How much fan power do i need?

H

Hightemplar89

Member
Hey guys, my 1st post here,, i've done a lot of reading here and it's great but i kinda need specifics because i'm just worrying myself about this..

I've grown a couple of batches before ina closet but now iv'e got a secret jardin 5' X 5' X 6'.

I live in the uk so it's always pretty temperate, the room the tent's in is around 65F.

I currently have a 170 CFM exhaust fan taking air outside the room.

I have a 600 HPS right now (open hood non air cooled) currently dimmed to 400 and i have temps around 75-80F in the tent.

I'm going to be buying another 400 HPS cool tube and a new air cooled hood (sealed with glass pane) to house the 600 i have and connect them both via ducting in the 1 single line and i will be buying a fan to pull air thru this line from air outside the tent, i need to know what power fan this would require? And is the air from outside the tent cold enough? (65F) to drag through these lights?

And also, will the exhaust fan for the tent be enough? 170 CFM?

By the way odor isn't an issue so i'm not using filters so no need to account those in your advice :)

Hope you can help me guys! thank you!! :sleep:
 
jondamon said:
Here you go.

Use this guide to work it out yourself.


http://urbangardenmagazine.com/2010/07/planning-your-grow


If you get stuck let me know.



J
Click to expand...

Nice thanks!

So from what i've gathered from that, my tent volume is roughly 150ft³ and since i'm not using filters i don't have to factor the 25% potential flow loss?

So my fan is about 170cfm so this is perfect right? As just the general tent extractor? Considering the lights will be air cooled by another fan (hoping 200cfm is ok), and this fan will be pulling outdoor air which is relatively cool.
 
If you are using 2 fans, one for exhaust and another for an air cooled lighting rig then yes 170 and 200 should do the trick.

BUT

IMO you would be better getting something like a 300CFM fan for the lighting rig. I used to use a 600w with a 400CFM fan air cooled like you are planning.

+300 if you want to add another light IMO. You can always speed control it if its too much.

If you are running a 200CFM on full, where do you go when its not enough? NEW FAN.

If you don't already have this fan I would get larger.


How come you don't need a filter?


Plants stink you know!



J
 
Because this house is like a good few yards from other buildings and its being blown right up the chimney ^^

I've changed my idea a little, i'm thinknig of keeping the open hood for the 400W and then house the 600 in the silverstar sealed hood so just have one aircooled light while the other kind of just helps keep the temps warm enough?

I just introduced a fresh air intake from outdoors (small active duct fan) and it really has helped bring temps down to mid 70s with 400W of lighting.

So what do you think? would 200cfm be sufficient for 1 single 600hps ? I can make it so it will be fed outdoor fresh air which should be effective at cooling the bulb?

Would temps be ok do you think inside the tent considering the 400W is sitting in the open hood.

Thanks.
 
If you are planning on using a 600w and a 400w that means you're going to have enough floorspace for either 10 big plants or alot of small ones.

Smell travels a great distance!!!!


Smell is the #1 reason for busts!!!!!


IMO get as big a fan as you can.

I currently use a 300CFM fan with filter attached open reflector with a 400w and my temps are ideal.

Ultimately its up to you to decide. I've given my recommendations.



J
 
jondamon said:
If you are planning on using a 600w and a 400w that means you're going to have enough floorspace for either 10 big plants or alot of small ones.

Smell travels a great distance!!!!


Smell is the #1 reason for busts!!!!!


IMO get as big a fan as you can.

I currently use a 300CFM fan with filter attached open reflector with a 400w and my temps are ideal.

Ultimately its up to you to decide. I've given my recommendations.



J
Click to expand...

Thanks.

Can i just ask your opinion, would you cool both the lights or just the 600 and leave the 400 in the open hood?
 
Hightemplar89 said:
Thanks.

Can i just ask your opinion, would you cool both the lights or just the 600 and leave the 400 in the open hood?
Click to expand...

To be completely honest I would cool both.

Cool air intake ducted to your 400w first then ducted to the 600w then fan then out.

Depending upon your temps inside the grow doing it this way you are only a Co2 regulator, bottle of co2 and solenoid away from a sealed grow room.

Have you contemplated a sealed room?

You could use your 170CFM fan with a filter inside the 5x5x6 area just free standing keeping the smell from entering the rest of the place.


J
 
Dude, i don't need filters i told you.

And really? you live in the uk too so i thought you'd probably think its alright for the 400 to be the 'warmer' of the tent since the 600 will practically be putting no heat out whatsoever.

If i cool both the lights my tent will probably be too cold if anything.

And i'm not using co2.

Why the 400 1st?? Shouldn't the 600w demand more cooling priority?

Fyi the tent is sealed.
 
Hightemplar89 said:
Dude, i don't need filters i told you.

And really? you live in the uk too so i thought you'd probably think its alright for the 400 to be the 'warmer' of the tent since the 600 will practically be putting no heat out whatsoever.

If i cool both the lights my tent will probably be too cold if anything.

And i'm not using co2.

Why the 400 1st?? Shouldn't the 600w demand more cooling priority?

Fyi the tent is sealed.
Click to expand...

FYI if you are exhausting the tent it ISN'T SEALED.

