Lowering Temperature

So I am pretty much doing everything possible to lower the temps and still cant get into the 70's. I have a 3x2x5 foot grow tent with a 400w HPS, 200 cfm inline fan and properly rated filter. The filter is in the tent and is ducted to the light then ducting goes out of the tent to the fan then out through the bathroom vent. I took the vent down and ran my duct to the existing duct in the bath fan housing. So its like:
hot air -> filter -> light -> fan -> bath vent
The intake is passive. The ambient temp of the room is around 72-73. What more can I do to get the temps in that nice range or what am I doing wrong?

Are you using a cooltube? Also you may want a bigger intake. More air flow makes the fan run/cool better. What are temps in the tent?

Yes I am running a cooltube. What do you mean by a bigger intake? Open up more vents for passive intake or an active intake? The temps right now are sitting at around 84

Yes more vents. It was broken down for me like this.

"Try sucking air through a straw all day and see how long you last."

But imagine that straw was a funnel bigger at the entrance and smaller at your u mouth(exhaust fan). Think how much air would move

Thank you so much! I have heard so many places your intake needs to be about a little bigger than your exhaust. So I didn't open all the vents because I thought I needed to keep them closed for negative pressure so no smell leaked. But after stating it like this it makes so much more sense, and I have opened all the vents on the bottom of the tent.

So my temps still appear to be high. But I don't know which thermometer to believe because one is reading 78 and the other is reading 84

Mine read two diff. temps two.But 84 Realy is a peak temp so try to put a fan an lights with it blowing hot air out of tent and a fan lower out of tent blowing fresh cool air in.Helps with Co2 a little to.

Ok so 200 cfm would require a passive opening or 8 inches round or 64 sq iches of opening at min , and you say you connected it to your bathroom duct if that is smaller then then the duct you are running to it or you are obstucting the flow the way you hook it up in yopur bathroom that also would need to be corrected.

This was one of my hardest lessons to learn. The actual room temperature is in the shade, the best place to read is the shade of your canopy. You have bright hot lights, any direct light will read false

dtowndabber said:

This was one of my hardest lessons to learn. The actual room temperature is in the shade, the best place to read is the shade of your canopy. You have bright hot lights, any direct light will read false

Click to expand...

yep, that or get an IR thermometer.

I have a slightly larger space with 400w and later (flowering) 600 watt. Active intake makes a huge difference for me (big ass zalman fan that cools the air, inaddition to a passive intake)

Those bath vents aren't that good though and that's a bit of an understatement, if you really want to improve things, get a real snail or tube fan. With the filter attached and the rest of the path it takes it won't reach that 200cfm, not even close.

I use a tube fan with thermostat, problem solved.