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Background: As the title says, I'm about to (within the next week or 2) install a dryer booster for a new (to my friend, not newly built) house. The dryer vent goes through a couple bends behind the wall but then goes straight up about 15-20 feet where it exits via the roof. After cleaning out two grocery bags worth of lint from the ducts I still couldn't feel anything blowing out of the roof exhaust so I took that to mean it was too much piping for the dryer and it needs booster fan.

Here's the dryer duct in the attic.:

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Rough plan: My rough plan is to get a few pieces of 2x4 or something (cue expert weigh in here) to make a support for the booster midway up the pipe in the attic so it is inline. The booster comes with a current sensor so I'll have to run romex up to the attic from the existing outlet (actually I'll add a new outlet just for the dryer so that washer doesn't trigger the fan). Luckily it's a gas dryer so it'll only be 110v which makes the current sensor hookup easier than alternative. The switch will be in the attic and since the fan has a 3 prong plug I'll add a plug in the attic as opposed to hard wiring. Here's a crappy drawing of my electrical plan.

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Questions:

Is my electrical diagram OK (not the diagram itself but the meat and potatoes of it)? I didn't draw them in but the switch will be in a junction box and the new attic outlet will be mounted to a beam, very close to one another.

The manufacturer says to install the fan 15' from the dryer and 5' from the termination of the exhaust. I understand the 15' is to ensure that the lint is dry before it gets to the motor but I'm not sure what the 5' from termination is for. In any event, assuming I put the fan directly inline of the existing pipe, I'll probably be cutting one of those clearances a little short. Should I add more piping with a couple 45s to make a U in order to ensure the 15' and 5' are strictly met or just get it centered as best I can?

Are there any other red flags that I may be neglecting?

  • One problem with your diagram -- the current sensor switch needs to switch the hot going to the new attic outlet, not the neutral. – ThreePhaseEel May 3 '16 at 2:50
  • @ThreePhaseEel oops....fixed. – Dean MacGregor May 3 '16 at 3:13
  • Also -- tips: 1) you can run 12/2/2 from the existing receptacle to the current sensor, and 2) the outlet in the attic can be a single receptacle instead of a duplex receptacle (unless you want a duplex receptacle up there for other reasons, in which case I'd make it half-switched). – ThreePhaseEel May 3 '16 at 11:40
  • The only thing I have heard about these boosters is they suck two much air through the dryer and the clothes take longer to dry. I understand wanting to get rid of the lint but it may be better in the long run to just clean the pipe once a year or so. – Ed Beal May 3 '16 at 13:28
  • @EdBeal from what I've read, dryers don't have the force to blow out of vents longer than 15 linear feet equivalent where a 90degree bend is worth 5 feet and 45s are 3. I've got about 20-25 feet equivalent of vent. To make matters worse it's straight vertical which shouldn't matter for air pressure but does make it much harder to push lint out. Additionally it's a gas dryer so the flue gas goes out the same vent as the lint so there's all the more reason to make sure it escapes the house. I looked for mentions of boosters making clothes take longer to dry and can't find anything. – Dean MacGregor May 3 '16 at 16:24

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