) or even get/make a tent.

drudown420 · Sep 14, 2017

My landloard is totally fine with it. She just want me cutting too many holes or modifying the house too much. Think I may have found a temporary situation until I can set aside the money for a mini and I think I'm just gonna upgrade to 4 or 5 1000w de lights instead of going with the standard 6 hps. Ill keep you guys updated and thanks again

mushroombrew · Sep 15, 2017

Make sure you have enough Amps before you upgrade AC. I just did a 4 light flower room on a 200A service(whole house).

Water heater is electric. Add a fridge and turn on the oven you don't have much left...

Ended up with two ballasts and two flip boxes(4000W total).

Half the load for 24hrs vs. Full load for 12hrs. Much better. Food for thought.

drudown420 · Sep 15, 2017

mushroombrew said:
Make sure you have enough Amps before you upgrade AC. I just did a 4 light flower room on a 200A service(whole house).

Water heater is electric. Add a fridge and turn on the oven you don't have much left...

Ended up with two ballasts and two flip boxes(4000W total).

Half the load for 24hrs vs. Full load for 12hrs. Much better. Food for thought.

Thanks I've got a 50amp sub panel in the room with a 8 light controller all my lights wired at 220 so I should be good if I add an ac. What I ended up doing is buying a sliding glass door adapter gonna run a portable a.c. and intake cool air to cool the lights and scrub the room on a closed loop. If it's by some change still too warm then I'll scrap the portable ac and go with a mini

stemznseedz · Sep 17, 2017

Best solution (most expensive) truly literally seal the room no air is to exchange from outside the room to inside or visa versa except when you open the door to enter the room. If air is coming in the room from outside the room (like your house vents) it's pressurizing the room and air is going to be escaping from random spots like cracks and under doors that have the least resistance stinking up the rest of the house. Get a mini split and plan on sectioning off 8 x 8 for growing under the 4k and use the rest of the room how you see fit (veg/mom/drying tents etc). get a co2 setup it doesn't matter if you are dispensing from a tank or producing with a flame as long as you have it.

cheapest solution - carbon filter exhausting to outside reducing the positive pressure in the room created by your house air conditioning. you would need enough air being forced out the room through your carbon filter that it exceeds the air coming in from your house vents. it won't be efficient in cooling because you are pumping the cold air right out of the room that you just pumped in. this plan is full of problems though becuase are you going to run the whole house AC in the middle of winter (assuming you live somewhere with seasons)? If not your grow will be doomed during those months. also exhausting 4k in a 12 x 12 and not using ac is going to be kinda difficult to keep temps acceptable especially since you can't increase co2 because it will just get pumped out the room by your carbon filter.

Need some advice on a 12x12 grow room with central ac setup

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