# help with fans



## highharry (Jul 30, 2013)

Hi all, 

I'm building my first grow box. It is 80x85x200cm. I'm going to put in a centrifugal extractor fan, but which is better, wall mounted or blower?

An online converter figured the fan would have to be 57cfm for that space, but how big does that make the fan? and what about vents etc...?
Will i need to use ducting or can it vent into the space?

The box is in a lean-to out the back with a three quarter roof so air flow around the space isn't a problem

Any help greatly appreciated.

Cheers, Harry


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## LEFTHAND (Jul 30, 2013)

highharry said:
			
		

> Hi all,
> 
> I'm building my first grow box. It is 80x85x200cm. I'm going to put in a centrifugal extractor fan, but which is better, wall mounted or blower?
> 
> ...



Lol. No lil more then that. 
Your going to want to exchange your air out of the room anywheres from 2-5 times a min. 
Go with the inline (centrifugal)
What kind of light is going to light this box??
You will want passive intake holes n of coarse light tight. 
It being a lean too is no worries ducting for fan can go top side. 

Pending on system ie air cooled hood Will slightly change all this. 
Being your box is on the smaller side a filter won't fit good in there so pull the heat out via ducting connected to fan outside box n connect filter to that when needed. Will suggest be exhausting it out if the room/are the box is in though. 
LH.


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## highharry (Jul 31, 2013)

yeah, that's what i thought, that it was a little small, but i have done the math again and again and keep getting really small results, so...

the equation is W x L x H = cubic area divided by 3 (amount of exchange) right?

so 2.62' x 2.78' x 6.56' = 47.78 cubic feet, call it 48for ease of the math.
    48/3 = 16cfm...

on another site i found a table that included % for light heat, % for CO2, % for carbon filter and % for climate differences, figuring all of that in, i still come out with 24.8cfm...what am i doing wrong here?

cheers, hh


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## LEFTHAND (Jul 31, 2013)

Stop trying to figure co2 light n all them %. 
Just gonna run you silly. 

If you have 48. Or 50 cubic ft. And we want to exchange air 3-5 times. 
At 50 cuft that's 150-250 cfm 
I'd say 170-200 cfm fan do you just fine sir. 

50 x 3 =150. Not 50/3
LH.


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## The Hemp Goddess (Jul 31, 2013)

I'm with lefthand--you are making this more difficult than it is.  Not all those calculators are necessarily right.  It appears that you are figuring your ventilation to exchange the air *once ever 3 minutes*.  We are recommending exchanging it *3 times ever minute*.  Hence, you multiply the volume by 3 rather than divide by 3.

IMO, you should always go with a larger fan than you believe you need.  Filters and ducting bends and sags will affect the cfm.  You should also pick up a fan speed controller.


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## highharry (Jul 31, 2013)

D'oh...thanks for the heads up on the math,
makes much more sense, the larger fan also, and the controller...
cheers, hh


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## LEFTHAND (Jul 31, 2013)

Just to help you out some. 
I dunno what you are going to use for a light. 

But you will want a min of 3000 for veg n a min of 5000 Lu per sqft. For flower. 
Thus being said your about 7.3 sqft so about 40,000 Lu ya need. This will put you just over 5000 Lu per sqft in there. A 400 does 50-55k Lu 
LH.


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## highharry (Aug 1, 2013)

so when the better half saw the frame going up in the space she did a bit of a nut and I've had to re-spec it. 

is now 5.5 sq ft; 40 cu ft, which means around 120cfm

as for lights, I'm going to use CFLs simply because where I'm living is not really an easy place to get better ones and CFLs are everywhere.
for veg, 7 x 42w =3563 Lu, for flower, 11 x 42w = 5600 Lu.
veg bulbs in a horizontal rack, adding 4 more on sides vertically for flower...

cheers, hh


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## N.E.wguy (Aug 1, 2013)

nope,some time you gotta do stuff that gets u yelled at.. you are wasting your money on cfls..
read thru my dummies tread you can save a few hundred by doing this right the first time.. htgsupply,,..com has "cheap" shipped to your house in a brown box lights hps 150w for like 70$.. for veg they have t5ho 4' or 2' setups for 30-50$,, even if u put all 18 of those cfl lights on at the same time which u will for flower your plants are Not going to produce!


trust me all the crap you will buy for the cfl way would be better spent on the right stuff and you need nutrients still i assume.. Amazon is your friend 

just read my thread my friend and listen to these folks, even if u have to wait a week or two to get the right stuff the plants will reward you in the end.

Fan that i got with shipping and a controller came to 103$ shipped for the 6"
hxxp://www.plantlightinghydroponics.com/inline-fans-hurricane-c-76_1219_1057.html


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## The Hemp Goddess (Aug 1, 2013)

highharry said:
			
		

> so when the better half saw the frame going up in the space she did a bit of a nut and I've had to re-spec it.
> 
> is now 5.5 sq ft; 40 cu ft, which means around 120cfm
> 
> ...



