hvac advice on btu's for room

[GreenGalaxyFarm]

The more dialed in you want your parameters the costly the build out becomes. just saw the first 10 seconds of the video you posted and that is cool but you are going to have to consider your budget. Just the HVAC in the start of the video is about 5 times the cost of a small mini split. That is where mechanical gets expense with VAV's and air handling units. So while gettogro might have had some stuff that was not perfect it comes down to what someone can afford.

perfectly understood and agree with that. the situation is that of i'm going to be spending more than i should i have enlighten the wife regarding this as well.

 

[GreenGalaxyFarm]

So about 48000 BTU's

you were correct as per engineering study i just observed! thanks for the good info
from: https://www.youtube.com/watch?v=V6WuLQZsMPc precisely minute 11 and later at 12min55s, although they are referring to growing 100 plants, double what i could handle. everyone is recommending co2 levels of 1200ppm

 

[Oldguy71]

I’m running 3800 led watts in a 180 square foot space in a shipping container with 1.5 inch styrofoam board insulation through the Arizona summer. A 24000 btu mini split does the job

 

[GreenGalaxyFarm]

I’m running 3800 led watts in a 180 square foot space in a shipping container with 1.5 inch styrofoam board insulation through the Arizona summer. A 24000 btu mini split does the job

Thanks yes it seems only half my ac needs will be met, with the current unit. would it be more optimal to run them dual on the same wall or at opposite ends?

 

[Oldguy71]

Maybe mounted on opposite sides at opposite ends of the wall or close to it. Is your room more square or rectangular?

 

[GreenGalaxyFarm]

Maybe mounted on opposite sides at opposite ends of the wall or close to it. Is your room more square or rectangular?

rectangular

 

[Oldguy71]

I think I’d go with opposite sides opposite ends, try to get the most air flow through the room.

 

[jamesmost]

Hello all....
Mini split question here:
-140 sq. Ft room
-2 x 4x4 tents
-1 x 4x8 tent
-1 2×2 tent
-4 x gavita 1700
-2 × 18w clone lights
-1 8" ac Infinity cloudline T6
-1 6" ac infinity cloudline T8
- few clip on tent fans.
-1 14" oscillating fan
-couple of other in line fans here and there

In a temperature controlled house...
Want to seal room, run a mini split and stop wasting co2....

What size mini split ?

Thanks

 

[Scotty420]

Hello all....
Mini split question here:
-140 sq. Ft room
-2 x 4x4 tents
-1 x 4x8 tent
-1 2×2 tent
-4 x gavita 1700
-2 × 18w clone lights
-1 8" ac Infinity cloudline T6
-1 6" ac infinity cloudline T8
- few clip on tent fans.
-1 14" oscillating fan
-couple of other in line fans here and there

In a temperature controlled house...
Want to seal room, run a mini split and stop wasting co2....

What size mini split ?

Thanks

What are the actual room dimensions, including height? Are any of the walls exterior walls? If so what size windows do you have & what general area do you live in?

I do load calcs as part of my job & have access to sizing software. With the above info I can definitely get you an answer. The fans, lights & really any electronics you put in the tent will put out 3.14 btu per watt. The only other thing would be plants which I would imagine won't put off much heat, but will introduce humidity which will cut into your cooling capacity.

 

[jamesmost]

What are the actual room dimensions, including height? Are any of the walls exterior walls? If so what size windows do you have & what general area do you live in?

I do load calcs as part of my job & have access to sizing software. With the above info I can definitely get you an answer. The fans, lights & really any electronics you put in the tent will put out 3.14 btu per watt. The only other thing would be plants which I would imagine won't put off much heat, but will introduce humidity which will cut into your cooling capacity.

12x12
8.5' high
2 outside walls
Old double pane pella casement windows approx 30"×40" x 2
Wood fram, brick and cedar shake
16 adult plants in various stages

 

[RootsRuler]

I'm going to interject here with what I've been taught which was for every 1000w HPS light you want, at minimum, 3000 btu but 5000 btu was ideal.

If I go by that rule of thumb BTU is decided by amount of wattage that is converted into light energy from the lamp. Room size also has a part to play but most people don't setup in a huge room and only light a few plants so, traditionally, BTU to wattage was the yardstick.

If I revert back to the formula above that would mean a 1 - 5 ratio of watts to btu. If I have 500w of LED light in my room that would mean I only need 2500btu to cool that 500w led. Whatever other sources of heat in the room would need to be added in but that's how I figure it.

If you factor in other heat sources like inlet air temp, humidifiers, dehumidifiers, fans, etc. your btu needs will rise but lights will be the number one heat source in the room.

HVAC guys please point out where my logic fails.....

 

[Scotty420]

I'm going to interject here with what I've been taught which was for every 1000w HPS light you want, at minimum, 3000 btu but 5000 btu was ideal.

If I go by that rule of thumb BTU is decided by amount of wattage that is converted into light energy from the lamp. Room size also has a part to play but most people don't setup in a huge room and only light a few plants so, traditionally, BTU to wattage was the yardstick.

If I revert back to the formula above that would mean a 1 - 5 ratio of watts to btu. If I have 500w of LED light in my room that would mean I only need 2500btu to cool that 500w led. Whatever other sources of heat in the room would need to be added in but that's how I figure it.

If you factor in other heat sources like inlet air temp, humidifiers, dehumidifiers, fans, etc. your btu needs will rise but lights will be the number one heat source in the room.

HVAC guys please point out where my logic fails.....

