lighting and exhaust

I got my grow room up today and now its time to figure out what lighting and air flow I'm going to use now that I have my exact dimensions to working with. My grow room is in a closet that i build a wooden frame in and used panda film to create my own tent if you will. The dimensions are 3' 8"x2'x5' 3".

Now for lighting i would really like to use a 400w hps with a cooltube. I'll have my ducting setup like this:

outside->ducting->cooltube->ducting->outside

If i use a 6" duct fan with this setup will it cool the lamp enough to control temp in an area that small?

Now for exhaust would a 4" duct fan with a 4" carbon filter be enough for a room that small? Is bigger always better? I can always use a 6" duct fan with a 6" carbon filter, price is not an issue.

This room is going to be used for 2 possibly 3 plants in a DWC system each in there own container. If you guys need more info just let me know.

most of this depends on he temp of your intake air however a 6 inch fan from 250 - 424 cfm will cool the cooltube quite well depending on your budget but the 424 does a killer job and the 250 only just does the trick.
as for 4 inch ducting . if you cool your hood with the 424 cfm 6" inline fan then the 4 inch will keep the temps down fine as long as your intake air is reasonably cool. if you go with a 6" 250cfm fan for the hood i would suggest no smaller than the same for your main exhaust

He gave you some good advice there. That should work

thx. thats exactly what i was looking for.

You can buy the smallest can filter combo for odor for that room..

Try this for example:

Alternative Garden Supply - Hydroponics & Indoor Gardening Super Store

You have a 50 cubic foot room so that will work really well. It's rated @ 200 cfm minus the filter(I use a 20% loss) so 160cfm. Just over 3 times a minute. Your plants will love you for it, especially when running a cool tube

Good luck to you