I really don't understand how someone can be not okay with 7.2 sq ft, but okay with 5.5 sq ft.  The smaller you make your space the harder it is going to be to work with.  What are your dimensions?

Do your homework and I believe you will see what a poor choice CFLs are.  You don't have to buy growing supplies locally.  The internet makes the world your shopping center.

Initial Cost--First of all, 42W CFLs are not cheap--each bulb is going to run a minimum of $8, probably more.  Then you need cords and reflectors.  You should also run different spectrum bulbs for veg and for flowering.  So, 17 bulbs (7 in the blue spectrum and 11 in the red spectrum) alone are going to be a min of $144.  I'm not sure what cords and reflectors will run.  

Operating Costs--CFLs are going to put out around 60-68 lumens per watt.  Compare this with HPS that puts out 100-150 lumens per watt.  A 400W HPS puts out 50-55000 lumens and uses 400 W. Eleven 42 W CFLs put out 30,800 lumens and use 462W.  What this means is that every single month you pay 30-110% more in electricity to produce poorer light that will result in less bud.    

Heat--I can tell you that 11 42W bulbs put out a huge amount of heat.  Lumen for lumen, CFLs are going to put out more heat than a HPS and be far harder to cool.  HID lights can be purchased in a cool tube or air coolable reflector which makes cooling your space substantially easier.

Penetration--CFLs are not going to give you the penetration of HID lighting.  Even with the same lumens, CFL will produce lighter airier buds than HPS.

You can get a dimmable 400W digital ballast with a cool tube, HPS bulb, MH bulb, hangers, and a timer from e-bay for around $135 on Amazon.  This ballast is dimmable and can be run at 50%, 75% or 100% (you cannot put regular rheostats on HIDs).  

hXXp://www.amazon.com/Apollo-Horticulture-GLK400CT24E-Digital-Dimmable/dp/B00547I5I8/ref=sr_1_11?ie=UTF8&qid=1375364767&sr=8-11&keywords=400+W+HPS


You will also need a 4" centrifuge type fan.  You may also need a carbon filter.  Here is a combo deal from Amazon:

hXXp://www.amazon.com/VenTech-IF4CF412-Inline-Virgin-Charcoal/dp/B004Q2ER5C/ref=sr_1_2?ie=UTF8&qid=1375365144&sr=8-2&keywords=4%22+fan+filter

You are going to get out of this what you put into it.  Scrimping on any aspect of a proper setup will affect your harvest.


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## LEFTHAND (Aug 1, 2013)

The Hemp Goddess said:
			
		

> I really don't understand how someone can be not okay with 7.2 sq ft, but okay with 5.5 sq ft.  The smaller you make your space the harder it is going to be to work with.  What are your dimensions?
> 
> Do your homework and you will see what a poor choice CFLs are.  You don't have to buy growing supplies locally.  The internet makes the world your shopping center.
> 
> ...



:yeahthat:

Both thg n new guy are spot on. 
I am using cfl's to veg cuz I'm out my t5s at moment. They run hotter cost more n don't do the same. 
Flower hps only. 
Sit n think before u but n build. Save a headache n money. 
LH.


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## highharry (Aug 1, 2013)

thanks for the great info, will have to look at this more, one thing i don't want to do is waste my $$

thg, the problem was the space isn't very wide and what looked good on paper didn't fit well with what is already in there. no room to get past it basically. is now 60 x 85 x 200

again, i grok the light recommendation, i have looked at a lot of info about cfls, what are the buds that get produced under them like? like most things the people who use them seem to rave about them and they are pretty cheap here in the third world, like the electricity, and noone would ever ask why the bill had gone up and if they did then 'I'm using AC' would mean no more thought about it because if you can you run AC...

hh


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## The Hemp Goddess (Aug 1, 2013)

*People who rave about CFLs have never used HPS.*  Not only do I not know anyone who has ever started with CFLs then gone to HPS ever go back to CFLs, I have not even heard of anyone.  There is nothing about them that is better.  They are not cheaper to buy, they are not cooler, they are not cheaper to operate, and the bud is lighter and airier.  Most people who use them mistakenly believe  that they are cheaper, cooler, and just as good.  They are not.  Cooling your space is going to be a lot harder with 11 42 W CFLs. 

You will use more electricity running CFLs than running HPS.  However, no one is going to ask why the bill goes up.  I small grow doesn't make _that _ much difference in your power bill.  People do not get busted for their power bills unless it runs in the thousands and you do not pay it.

I understand things looking better on paper than in real life.


