Fan questions...

[Flange]

Hey all, just afew questios hopefully someone can help with.

 

im just setting up a small cupboard about 1.5m wide, 1m deep an about 2.5m high.

im going to be using a 600w Hps and was just wondering how much air id need to flow through there?

 

Are the fans more to keeps the tempretures down or for circulaton? I guessing both yeah?

 

So what size fans would you guys reckomend i use for intake/exhuast and circulation? Im just aliitle worried the rooms too small and will heat up too much.... What temps should i be aiming for?

 

Thanks in andvance.

 

Peace

[Luke Skywalker]

Hey all, just afew questios hopefully someone can help with.

 

I'll do me best.

 

im just setting up a small cupboard about 1.5m wide, 1m deep an about 2.5m high.

im going to be using a 600w Hps and was just wondering how much air id need to flow through there

 

Well, a good way to work out the approximate size of fan you'll need is to take the volume of your growroom, and try and exhaust all the air in the room within a minute. If you can do that, you're laughing. For instance, here we have an example where the room volume is 1.5 x 1 x 2.5m = 3.75m3. So you'll want a fan that can move that amount of air in a minute. Most fans are rated by m3 an hour, so to convert this, just multiply the above figure of volume x 60 and you'll know how much m3/hr speed you'll need as a minimum. You should seriously consider buying a fan which is rated above this speed though, to ensure that you have more, rather than less air exchange than you need.

 

So in this case, 3.75m3 x 60mins = 225m3/hr.

 

So you're going to be looking for a fan which can move 225m3/hr minimum, to boost that up and be safe you may want to go with about 300m3/hr, as 600w lamps put out a fair amount of heat energy.

 

A centrifugal fan will be able to move the air at much more pressure than an axial fan, and these are usually preferred. I'd suggest calling around a few places and see how much their various fans can move, and if you can see them running, how loud they are. You can silence fans using various methods, although that's another discussion.

 

Your fan should also ideally be able to handle connection to a carbon filter suitable to your circumstances; axial fans won't really cut it in those circumstances.

 

Are the fans more to keeps the tempretures down or for circulaton? I guessing both yeah?

 

The exhausting of air is there for two main reasons, firstly, to ensure that the heat from the lamps, and humidity from the transpiring plants is moved out of the space. This ensures that temps are in a reasonable range, and humidity doesn't build up. The second reason is that the air in an enclosed space will quickly be depleted of CO2 with fast growing plants in there, and plants need that to photosythesise. Without regular air exchange and fresh CO2, the plants simply cannot grow as they cannot get the basic ingredient for making sugar.

 

So what size fans would you guys reckomend i use for intake/exhuast and circulation? Im just aliitle worried the rooms too small and will heat up too much.... What temps should i be aiming for?

 

I'd say for the space you have, a 200mm centrifugal, or perhaps even just a 150mm would be more than adequate. A small growing space doesn't necessarily need active intake though, as if you use passive intakes the fan will simply pull air through this. The passive inlets should be about twice the size of the outlet fan, and placed at the bottom, and opposite side of the room to the exhaust. An inlet fan for such a system could be a small 150mm 2 pole or even just a 125mm 240v computer style fan or two, as well as some passive inlets to take any potential pressure off them from the stronger exhaust.

 

An oscillation fan in the growspace simulates wind, thus strengthening stems, (you don't want it blowing the plants over mind you, or they'll spend all their time growing super strong stems and not super big buds. ) and it also ensures that air in the canopy of the plants is constantly circulating. This prevents any humid, still and dark areas from forming for mould to attack within. You can't keep mould out, you can only prevent it from having conducive circumstances for germination.

 

Hope that helps.

[F420]

I like my fan its done me really good.

So i suggest you take a look at a " turbo hydro 250mm"

they are good fans. :scratchin

[Flange]

Cool thanks Luke.. the force is trully with you, dont let anyone tell you otherwise

 

And yea ive kinda decided to get a 200mm-300mm exhaust, and just have like 1 or 2 quiet 120mm 12v pc fans helping the intake.

 

Would afew pc fans of say 30-40cfm each be enough to circulate air around 2-3 plants ?

 

Thanks again guys, and an soon as everything im learning gets put to action ill keep you updated with a grow diary.... hopefully

 

Peace

[lazlo Woodbine]

Just to add a word of caution ....

 

unless you take lukes advice... you will most likely fry your plants with 600w!

 

imo.... I would consider dropping to 400w... far fewer heat issues and less need for expensive extraction... given the size of your grow space.

 

 

Laz

[Chev]

Yup, I have to say I know this one from experience I changed up to a 600W from a 400W using a 250mm bathroom exhaust fan in a double wardrobe. BIG mistake, I fried my plants straight out. Had to change back down to a 400W. I'd be careful playing around with a 600W in your space for sure, unless your exhaust/ventilation is tweaked to perfection

[trumpet]

I am using a 600 in a smaller space than that, just make sure ventilation is up to scratch.

[Flange]

Hey guys, ive jus set up the light and switched it on for a test run, and boy is it hot, not to mention bright!

 

Im gonna have to have a few fans going.... would a duct sucking air directly off the globe be a good idea aswell?

 

Peace

[hardb0iled]

I am using a 600 in a smaller space than that, just make sure ventilation is up to scratch.

<{POST_SNAPBACK}>

 

I have a 600W in a wardrobe, my fan set-up uses an 250mm axial fan mounted in the roof of the wardrobe, I run ducting inside the wardrobe which extracts air from under the hood of the light - this helps take some of the heat away from the globe before it heats up the whole wardrobe. I have passive intakes around the bottom of the wardrobe - this way fresh air comes in under the plants - up through the canopy.

 

My fan is pretty powerful (and noisy!), so powerful that the air from my passive intakes was rushing in so fast that the plants were getting battered about! so I bought a fan speed controller - this is great. Now when the weather is very hot I can crank the fan speed up to compensate, and when its cooler or when the lights are off, I can slow the fan right down - makes it very easy to tweak the temp/humidity etc. On top of this when I'm home by myself and the lights are on I will open up the wardrobe and direct an oscillating fan at the plants to give them some simulated breeze. 600w HPS rocks! But without good ventilation in a small area you will toast your plants :angry:

 

I wouldnt bother with intake fans, just get a decent extraction fan and use passive intakes(cover with flyscreen or something to stop bugs coming in). If you hold your hand over my passive intakes when the fan is on, you can feel the air being sucked in.

 

cheers,

Edited February 6, 2005 by hardb0iled

[Luke Skywalker]

An aircooled shade, (125mm fan mounted on the shade exhausting air via 150mm duct) can make very big differences in heat, I would suggest that if your temps are over 30 you look into it.

 

Centrifugal fans are far better than axial, as they can push air for long distances without backwash, whereas an axial fan is substantially reduced in strength with even slight backpressure from impedance.

 

And yeah, an intake fan is not necessary for growing with a single light, I would suggest a couple of low down passive intake vents.

 

Hope that helps.