Mini split questions?

Merkin Donor said:

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.

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Corrent me if i am wrong, but did you not just prove my point for me? "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." When you reach that set point, and the system has to modulate, its because your BTU supply, is greater then BTU demand at that moment. Point is, when supply is greater then demand, is ramps down, but does not cycle, thus you avoid major RH spikes.

Granted, when that compressor is ramped down, your dehumidifying power does go down, just like the cooling power, however it does not stop all together. Have you ever mapped your spikes on a cycling AC on a hot humid summer day? Ive seen it spike as high as 70%, would not happen if my AC would have had a inverter compressor.

coughphee.connoiseur said:

@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.

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You can run a carbon scrubber exhaust fan, but just exhaust into the room your cooling, not into another room, or window, or the room will no longer be sealed. I have a carbon scrubber in my tent, connected to a fan that is also in my tent, but that fan just dumps the hot air into the room the tents are sitting in. Since my AC is cooling that room, and not the tents directly, its still a closed loop system.

I do it that way because, it eliminates smell, since all the air leaving the tent is forced through the scrubber, its good airflow, and its actaully needed. Because your cooling the room the tents are in, and not the tents themselves, you need that air circulation to draw the cool ACed air into the tent, otherwise your girls will roast. You can drop the scrubber if you don't care about smell, but you need a fan to exchange that air, and it needs to run continuous, even during lights off, cause plants sweat, and will jack your RH.

coughphee.connoiseur said:

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).

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Unless you have a inverter compressor, it will cycle some, but not too bad i would think. But then again, i live in Maine, if i lived in a state like Arizona, i would not have read half as much on the subject, as i just would not care. It really depends on what your local climate is, PM is bad in my area as well, so i have no choice but to be anal about these things.

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:

Corrent me if i am wrong, but did you not just prove my point for me? "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." When you reach that set point, and the system has to modulate, its because your BTU supply, is greater then BTU demand at that moment. Point is, when supply is greater then demand, is ramps down, but does not cycle, thus you avoid major RH spikes.

Granted, when that compressor is ramped down, your dehumidifying power does go down, just like the cooling power, however it does not stop all together. Have you ever mapped your spikes on a cycling AC on a hot humid summer day? Ive seen it spike as high as 70%, would not happen if my AC would have had a inverter compressor.

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What I did was do a poor job of trying to make my point. First thing is that what you are describing is the "perfect" hvac system (that doesn't exist). Given the wild range of efficiency you're attaching to "inverter" systems why would manufacturers offer 7k,9k,12k, 18k and up systems? The inverter simply gives you the ability to run a DC motor which you can stop, start and run more efficiently than an A/C motor. An inverter system doesn't run the compressor 100% of the time, it cycles on and off just like a non inverter system. Remember too that mini splits are designed for people who live in climates from the most humid to the most dry using an algorithm that some engineer decided would work across all those various climates and not for indoor agricultural. An oversized inverter system will give you RH problems just like a non inverter will. If you want the best system that can handle all the needs of indoor growing you would be best served with a traditional split system designed for exactly what your heat load is and serving two rooms that are running opposite light cycles or a multi split with 2 or 3 heads that their total sum btu's covers lights on and 1 head covers lights off.

CrazyKappa said:

You can run a carbon scrubber exhaust fan, but just exhaust into the room your cooling, not into another room, or window, or the room will no longer be sealed. I have a carbon scrubber in my tent, connected to a fan that is also in my tent, but that fan just dumps the hot air into the room the tents are sitting in. Since my AC is cooling that room, and not the tents directly, its still a closed loop system.

I do it that way because, it eliminates smell, since all the air leaving the tent is forced through the scrubber, its good airflow, and its actaully needed. Because your cooling the room the tents are in, and not the tents themselves, you need that air circulation to draw the cool ACed air into the tent, otherwise your girls will roast. You can drop the scrubber if you don't care about smell, but you need a fan to exchange that air, and it needs to run continuous, even during lights off, cause plants sweat, and will jack your RH.

