Thoughts on these 2 ducting alternatives?

[JJohnston]

My ultimate plan is to build a shed (8x6) behind my garage for the DC with the duct going through both walls. The shed will be pushed up against the outside wall, but not attached to the house.
Here’s the choice: my miter bench is right up against the back wall of the garage, and that makes duct routing more complicated. I can either take a separate duct for the miter saw through its own hole down low, then take it up to meet the mainline IN the shed, or I can route it up and away from the wall a few feet and join it into the mainline up high before it goes through the wall. Here are some drawings to illustrate what I mean.
I can’t go straight through from the back of the miter saw hood, because that would put the shed too close to the side wall of the house. I’d like to have the space shown in the plan view, because I’ve got an air conditioner near the upper right corner of the shed, and the outlet for the bathroom fan is up on that side wall, and I don’t want to block it.
Any thoughts? Once I put down a few specific pros and cons, I started leaning toward option 2.

I don't plan to return air to the shop; I live in a mild climate. I do plan to filter anyway, just to be a good neighbor, and to soundproof the shed.

Here's alternative 1:

[JJohnston]

Here's alternative 2.

[McRabbet]

I'd agree that Option 2 provides a better solution for the shed space, but there are lots of bends in the route that you've taken to get from below the miter station to the wye that enters the main duct run -- I can't tell exactly from your drawing, but it looks like 8-10 45's are used to get there. Here is one application where flexible duct would be preferable -- I'd run flex from the bottom of the miter station in a "U" to connect to a blast gate and then a vertical straight section ending in a sweep made of two 45's with short straight sections to run toward the main. I'd angle this slightly off the wall and use flexible duct to finish the connection at the wye. I presume you are using PVC (D2729) S&D pipe and associated fittings.

[JJohnston]

I'm not sure yet how I would connect the duct to the miter saw funnel, but yeah, I count 8 45s. But I'm not following you, McRabbet - it sounds like you're describing the same routing I am, except with flex instead of 45s.

[dwdrury]

What I'm thinking is if you position the wye so that with another 45 el and short section in between, your vertical comes down along the common shed / shop wall, inside the shed, to a convenient height, maybe 2 ft off the floor. Then run flex from there through a hole in the wall to the saw. That shouldn't chew up too much shed space. Two problems, though: First, you're going to have to figure out a decent place for a blast gate, maybe rig up an interface point with gate where the duct enters the saw's base. And second, you'll have to run the vertical a sufficient distance away from the wall to make the turn, unless you enlarge the hole sufficiently to make a part of the turn inside the wall.

Really, when you get right down to it, if you're going to use flex, it probably doesn't matter which side of the wall you run the vertical. As Rob (McRabbet) alluded, you could attach a wye to your main line, make an additional 45 turn, and run a convenient vertical on the shop side (not necessarily against the wall), and run flex from there to the saw.

It may also be possilble, as I ponder, to "combine" the two. Put the wye in the shed, and run a piece of straight pipe to another hole such that with the addition of a 45 that's sort of "inside" the wall, the resultant vertical comes out on the shop side, just off the wall. Which also might be what Rob envisioned (I can be slow on the uptake).

Suppose another question is if the shed isn't going to be structurally attached to the shop, how do you feel about shop wall penetrations? You noted temperature isn't much of a factor, but what about pests, critters, rain or resale? If none of that bothers you, would it be possible to make one large opening, as one might for a window, and run the pipe(s) through that? Might make for an easier, neater installation.

With the saw hookup so close to the cyclone, I don't think any of the proposed solutions will choke your airflow too much. Thus the bottom line becomes cost (els vs flex), ease of installation, and asthetics, or at least not chewing up space you'd really rather have for something else.



Regards,
DWD

PS: How's your shoulder, Rob? Neighbor's still struggling with his, been about 6 months in his case. And your wife's heart problem under control?

[McRabbet]

JJ,

DWD is right with his short summary of my scheme:

Really, when you get right down to it, if you're going to use flex, it probably doesn't matter which side of the wall you run the vertical. As Rob (McRabbet) alluded, you could attach a wye to your main line, make an additional 45 turn, and run a convenient vertical on the shop side (not necessarily against the wall), and run flex from there to the saw.

Being so close to the cyclone, it is easier with flex and which side of the mitersaw you go to is a matter of convenience for placing a blast gate. I was thinking flex off the wye at more than a 45 to get the run back to the wall on the right side as you had it -- basically saving you $$$ in fittings.

