Help with 6,500sqft grow space design and HVAC/ Electical

Hi all,

I’m new to the industry and growing, and have been drafting my plans for a 6,590sqft cultivation site. I am requesting a review and advice for my layout and plans. Currently, I have received an estimate from an HVAC tech with experience in the industry, he advises that we install about 53 tons (642k BTU) HVAC via several mini-split units. The cost is $87,000 for Daikin low-ambient mini splits with wind baffles and wall hangers and an additional $12,000 installation cost.

We’re running high performance LED that runs at 636w/ 3amp on 208v (our bldg is 120/ 208v with a 833a transformer on-site), which are expected to produce 2,700 BTU/ LED.

Our expected load is about 1200a, however we will be using a 12/12 cycle for flower to lower the draw. Planning to have a 1000a main installed once the feeders are increased from the transformer to the main. Then, my plan (waiting to hear back from the electrician) is to run sub-panels to each room. Probably some 125a and 200a to the three largest rooms. Any suggestions?


@bullfrog420 @PreyBird1 @hoppiefrog


Is the building already laid out as you have it drawn, or are you planning on building the walls?

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this is how it is currently built

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I have enormous amounts of experience in what your wanting to do. Theres a couple things to consider. If your new to this and have never grown large scale then you mite want to reconsider things. Like CO2 for instance. I know experienced growers who have trouble using co2, and then top that with it running in multiple large rooms. Your humidity levels will be altered a lot, depending on if you use a gas burner or food grade co2. Lots of humidity in and out, your equipment is super important here.
How tall are your ceilings going to be in there? This is also a huge part, as well as the location or height of your hvac gear.
I just finished designing and building a 6000sq ft building too. Lots of work. Lot and lots and lots of work and tons of $.
I hope you have more experience than what you said in your post. No disrespect intended at all. Just being upfront. Your staffing is gonna be huge important too. When the laws changed in colorado every swinging dick out there was mysteriously a pro whos grown for years. Specialy the dispencary owners there. Rarely did I see experienced growers get licensed, the states gave it all to people from the housing market crash. So, In reality, even less than 1% of the growers Ive met can truly work and handle grows of this size, even with a full staff. Your gonna need some people with serious experience and the closet and bedroom or basement growers will not work. I only say this cuz of how many people ive seen loose their life savings and inheritances chasing the green rush.
You also need to consider if your dry area is large enough. Your going to need a bigger dry area than you do a trim in my oppinion. How are you going to hang or dry your plants? What about your trimmings and stuff,are you going to have a processing area for extractions and what not? Thats a lot of material thats going to need processed, and Im not even talking about flower or bud itself.
Sorry if Im disecting this apart, but Im blunt and upfront. Again, ive watched too many loose their asses off. Its hard, but Whats worse is when i give someone advice and they ignore it then have tons of problems and expect me to help them recover. Don’t be that guy. Make sure who ever helps design it is legit. If your truly about to jump into a grow like this, then I am think you probably know most of his already.
Also, every hvac guy ive met has talked about how experienced they where. Growing like this is a whole different ball game. Designing and running a super walmart would be easier. So make sure he is legit too. I can go through and disect this all day, but ive also been designing grows like this 20 years solid. I think your smart to split the rooms up into smaller ones too. Your also smart to have multiple a/c on different breakers and different thermostats in case of partial failure. Always think plan A-B-C. Have 3 back uo olans and ststems. I tried the giant rooms before and, well, lets just say i learned a hard lesson way back. Hahaha Good luck!
Almost forgot, had to edit this in. You better make sure your veg and clones are mint and the rooms are big enough. Its your veg phase rooms and clones that will be a huge deciding factor in your success. Ive cut 50k clones in a season before to maintain peoples hemp grows, thats not simple…and I root my clones and trasplant in 5-7 days after I cut. Most people are anywhere from 2-6 weeks for their clones to root. That is important. My flowering grow rooms get 6 full harvest in 1 year every year. Think about that for a few. I didnt say that to be cocky. Again, good luck to you. I do wish you the best of success in what you end up doing!


