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Mini Split?

Discussion in 'Indoor Growing' started by sourdieselyumyum, Jan 22, 2018.

  1.  
    sourdieselyumyum

    sourdieselyumyum Well-Known Member

    I am looking at getting between a 36000-48000 btu tri zone or quad zone unit. I was wondering what would be the best way to place the wall units. the veg area will be 4000 watts and the flower will be 8000 watts. I was thinking maybe 2 larger btu wall units in flower side and the 2 smaller units on the veg Side. or 2 smaller units flower 1 larger veg side. Anyone have any experience with this? or would it be best to run just one wall mount per side?
     
  2.  
    Gilbertslab

    Gilbertslab Member

    What is the square footage of the rooms? Are they sealed rooms or vented rooms? What are the indoor coils rated for btu/h wise?
     
  3.  
    sourdieselyumyum

    sourdieselyumyum Well-Known Member

    Sealed set up. veg room 225 sqft flower around the same
     
  4.  
    Gilbertslab

    Gilbertslab Member

    As a rule of thumb, an air conditioner needs 20 Btu for each square foot of living space. Some would suggest up to 30 btu per square foot. 225sqft x 20bth = 4,500btu/h. Also you need to add 4,000 btu/h for each 1,000 watt hps. So for veg you have 4 lamps equalling 16,000btu/h plus 4,500btu/h = 20,500btu/h of cooling needed. Flowering is 32,000btu/h for the 8 lamps plus 4,500but/h for the square footage equals 36,5000but/h of cooling needed. Total cooling requirements of 57,000btu/h so I would say the equipment you are looking at is undersized for your needs. If you have a dehumidifier and or ballasts in the room you will have to add to the cooling needs to accomodate the heat they put off as well.
     
  5.  
    Gquebed

    Gquebed Well-Known Member

    In a sealed room sq ft doesnt matter so much.
    Also, general rule of thumb for growers has been about 6000 btu per 1000w (bare bulb) or 4000btu per 1000w (air cooled hood).
     
  6.  
    Gilbertslab

    Gilbertslab Member

    So are you saying that if the room is sealed it doesnt matter if it's 225sqft or 1000sqft the cooling needs would be the same?
     
  7.  
    somedude584

    somedude584 Member

    I have a Daikin 36000btu multi unit for a flower room with about 4500 watts and a veg room with about 2400 watts. In hindsight I would have gone bigger, as the 24k struggles in the flower room.
     
    Gilbertslab likes this.
  8.  
    somedude584

    somedude584 Member

    Sq footage definitely matters, as well as whether or not the exterior walls receive direct sunlight. This can account for added heat load as well.
     
    Gilbertslab likes this.
  9.  
    Gquebed

    Gquebed Well-Known Member

    No. Don't be purposely stupid.

    In a 225 sq ft room you would need a 1/4 of the amount of lights that you would have in a 1000 sq ft room.

    Would you put only 8 X 1000w in a 1000 sq ft sealed grow room? Obviously not. 8 would not cover enough. You would need 40ish X 1000w for ideal-ish coverage.

    So think of it these terms - your lights sort of represent the sq ft of the room. If the general rule of thumb says 6000 btu to cool 1000w of hps light and that light covers 25 sq ft then what do you have?

    You have the square footage already included in the calculation, which is why I said sq ft is not important.

    Is it not obvious to you that we are saying the same thing two different ways? You're counting 4000 btus for a 1000w light + some btus for the square footage that light covers, which works out to be pretty much the same as general rule of thumb 6000 btu per 1000w light. You're calc says 57,000 btu and the general rule says 54,000 btu...

    Weird huh?

    You're just complicating the calculation by breaking it down to its components that's all.
     
    Last edited: Jan 25, 2018
  10.  
    BigHornBuds

    BigHornBuds Well-Known Member

    In a sealed room, if you figure about 1ton per 1000w you’ll be ok.
    I run a 3.5 ton mini split in a 4 x 1000w sealed room , with Dehumitifer, fans , CO2 etc . It works good, but if I wasn’t running CO2 I’d want a bigger unit so it doesn’t have to work as hard , hopefully extending its life.
    I keep my rooms in the mid 80s .

    I also wouldn’t split my space 50/50.
    You shouldn’t need the same amount of veg space as flower, 75/25 .
    Stack vegging plants to make better use of the square footage. And manipulate growth n size with pot sizes n Watts .

