Static Pressure Question - Ducts and Carbon scrubbers

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Originally Posted by Graywolf

The best way that I have found without information, is to just measure static pressure, which is easy to do with a length of clear plastic tubing. If you drill a hole in the duct and attach a length of clear hose to it, it is possible to loop it around so that it makes a vertical â??Uâ?�, add water to the hose, and see how much higher it lifts the water in one leg vis a vis the other.

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Agreed, the details of the fan involved are important. Wouldn't the diameter of the clear hose be a factor? If the diameter were a quarter inch it would take less pressure to lift the water than if the diameter were say 3". Regardless, my comments still stands. In general terms, a large fan dialed down will produce less noise than a small fan running at top speed. And again, increasing the diameter of the downstream duct will also greatly reduce noise.

The funny thing about pressure is that diameter doesn't matter. You could poke a pin hole in the bottom of the hoover dam, and the pressure would be the same as if you punched out a 3 foot hole. Of course more water would come out of the bigger hole, but the pressure is just dependent on the height of the water column above the hole, not how much water is actually above it. Hope that makes some kind of sense...

You're right, it would be easy to measure the static pressure at different flow rates once I have my system built. It wouldn't do me nearly as much good as knowing beforehand, so that I could design my cabinet around the ventilation system.

Sizing the fan for the grow box is pretty straight forward. Have a look a the fan link in my signature thread.

[quote=Graywolf]
the cfm is directly proportional to the fan rpm, but an increase in rpm requires the cube of the increase in horsepower.QUOTE]

Isn't horsepower increase the cube root of RPM2 minus RPM1?