Ducting question... Can you oversize the ducting in anticipation of future "upsizing"

I currently have all 6" gear ready to tackle my ventilation problems.

The thought occured to me while shopping... Gee... this will be a pain
in the ass and something I don't want to do twice... if I were to have
to go 8" later it would suck to re-do all this work.

Can I use 8" ducting and just have a 6" fan/filter attached? That way
the run that will be difficult to "re-do" would just need a size adapter
for now and be ready for the 8" use in the future - if needed.

Any downside to oversizing?

Also I bought 4" ducting to serve as my intake (passive for now)... The
thought is that you'd maintain slight negative pressure...

Am I correct on that last assumption?

You just need to get a 8" to 6" reducer. No downside to exhausting into a larger duct at all, probably makes it quieter too. Can't say whether a 4" duct will get you enough air for a passive intake without knowing the dimensions of the room.

i think that would work like a charm and yeah i think you would maintain a decent amount of negitive pressure

Room is 5x9x8 approx.

If you eventually want to suck 500cfm+ out of the room then go 8 inch. A bigger duct just means less noise from a reduced air velocity and less static pressure.

absolutely..the bigger the better.....Not only will the bigger duct allow you to upgrade in the future to bigger fans it will also make your system run less noisey with less air restriction.... its a win win really

when fans get to 8 inch they start to have some decent power and efficiency , so bigger is better as everyone has said
a 6 inch fan needs 2 x the power to compete with an 8 inch fan

my 6 inch turbo fan is 250watts my 8 inch only 120watts both removing roughly the same amount of air

skunkd0c said:

when fans get to 8 inch they start to have some decent power and efficiency , so bigger is better as everyone has said
a 6 inch fan needs 2 x the power to compete with an 8 inch fan

my 6 inch turbo fan is 250watts my 8 inch only 120watts both removing roughly the same amount of air

Click to expand...

+rep sir........

So, given my room size... I'm trying to figure out a few more angles here...

#1 - I'm looking to confirm if it sounds like my existing 6" fan with 6" ducting is adequate for the current room/lighting...

That 6" setup should handle roughly 1000w overall of T5 lighting - right?

The sticker on the BadBoy's says something like 430+ watts or so (IIRC)... 8 bulb T5/HO...

So I've got my 2 main T5 fixtures and another small 2 footer... The only other heat would come from 1 or 2 fan(s) maybe
an air pump or two and a res pump if I went hydro/aero sometime... etc... Maybe CO2 controller...

#2 -What is the upper end of the heat my existing 6" equipment (with 6" ducting let's assume) can accomodate in my room?
Could I get away with say 2x600 HPS? Push it further to 2x1000 perhaps? Could I push higher wattage sticking with T5? Etc...

#3 - Let's say I did go 8" on the ducting and then upgraded to an 8" fan later.... What type of wattage could I likely get
away in my room with in that scenario? I don't see myself ever going over 3 lights physically... maybe 600's or 1k's...
But it'd be nice to 'forecast' what I could expand to - would help future purchase decisions...

#4 - If I bump up to 8" on the exhaust... that means I need to go 6" on the intake most likely... correct?


#5 - Use the insulated ducting for between the room and the exterior and the plain flex-duct inside the room? Or stay
with the flex duct throughout... I can think of pros/cons to using the insulated for the run through the attic space...

Also what are the general thoughts on mufflers for the exhaust? DIY it? Are they really that needed & effective?

Anyone? Planning on hitting the hardware store tonight... return stuff if needed and pickup the last of what I'll need...

I think I've convinced myself to return all the 4" gear for 8" gear... that will give me a 8" exhaust with 6" intake...

Also - I'm definitely getting a variac-based speed controller... I started another thread on that topic and included a link to a good source (I think)...

you seem to be on the right track m8, i have used 4,6,8,10,12" inline fans
8inch are my favorite for power to noise ratio an 8inch will be easy good enough for 2kw + of lights
and the 8" ducting is not so unmanageable .. unlike 12" ducting which is just plain ridiculous

I think if I do move to an HID setup I think I might go 4 x 600w - seems a lot of ppl saying 600w is more efficient watt per lumen than the 1ks....

If buying though... that means 4 ballasts instead of 1... 4 hoods instead of 1... etc... Only possible savings would be to setup room with
a flip/flop and run 2 ballasts at opposing 12/12 schedules... not sure if the flip/flop would be less than 2 ballasts...