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Thread: Proper pipe size for outdoor venting???

  1. #1
    Join Date
    Jan 2006
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    Grand Forks, ND
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    2,216

    Proper pipe size for outdoor venting???

    Ok I have a PM1300 dust collector that I have setup with an Onida super dust deputy, I have the fan and motor assembly mounted to my wall and the DD mounted directly onto the housing, so I'm not using any other parts of the original dust collector just for clarification. I plan on venting outside now that I'm in the country with no neighbors. I have made an adapter for the exhaust that is 4" ID that will exit out the wall.My DC unit was rated at 1300CFM at 6" and I'm assuming that is measured at the inlet? I'm using 5" ducting for my system right to the machine. So Im curious....... if Im using 4" for the exhaust with no filters am I restricting the performance of the DC?
    A bus station is where a bus stops. A train station is where a train stops. My desk is a work station.

  2. #2
    I have a 6" pipe system with 3hp cyclone, and ran my vent outside 8", same as it goes to the filter. I made an 8" blast gate so on really cold days can use the filter instead of venting outside, and it really does restrict my system. Built my own dryer vent style vent to avoid having birds or hornets in the pipe.

  3. #3
    Jeff,

    I believe the answer to your question is yes. Restrictions anywhere in the flow path reduce performance. I increased the size of my exhaust vent to 6 inches to reduce restriction. I found it easy to find a 6 inch dryer style vent to put in the wall.

    Jim

  4. #4
    Join Date
    Jan 2013
    Location
    Williamstown,ma
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    981
    In the simplest terms, whatever the inlet size is on the collector, so should the replacement air source be.
    Anything other, and there will be sacrifices to collection ability and efficiency.

  5. #5
    Join Date
    Mar 2008
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    Between No Where & No Place ,WA
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    Question in mind: you live in North Dakota with cold winters, how much warm shop air will you be loosing by outside venting?

  6. #6
    Join Date
    Nov 2012
    Location
    North Dana, Masachusetts
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    111
    Quote Originally Posted by Jeff Monson View Post
    Ok I have a PM1300 dust collector that I have setup with an Onida super dust deputy, I have the fan and motor assembly mounted to my wall and the DD mounted directly onto the housing, so I'm not using any other parts of the original dust collector just for clarification. I plan on venting outside now that I'm in the country with no neighbors. I have made an adapter for the exhaust that is 4" ID that will exit out the wall.My DC unit was rated at 1300CFM at 6" and I'm assuming that is measured at the inlet? I'm using 5" ducting for my system right to the machine. So Im curious....... if Im using 4" for the exhaust with no filters am I restricting the performance of the DC?
    One advantage to venting outside is that you can put the cyclone outside, and also the bin that collects the dust. When emptying the bin, all the dust that comes out stays out of the shop.

    On pipe size, I increase the diameter when the pipes go through the wall. This causes the air to slow down, so that the dust falls out of the air stream sooner. My "cyclone' is just box trailer. I installed blast gates just building wall to be able to close up when the blowers are off. he reason to put the blast gates outside is that they are pressurized, and a small amount of dust come out.

    Concerning heat loss, in a one person shop it's manageable. Having the right size blower for the job at hand helps. I have a little blower for most stuff (6" inlet), a central vac, and a large blower (12" inlet) for milling. Even on cold days, like two weeks ago when it was a high of 10 degrees (F), it will stay above 55 degrees in the shop. It's worth it for clean air.

  7. #7
    Join Date
    Jan 2006
    Location
    Grand Forks, ND
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    2,216
    My shop is 60x40 with 12' sidewalls, I have floor heat so heat loss from running a DC for an hour doesn't really scare me. I just thought a filter would have to reduce the efficiency of the system even when it's new? So I was looking for opinions if a smaller pipe would reduce performance as much as a filter.
    A bus station is where a bus stops. A train station is where a train stops. My desk is a work station.

  8. #8
    Join Date
    Sep 2016
    Location
    Modesto, CA, USA
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    3,478
    Pipe should be the same diameter or larger as the fan intake and exhaust, whichever is larger. Even bigger is better as it will help reduce noise. I suppose you could exhaust in metal pipe and have it inside a duct for incoming makeup air to reduce heat loss.
    Bill D

  9. #9
    A dirty filter is more restriction than a smaller pipe (in the range of 4-6 inches) in my experience. I like outside venting. No filter cleaning is a big plus.

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