400w first so that it doesn't overheat the bulb from the 600w being first.


You'll still get radiant heat from the 600w air cooled.

Like I've said I use a 400w with 300CFM fan and on full hit it keeps my grow room at 24C during night time when I run my light.

During winter it utilises a speed controller to keep it at 24C.


With a 170 and a 200 fan you'd still experience heat problems during summer.



Try not to get too shirty mate or I won't help you.


I'm trying to give you my advice based on buying inferior fans from my own experience and then having to rebuy higher spec.



J
 
If you don't have any neighbours for a good 200 yards then filter less should be ok.

Just don't want you getting busted.



J
 
I didn't mean to sound 'shirty' dude, but you started going on about co2 and solenoid? like wth, that's not what i'm doing lol.

I guess i have to cool both the lights then? i assumed the cool air outside would be suffice to keep the bulbs cool even with a not so powerful fan, clearly im wrong since your 400 puts out 75 under 300cfm? blah, almost makes me wanna just go a/c because this is just too much fan shit.

And i get you about the 400w first i think, but wouldn't the 600w end up being overheated with warm air from the 400? lol
 
Hightemplar89 said:
I didn't mean to sound 'shirty' dude, but you started going on about co2 and solenoid? like wth, that's not what i'm doing lol.

I guess i have to cool both the lights then? i assumed the cool air outside would be suffice to keep the bulbs cool even with a not so powerful fan, clearly im wrong since your 400 puts out 75 under 300cfm? blah, almost makes me wanna just go a/c because this is just too much fan shit.

And i get you about the 400w first i think, but wouldn't the 600w end up being overheated with warm air from the 400? lol
Click to expand...


600w wouldn't over heat due to running hotter anyway.


A portable AC for an area your size would cost you around 1kw of electricity for every hour of use.

Its doable with fans though. My RVK150E2-A1 runs around 65w an hour.

An AC uses roughly the same electricity as another 600-1000w of light.


About the Co2 its just you are talking of a setup that could quite easily convert into a sealed Co2 setup quite easily. Bigger yields are achieved using Co2.

When I had my own 600w with a BLOCKBUSTER air cooled hood (cost me £225 for just the reflector) it had its own cool air intake and exhausted out of the room. Sealed like you're planning. I did run a second fan as exhaust with a filter. Summer 2011 I struggled at times keeping my room under 31C even with a 400 CFM fan on the lighting rig and a 150CFM fan and filter.

So it can get tough in the UK for temp control at times.

IMO its always best to spec your room for summer running and be able to control it for winter.




J
 
Yeah, which is why i'm trying to perfect it all right now (summer).

And damn, didn't know a/c ate that much watts, guess fans it is then..

So i should cool both the 400 and 600? Would a cooltube be fine for the 400? Because i'm hitting my budget limit and cool tubes are much cheaper than the hoods, the 600 however will be inside the silverstar hood.

The cooltube and silverstar are 5" duct diameters, will this be a problem? since most fans above 200CFM are at least 6" i will have to use reducers or something, ugh.
 
If you are reducing then definitely go bigger on fans.

The blockbuster that I had was a 6" duct.

Cooltubes aren't the greatest as they leak a little around the hanger hooks, they're ok for a budget air cooled setup though.


I would definitely cool the 2 lights. Realistically you want to be looking at the SYSTEMAIR RVK 6" high output L1 version. 400CFM or 660m3/h.

Fans in the UK generally use m3/h not CFM. CFM is USA rating.


Then for winter you can speed control the lighting fan dialling it down as you need to.



J
 
Thanks for quick response!!

Damn, a fan like that must be loud as shit, is it better to pull the air thru the light sys or push it through?

Also my extractor is fine right? 170cfm for 150 ish cubic feet? So my air is getting exchanged less than a minute each time? is that the correct logic? (stoned)
 
Hightemplar89 said:
Thanks for quick response!!

Damn, a fan like that must be loud as shit, is it better to pull the air thru the light sys or push it through?

Also my extractor is fine right? 170cfm for 150 ish cubic feet? So my air is getting exchanged less than a minute each time? is that the correct logic? (stoned)
Click to expand...

Yes. Between 1x-3x a minute exchange is the recommended. Anything over 3x per minute and you should consider AC.


I must admit my 6" L1 was exceedingly loud. But suspended from bungees and using insulated ducting kept the noise down.



Here is a link to the build of my original room.
https://www.rollitup.org/grow-room-design-setup/441212-my-new-closet-re-design.html





J
 
Hightemplar89 said:
http://www.amazon.co.uk/Systemair-R...d=1370563796&sr=8-6&keywords=systemair+rvk+L1

Is this the fan you're on about?
Click to expand...


Yes. That's the fan.







Hightemplar89 said:
Nice thanx..

Yeah think i will get acoustic ducting, i got the speed controller for my extractor i guess i can use that for the light fan instead.

You sure i really need a beefy fan like that? i was thinking of this tbh http://www.hydroponics.eu/fans-and-...-extractor-blauberg-max-15cm-460m3h-9067.html

I know everyone raves about the RVK's but Blauberg is german too so maybe theyr good? lol
Click to expand...


I use more than that just on my 400w.




J
 
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