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Only thing is I'm not running tents.

Merkin Donor said:

What I did was do a poor job of trying to make my point. First thing is that what you are describing is the "perfect" hvac system (that doesn't exist). Given the wild range of efficiency you're attaching to "inverter" systems why would manufacturers offer 7k,9k,12k, 18k and up systems? The inverter simply gives you the ability to run a DC motor which you can stop, start and run more efficiently than an A/C motor. An inverter system doesn't run the compressor 100% of the time, it cycles on and off just like a non inverter system. Remember too that mini splits are designed for people who live in climates from the most humid to the most dry using an algorithm that some engineer decided would work across all those various climates and not for indoor agricultural. An oversized inverter system will give you RH problems just like a non inverter will. If you want the best system that can handle all the needs of indoor growing you would be best served with a traditional split system designed for exactly what your heat load is and serving two rooms that are running opposite light cycles or a multi split with 2 or 3 heads that their total sum btu's covers lights on and 1 head covers lights off.

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I stand corrected, i thought a inverter would not cycle. I am all for sizing an AC right, but what about additional load due to nature? How much capacity can i leave for that, and would a inverter system allow for more?

Power wise, would it be better to run the AC lights on, and a dehumidifier lights off, then run the AC continuous? A dehumidifier is more efferent at removing moisture then a AC. I get what your saying about opposing light cycles, there are certainly advantages, but what about when it simply can not be done? While it is a serious consideration for my next expansion in 5-6 months when i move, right now i am growing in my bedroom, its a large bedroom, but still my bedroom.

Prior to it getting hot and muggy, i was getting away with running my lights at night, and just venting out a window, while drawing fresh are in another. But the humidity is getting too much i recently noticed some PW on 3 leafs, just the very start of PM, but still, if i don't address it it will get worse. With the one light i have now, even the smallest powered AC would be overpowered, (though my second 3x3 flower tent will be up and running in a few weeks) so running 24/7 does not solve my RH spikes. So my plan is to flop my light cycle, so the light is running during the day, the extra heat will help fill the gap, and when my second light is running, along with summer temps, my AC will be sized correctly.
Then i will just run a dehumidifier at night, when its the most humid, and lights off, when the plants sweet.

When i move in 5-6 months, i will have 6 flower lights, and i will not be sleeping in the room i am growing in. But even then, efficiency wise, would i be better running offset lights, with AC running continuous, or all lights/AC during the day, and dehumidifier at night?

Thanks for setting me straight on that. Glad i did not go buying one, thinking it would solve all my problems. But since it does modulate, it must have a range of advertised BTU that it will ramp down to, without cycling right?

coughphee.connoiseur said:

Only thing is I'm not running tents.

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That is simple then, obviously that room gets the AC, and you do not run a intake or exhaust out of that room. Though you can run air cooled lights with both the intake and exhaust running into another room, or outside, so long as the system is properly sealed.

If you need to deal with smell, you place/mount your carbon scrubber on one side of the room, with the exhaust dumping out clean air into the other side of that same room. You could just attach the fan to the scrubber, with no ducting, but that wont be as effective i would imagine. But if your scrubber, (intake) and your exhaust is spread apart, that along with proper air circulation via fans, smell should be covered.

Indefinately said:

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 "

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If you put twice the BTU size AC for what you need, it will continuously cycle, causing RH spikes, and will use more juice cause of initial load to startup compressor every time it kicks on. You don't want a portable if your want to run a sealed room, and out of the three, its the least efficient. Go with either window or split, but split if you can afford it, as its most efficient.

Have not done enough research about ACs yet to answer the reverse cycle question, as i am still months off from it being a priority, and i already made enough assumptions on the subject.

CrazyKappa said:

That is simple then, obviously that room gets the AC, and you do not run a intake or exhaust out of that room. Though you can run air cooled lights with both the intake and exhaust running into another room, or outside, so long as the system is properly sealed.

