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Thread: HVAC duct for 10hp dust collector?

  1. #1

    HVAC duct for 10hp dust collector?

    So I am looking to run a 12 40ft trunk line with 6 drops from my generic brand industrial 10hp dust collector. It has 3 large 24 bags and 3 large 24 x 72 filters. Not sure on the impeller size but its not huge. My question is would it be ok to use standard off the shelf 12 HVAC duct instead of spiral pipe? I can not get spiral pipe locally except in 10 foot lengths and it is very expensive as a special order only item at my local HVAC supply house.

    I would prefer to use standard HVAC duct instead but I am concerned that my dust collector will implode the duct. What do you guys think? The HVAC duct will only cost me about $120 or so for 7 pieces. If you guys think that it will implode the HVAC duct I guess that I could save up and order the spiral pipe and cut it into 5ft sections myself. If I do this I would still use the HVAC wyes and elbows as I am not spending $60+ each on the spiral pipe wyes and $40+ on their elbows.

    So....will the HVAC duct implode under the pull from my 10hp d/c? If so, is there anything that I can do to strengthen the duct or prevent this from occurring?

  2. #2
    Join Date
    Feb 2003
    Location
    Bellingham, WA
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    1,850
    Years ago I upgraded from a 2 HP cyclone to a 10 HP that a friend gave me. I hooked it all up with revised HVAC ducting and eagerly flipped the switch. All of that snap-lock ductwork was sucked flat in 30 seconds...
    JR

  3. #3
    Join Date
    Mar 2003
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    49,634
    "Off the shelf" HVAC duct is very thin gage metal...no way would I attempt to use that for that big system, let alone a smaller one. Even 26 gage stove pipe might be challenged for this particular air mover. Try Spiral Manufacturing or KenCraft to see what they can do to provide you with appropriate duct for your application. You may also be able to get a local firm to make what you need...there are places that fabricate custom duct work for various applications and most can work with heavier material.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  4. #4
    Quote Originally Posted by J.R. Rutter View Post
    Years ago I upgraded from a 2 HP cyclone to a 10 HP that a friend gave me. I hooked it all up with revised HVAC ducting and eagerly flipped the switch. All of that snap-lock ductwork was sucked flat in 30 seconds...
    That is what I am afraid of. I found a place locally that can order 12 spiral pipe. Its like $60 per 10ft but I would have to cut it into 5ft pieces myself and figure out a way to connect it to my HVAC wyes. The wyes will hold up fine I have been told. Its the HVAC duct pipe that work work.

    If I get the 10ft sections of spiral pipe, what would be a good way to cut it up? I have most every kind of power tool for wood working. No metal working equipment. Would a jig saw or saber saw work? Or a grinder? And how would I attach it to the HVAC wyes? I guess they make female to female couplers just not sure if they can be found in 12?

  5. #5
    Join Date
    Mar 2003
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    SE PA - Central Bucks County
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    Be aware that HVAC wyes are "backwards" for dust collection purposes so you'll need to modify them. You can cut spiral with a jig saw and a metal cutting blade quite easily. Don't forget you'll need the sleeves for joining the pipe...spiral doesn't have crimps.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  6. #6
    I think the key to success here is how much you "leave open". Cyclones won't work properly unless there's enough airflow. My 3hp Laguna requires that at least 2 of the 4" ports be open at all times.

    I visited a large production cabinet facility recently...the kind with the big Torit units outdoors...all of their main ducting branches were wide open (the entire diameter) of the duct at the "far end". Numerous drops along the way to all kinds of machinery. Those drops would still "suck a cat off the floor".

    You don't NEED to be pulling enough suction to flatten your 12" ducting. For that matter, with a 10 hp collector you don't need anything like 12" duct in a run of "only" 40'. What you're concerned with is that you get adequate cfm at your furthest drop from the collector. Go ahead and build your HVAC duct system and run the main line straight beyond the Y for the last drop. Leave the end wide open and (either by measuring the airflow or experimenting while the "last machine" is operating), determine how much to choke down the open end. You can do this with a sheet of heavy cardboard. If, for example, you determine that you need to choke it down by 50%, then put an end cap on it with an appropriate sized hole. You may find that you don't need to close ANY blast gates in order for your system to work properly.

  7. #7
    Do you have a bandsaw? A metal cutting blade at slow speed would work well. Alternatively, borrow, rent, or buy (on Craigslist, for example) a hand held metal cutting bandsaw and use two people. One holds the saw while the other rotates the pipe while it's flat on the table.

  8. #8
    I believe they make female to female couplers. That is all that I will need. Nothing on the wyes need modified to my knowledge. The spiral pipe is all males on both ends. The spiral pipe should mate up to the female end of the HVAC wyes no problem and for the male end of the wyes I can use a female to female coupler. Right?

  9. #9
    You need to modify the wye because it's made for air flow in the opposite direction. You don't want any crimp that's inside another pipe facing INTO the direction of the airflow, so you'll need to cut the crimped end off of the wye and crimp the end that wasn't crimped to begin with. The tool to do this is about $20 online. You'll want to use tin snips, wrap blue painter's tape around the pipe behind the crimp and "creep up on it" with the tin snips from the open end.

