4kw bare bulb, sealed and burning CO2 - how many BTUs of AC needed?

[SofaKingHigh]

As the title suggests, I've got a sealed 8x8 space I'm looking to run with 4kw bare bulb, burn approximately 6k BTU of CO2 and have enough overhead cooling power to be able to bring the temperature down to 75*F.

I have the lights air-cooled now and have an 18k BTU window mount with the ass-end dumping heat into a garage containing the room, essentially. High temp of 86*F.

If 24k BTU is going to be enough then I believe this Klimaire 2 ton mini-split will get the job done.

Your input is appreciated. Thanks.

 

[gooey]

24 will be enough...that link should be fine as well although pricey but nice. Gl peace

 

[Chillville]

When you say high temp of 86, is this the current high temp for the garden or the garage? If 86 is the high temp for the garden what is the high temp in the garage? On this new a/c placing the compressor outside will make the unit more energy efficient.

What is the outdoor high temperature?

Also if the room is sealed and only 8x8 then 6,000 BTU from your generator seems excessive, should only need about 1,500 BTU for a room that size at most. You generator should only kick on for a couple minutes every 10-15 minutes. If you can monitor your co2 generator to see what it cycle on and off times are....and you know the BTU of your generator....you can actually figure out exactly how many BTU its creating per hour.

 

[cemchris]

Yea your fine. Mine room is 10 x 6 1/2. Burning 3k right now and C02. 24K mini and I can drop the room to 60 no problem if i wanted to. Its about 110 here outside and hotter in my garage. I also have about 2 to 3 ft of spray foam on the walls and ceiling so that helps. My ac still kicks on and off.

 

[Chillville]

I don't think that you will be able to pull it off with only a 24k BTU especially if you are dumping the heat in a garage. If you are actually creating 6k BTU with your generator it's probably because you are air cooling the lights and some of your co2 is escaping. Once you actually seal the room your generator should run much less. Here is how the heat breaks down.

16,000 BTU for lighting (3.500 per 1k bulb and 500 for radiant heat per bulb)
6,000 BTU or possibly less for co2
3,500 BTU's (approx) are needed for an 8x8 even without any equipment running
---------------------------------
27,500 BTU total

I'm assuming that your ballast are out of the room right? This will add much more heat if they aren't.

This is obvioulsly more than the 24,000 BTU factory rating. A 17 seer unit actually only ouputs about 20,000 BTU leaving you with a 7,500 deficit. Assuming that your co2 BTU's will drop you are still well above a 24,000 BTU unit. I personally wouldn't go any smaller than a 2.5 ton (32k BTU unit). Especially since you are trying to reach 75 degrees.

Now I'm sure that there are people out there that make it work....and it will sort of. Your room will start out at 75 degrees when the lights turn on and then every hour the temp will go up until the 12th hour, then you are going to be well above the 75 setpoint. I always size systems for the hottest day of the year and for a consistent temp during the lights on cycle. I also size systems 20% over the BTU's needed, this way your compressor is able to cycle (turn on and off) while under a load. This is very important for the longevity of the cooling equipment and gives yourself a little cushion.

 

[Chillville]

Yea your fine. Mine room is 10 x 6 1/2. Burning 3k right now and C02. 24K mini and I can drop the room to 60 no problem if i wanted to. Its about 110 here outside and hotter in my garage. I also have about 2 to 3 ft of spray foam on the walls and ceiling so that helps. My ac still kicks on and off.

There is a significant difference in the BTU needs of your room vs sofaking. Your sq ft would only require about 3,000 BTU (or even less because of your high R value insulation), your lighting would only require 12,000 BTU, and your co2 is on a room that size should be around 1,000 BTU. This is a total of 16,000 BTU so a 24,000 BTU minisplit (approx 20,000 output) is perfectly sized for your garden IMO. This even gives you the 20% that I would always figure.

 

[TrichromeFan]

My 24k friedrich mini split cools my 4k in open hood, with a 4 burner cap co2, and a 70pt frigidaire dehuey. Later in flower I will also add in there a 50pt as well. I don't run mine @75, but it can definitely be done. Insulation is key, and really sealing the room helps the co2 not run so much. If you had more btu's it couldn't hurt. I do love the friedrich unit. I also would advise some pro help on the install on such a unit. Best of luck.

-TF

 

[SofaKingHigh]

When you say high temp of 86, is this the current high temp for the garden or the garage? If 86 is the high temp for the garden what is the high temp in the garage? On this new a/c placing the compressor outside will make the unit more energy efficient.

What is the outdoor high temperature?

Also if the room is sealed and only 8x8 then 6,000 BTU from your generator seems excessive, should only need about 1,500 BTU for a room that size at most. You generator should only kick on for a couple minutes every 10-15 minutes. If you can monitor your co2 generator to see what it cycle on and off times are....and you know the BTU of your generator....you can actually figure out exactly how many BTU its creating per hour.

Thanks for your information and willingness to help.

My garden's highest temperature is 86 at the moment. The garage space probably up to 80-85 while the outside temperature at nights is 60-70.

The 6k BTU is with 2 of 10 burners on the Sentinel CO2 generator. Lowest setting. It only runs for a minute or two every 10-15.

I have the option to reconfigure the space to be as large as 8x16' and reduce my target setup to 3kw over a UC16 rather than 4kw over a couple UC8XL. Or look into larger AC setups.