Also…you need to anticipate way higher heat numbers for your expected led btu. Im still on the experienced hvac guy saying use a bunch of mini-splits, your going to pay around 100k just for the a/c. Wow. I like splitts, and They work yeah, but thats a lot of those and super costly. I know some things are hard to get around, but doesnt that number give you heart burn like it does me.? Hahahaha Anyway, i had to add that about your btu. The numbers rarely come out exactly like whats on paper. Always go with way more a/c btu than you estimate for. ALWAYS! Remember when you have that many plants rocking all over, the heat is going to be increased even more. Same with humidity. Up and down theough its life cycle. Ok, I have to get away from this post hahaha Ive still got a 50’x50’ grow i have to finish designing this morning. Lol
When you tell contractors and such what your doing, ALL of them see gold from you. Remember that in this business. All these people see you as a rich pay out. The only people that disagree with me are the contractors wanting the job and the people who are inexperienced. The biggest problem with all of the builds we have done has been when we where swamped and had to subcontract out to the hvac and electician workers how much they wanted to charge, and again, ALL of them told us how awesome and experienced they where. Again, Im not just a shmuck throwing fake advice, I had built my 300th commercial grow by 2010, then the laws changed. Im not bragging or trying to talk smack, I am just realy trying to make sure who all reads this takes my advice seriously and not blow it off as useless. I wish you all the luck. Sorry if my i fo is so scattered, thats how my ocd brain gets to rockin. Lol


I didn’t read the whole post but I want to address some mistakes in comment, I run a co2 generator in a sealed room no air in no air out if I run my room at 1400 ppm my humidity gos up 2-3%. And any issue with using a generator is easily solved if you have enough space to allow air coming off generators to cool before they hit the canopy.

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Also you will save massive bucks to run a relay set up (a flip switch) run half rooms at a time half amperage required.also if buying mini splits you could run two or three head units and cool 2 rooms on different cycles with one machine ,this would work well with your back to back rooms. You would probably do good to set up a commercial roof top heat pump unit tho, it will cost mu h less so long as you can set it up central to your space to cut down on ducting. Anyhow I have to do some chores I’ll try take a better look in a bit

Ive ran co2 for years. Ive never seen an Lp burning co2 generator only change a room humidity by 2-3%. Even the pics of the tight room Ive been posting in my grow journal has a higher percentage than that. That room is sealed as tight as a room can be. No air in or out unless I want. Plus, take in the fact of the size of the rooms the build is blue printed for. 2-3% doesn’t add up. Just my oppinion. I have 10 burner Lp generators rocking in a couple rooms and food grade co2 gas in a couple others. Big difference between the rooms and the humidity levels. I also recommend not using any co2 unless you have a controller to run it.
What size are your rooms you run co2 in Hoppie? Just curious. I get ocd geeked out on grow builds. Lol

“The great thing about science is you don’t have to believe it for it to be true” tell ya what I’ll get @oldguy & @kapouic help me post a video to prove my point… I have a great environmental controller that will show solid numbers, man I love a good challenge.numbers are science words are easy to use but science don’t lie!


I have a feeling the different numbers have alot to do with differences in variables in said grow rooms, canopy space vs open space, temps effecting the relative humidity, the speed the plants are using up CO2, grow media, watering schedule ect. The fuel should release moisture at a constant when burned but the room, plant and equipment conditions will all vary.

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Sorry it’s taken me so long to get back to you.

“I’m new to the industry and growing”. Unless you have some very trustworthy and reliable people guiding you, you will be taken advantage of at every turn.

I don’t want to seem negative, but this looks like a nightmare in the making and unless you have deep pockets to cover the cost of the learning curve you could be getting yourself in trouble. If you are planning on dumping your life savings into this, with no worries because you are going to make it all back in the first few harvest, be careful, things go sideways very quickly.

The building layout frightens me. Are there any corridors connecting the rooms or do you have to walk through the rooms to get to the next room?

Which room is going to be your veg room?

Is there a reason you have chosen to separate the trim room and the drying room with a flower room? You may be better off having them next to each other, for example, rooms 2 and 3, or rooms 7 and 8.

If you have 49 lights @ 3.06 amps in room 9, that’s 150 amps, then add 2 dehumidifiers @13.2 amps (26.4 amps) you have already just about maxed out a 200 amp panel at 80% continuous load.

There are so many considerations that need to be fully figured out before you should go ahead with this, even down to the point I’m not sure it’s even the right building for this project!

You need someone like bullfrog420 or myself to guide you, there is a lot more to this than hanging a few lights, AC’s and dehumidifiers!