DWD: My shoulder is back to 100% and I'm back playing golf and working in the shop -- still haven't finished getting my CV1800 installed, but I've made a little progress -- other things keep getting in my way! My wife's challenges have been orthopedic, not heart-related -- she has recovered very well from neck surgery in April and knee replacement surgery in June. In mid-October, she has rotator cuff surgery to remove a bunch of bone spurs and that has been more painful, but she's coming along.

We're headed down to the good old Palmetto State (Columbia) for the weekend to visit our eldest son and DIL.

[JJohnston]

Originally Posted by dwdrury

What I'm thinking is if you position the wye so that with another 45 el and short section in between, your vertical comes down along the common shed / shop wall, inside the shed, to a convenient height, maybe 2 ft off the floor. Then run flex from there through a hole in the wall to the saw.

I must still not understand what you mean, because this sounds exactly like my alternative 1. Can you sketch it?

Originally Posted by dwdrury

Really, when you get right down to it, if you're going to use flex, it probably doesn't matter which side of the wall you run the vertical. As Rob (McRabbet) alluded, you could attach a wye to your main line, make an additional 45 turn, and run a convenient vertical on the shop side (not necessarily against the wall), and run flex from there to the saw.

Again, that sounds just like my alternative 2. Or are you talking about coming straight up from the saw instead of under the bench?

As far as putting holes in the wall, I'd like to keep it to a minimum. Ideally, I'd bore with the smallest hole saw necessary and patch the stucco right up to the pipe on the outside. The hole in the shed wall can be bigger if necessary. There will be another hole in the shed wall to access the outlets I've already had installed on the outside of the shop wall. It's not shown on the drawing, but a lean-to style shed with the same pitch as the garage roof can be 10' high on the high side (the side parallel to the mainline and closest to the cyclone) and will go under the overhang on the garage with about 1 foot clearance. I won't have any overhang on the shed roof along that side, so I will be able to push the shed right up against the garage. It won't touch perfectly, but with a piece of soft, fat weatherstripping around the holes in the shed wall (on the exterior surface), I don't anticipate any weather-related problems there. I'd rather not have a window-sized opening due to the noise.

[dwdrury]

Probably can't make a sketch that would add much to the discussion. Sorry. Yes, they are similar to your sketches, but with the verticals closer to the wall, and eliminating the huge number of 45s in your #2 alternative. I think both Rob and I envision using flex from the saw outlet to a vertical wherever it ends up once you've put in the wye and one more 45. Or maybe even skipping the one 45.

The only point I was trying to get across, and obviously failed, was that you may be able to run the vertical much closer to the wall than is in your sketches, and that, like Rob, was trying to scheme a way to avoid that large number of 45s, which can jack up the cost. That plus the more you can bury the turn in the wall, the closer you can run the vertical to the wall. But that would mean a larger hole, which would give me pause if that wall is the main weather seal for the garage. Over the years I've become a believer in making mods reversable if one needs to bail out.

So, that coupled with your latest comment, I have to agree that the one hole for a main line, then a wye right after the penetration into the shop would probably be best. From there, either all flex down to your saw or one 45 to turn it vertical, maybe a piece of straight to come down to a convenient location for a blast gate but still above head level, then flex over to the wall, then down, then over to the saw. Hope that's more clear. You'll have to weigh the cost of the flex versus the number of 45s you'd need.

As for the large hole saws, largest I've been able to find is 6", and one really needs 6.25 or 6.5 for the pipe. And those 6" ones aren't cheap either. Am still trying to figure out how I'm going to make the holes for my pipe runs. I have to go through some overhead racks (think soffets but with open fronts) in my shop. Right now I'm thinking one of those small palm grip routers and a jig, but that will limit how close I can get to the wall.

Glad to hear your shoulder's back to normal, Rob. Sorry, for some reason my faulty memory had the wrong problem for your wife. Hope she's making progress at least as good as yours. You won't be too far away as I'm down near Hilton Head. If you dont' have a good source where you live, and want some PTEG sheets, there is a Piedmont Plastics in West Columbia. Might have to call first to ensure they have what you want in stock, and have a pickup or trailer to get it home.

Regards,
DWD

[JJohnston]

Here's a 6 5/8" hole saw from Klein tools. And you're right - it's not cheap.

http://www.amazon.com/KLEIN-TOOLS-Di...5727189&sr=8-1

[dwdrury]

Yikes! Probably over $100 after shipping. For three holes, think I'll stick with trying to scheme something cheaper.

Thanks, though.

Regards,
DWD