    Use aluminum foil tape and tape the full length of every "pop together" piece of pipe BEFORE putting the pieces together, then tape every joint and every seam on the "adjustable elbows". Never use a 90 degree turn...make 2 turns of 45 degrees by putting two adjustable elbows together any time you need to turn 90 degrees. This "sweep" makes a huge difference in resistance and keeps down clogging.
    Last edited by John Brougher; 08-23-2019 at 10:56 AM.

  10. #10
    Closet Piping.jpgPipe Run to Shop.jpg

    You'll have to tilt your head to the left because both of these photos are sideways. This shows my piping within the soundproof closet where my dust collector resides. The intake to the DC is 8" and immediately reduces to 6" with a short piece of 6" flex to keep vibration from the machine from transmitting through the metal duct.

    The first wye is turned 90 degrees downward using two adjustable elbows and a short piece of flex hose which is tied into a 6" to 4" reducer and a 4" blast gate on the through wall (DustRight) port. My CNC machine is immediately adjacent to this on the other side of the wall.

    The second wye is angled upward and connects to the 6" duct visible in the 2nd photo. It rises to the just below the ceiling height before another (approximate) 45 turn takes it through the wall parallel to the ceiling and through the next room. The straight out end of this second wye is reduced to 4" and passes through another DustRight through wall port. The "shop cleanup" hose is connected to that.

    I'm not done running duct through the rest of the shop just yet, but I'll have a straight run 6" main line running along a wall (about 10' off the floor) for 30' where it will make another "double 45 degree" turn and continue for an additional 12' to the last drop (for a hose that will be shared between the lathe, the miter saw, and the table saw). The long (30') run will have three drops constructed from 6" wyes which will reduce to 4" just before the blast gate & hose connections. I'll share these between the drum sander (which needs two when running), the jointer, the planer, the band saw. the router table, the radial arm saw, and the downdraft table. I'm a one-man shop, so the most I'll have going at once is the CNC and any one other tool.

  11. #11
    Find a real sheet metal hvac shop.

  12. Quote Originally Posted by Darcy Warner View Post
    Find a real sheet metal hvac shop.
    The original poster said that the price of the spiral pipe (available to him only through the local (real?) HVAC shop) was higher than he wanted to pay. It's pretty rare that any HVAC shop would have the capability to fabricate round ducting in this day and age, so his whole point was to come up with something cheaper that would work.

  13. #13
    Quote Originally Posted by John Brougher View Post
    The original poster said that the price of the spiral pipe (available to him only through the local (real?) HVAC shop) was higher than he wanted to pay. It's pretty rare that any HVAC shop would have the capability to fabricate round ducting in this day and age, so his whole point was to come up with something cheaper that would work.
    Really? I don't live any where near a huge city, but I know of no less than 6 places I can drive to in 30 minutes and pick up almost any size pipe, fitting or custom part needed.

    Sometimes being cheap, is very expensive

    4 of those shops, make their own spiral pipe.

    Find the actual tin knocker shop, not a walk in HVAC supply house.
    Last edited by Darcy Warner; 08-23-2019 at 3:38 PM.

  14. #14
    Join Date
    Feb 2009
    Location
    Bay Area, CA
    Posts
    322
    It can't collapse if it stays round. Yeah, I know ... duh ...

    A friend of mine built an airplane from carbon fiber tubing. To prevent buckling, they glued 'biscuits' laminated from balsa and foam inside at increments of 'X' x the diameter of the tube.

    You could make split rings of plywood, spaced along the outside at 3 or 4 foot intervals. You need something snazzy to hang it with anyway, right?

    And, 12" sounds kinda big for 10 hp.

  15. #15
    Will keep in mind what everyone is saying. Do you guys agree that 12 duct in a 40 to 50 run with 6-8 drops on a 10HP d/c is not necessary? Or would I be fine with 12? The inlet to my d/c is 12. Would it be ok to put a reducer on the front end and instead use an 8 trunk with 6 drops? I will experiment with leaving various blast gates open in order to improve overall performance.

    I will be ordering spiral pipe from the only local vender that carries it and will be forced to cut it myself. The spiral pipe comes in 10ft lengths but I will cut it down to 5ft lengths in order to fit the wyes in their optimal locations. Will cut it with a jig saw using a metal cutting blade. Or I might borrow a metal cutting bandsaw if I can talk my buddy into it. Will order the crimper tool and modify the wyes as suggested above. Although, I should note that I used standard 6 HVAC duct, wyes, elbows, reducers, ect in my previous dust collection setup at my old shop and did not modify the wyes or anything else to ensure that the crimped seams were not in the direction of air flow and I never had any performance issues with that system. Never even had a clog. Of course I always use two adjustable 45s instead of one single 90 degree elbow.

    Hopefully the spiral pipe wont break the bank! I believe that it cost around $55-$60 per 10ft here where I am in the rural south. There are only 3 HVAC suppliers in a 2 hour radius so my options are limited. I did manage to get a quote from Blastgate dot com and they wanted $40 per 5ft but for 7 sections shipping was over $300. The total was $655 for 7x 12x5ft sections. Which is more than I wanted to spend on just those parts.

    Anyone know of what the connectors that I will need to hook the spiral pipe up to the standard HVAC wyes are called and where I can find them to purchase? Or any links to good sources for them?

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