Cooling a 400w HPS with 120mm fan?

I ordered a new HPS but for some reason I completely forgot to order an inline fan. So my question is, could I use 1 or 2 120mm computer fans for the cooltube? I'm tight on funds after ordered the HPS so it would be great to not have to spend 70 dollars on a fan.

Thanks in advance for the help!!

No one has ever tried this or knows if it would work? I'm not using a carbon filter by the way.

Calculate the cubic capacity of your grow area, divide by the CFM of the fan and see how long it would take to turn over the air and go from there. A good turn-over rate will give an indication of it's capacity to move air over and around the bulb.

I hate sounding like a dumbass, but how does one calculate the cubic capacity of my room?

To calculate Volume of you grow space: HxWxD. For example 10ft(h), 5ft(w), 10ft(d) 10x5=50... 50x10=500... 500 Cubic Feet

If you must get a PC fan, get one with good 'Static Pressure', as well as CFM rating, though I'm not sure one or two would be enough for 400w unless you spend a lot of money.
(You might be actually saving money by getting a proper fan)
PC fans are tricky, as lots are good at Blowing rather than Sucking, so make sure you look for static pressure (i think it's measured in 'mm H2O')

Good Luck

Zip.

I highly doubt a pc fan has the cfm to cool a 400w HID light. My 4" inline hardly does the job.

Yea you can do it... You need a cooltube. Get two 120mm fans. The cooltube is cooled by both of the 120mm fans. So one 120mm fan on left side of cabinet with 4" hole, then one 120mm fan on right side of cabinet with 4" hole. So now you have two fans on opposite sides of the cabinet, connect ducting to the left fan, run the ducting to the cooltube, than to the other right fan that draws the air out by facing it in the opposite direction. So one fan blows towards the light, while one pulls the air out.

After you do that, you then will need probably 2 more 120mm to exhaust the cab air... The two 120mm pc fans exhausting the cab can be made with a generic fish filter at walmart for your carbon filter.

Someone on another site has done this exact thing... Worked out well. However, from personal experience, 4 x 120mm fans isn't going to be cheap nor quite. You might as well just get an inline. Hope this helps, honestly, there is a reason no one uses PC fans to cool a 400. An inline connected to a carbon filter isn't as loud as you think... Unless your a kid growing in your parents house...

It's loud if it's in your bedroom and you're trying to sleep

i use a 6 in for my 600 watt in a cooltube, you can buy mufflers for them too

Yeah I saw some of the diy ones as well. Looked liked some brands use fiberglass filler and shouldn't vent into habitation. I've worked in a fiberglass shop and know how that stuff is. I haven't learned how the mufflers cut down on flowing air sound though.

honestly buy a fan... sell/or trade for one. you will need it.-S0uP