    I’d think bigger , or doubling up.
    Mitsubishi if you got the $$$
     
  11.  
    sourdieselyumyum

    sourdieselyumyum Well-Known Member

    So do u guys think a 42000-48000 btu would work. Also are LG units any good? Was told from hvac contractor they are junk but I think he is biased since he is contracted with carrier
     
  12.  
    Gilbertslab

    Gilbertslab Member


    Purposely stupid? I was just trying to help the guy out. I'm an HVAC technician so my calculations are done the way I was taught. I was not trying to confuse the OP, I was just lending advice. Then you said square footage doesn't really matter so I asked you a simple question. I wasn't trying to argue, I was just wondering why you thought square footage doesn't matter in a heat loss calculation. There is always more than one route to get to the final destination and I never said you were wrong. Not everyone uses exactly 25sqft for each 1000w lamp even though thats what is optimal. So square footage can vary from one 8000watt grow to another and so can the cooling needs for the room.
     
    Last edited: Jan 26, 2018
  13.  
    somedude584

    somedude584 Member

    I would look into Daikin and Mitsubishi, they're worth the money and are by far the best for cold weather climates in the winter. 48,000 might work for your flower room if you use air cooled bulbs, no co2 burner, no dehumidifier, and have efficient ballasts. Lights are a bit different, but otherwise, and correct me if I'm wrong Gilbert, 1 Watt of electricity generates 3.41 BTU of heat, so a 60w ballast will give off approximately 200 BTU of heat. I believe 1000w ballasts run at about 100-150w typically, so in your case that's an additional 2,700 BTU. Even things like your fan motors give off small amounts of heat. To see this, just place your hand on your router or computer, it'll be warm. Calculating heat load for dehumidifiers is a bit more complex than just 3.41 BTU per watt, as they remove water from the air latent heat is released, suffice to say a 400w dehuey will generate a lot more heat than 1364 BTU (3.41*400) depending on how much moisture is removed from the air.

    I'm no HVAC specialist but my research took me pretty deep into this field. If I could go back in time, I would have purchased two units, a 36k/32k BTU unit for my 4500w flower room and a 18k BTU unit for my 2500w veg room.

    Suffice to say, it's important you figure out the entire heat load generated by all of your equipment and account for the size of the room and its proximity to sunlight and add an additional 10% on top of that. Trust me when I say, if you go too small, it'll be an expensive irreversible mistake that will drive you crazy for years to come.
     
    Gilbertslab likes this.
  14.  
    Gquebed

    Gquebed Well-Known Member

     
  15.  
    Gquebed

    Gquebed Well-Known Member

    Re-read your question to me.

    Either you were being purposely stupid to belittle me or you really thought I was so stupid to make that mistake which is insulting.

    Pick one and own it.
     
  16.  
    Gilbertslab

    Gilbertslab Member


    Anybody that knows how to do heat loss calculations to properly size an A/C would question this statement. You can believe what you want, I'm not here to argue. Arguing on the internet is like the special Olympics. Even if you win you're still retarded. Peace and blessings✌
     
  17.  
    sourdieselyumyum

    sourdieselyumyum Well-Known Member

    if I run 4 600s for veg that would put my light wattage down 10400 watts of light so that would be around 36000 btus of heat rounded up. the veg would run from 6 to 12 and flower 6 to 6. so there would be a 6hr period where all the lights would be on at same time. based on that do you guys think it would work or am I still pushing it. Also what if have 3 12000 but air handlers in one flower side and other one in veg side?
     
  18.  
    Gilbertslab

    Gilbertslab Member

    With those numbers and my calculations you're still at 2400watts veg so roughly 10,000btu/h plus the 4,500btu for square footage. (14,500 you can round down to 14,000 total btu/h) That's before factoring ballasts and dehumidifier if you have one. So one 12,000btu/h head for veg is a bit undersized but will work if that's the equipment you go with. You may have problems keeping it cool on the hottest 5% of the summer days but for the most part should be suffice. The 36,000btu/h for the 36,500btu/h is perfect. A/C should be under sized by about 5% to efficiently remove humidity. Your veg is under sized by about 16%. If the equipment is oversized it wont cycle as long and will remove less humidity. Hope this helps.
     
    sourdieselyumyum likes this.
  19.  
    Smok3yMcChok3y

    Smok3yMcChok3y Well-Known Member

    Sounds like a hvac tech if I've ever heard one
     
    Gquebed likes this.
  20.  
    sourdieselyumyum

    sourdieselyumyum Well-Known Member

    would one 24000-36000 btu single wall mount cool as good as 3 wall mounts adding up to same but spread out. Basically im asking if the single wall mount unit would be able to cool whole room equally so that there wasn't any hot spots
     

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