View single post by asteysn2
 Posted: Sun Oct 8th, 2006 09:31 pm
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Joined: Mon Mar 21st, 2005
Location: San Marcos, (San Diego North County), California USA
Posts: 159
Trying not to get too technical but a "good" vent length is one that will not cause the "static pressure" to rise above 1/2 to 3/4 inch W.C.
A rise in static pressure will mean an accompanying drop in velocity pressure, as the two are inversely related.
Anything that will cause a rise in SP should be avoided as it will slow down air movement through the dryer.
Avoid long runs (12 feet and on would be considered long)
Avoid multiple bends. (a 90 deg bend is the same as effectively adding 5-9 feet of line)

I saw a house dryer instalation last month where the actual length of the run was about 35 feet, and there were 4 90 deg bends in it as well. Thats about 63 feet of effective run!

Since there was no way the run could be shortened, I installed a dryer boost fan in the last 1/3 of the run with a current sensing switch to activate it.

BTW, if youre wondering what the dryer insides and the venting looked like, it was about as clogged with lint as one can be... A REAL FIRE HAZARD

One more thing to consider.... why is it that we commonly light a fire in a lint filled machine and theres no fire extinquisher anywhere in the vicinity???
Bob Sankie,
Coastal Appliance, Heating & A/C
Serving San Diegos North County

Robert Sankie
Coastal Appliance, Heating & Air