Duct Sizing for Light Ventilation

This diagram shows how my sealed room is arranged.



The blue arrows show how I have laid out the ducting for the air that will cool my two air cooled hoods (one for veg and one for flower). My plan is to use a 6" vortex fan with 6" insulated ducting throughout. The fan would pull air through the floor of my room then split that air flow into 2 separate 6" ducts that cool the two hoods. After the the cooling air leaves the hoods, the two ducts will merge together with a wye connector prior to the fan. I really want to stick with one fan for this.

Is my ducting sized appropriately? I am concerned about the airflow being unbalanced between the two lights. My gut tells me that I should be using 4" ducting for the lights where they combine into a 6" duct at the fan.

What do you think GK?

 

I am using a vortex powerfan 6" (this one). Would you be concerned that the air flow would be uneven between the two lights if I stick with the 6" ducting? This is for a sealed room setup, so the intake is passive and the ducts run from the intake, to the lights, then out the wall with the fan on the outside of the room.

 

If possible use the hard duct lines, with that long of a line the stuff from the hydro store slows the flow a lot.
Also for the trunk 8" with a reducer for the fan would be best.

 

Thanks greenjah, why should I use the 8" for the trunk line? Is it to help equalize the vacuum on both light ducts?

 

What's up folks!! First post in quite a while. Greenjah,s got a great point, the bigger line would create less resistance and smoother air flow. His advice on the solid duct is spot on as well, far less resistance with a smooth interior surface in the duct. Also try to keep the angle down at the connections, the air flow will be better with 45 degree compared to 90. Looking at your diagram, you've probably already thought about that!! Keep the air flowing, it can make all the difference. Good luck!!
Be Cool, CG

 

Thanks for the feedback CG! So here is the new plan.

Updated Ducting Design by MedicineMan posted Sep 9, 2016 at 3:03 PM

Thanks all for your contributions! I'll post some pics after I get it set up.

 

452 CFM

 

The 425 should work fine. I Would run the system for 24 hrs like you have plants in there to see what your max temps run in the room.

 

Nippie makes a good point. I have ac to my grow room, and run a 400 and a 600 I added a ac vent to my central air.
I also exhaust into a sewer line. All my stink goes out the sewer line.
If your running a carbon filter your going to need a bigger exhaust fan.

 

If you go the portable AC route, figure on a dehumidifier too. Then add CO2 to your sealed room.

The drawings seem to only show fan cooling air. If you don't use a sealed room, you'll need a source of fresh air, an exhaust fan and a carbon filter. This can work in the right climate, but you'll be at the mercy of the weather.

 

I guess I had a brain fart. I just saw the 1000 watt bulb in the room. Nippie I'm glad you noticed.

 

Wow, I really appreciate the feedback guys! You are making some good points. I did not give you all of the details about the room to try to simplify things but I realize now that you need this info…so here goes. There are seedlings in the room now (and they are starting to smell delicious). They will be heading into veg (600 W HID) in the next few days, so I need to get this ducting situation sorted out soon. J

I live in Virginia, where the summer temps and humidity are too high to grow without A/C. I built this room in a corner of my detached garage with the intention of running it as a sealed environment during the hot months (May – September) and as an open environment during the rest of the year when humidity and temps are lower. The design that I provided before is for Sealed Operation. In this setup, air is pulled through the floor of the room > through the lights > then out of the room > and into a fan with a duct silencer on the exhaust. During sealed operation, there is a portable AC with dual exhaust. I don’t have a tank yet, but I am planning to put run with CO2 when sealed. I still want to run the fan through the lights to keep the temps down even with the AC because the AC is 1,000 Watts and the fan is much more affordable.

I was running the 600W for a couple of days (when it was 85 degrees) outside and the room temps got over 90 degrees really fast.

For the Open Room Setup:

The ducting inside the room (that cools the lights) is disconnected from the floor intake and attached to a carbon filter. The floor air intake is now open to the room and provides passive airflow into the space. Air is continually exhausted from the room through the carbon filter with no other changes to the ducting. So the air flow goes like this: Can Filter > through the lights > out of the room > into the fan > exhausted through duct silencer.

I currently have 2 20Amp circuits dedicated to the room (one for lights and one for outlets). I can add another one if needed.

It sounds like I will need to upgrade my fan from 6” to 8” to be safe. With this new information, would you change anything? Do you agree that I need a bigger fan?