ventilation gurus help!!!

quick question,right know i have an ideal setup of 2 x 600 watt in a 5 x 10room,however i need another lamp a.s.a.p. up until this point the room gets ventilation from a seperate room and exhausts into our main room"wich gets pretty hot. im afraid by adding another lamp its going to affect my veg room.i need some input on my idea, i have 30 ft of 4 inch schedule 6 abs pipe.my plan is to run all three lamps with my current 6 inch fan then reduce to a 4 inch reducer" to accomodate the piping" and then there is a 15 foot straight run then one 90 deg bend and another 10-15 foot strait. my plan was to use a 150 cfm booster fan after the 90 to help move things along. oh also the 6 inch fan is 325 cfp pulling air. is there some formula to figure out, cfm x length x diam that i can use to help me out.

ok let me put this in a different format.does any one have 3 lamps linked together "ventillation wise" with a 35-40 foot run of 4 inch ducting.if so what cfm fans are you using.at the moment i have a 10 foot run with 2 600 watts and a 325 cfm. fan pulling the air. before i go ripping everything apart is there a minimum cfm rating for 3 lamps at 40 feet????

i'm no guru, but here's a couple of links that helped me figure ventilation.

this one has some math in it, but you should be able to figure out your cfm:
http://boards.cannabis.com/indoor-gr...-progress.html

and this one is all about fans:
http://boards.cannabis.com/growroom-...g-hot-air.html

Interested in this topic since for my next grow I want to do house-external exhaust - zero detection risk - aerial heat sensing wise, and of course do the ever coveted HID brilliance.

Still waiting to hear how "quiet" my new Elicent 6" Blower will actually be when it arrives - for my particular indoor stealth plan. I just thought maybe rhizome would need to know how much noise you can get away with security wise.

For long runs, I am still conceptually trying to wrap my ultra newbster brain around what wider fan and ducting widths can do - or demand - but with a focus on keeping Fan speed lower and, thus quieter.

Rhizome. You must try to flesh this out some time.

Correct me if my thinking is wrong, please.

4 inch ducting means - for these long runs- that this bros 6" Fan is going to have to scream. Right?

Am I wrong to assume that an 8" inch ducting would more comfortably (lower amperage draw - rheostated-down - fan speed) would keep fan somes down - yet still support the submitted 3x 600W heat exhaust scenario.

What if your indoor - mainstream social - situation requires no unusual hum, in other words. Not tryin to be a pain outta go into my signature, eh? Lol.:smokin:

Haven't done three 600's but I do have two 1000's with a 6" venting system. I have fans everywhere. A/C, veg room and mom room plus 740 and 430cfm carbon scrubbers. A little noisy. Insulated duct reduces the noise a bit. I like to use more rather than less with fan size, then I use a 5 amp ceiling fan controller to adjust speed if I wish. 3 600's should be fine with 6" ducts but I'm not sure about the 4". Regardless, even the 4" will help some.

my current hydrofarm 454 cfm fan is pretty damn loud.its the only thing that gives away my hidden room that i spent a ton of money trying to make incognito. one thing i have done before and will be doing again for my big fan is building a box around it from fiber board and just set the fan in there,it works pretty well,this time around i was just anxious to try out the new setup.and its fine how it is,but im trying to vent my lights out side like Rezinator sed"hence such a long run of ducting...ill keep searching thanks guys.