Would an installer need to be involved to charge a lineset and require entry into the residence for residential sized units?

Thanks again for the info, hopefully it'll help others as well.

 

[cemchris]

Im with ya on the 6K from the gen. Mine puts out something near 4K with 2 burners. Gonna cut it down to one because it burns for less than 2 minutes. Really only need 1 burner.

 

[SofaKingHigh]

Good to know TF! I plan on adjustawings and have similar spec DriEaz dehu.

75 degrees is just for end of days purpling. Able to hold at 85 on the hottest of days would be legit.

 

[SofaKingHigh]

cemchris, does anyone have a decent single burner generator?

 

[Chillville]

Trichrome is right, insulation is the key. Knowing that you have cool outdoor temps helps alot. My recommendation before is with ambient temps at 100, not 65. With 80 degree outdoor air temp or lower your a/c becomes very efficient coming really close to the 24k its rated for. Also if you are running 2 burners on your gen for 8 mins an hour that less than 1000 BTU an hour. So knowing that you can probably get away with the 2 ton after all. You would be at roughly 1,500 BTU to cool the room, 1,000 on the gen, and 16k on the light for a total of 18,500. That a/c should be fine for you, and BG Hydro is a great store to buy from.

 

[SofaKingHigh]

Shitfaced grinin' right now. Thanks guys for your input and help.

Pretty sure my garage space, which is insulated, will be in the 60s as well with the compressor running outside. Removing the warm pocket surrounding the room as it is now.

Rock and roll!

 

[TrichromeFan]

Chillville,
Thanks man.
I take it that you are in the HVAC trade? I assume that you are canna med friendly as well. What area do you work in? Maybe you could be of future service to the farmers here. Good for you for posting up with some helpful info here. What's your thoughts on pro or amateur mini split installation?

-TF

 

[Chillville]

Thanks for your information and willingness to help.



I have the option to reconfigure the space to be as large as 8x16' and reduce my target setup to 3kw over a UC16 rather than 4kw over a couple UC8XL. Or look into larger AC setups.

Would an installer need to be involved to charge a lineset and require entry into the residence for residential sized units?

Thanks again for the info, hopefully it'll help others as well.

Some units come precharged and you hook the lines together, test for leaks, and open a couple of valves. I wouldn't say its easy but with some mechanical experience you should be fine.

My favorite system has been with 3k watts over and around a 6 site 13 gallon UC. I put 2k watts over the center and (4) 250 watt verticals in cooltubes around the outside. Very productive and very efficient setup, esecially only having to deal with 6 plants. If I'm setting up these systems beside each other I take out the reflector in the cooltube so the 2 systems share the center 250's.

 

[SofaKingHigh]

Sounds like a sweet UC setup. Your lower nugs end up pretty chunky with the 250s like that?

 

[Chillville]

Chillville,
Thanks man.
I take it that you are in the HVAC trade? I assume that you are canna med friendly as well. What area do you work in? Maybe you could be of future service to the farmers here. Good for you for posting up with some helpful info here. What's your thoughts on pro or amateur mini split installation?

-TF

I have worked in the HVAC trade for years, mostly design and consulting. I'm from the deep south but I've worked with companies everywhere. I've been paid for consulting for years and its made me a good living, I thought I could give back by offering my consulting here at no charge. In no way do I claim to know it all and I'm here to learn too. I asked Logic if he would start this new section of the forum becase I thought cooling needed some attention around here :). Environment is so important to a healthy garden and I thought that having a separate section of the forum was important especially to newbies. Many times stores do not recommend the right cooling systems for people and they end up having heat issues, hopefully we can get people off to a running start.

About the mini split install
If you have a set of standard tools already and you can follow instructions you should be able to setup a mini split with quick disconnects and precharged lines. No way do I recommend anyone without a refrigeration license to install units that need to be charged, in other words units that do not have precharged quick disconnect fittings.

 

[Chillville]

Sounds like a sweet UC setup. Your lower nugs end up pretty chunky with the 250s like that?

I call it the wall of weed, I honestly think I get more off the sides than I do off the tops. We grow 4-5' tall plants so the sides are a large surface area to grow buds.

 

[jyip]

I also have about 2 to 3 ft of spray foam on the walls

is thata typo? 2-3 FEET of spray, not 2-3 inches? if feet, how? u musta sprayed a layer, then another, another, until ?


sofa

tho not in a garage, i have a similiar situation with ac n gro room withina room setup...i was able to keep my groroom temp @78F, w/it at times reachin lo-mid80's during heat waves...the container room was scorching hot, i never checked temp in it tho, anyhow, to the point here,
I was just adding that my room functioned perfectly for my needs with my ac dumping into containing room, agreaably not the ideal setup , but if not other way i couldnt hav a room


also thx chillvill for spending time to help peeps out here, way cool, no pun intended hehe,,, i hava 5000 btu ac for a 1 k light thats aircooled ina smll 9x7 x 7 area, roughly 450 sq ft, it cycles on n off properly and i was pleasantly surprized how well it cooled the room, it was more comfortable than my TV room was..lol

anyhow, good looking out man !! positive karma to you!

 

[cemchris]

lol yea its about 3 inches thick. My bad.

Well actually it gets as thick as 6 inches in most spots. Without the ac and lights on room will stay at about 80 when its 100 + outside. Best investment I made hands down!