If you need to deal with smell, you place/mount your carbon scrubber on one side of the room, with the exhaust dumping out clean air into the other side of that same room. You could just attach the fan to the scrubber, with no ducting, but that wont be as effective i would imagine. But if your scrubber, (intake) and your exhaust is spread apart, that along with proper air circulation via fans, smell should be covered.

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Touché' it won't be as effective but it would work better than nothing for sure. I like that idea because its less hassle and eliminates all the cutting drilling etc. Not air cooling lights at all. Thats why we spent so much a/c and also not running air cool hoods.

Will just have to see, want to get everything out the way and not have to go back and make changes.

One of the other ideas was to install filter/fan outside the room, drill and cut a hole to size and very little ducting and just pull from the room, where it exhaust into the same room the fan/filter combo is in. Not solid on this one either.

coughphee.connoiseur said:

Touché' it won't be as effective but it would work better than nothing for sure. I like that idea because its less hassle and eliminates all the cutting drilling etc. Not air cooling lights at all. Thats why we spent so much a/c and also not running air cool hoods.

Will just have to see, want to get everything out the way and not have to go back and make changes.

One of the other ideas was to install filter/fan outside the room, drill and cut a hole to size and very little ducting and just pull from the room, where it exhaust into the same room the fan/filter combo is in. Not solid on this one either.

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If you place your fan or filter outside your grow room, (or in any way vent outside your room) you will be running negative pressure, so all that nice ACed air is wasted, CO2 if your have it is wasted, and you will never control your humidity.

The only thing you can vent without worrying about all that is, your lights, but only if your intake and exhaust is drawing/dumping air into another room, or outside. And only if your make sure your system is truly closed loop, aka, no air leaks.

CrazyKappa said:

If you place your fan or filter outside your grow room, (or in any way vent outside your room) you will be running negative pressure, so all that nice ACed air is wasted, CO2 if your have it is wasted, and you will never control your humidity.

The only thing you can vent without worrying about all that is, your lights, but only if your intake and exhaust is drawing/dumping air into another room, or outside. And only if your make sure your system is truly closed loop, aka, no air leaks.

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Well guess that kills that idea, i wasn't ever solid on it i kinda figured it would have some cons about it, and i knew it would create negative pressure ( at least i think).

I was hoping and thinking it wouldn't just waste the a/c, i was thinking it would help the a/c system by taking some of the work load off the a/c unit.

The air outside temps through out the day flux on average between low 60's and high 70's. So if I'm exhausting outside the room and a cut intake vents these temps would help cool the room yeah?

Co2 or humidity isn't much of my concern in the area.

coughphee.connoiseur said:

Well guess that kills that idea, i wasn't ever solid on it i kinda figured it would have some cons about it, and i knew it would create negative pressure ( at least i think).

I was hoping and thinking it wouldn't just waste the a/c, i was thinking it would help the a/c system by taking some of the work load off the a/c unit.

The air outside temps through out the day flux on average between low 60's and high 70's. So if I'm exhausting outside the room and a cut intake vents these temps would help cool the room yeah?

Co2 or humidity isn't much of my concern in the area.

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If humidity is not a big deal, you might be able to get away with venting, but it would still waste AC. One thing to remember is that plants sweat lights off, and if your not somehow dealing with that, it will cause problems late flower. In the winter i have no problem with venting, cause RH is low in the winter. Also remember that RH goes up at night.

If your exhausting outside the room, even without a intake vent, your still running negative pressure, only difference is, instead of outside air coming in through the intake vent, it get pulled in through every crack in the room. When you suck air out of a room, that air get replaced one way or another. If it did not, like if your managed to totally seal your room, (impossible) you would create a vacuum, and everything living in that room would die. But as i said, for you to do that, would be nearly impossible, a vacuum chamber that size would cost WAY more money then either of us have. Unless that is, if your have millions in the bank, and want to spend it all on something totally useless. lol

The number one reason why we run sealed rooms is humidity, if your not worried about humidity, and your not worried about wasting AC, go for it. If you want some passive cooling though, your best option is to cool your lights with a closed loop system, so your room is still sealed. But again, work with you have, i live in Maine, humidity is a big deal for me, if i lived some place like Arizona, i might be singing a different tune.

