Hi David –
Air Cooled Set Up 1
The easiest — and cheapest — way to set-up an air-cooled grow light reflector and carbon filter is to hang the filter before your hood and connect the two using a short piece of flexible ducting. Attach your inline fan on the other side of the reflector and vent the hot air directly out of your room (or tent) using more ducting. For best results, keep this path as short and straight as possible. Kinks will restrict airflow and the exhaust/ cooling system will become less efficient the longer the hot air has to travel. Also, keep enough slack in the duct work to allow for your lights to be raised and lowered.
Air Cooled Set Up 2
In my opinion, a much better way to set up your grow room is to use cool, filtered incoming air to remove the heat from your lights and a separate fan and filter to exhaust the air going out of your garden. While this will initially cost you more, it provides greater flexibility, a better growing environment and it’s much easier on your equipment.
Start by attaching your in-line fan to a HEPA cleaning filter outside the room (this is your clean, cool air supply). Run flexible ducting from the fan through your grow room wall and attach it to the vent on the reflector. Attach more flexible ducting — preferably insulated — on the opposite side of your reflector and run it outside. Here’s the layout:
Filter >>> Fan >>> Ducting >>> Wall >>> Reflector >>> Ducting >>> Outside
Tip: You can exhaust this hot air to a garage or other area that you want to heat during winter months.
It is always best to push cool, filtered air from outside your room (or tent) through your air-cooled hood(s). This is preferable for the following reasons:
• All of the air being pushed into your room will be filtered and free of insects, mites, mold or mildew.
• Pushing air into your room will create a positive air pressure which can help keep potential nasties outside.
• Your fan will last longer because it’s not always sucking hot, damp air through it.
Fan & Filter Exhaust System
To get rid of the potentially smelly air inside your garden, attach a separate inline fan to a flange kit on top of your carbon filter. Make sure that the fan and filter are large enough for your growing space and vent this air outside your room using flexible ducting.
Proper Fan Size
It is important that you are using the right size in-line fan (CFM) for the job. To do this, measure the size of your room (tent) length x width x height and divide by 3. This will give you the minimum fan size CFM for your area.
Example: 12 ft. x 10 ft. x 8 ft tall = 960 cubic feet / 3 = 320 CFM
In this example 320 CFM is the minimum fan size that you will need to replace the air every 3 minutes. Once fan size is determined, match it to the appropriate sized filter.