just found this while looking for a computer fan for my grow box, there are two fans (3" & 4") all you do is stick a plug on them, no transformer needed.
http://www.maplin.co.uk/module.aspx?Module...=26m11#overview
ive just read the FAQ's and i might of got it wrong ("Q) How long is the lead to the mains supply? - ct
A) The 120mm fan has solder tag connections and the 80mm fan has 280mm leads (for connection inside equipment only")

Peace

They are a bit piss poor 12volt ones are better - get an old pc power supply and you can power loads of them

¿£13 for the 80mm and £17 for the 120mm?

They're pretty damn costly for what they are, and how useful they would be - you can get them from old server cases.

if u want an old computer fan hack one out of a case, and take the power supply as well and boom uve got a mains operated computer fan for nothing, that wont stop it being rubbish tho.

Unless you are trying to extract something the size of... oh i dunno... a computer case, maybe a bit smaller (imagine space taken upby components and dead air created.) then it really isn't worth the money, effort or time (alwlays sounds better when u give reasons in 3s ).

My computer has 2 intakes and 2 exhausts, and a cpu fan, and that is a proper ammount of heat extraction, a single one of those in a grow room......

eta: How big is ur grow space, what light have u got (fill in ur profile!) it may be worth gettin urself at least one little rvk and a speed controller.

have'nt ever used them myself, just heard people using them, []D [] []v[] []D when its put like that it puts things into perspective

nice one fella, best of luck.

I don't see that there is a simple answer of mains fans being better (or not) than 12 volt fans, since several factors have to to taken into consideration;

a) Power consumption. Which uses the most electricity? The 80mm mains fan uses 13w at 85ma and the 120mm mains fan uses 22w at 140ma, but how much power does a 12volt PC fan running off, say, a 300w PC power supply use?. Or even, how much power does several 12volt fans use when running off the same PC power supply? And I'm sure the answer isn't 300w. How much power does a PC power supply use to provide a 12volt supply?

Capacity. The 80mm mains fan moves 28cfm and the 120mm mains fan moves 80cfm, but how much does one PC fan move? or how much does several move when connected to the same PC power supply?

c) Noise. How noisy are the mains fans? Some PC power supplies can be noisy even without powering 12volt fans or anything else.

d) Space saving. Using a PC power supply in a small space, like a PC case, means that a lot of space is taken up by the power supply. Sorry for stating the obvious, but a mains fan can be wired straight to the mains, without the need for a bulky power supply. I'm collecting ideas and materials for converting a PC case, and as much as I like converting PC power supplies, I don't think I'll be using one. If you need a 12volt PSU, look at the compact fanless ones used by some smaller printers, freeview boxes and older TFT monitors.

e) Cost. As been said by others, these mains fans are expensive. Look out for old servers etc. Don't ever pay for these type of fans, there is always some old equipment lying around.

f) Simplicity. Working with electricity doesn't suit everybody. It is easier to wire a mains fan to a bit of mains cable and a plug, than it is to modify a PC power supply to give a 12volt supply.

Thanks to everybody for making me considering using fans rather than 12 volt fans.

urban spaceman have you powered a pc fan straight from the mains?

no cj, not straight in that would probably go bang, mains leccy = 20 times the requred voltage.

a) power consumption of fans is bugger all compared to grow lights, it just pales in comparison, if ur counting the watts so much u cant budge to power the biggest RVK ur should probably growing under energy saving cfls, my intake, extraction and circulation come to 40W.

A 300W PC PSU means that it can, theoretically, provide up to 300W (totalled over all it's rails, 5V, 12V etc) if needed.

It will take next to nothing if it's just on with a small load across it, like a PC fan.

There are two types of PC fan - the common ones that are found in virtually 100% of desktop PCs, which run at 12V, and the less common type (which the hideously-overpriced Maplin ones above are), commonly found in server cases which run at 230V - mains voltage.



e2a: Even though the utility of any PC fans at all is questionable, the 230V ones are definitely the better ones, as they not only shift more air, the motors have a lot more torque, meaning that they move the air a lot more powerfully than the 12V ones.

e2a2: Personally, I use a couple of 230V PC fans from an old server to provide ventilation to air-cooled HID lamp reflectors.

im not bothered about the leccy, you misunderstood. i didnot think it was possible to power a pc fan from the mains so that why i asked when ur man said it.

is there a light source that doesnt produce soo much heat i need an extraction fan in a grow box thats only 21"x44"x15-30"?
its exactly the shape of a skip, hence the 15-30". i dont have any other option because of the lack of space so what can i do, what are my options. a couple of those high output floresents, they're two foot, 24watts @ 95lumen/watt. i was thinking 3 or 4 but they will produce much heat. what about a pc fan-cooled 70watt hps, i only have 21inches hight, absolutely shite i know but as i said its that or notting. i will only be able to grow lowryder, basicly i need a light source that can be within 5 to 6 inches of plants and powerfull enough for flowering. check the link for pics half way down page http://www.uk420.com/boards/index.php?show...11116&st=10

I've seen both in the same 1.5msq room just used for air movement and the 12 volt one shifts way more air than the 240v one - it's running off a 1 amp Linksys power supply though. I'd imagine that there are both voltages that are good but that Maplin one isn't.

You could use a blower fan instead. They push a lot more air but watch the noise ratings coz they are a bit louder. CPC's website list quite a few both at 12vDC and 240AC. If the performance you need (work out your volume and decide how often it needs the air replacing) is available in 12 volts I'd go for that coz lower voltage is always safer.

ETA Spellin'

cheers Sin Humo

Do you mean have I powered a 12volt pc fan straight from the mains? No, I know the result without having to experiment. I work as a Field Service engineer dealing with IT equipment.

Do you mean have I powered a mains voltage fan, from a PC (or similar) case from the mains? Yes, for example, a few years ago, during a hot summer, I wired one up for a laugh and attached it to Mrs Spaceman's deck chair in the garden. It didn't do much good, like keeping her cool, but I was bored anyway.

Plenty of old, unwanted, IT gear passes through my hands, so I can afford experiment with it. If it gets wrecked, it just goes in the skip and hasn't cost me anything.

Sorry about the late reply, haven't had internet for a couple of evenings while I re-installed Windows.

that statement below means powering a pc fan straight from the mains?


"It is easier to wire a mains fan to a bit of mains cable and a plug, than it is to modify a PC power supply to give a 12volt supply."

Aye, because a 240 volt fan only needs a mains lead and plug, you can just chop up a kettle lead and connect it to the fan using a bit of chocolate block (plastic stuff with brass screw fittings for connecting wires) and plug it in. Whereas with a PC power supply, you need to connect the fan to the yellow and black wires of a connector and also con the supply into thinking it's attached to a mother board - usually shorting 2 pins out on another connector. Some PC power supplies also need a load on the 5 volt supply too and you connect a resistor across the red and black wires to sort that bit. So a bit more involved but not rocket science and if you don't have loads of fans you can just use a 12volt transformer of the correct amperage and connect it up in the same way you would a 240volt one.

ETA the PC fan going strait to the mains is a 240 volt one though and the other is 12 - just in case you'd missed that point - like diesel and petrol - don't mix 'em up.

i misread your post, niceone for clearing that up

It's not too hard at all to wire an old (ATX) PSU from a PC to power 12V and 5V devices - you just have to put a jumper wire between the SENSE (usually green wire) and GROUND (black wire) pins on the block connector that went into the motherboard.