I think your logic is pretty sound. While I've never tested any of this out my understanding is that anything electric will put out 3.41 btu per watt, so a 1,000 watt light would put out 3,410. So 3,000 would be pretty tight, technically a little short, 5,000 would give you some wiggle room. In fact we usually size to 130% of load which would be almost exactly 5,000 on a 3,500 btu load. And yes I would assume lights would usually be the biggest cooling load in a grow room.

 

[Scotty420]

12x12
8.5' high
2 outside walls
Old double pane pella casement windows approx 30"×40" x 2
Wood fram, brick and cedar shake
16 adult plants in various stages

OK give me just a bit I'm doing a house right now, once I get it finished I'll draw yours up real quick.

 

[RootsRuler]

I think your logic is pretty sound. While I've never tested any of this out my understanding is that anything electric will put out 3.41 btu per watt, so a 1,000 watt light would put out 3,410. So 3,000 would be pretty tight, technically a little short, 5,000 would give you some wiggle room. In fact we usually size to 130% of load which would be almost exactly 5,000 on a 3,500 btu load. And yes I would assume lights would usually be the biggest cooling load in a grow room.

How would room size play into that formula and is there a way to include it to be able to pinpoint actual BTU needs?

I like to size my cooling with a minimum of 20% headroom. I don't want my compressor working full blast 24/7. That will get you a dead compressor in week 7 of flower......yippee......

Also, how do you secure accurate info on the units? I've bought MS units that claim to be 2 tons and turn out to be 18,000 when the HVAC tech shows up. Is there a way to push past dealer claims and get to the truth?

 

[Scotty420]

12x12
8.5' high
2 outside walls
Old double pane pella casement windows approx 30"×40" x 2
Wood fram, brick and cedar shake
16 adult plants in various stages

OK so the room is calling for 8,000 btu empty. That's calculated to keep the room 72 degrees/50% rh on a 99 degree humid Missouri summer day.

You have by my math 2636 watts of light
exhaust fans are 116 watts
I would guess about 100 watts for circulation fans
Thats 2,852 watts (92% of which are lights) which is 9,725 btu

Combined with the 8,000 btu that gets you to about 17,000. So you would want to probably round up to at least a 2 ton (24,000 btu) that also doesn't account for plant humidity, you could add a dehumidifier which should pretty well eliminate that.

How would room size play into that formula and is there a way to include it to be able to pinpoint actual BTU needs?

I like to size my cooling with a minimum of 20% headroom. I don't want my compressor working full blast 24/7. That will get you a dead compressor in week 7 of flower......yippee......

Also, how do you secure accurate info on the units? I've bought MS units that claim to be 2 tons and turn out to be 18,000 when the HVAC tech shows up. Is there a way to push past dealer claims and get to the truth?

Room size is tricky, I have computer software that does that for me. You can use some "rules of thumb" like x square feet per ton, but that's dangerous as not all square feet are created equal. For instance a four seasons room with 3 walls entirely of windows will have a way bigger load than a room in the center of the house with no exterior walls even at the exact same square footage.

The only way to know the unit size is the model number. Most manufacturers put the btu rating in the model number. A ton of cooling is 12,000 btu, units are sold in half ton increments so your looking for a multiple of 6 usually. 018, 030, 042 something like that. The other thing is that you have to go by the unit model number not the compressor. Often times a 3 ton (36,000 btu) unit will have a 30,000 or 32,000 btu compressor, but they still put out 36,000 btu (at least per the manufacturers anyway)

 

[RootsRuler]

Probably best to just stick with the 1 - 5 or even go 1 - 6 to compensate for whatever heat producing gear you'll have in the room.

 

[jamesmost]

OK so the room is calling for 8,000 btu empty. That's calculated to keep the room 72 degrees/50% rh on a 99 degree humid Missouri summer day.

You have by my math 2636 watts of light
exhaust fans are 116 watts
I would guess about 100 watts for circulation fans
Thats 2,852 watts (92% of which are lights) which is 9,725 btu

Combined with the 8,000 btu that gets you to about 17,000. So you would want to probably round up to at least a 2 ton (24,000 btu) that also doesn't account for plant humidity, you could add a dehumidifier which should pretty well eliminate that.

Room size is tricky, I have computer software that does that for me. You can use some "rules of thumb" like x square feet per ton, but that's dangerous as not all square feet are created equal. For instance a four seasons room with 3 walls entirely of windows will have a way bigger load than a room in the center of the house with no exterior walls even at the exact same square footage.

The only way to know the unit size is the model number. Most manufacturers put the btu rating in the model number. A ton of cooling is 12,000 btu, units are sold in half ton increments so your looking for a multiple of 6 usually. 018, 030, 042 something like that. The other thing is that you have to go by the unit model number not the compressor. Often times a 3 ton (36,000 btu) unit will have a 30,000 or 32,000 btu compressor, but they still put out 36,000 btu (at least per the manufacturers anyway)

Think ur spot on...my guru w/o thinking said 18,000 btu Mr. Cool

Wanted to get away wirh 12k, 120v
18k needs 220v

 

[RootsRuler]

Think ur spot on...my guru w/o thinking said 18,000 btu Mr. Cool

Wanted to get away wirh 12k, 120v
18k needs 220v

Go big my Brother! Better to have slightly more than you need. 220v will save you a chunk o'cash so if you can, do it.

 

[jamesmost]

Go big my Brother! Better to have slightly more than you need. 220v will save you a chunk o'cash so if you can, do it.

Yea....

 

[jamesmost]

Flowering tent few days ago...
Turned on house central ac 2day...was getting hot in room
Ran some better venting too for now