Mini Split Question

[woodman420]

Hi 420'ers,

Questions about min split coverage. I often see the various BTU ratings that mini splits spew paired up with the square footage of the space they will cool. Shouldn't they be rated with the cubic foot area? For example, I have a shed that is 64 sf, but the area is ~ 700 cu ft. It is cu ft that is the better measure vs sq ft when determining the right size min1, yes?

In this space i'm estimating for ~ 2000 watts. Components being :

Advanced XTE 300 @ 252W X2
Ideal-Air 50 Pint Dehumidifier @ 636w
HyperFan 10" @ 252w
Oscillating fans @ 150w

Total ~ 1542 watts; allowing additional ~ 500 to arrive at 2000w; so if I assign 6000 BTUs per 1000 then a 12000 mini split unit should suffice. Does this sound right ? Other considerations are:

- the shed has direst exposure to Sacramento direct summer sun starting at 1PM
- it is well insulated
- this is a sealed environment

I want to do this right (read newbie) and strongly prefer to install a 120V mini ($$ issue). Currently have 3 dedicated 20A circuits installed. If a 12000 BTU mini is stretching it I'll go bigger.

Any advise is most appreciated - thank you

 

[Mcjoint]

the rule of thump is 400 sqft per ton (12k btu) of cooling but that's just kind of something to guess by. if your really wanted to be efficient and accurate you would need to calculate heat load. a one ton unit should be plenty for you, just make sure your shed is well insulated. if your shed is poorly insulated it is possible that 1 ton unit could struggle at peak heat hours. also running your lights at night will also help you out.

 

[Kalimaki420]

You wont get happy with your calculation.
2000W usage with only 500W light is the wrong way around.
With ac you should look in a 200W dehumidifier ect.

Please tell more how you going to grow.
Sealed with CO2 or not ? If not what the very big Hyper fan suggest grow at night or a 9000btu will do.
I grow at nights with 1200W Light and a 120W Exhaust fan and 2 x 40W oscillating fans.

 

[Jedthedog]

subscribed as I am starting to lay out my new room and looking for ideas .

 

[woodman420]

Thank you Mcjoint -

When you say 'the rule of thump is 400 sqft per ton (12k btu)' you referring to the CuFt area, yes?

i think the insulation should be OK. When it came to insulation i was concerned mostly w. keeping the noise factor in check, so I bought Roxul Safe n Sound (3.5" thick) for the walls and roof. I was concerned after installing the S&S since there was no R rating (its meant for interior walls), so i contacted Roxul who tells me the S&S is rated @ ~ R11. I will have 2 layers of 5/8 wall board put up next.

 

[woodman420]

You wont get happy with your calculation.
2000W usage with only 500W light is the wrong way around.
With ac you should look in a 200W dehumidifier ect.

Please tell more how you going to grow.
Sealed with CO2 or not ? If not what the very big Hyper fan suggest grow at night or a 9000btu will do.
I grow at nights with 1200W Light and a 120W Exhaust fan and 2 x 40W oscillating fans.

Hi Darkgrow -
- i live in the Sacramento area, and the summers can get hot. At ~ 1PM i have direct sunlight on one side of shed till the sun sets;

- shed is 8’ x 8’ x 8’ w/ 6/12 pitch, an area of ~ 700 cuft;

- the shed has 3 dedicated 20amp circuits (120v) installed; i am concerned i'd need a mini split larger than 1 ton requiring a 240v; this prompted my initial question;

- the grow area inside the shed will be 6ft x 6ft; looking a qty 2 Advanced XTE 300 lights having a core coverage of 3ft x 3ft each;

- this is a sealed grow w/ C02 tank, dehumidifier, inline fan (maybe 8" ?) w/ carbon filter, and various oscillating fans;

Keeping the noise in check (live in suburbs) is important. I’m OK to over-spec on some components to run them ‘half throttle’(e.g., 10” vs 8” hyperfan) when it makes sense.

The big question is whether a 12K BTU mini is adequate without it having to run all the time in the summer. After this is settled I will look into a Freiderich, LG, or Mitsu (or at this tier).
Thank you for your time……….

 

[Kalimaki420]

Ok I see.

But you just need a little fan if so.
The exhaust fan is for keeping CO2 up and get hot air out.
If you put in CO2 you don't need an exhaust and with an ac you fight the temps.
In your place I would go for 12000btu as they are not to much more than 9000´s
I had no issue running 2 tents with 700W at 100°F outside with my 9000btu but that is only for some days .

Outside units make the noise so look for a quite one and sealed it will run most of the time.
Newer ac run longer with less power as they dial down and keep running it is more efficient than the old on/of models.

You my have a look for LEDRF
LEDRF's Grow - Auto Mazar - Auto Dark Devil - Etc - Huge Yields
I remember he is using CO2 with ac and could help much better.

 

[woodman420]

Thanks Darkgrow for your advice and the video link - very helpful !

 

[Mcjoint]

Thank you Mcjoint -

When you say 'the rule of thump is 400 sqft per ton (12k btu)' you referring to the CuFt area, yes?

i think the insulation should be OK. When it came to insulation i was concerned mostly w. keeping the noise factor in check, so I bought Roxul Safe n Sound (3.5" thick) for the walls and roof. I was concerned after installing the S&S since there was no R rating (its meant for interior walls), so i contacted Roxul who tells me the S&S is rated @ ~ R11. I will have 2 layers of 5/8 wall board put up next.

No I mean sqft, it is just is just some to kinda go by. Houses are normally measured by sqft so hight is normally over looked. Your right in thinking in volume but most homes are for the most part typical in height, Which is normally about 8 ft.

 

[Jedthedog]

So would I be right in my way of thinking that 2 or 2 1/2 tons of A/C would be right for me ?
Room size 13' x 15' with a 8' ceiling.
probably a total of 2000 watts of light
co2 enclosed set up

Kicking the idea around to have a 4 x 6 or 4 x 8 table with a 1000 watt on a light mover and a separate area for a couple mother plants under a 4 or 600 watt .. any help or layout suggestions Welcome ...

 

[Mcjoint]

So would I be right in my way of thinking that 2 or 2 1/2 tons of A/C would be right for me ?
Room size 13' x 15' with a 8' ceiling.
probably a total of 2000 watts of light
co2 enclosed set up

Kicking the idea around to have a 4 x 6 or 4 x 8 table with a 1000 watt on a light mover and a separate area for a couple mother plants under a 4 or 600 watt .. any help or layout suggestions Welcome ...

If every thing is well insulated you should be more than fine. Air conditioners don't actually do any type of Actually do is remove heat. A one ton unit can remove 12k btus of heat. The better insulated your space is, the less heat can enter your space. So if you really wanted to know how big of an A/c you would need to added up all the heats loads in your space: lights, fan motors, pump, people.

 

[woodman420]

1 watt = 3.41 BTUs......