Mini split questions?

CrazyKappa said:

How many windows do you have in that room? If your running air cooled lights, you can duct the intake and exhaust to a window, and still maintain a sealed room. A window AC recirculates the air, there is no negative pressure, so long as you do not have any intake or exhaust going in or out of the main room, its a sealed room. Its the problem with even most portable ACs, there is that heat duct, well that air come from your room, and unless you have a separate intake duct, (very few have this setup) your room is no longer sealed.

To answer your question, yes if your run a ac in the window, (or mini-split) then duct from the top of that tent to exhaust into that room, and open up one of your lower vents on the opposite side, it will work great, and you will have a sealed room, that you can now control humidity, and run CO2.

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I just got a 12000 btu ac.
I'm thinking the ac goes in the window in the room my tent is in.
My tent gets exhausted to a different room via a 440 cfm fan that blows into my phresh filter. This should keep a negative pressure on the tent which will passively pull in the conditoned air. My lights can also suck air out of the tent and to that other room.

The reason i do it this way is so no chance of smell. That other room with the filter also has an o3 generator for fail safe.
What do you think?

Unless you think it is essential to exhaust into the room?

Then n I would put the filter on the other side.
But then if I have a smell I have to run the ozone in that room where it could be taken in to the plants. Plus I would have to breath that shit everyday when I go to check them...

Also, if the ac does a good job I could put the light ventilation into a tee with the exhaust as I only have one phresh filter...

You cant dump your carbon filter exhaust into another room, or your room is no longer sealed, and your wasting AC and CO2. You either have your carbon filter in your tent, hanging at the top, then have your fan exhaust into your ACed room, or have the fan mounted at the top of your tent, then duct it to a carbon filter outside the tent, but inside the room.

Your tent will still have negative pressure, so no smell will get into your ACed room, unless you open up the tents. You want your tent to have negative pressure, but your room the tent is in to be sealed. You can however run both the intake and exhaust of your air cooled lights to another room, or simply mount both ducts to a window, as its a closed loop system, (air comes from outside room, cools your lights, then leaves room again, never interacting with the actual air inside the room) and will not effect pressure inside either your room, or your tent if you do it right.

Ok. But I'm not using co2. First grow. Maybe the 3rd grow I will.

So am i correct in thinking that the only downside would be that the exhaust is pulling ac air and to another room?

The room isn't sealed. It has doors that I replaced with sheets. I feel like that's a good thing because I need to have air seep in with fresh co2....

Thanks so much for the input dude. I'm installing right now.

Sealed room does not necessarily mean sealed, (though the more the better) it just means closed loop, neither negative, nor positive pressure. Yes there are more downsides that just spilling your ac into the next room. You will never control your humidity, as all your treated dry air goes right out the room, and to replace that air that just went out, new air has to come in, its not treated, and will spike your RH.

Then again, if your live in a really dry area, and its not spiking higher then 50%, you could get away with it till you went with CO2. Ideally you want your AC running continuous when lights are on, (along with a sealed room) to control your RH, then when lights out you have two options, a dehumidifier, or a space heater, and regardless you still run your fans as if would if the lights are on.

Not only does RH go up at night naturally, (lower in the daytime) but plants sweat on lights out, jacking it up even more, so run those fans at speeds 24/7.

You've convinced me.
I just installed everything.
I'm going to bring the filter and light venting in to the room tomorrow.
I'll have a tee for both exhaust and lights to go right into the phresh filter.
I have a cool tube and I have a hood with the old style glass and it was leaking smell when I had a closed circuit. So it wasn't closed. Lol.

Thanks much on the info and idea. I will let you know how the temps are.

Think of the room as your buffer, or your rez, you treat the rez, then pump it into the tents. Yes your temps will be a bit higher inside the tent, then your room temp, but that is expected, and needed. Bud rot take hold the lower the temps your running, (typically under 70deg) i like to keep my tent 80ish, so long as your under 85, temps are not as big as deal as RH. Over 85, yes it is a big deal, but keeping it below 85 is not hard, what is hard is keeping your RH stable, although once you add CO2, RH spikes ability of induce bud rot, and powdery mildew diminish, but does not go away either.

How much wattage you running in lights? If you intend to step into the big league, sizing your AC to the full potential of your room is a must. Otherwise your AC will continuously cycle, and you will get wild RH spikes like i am now. My AC is sized properly, but i have yet to build out the other half of the room, so the AC is cycling. Obviously use what you have, just keep it in mind once you get it more dialed in, or have mold/mildew issues.

I am actually looking a automated duct diverter, so during lights on the fan dumps hot out into the room, so fresh ACed air gets pulled in, but at night have the diverter divert it back into the tent, so that the tent would be a closed loop. Then you run a small efficient space heater in there, that controls your RH, and keeps your nighttime temps around 78. Or so i hope, due to current constraints, i cant run a full blown dehumidifier right now, (moving in 6 months) so i am trying to get creative.

Those considering an AC unit for grow chamber cooling might want to check out "inverter" type ACs. The compressor motor speed is adjustable (unlike non-inverter type), so you only need to use as much cooling power as your particular chamber requires, and it should also be quieter. If the AC is only extracting as much heat as required, it should be easier to get rid of it. Might actually be able to have it inside the room. There's some on this Amazon page.

Yeah Ive been looking at them, it solves the problem of exactly matching your AC to your grow, you can ramp down the compressor, so that it runs continuous, thus eliminates RH spikes, but you still have capacity left if you expand.

CrazyKappa said:

Yeah Ive been looking at them, it solves the problem of exactly matching your AC to your grow, you can ramp down the compressor, so that it runs continuous, thus eliminates RH spikes, but you still have capacity left if you expand.