I think youre gonna need more juice. Granted youre lights are only pulling 3 amps vs. 5 for 1000 watt hps att 220v but I used every bit of 600 amps in a 2400sqft grow last couple runs… I ran in winter to avoid using ac even. I ran a total of 57- 1000 Watters plus scrubbers, fans, air pumps, inlines for hoods, water pumps etc. Anyway, get 50 percent more juice than you think you’ll need! And pay the bill the day it comes!!! :rofl::rofl:


1000w hps @ 220v runs 4.4 amps each
@110v it runs 8.8 amps
I agree with you in the massive power consumption. Hahaha and absolutely pay that electric bill on time!!! Hahahahaha
Its funny cuz when I get asked questions like why do I knit pick the designs so much or why i have told more people they should not go forward with their grow plans is because I have designed and rocked several gigantic grows in the past and my gawd the things that can go wrong. Hahahaha

We pay for electricity by the kilowatt hour, not based on amperage. So if you are running 10 x 1000-watt ballast for 12 hours, or 5 for the first 12 hours and 5 for the next 12 hours you have still used the same amount of billable electricity.

It’s the same with running a ballast at 120 volts, or 240 volts, they both “use” 1000 watts, it’s just the 120V draws twice the amperage, so puts a higher demand on the electrical system components.

Watts = Amps x Volts

So if you double the volts you half the amps but the watts stay the same

8.3 amps x 120 volts = 1000 watts

4.1 amps x 240 volts = 1000 watts

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I don’t get your reason for explaining to me lol but I’m sure some ppl don’t understand power usage lol :wink:

Lol I get it now haha u didn’t understand where the savings are… Less equipment needed when running relays (I can explain further if u still dont understand)

It was this statement in your post that made me think you thought, reducing the amp draw would reduce your electricity usage.

“Also you will save massive bucks to run a relay set up (a flip switch) run half rooms at a time half amperage required.”

I’m sorry if I misunderstood something.

I don’t recommend flip switch setups. Yes, it will save a little money on equipment to start, but a simple relay failure, (and relays fail all the time) can turn the lights on in the dark room and ruin a harvest. For me, the risk of losing a harvest isn’t worth the cost of a ballast.


Ice cube relays are replaceable within a minute or two and do not create sparks and are cheap to replace and last sooo much longer than a magnetic relay, it’s what an electrical engineer suggests for a safe and reliable set up for the average user. One can save on so much equipment it’s just crazy, half the AC needed half the lighting required half the fans needed and half the amperage supply required so no need to bring a larger Pannell into the building.its an obvious solution for mid size grows that do not have access to three phase power supply imo

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I am an electrical engineer and I was only addressing the use of flip-switches with my last comment.

Of course, depending on the available power supply, square footage and current layout and of the building, dividing the rooms is almost always advisable.

An “ice cube” relay is just a cute name for a relay in a clear case, generally used so you can see the moving parts inside a magnetic relay. Solid state relays don’t have any moving parts. Plug in relays are replaceable in seconds, but it often takes much longer to fault find and identify the problem.

It doesn’t matter how cheap a relay is and how quickly you can change it, if your room has been in the dark for hours on its “night” cycle, let’s say 7 hours and your cheap, quick change relay fails and turns the lights on, it could easily ruin a crop you have spent months growing from seed or clone.

The only thing a “flip-switch” is saving you, is the cost of the ballasts for the second room.

As an example, if you have a 2500 sq ft building with a 200 amp, 240 volt supply (normal in the average building of this size) and you split your flower room into two, (advisable in this scenario) you can safely power around 16, 1000 watt flower lights per room on 12/12, plus the necessary AC, pumps, fans and lights for a veg room to keep the flower rooms in a perpetual harvest.

With a “flip-switch” you only need 16 ballasts to drive the 32 lights, so you save the cost of the 16 ballasts. If we say a ballast cost $250, that’s a saving of $4000. Now imagine a year in to your new business a relay goes bad, the dark room gets lit up in the middle of it’s dark cycle and the crop gets ruined.

16 x 2 pounds/ light = 32 pounds

32 pounds x $2000/pound makes the $4000 initial investment of 16 extra ballast look cheap.

It’s an “obvious solution” in almost any size grow over about 10 lights, no matter whether it has three phase power or not, it just makes sense to split the lights into multiple rooms.

The building layout that started this thread already had multiple rooms that they were dealing with, it didn’t appear to me that the existing layout would work well.

Of course you can nitpick the above scenario all you want, but it doesn’t change the fact that the average flip-switch setup, is a potential problem not worth the savings, but most people are like you and aren’t aware of what could happen.

The only reason I have given any input to this thread, is to hopefully help people understand more and avoid problems, not to upset you, so please relax and don’t be so defensive.