DC: Bigger is better, no?

[Eric DeSilva]

[start rant]
I moved to a new place in late Sept., and for the very first time, have space for a basement shop. Between shopping CL for stationary tools, moving very heavy objects, and rewiring the basement for 230V and supplemental 115V outlets, this has been a lot longer process than I expected. But, I now have a running Delta Unisaw Platinum Edn TS w/a 50" Bies. fence and a 14" powermatic BS (wasn't really shopping for a BS, but this was in mint condition and too cheap to pass on). Still considering options re: jointer, but thinking I may give the wallet a bit of a rest. Also hadn't reckoned on the difficulties of getting a DC set up... (When do I actually get to build something!!)
[/end rant]

Anyway, on to the real question. For DC, I bought a JDS Cyclone 2000. It has both an 8" and a 4" inlet. I've heard of people recommending using 6"--is installing 8" overkill? I have to believe working with 6" pipe is easier than 8" pipe, and I could just put a 8-to-6 adapter at the DC unit. Or, is going 6" penny-wise pound foolish?

[Lee Schierer]

In a DC system you want more volume than velocity. Reducing the 8" to 6" will give more velocity and less volume and will most likely decrease the overall performance to some degree.

[Steven Wilson]

Run an 8" main for awhile and then branch to two 6" trunk lines

[Eric DeSilva]

Thanks. Guess that is what I figured, was just hoping someone would tell me running 8" ducting was way overkill.

[glenn bradley]

Thanks. Guess that is what I figured, was just hoping someone would tell me running 8" ducting was way overkill.

That would be nice . . . to your pocket book. However, I agree; 8" main and 6" drops. Maybe drop again to 4" for the BS just because hooking a 6" port to a 14" BS can be a chore.

[Jim Becker]

Thanks. Guess that is what I figured, was just hoping someone would tell me running 8" ducting was way overkill.

You should be able to assume 8" is not overkill for the initial portion of the main run for that particular machine...presumably, they have designed it to perform well with the volume of air necessary to fill that pipe. (I'm not really familiar with the specifics of the JDS system, only Oneida)

The general method for ducting that Oneida and some other dust collection focused firms use for design is to carry the main at the inlet diameter at least to the first major branch and then reduce as you move out into the shop. This is partially assuming that multiple gates will be open as they would in a multi-person shop. For shops like most of us have with only ourselves to contend with, a constant diameter is more workable (and sometimes more economical), so once you drop to 6" at the first major branch, you can likely maintain that for a good part of your system with good performance since we generally only use one machine at a time. Your drops can be as appropriate for your tooling.

Most of my duct work is 6" beyond the first major branch, although the main drops to 5" half-way across the shop due to the legacy design. (My cyclone has a 7" inlet) Drops are 5" or 4", depending on the tool and location...most being 5". Performance is excellent.

[Eric DeSilva]

Is 8" duct commonly available? Are straight runs and elbows something I can get at the borg, or am I going to have to resort to some sheet metal fabrication place? For those with systems in place, did you guys do it yourself or contract it out? My few forays into running ductwork left me bleeding profusely...

[Steven Wilson]

8" (and larger) is readily available from suppliers of air handling equipment - not the Borg. Or you can just go to Oneida. If you're dealing with lower HP systems (say 5hp and below) you can get away with snap lock pipe and adjustable elboes which are fairly inexpensive.

[Alan Schaffter]

I hope you are prepared for sticker shock. 8" PVC is too heavy and expensive. 8" metal is even more so, especially the fittings!!!

Personnally, there are few DC systems out there except the larger commercial ones that need larger than 6" pipe. I would go with 6" (thin wall) ASTM 2729 S&D PVC. I would run 6" from blower all the way to most machines.

[Eric DeSilva]

Ouch. Amen on the sticker shock. Based on what Steve said, I checked the Oneida site... Pricing things out for a mostly 8" run and three splits, dropping down to 6", plus other hardware... I'm looking at $875. Not wallet-friendly.

[Bill Arnold]

Ouch. Amen on the sticker shock. Based on what Steve said, I checked the Oneida site... Pricing things out for a mostly 8" run and three splits, dropping down to 6", plus other hardware... I'm looking at $875. Not wallet-friendly.

When I bought my Super Gorilla, Oneida provided a duct design based on the configuration of my shop. An 8-7-7 wye was specified at the inlet with 7" duct to the first drops in each direction. The first drops are 7-6-5, changing the 7" to 6" duct for the continuation of the runs. Drops to each machine are 5".

[Steven Wilson]

Eric, how you design your runs and what fittings you choose will greatly influence how large the wallet biopsy will be. The important run of 8" is only a few feet and that is to get a proper flow going into your cyclone. If you're under 5hp then you should be able to use snap lock pipe and adjustable elboes (a lot less expensive than smooth wall welded elboes). A typical first section will be 2-3' of your largest pipe (8"), a couple of adjustable elboes and a small piece of pipe to get your pipe onto to ceiling (a big S), then a couple more feet of large pipe and then to your first wye (8x6x6). From there you're running 6" until your drops at which point you could terminate to a 6x5x5 wye, 5" blast gates, and 5" flex or run 6" all the way and terminate in 6" flex. Now that you know the price of fittings you should be able to modify your piping diagram to minimize cost and still meet your needs. Just by rearranging my design a little bit I was able to save 30% in total piping cost. For example I needed 3 blast gates (5") fairly close together. I ran a 6" drop to a 6x5x5 wye and on to a 5x5x5 wye. That gave me three 5" ports by using the two wye's. This is cheaper than buying a 6x5x5x5 wye.

[Jim Becker]

Check your yellow pages for local suppliers of spiral pipe...you can often find locally manufactured product for not much different cost than snap-lock. But honestly, a few feet of 8" 26 gage snap lock isn't going to break the bank (go to an HVAC supplier or order from Oneida, Kencraft or Air-Handling Systems) and from there you can reduce at your first branch to 6"...and choose to use the material you prefer to use. Getting the right fittings, IMHO, is more important as the direction of flow is different than metal HVAC work and longer-radius components for PVC are not necessarily ubiquitous, either.

[Mark Hulette]

wallet biopsy

That's a new one. Just thought its funny.