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How the hell are you a member for so long with only 10 posts. That can't be right.

Mostly just read, i have not been really active on the forums since the days of overgrow.com. Every now and then i would pop on here or other sites, check out the latest lighting, growing technique and such, but since i was not growing myself, was never fully committed. Past 6 months however, i been catching up on everything i have missed since my last real grow, 12 years ago. While i have many of successful grows under my belt, (using Aeroflow 60, and a 240 site coliseum) a lot has changed, and its a lot to catch up on.

Now i am running with scrog instead of sog, using the hempy system, (soon to be a modified hempy system, as there are a few big flaws in the original) in a 3x3x6.6 flower tent powered by a Greenbeam, a 2x4x4 veg tent, and i have a second 3x3 tent on the way, along with all the parts to make a custom 9 Cree CXB 3590 light. Will eventually have 6 3x3s, (or the equivalent) but that will have to wait till i move in 6 months, don't have the room right now for more then the 3 tents.

CrazyKappa said:

Yeah Ive been looking at them, it solves the problem of exactly matching your AC to your grow, you can ramp down the compressor, so that it runs continuous, thus eliminates RH spikes, but you still have capacity left if you expand.

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Not really, if you've over sized the system it won't compensate. Inverter systems will be more efficient than a comparable non-inverter system in the same setting if it's an apples to apples comparison (identical heat load, btu's and room size.

If your cooling needs are 9,000 btu, and you buy a 12,000 btu inverter system, the compressor runs at 75% continuous. If your cooling needs are 12,000 btu, and you buy a 24,000 btu inverter system, the compressor runs at 50% continuous. A inverter compressor modulates from 15 or 25% up to 100% at full capacity with a single inverter or from 12 to 100% with a hybrid tandem. That is a whole lot of room left for expansion, you would need to seriously over size the system to get it to cycle.

Would you link a manufacturer that claims that and then proves it in real world tests (please). Real world is you buy a 12k btu system and put the set point at 72f the system runs until it reaches set point then modulates to maintain the set point. It's not running continuously at a lower btu rating at 100% efficiency. Once it reaches the set point put a psychrometer on it and see what is happening with the relative humidity. It will only be a few percentage points less than the return air RH.

Hey guys,

What's the difference between a portable a/c and a split system or window a/c ?

Reverse cycle Vs Cooling Only?

Same difference?

If you put an A/C twice the size you require will it cost the same to run as it will be running at a reduced capacity?
Eg, using a 20,000 btu unit instead of a 10,000 btu unit?

Cheers for clarifying

Indefinately
" Let there be Green in 2016 "

CrazyKappa said:

It sounds like you did not properly size your AC to your room, you want it sized properly so it runs continuous, it will eliminate both temperature, and RH spikes. You have two real options, add more lights, or get a smaller mini-split. Or just deal with the spikes, your temps are well within norm, just not consistent, its your RH you really have to worry about, those spikes can cause real trouble if they are too high.

You would need to see if your AC can handle it, but you could buy an external controller, i have one that has settings where i can choose 3,5, or 7 deg intervals. So if its set to 70, when it goes above 73,75, or 77 deg it will kick whatever is plugged into it on.

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Your right about the sizing of the a/c i went for the over kill just to be sure... i later discovered it won't cool properly but it definitely cools.

I said the same thing as well more light... which has been added, and could honestly take a little more but at this point its out of the pocket unless i can get some credit from some where.

Can't pocket the smaller mini split option, nor the time currently. No problem with high humidity when lights on at all... not even close actually will need to supplement humidity and co'2 is rich without needing any supplemented.

As you said may have to just deal with the spikes... i was looking into the external controller just wasn't sure how much that would actually help.

and also which what kind etc to go with... when you say external controller are you meaning like a humidistat specially design for the mini splits? something like this:

http://www.compactappliance.com/lg-mini-split-programmable-thermostat-white/PREMTB10U.html

maybe?

If not any recommendations ?

@CrazyKappa

So if the room is "sealed" with inverted style mini splits. Don't run carbon filter exhaust fan?

Haven't set one up but was thinking might need to, was hesitant to just because it was decided on to leave it out and just run sealed mini split... didn't wanna have to deal with negative pressure cutting holes extra cost etc... ... now we are 2nd guessing.

Whats your take on it, you seem to have knowledge in the area would be greatly appreciate your expertise on this.

CrazyKappa said:

If your cooling needs are 9,000 btu, and you buy a 12,000 btu inverter system, the compressor runs at 75% continuous. If your cooling needs are 12,000 btu, and you buy a 24,000 btu inverter system, the compressor runs at 50% continuous. A inverter compressor modulates from 15 or 25% up to 100% at full capacity with a single inverter or from 12 to 100% with a hybrid tandem. That is a whole lot of room left for expansion, you would need to seriously over size the system to get it to cycle.

Click to expand...

ok makes sense now.

CrazyKappa said:

If your cooling needs are 9,000 btu, and you buy a 12,000 btu inverter system, the compressor runs at 75% continuous. If your cooling needs are 12,000 btu, and you buy a 24,000 btu inverter system, the compressor runs at 50% continuous. A inverter compressor modulates from 15 or 25% up to 100% at full capacity with a single inverter or from 12 to 100% with a hybrid tandem. That is a whole lot of room left for expansion, you would need to seriously over size the system to get it to cycle.

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Just so you know C/K. The BTU's need for the room in particular is 20k-24k BTU. The mini split is a 30kBTU (brand:LG).