Originally GypsyBush... Posting as Cali Cali ... Long story... Im waiting to get my old handle back....
Anyways....
I have used 600s in tight spaces.... Very tight.... And if you exhaust and ventilate properly, you can maintain a small space around 5 degrees F warmer than the ambient temp outside the grow...
a 4" CENTRIFUGAL fan is plenty to cool a couple of 600s....
but I would not use one fan to exhaust and cool the lights... You loose some precious temperature control....
run one fan to cool your lights and that air will never mix with the grow's air... And I would put the fan on the cold side for 2 very important reasons....
#1- the fan will have a longer life if it runs cooler... Period...
#2- if your fan is SUCKING the hot air through, it might pull some of the stinky grow air with it... But if your fan is blowing, any leaks will be of fresh air into the grow....
both those factors are minimal, but if you are looking for optimal, there it is....
Right now I am running a 600 in a Growlab GL 80 2.6ft x 2.6ft x 5ft... Or close to that...
axial fans, like those duct fans are cheap... But by design they do not suit the purpose... Axial fans have a cfm rating... But that is unobstructed, add some minor back pressure and you loose cfm BIG TIME...
they may be ok for the kids running cfls in a cooler, nut they have no place in a compact 600w grow...
I would stick a 4" centrifugal fan on the lights... And a 6" centrifugal fan with a carbon filter for the exhaust...
I also use a
TITAN Mercury 4 Fan Controller and I FUCKING LOVE THIS LITTLE BOX!!!! Click on the link... Take a peek.... They work really good!!!
it allows my exhaust fan to go full blast when needed, but instead of shuting the fan down completely, it brings it down to a user selectable low idle when your temps are in check...
it saves the life of the fan... Electric motors suffer with start up...
It quiets down the grow significantly, as my fan NEVER kicks on full (it will of needed)... About a 30% idle speed keeps my grow happy and stealthy...
remember a more powerful fan at 50% rpm consumes less power and makes much less noise than a smaller fan at 100% rpm...
also, separate grow areas may share a cool tube fan, but they should have completely independent fans and thermostats...
Slaving grows like that can be tricky if things are not dialed in 110% and with contingency plans ready.
each environment will have it's own quirky needs....
hope this helps...
i'm subbed now so feel free to ask away....
Cheers...!