CrazyKappa said:

If humidity is not a big deal, you might be able to get away with venting, but it would still waste AC. One thing to remember is that plants sweat lights off, and if your not somehow dealing with that, it will cause problems late flower. In the winter i have no problem with venting, cause RH is low in the winter. Also remember that RH goes up at night.

If your exhausting outside the room, even without a intake vent, your still running negative pressure, only difference is, instead of outside air coming in through the intake vent, it get pulled in through every crack in the room. When you suck air out of a room, that air get replaced one way or another. If it did not, like if your managed to totally seal your room, (impossible) you would create a vacuum, and everything living in that room would die. But as i said, for you to do that, would be nearly impossible, a vacuum chamber that size would cost WAY more money then either of us have. Unless that is, if your have millions in the bank, and want to spend it all on something totally useless. lol

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LMAO. Thanks bro i really needed that laugh no joke ( no pun attended).

Also thanks you have been very informative and pleasant to speak (network) with. So i thought that creating intake vents get rid of the negative pressure.

Yeah see where i am its weird my humidity during daytime ranges from 10% to 20% R/H and at night its around 27% and maybe up to mid 40's %r/h. So in the room with nothing on no a/c running etc i get 40-50%. When the lights cut its drops between 20-30% r/h and can get even lower with a/c running. Where i am its drops in the summer and raises in the winter so id like to come where you are in the winter time.

So ill most likely go with just scrubbing back into the room that you mentioned seems like it would be better air circulation anyway. I'm not worried about humidity currently i think thats a battle i can win...but i don't wanna waste any a/c at all. My only issue to date that i know of is that temp flux from 70-80 soon as the a/c cuts off with in 5 minutes its back up to 80 just concerns a little if the plants can't take flux like that and also makes me wonder about the inverter mini split.

I want to go with an external controller as you pointed out just want to make sure i get a quality one thats compatible but doesn't break the bank as I'm well over budget as is.

Having a intake vent sort of eliminates the rooms negative pressure, still a bit, but not a much as with no vents. However, the end result is the same, you have non-conditioned air going into your grow space, full of conditioned air, and your conditioned air is being sucked out the exhaust.

The only way to run with intakes/exhaust is with a sealed system for cooling your lights, so the air circulating within that system, never comes into contact with the air in your room.

Are you running your lights during the day, or at night?

CrazyKappa said:

Having a intake vent sort of eliminates the rooms negative pressure, still a bit, but not a much as with no vents. However, the end result is the same, you have non-conditioned air going into your grow space, full of conditioned air, and your conditioned air is being sucked out the exhaust.

The only way to run with intakes/exhaust is with a sealed system for cooling your lights, so the air circulating within that system, never comes into contact with the air in your room.

Are you running your lights during the day, or at night?

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Thats makes sense though, I always wondering how people got away with that but its was because they were air cooling lights.
Which is not option for me, i was hoping and wishful thinking that if the air coming in via intake although non-conditioned would help out a little with cooling as it wouldn't be any hotter than 60-65 degrees f/h but as you said its also wasting plenty of conditioned air through the exhaust.

I like the scrubbing back into the room idea better anyway ( i think ) seems it would provide great air circulation and i could possible remove a wall mount fan or two by doing so.

At night! i think its a standard over here in the spring/summer times.

https://www.storeitcold.com

Anyone ever seen or looked into these devices? thinking of investing into one to maybe drop temps in the mid 50's for the deep purple. last week of bloom.

My post was thoroughly hijacked. Lol. Love it.
Update. The only 12000 btu window ac is working great.
Thanks so much @CrazyKappa