Heat, Hoods and A/C Questions?

[tonic12]

I'm designing my flower room, it is already insulated, drywalled, and covered in plastic. I will be running sealed rooms from now on, as my last grow with filtered ventilation ended in the PM nightmare:no

I have a few questions pertaining to Heat, Hoods and A/C

Here is how I understand the cooling requirements of my space

~3,500 btu's of cooling per a 1kW light w/ vented hoods
~4,500 btu's of cooling per light w/ open reflectors

My room is 12'x15'x7' in the basement and will house 4kW of light

1. Is the increase in light output from the adjust-a-wings worth the required additional cooling capacity? Or does running the vented XXXL Magnums in conjunction with less A/C make more sense? (i.e. 18,000 btu's in the open reflector situation vs. 12,000 btu's in the vented hood configuration)

2. Which setup do you think will be more expensive to operate monthly? I am planing on installing a ductless mini split system as those have finally come down in price.

I hope these questions make sense, I thank you all in advance for your help

 

[CannabisJohn]

I'm designing my flower room, it is already insulated, drywalled, and covered in plastic. I will be running sealed rooms from now on, as my last grow with filtered ventilation ended in the PM nightmare:no

I have a few questions pertaining to Heat, Hoods and A/C

Here is how I understand the cooling requirements of my space

~3,500 btu's of cooling per a 1kW light w/ vented hoods
~4,500 btu's of cooling per light w/ open reflectors

My room is 12'x15'x7' in the basement and will house 4kW of light

1. Is the increase in light output from the adjust-a-wings worth the required additional cooling capacity? Or does running the vented XXXL Magnums in conjunction with less A/C make more sense? (i.e. 18,000 btu's in the open reflector situation vs. 12,000 btu's in the vented hood configuration)

2. Which setup do you think will be more expensive to operate monthly? I am planing on installing a ductless mini split system as those have finally come down in price.

I hope these questions make sense, I thank you all in advance for your help

I am a HVAC pro. So I can answer which costs more to operate. Lights are lights (1k watts is 1k watts.). But of course it will cost more to operate the a/c unit. Theoretically it will cost 50% more but keep in mind the a/c will most likely only use about 15-20% of total electricity usage. Realistically the bigger a/c will probably only use 25-35% more then smaller unit. So here are some theoretical numbers to use for comparison. If you use $400 per month then a/c costs for smaller unit will be around $75-100 per month. If you go bigger (18k) then I would say your electrical usage will go up about $30-40 per month. These are rough numbers based upon real to life situations. The main reason I say this is because if you get an inverter type mini it will not be running at full bore all the time. Even if bigger and smaller unit ran 100% capacity then bigger unit will add about $50-60 per month. Just buy an inverter type with highest seer rating you can afford. Also check the lowest outdoor temp it can withstand. Most can't go below 30F or so. Some can go down to 0F.

 

[tonic12]

Thanks John

Your reply reminded me of your A/C thread, which I believe is where I started learning about this in the first place.

Thanks again for your help, you have confirmed me decision to go with 1.5 ton of A/C and to do it with an mini split unit versus a PTAC, window, or even the ubber expensive water chiller route.

I can do the math of expected electricity usage all day long, but I am glad that you included some probable numbers. I pay aprox. 0.11/KWh, so around $150 is acceptable.

:rollj:

 

[AZPRO]

dude ever try running canadian style? NO HOODS i have found a paint that has the highest reflection for warm lighting i paint my entire room this color 18x14 ft. i set up my lights free hanging about 3x3 feet apart from eachother i use a 14 seer train and it runs about 10 of the 12 hours my room is sealed and i run co2 burner so extra heat but my room never goes above 78 degrees and im pulling top quality super heavy weight.

 

[TopDog]

First: 3,500 btu for an already air cooled light is ridiculous. Who told you that? If your lights are properly air cooled with enough flow and insulated ducting 3,500 btu can cool all 4 of them. The problem with over-sizing the AC is that it will not run long enough to remove humidity. In this case bigger is NOT better.

 

[pitbull21]

Nice room set-up

Just wondering if you could break down that 20lb per month capability. I am about to set-up a 24k flower room as well and was just wondering what your rotation, growth cycle, plants per light and weekly harvest numbers would look like to harvest 20lb per month. Thanks for any info.

 

[blackcat]

dude ever try running canadian style? NO HOODS i have found a paint that has the highest reflection for warm lighting i paint my entire room this color 18x14 ft. i set up my lights free hanging about 3x3 feet apart from eachother i use a 14 seer train and it runs about 10 of the 12 hours my room is sealed and i run co2 burner so extra heat but my room never goes above 78 degrees and im pulling top quality super heavy weight.

what paint do you speak of?

 

[CannabisJohn]

First: 3,500 btu for an already air cooled light is ridiculous. Who told you that? If your lights are properly air cooled with enough flow and insulated ducting 3,500 btu can cool all 4 of them. The problem with over-sizing the AC is that it will not run long enough to remove humidity. In this case bigger is NOT better.

The reason why that number is used is because the inlet air to the lights usually varies greatly (unless you are cooling that air). If you use an inverter mini split then you should not have oversizing problems. I have seen rooms that have lights that are cooled with 70-72F air and they need 3500-4000 btus/hr per kw. So I am using real life situations also.
So I don't know how you are cooling your lights and only using 800-900 btus per hr per kw. Also there are other small heat loads in room including the room itself. The a/c is not to be used as primary dehumidification device anyway.