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## N.E.wguy (Aug 1, 2013)

they are great if a bulb goes out and you have 20 of them laying around while u run to the store to get a replacement bulb LOL


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## highharry (Aug 1, 2013)

i just died and went to heaven... i had searched through the commercial light suppliers to no avail re HPS bulbs, then last night found an industrial lighting shop that has both HPS and metal halide and it's a 20 minute drive away...oh happy day!! so which is better and what size would you recommend for the space i have? 
hh


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## pcduck (Aug 1, 2013)

5.5 x 5000 = 27,500 lumens needed for your square footage.

A 250 watt hps produces around  28,500 lumens.

A 400 watt hps produces around 55,000 to 60,000 lumens.

If you can control the heat I would use a 400 with your square footage


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## The Hemp Goddess (Aug 1, 2013)

highharry said:
			
		

> i just died and went to heaven... i had searched through the commercial light suppliers to no avail re HPS bulbs, then last night found an industrial lighting shop that has both HPS and metal halide and it's a 20 minute drive away...oh happy day!! so which is better and what size would you recommend for the space i have?
> hh




WHOA, slow down.  I don't mean to burst your bubble, but....What exactly do they have (and I really mean exactly)?  I am going to ask that you run by us exactly what you are looking at.  Be aware that these high bay commercial lights are going to need some modifications  to make them work for growing.  The reflectors are not good, you need to separate the ballast from the fixture, and they are sometimes vertical bulbs.  Are you comfortable doing electrical work on high wattage equipment?  You will need to separate the ballast from the light and find a suitable box to mount the ballast in.  You will have to add wiring.  It will need to be wiring meant to withstand high heat.  Can you figure out some way to cool the bulb?  These generally come with dome shaped "reflectors that are meant to disburse light in places like warehouses.  You will need to be able to mount the socket into a suitable reflector (or buy one).  Many of these bulbs can only be oriented one way, either vertical or horizontal and you do not have enough height for vertical bulbs, so this is something to check out.  If you are comfortable doing all these things, and can find the "extra parts" that you are going to need, we can make this work.  You might want to check out the thread in my sig on making a cool tub fixture. 

Otherwise, can't you order on line and get a light that you can air cool?


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## highharry (Aug 1, 2013)

sure will, on the list for Sat. morning, 

cheers, hh


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## highharry (Aug 3, 2013)

i have been reading the recommended threads, all really informative and eye-opening...went to the light store today, have their nice glossy catalog in front of me now,

the HPS lamps available are:

250-400W
HPS250/T-E40(26000Lm)
HPS400/T-E40(55000Lm)

70-400W
HPS250/E(26000Lm) 
HPS400/E(47000Lm) 

hh


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## The Hemp Goddess (Aug 3, 2013)

Tell us more.  Do they have separate ballast and reflector?  What is the reflector like?  Is this high bay lighting?  Like they use in warehouses?  

I would like to see you get a 400W dimmable electronic ballast (which also takes MH bulbs) in a cool tube.  Can you order stuff on the internet?


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## DrFever (Aug 3, 2013)

Light Requirements of "High Energy" Plants
1000 - 5000 lux	Min. necessary for life
10000 - 15000 lux	Min. necessary for consistent but sparse growth
20000 - 25000 lux	Min. necessary for robust growth
25000 - 30000 lux	Max. Efficiency for Sub Tropical varieties
25000 - 50000 lux	Max. Efficiency for Equatorial varieties
Plants need 25000-50000 lux too grow fast.
90000 lux Max. Sunlight Intensity on Earth's surface This is too much light, it is not good for the plant.
Plants subject to intensities at this level or greater are at risk of "solarization," whereby photosynthesis is retarded. This can happen at noon on a clear Tropical summer day, especially at high altitudes.
140000 lux Sunlight above atmosphere (Solar Constant)


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## highharry (Aug 4, 2013)

thanks for the light requirements DrFever

the lamps have separate ballast, but would have to buy reflector
been looking at the air cooled models on amazon
comparing pictures on the net these are proper hps lamps
have the threaded socket, look exactly the same, same specs
one model is more bulbous around the middle, the other long and straight

hh


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## highharry (Aug 4, 2013)

so dumb question time...

if you have an air-cooled hood, do you need to run a second fan to remove the air from the box just for the humidity? because where i live has pretty high humidity...
if i run a simple (uncooled) reflector, will 120-250 cfm fan cover the heat removal?

thanks,hh


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## LEFTHAND (Aug 4, 2013)

I would go 250-300cfm range. You can always dial it down but have the option of cranking it up too. 
You can run 2 fans if you like. 
Or you can suck out of the box through the hood n out a filter if there is no room for a filter on the box. 

I use to run 1 fan. Now I've hooked my 6" ostenberg for my 2 600w and me vortex is controlling heat in box 
I am likening this more Cuz I'm finding a nice temp control range. 
But this is also in my situation.  

LH


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## highharry (Aug 5, 2013)

thanks for all the great info folks.


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