Need some advice on DC Plumbing

[ryan.s]

I'm getting ready to layout my duct work for my DC and need some advice on a few items. I'm running the delta 50-570 on a 110 volt circuit. I have about 11 tools I'd like to connect to the DC with the longest run being about 20 feet plus or minus a few feet. Here go the questions;

1. I've read that for this class of DC a 5 inch main duct is optimal. The only problem is 5 inch piping is hard to find and what ever is available costs an arm and a leg. Will I regret going with 4 inch ducting all around instead of the 5 or will I not notice enough of a difference to make it worth while?

2. Seems like a lot of guys run the duct work on the ceilings of their shop. Is there a reason for this other than to keep the duct work out of the way? I was thinking of running the plumbing about 3 or 4 feet from the ground along the walls. Most of the connections to my tools would be at this height and don't anticipate I'll be losing any wall space to the plumbing. The only draw back is the hose that will be connected to the table saw which sits in the middle of the shop. It will have to run along the ground which I hope won't cause too much of a tripping hazard.

3. If I decide to the go with the 4 inch hoses will PVC help the flow of air versus the flex hoses at least for the main runs? I already have 40 feet of flex hose but am thinking of using the black pvc pipes they have at my local home depot for the main runs to the DC.

Thanks in advance for the help!

[JTimmons]

1. I've read that for this class of DC a 5 inch main duct is optimal. The only problem is 5 inch piping is hard to find and what ever is available costs an arm and a leg. Will I regret going with 4 inch ducting all around instead of the 5 or will I not notice enough of a difference to make it worth while?

I am not sure you're going to notice that much of difference between 4" and 5" at least I can't see there being much difference, I got 4" myself.

2. Seems like a lot of guys run the duct work on the ceilings of their shop. Is there a reason for this other than to keep the duct work out of the way? I was thinking of running the plumbing about 3 or 4 feet from the ground along the walls. Most of the connections to my tools would be at this height and don't anticipate I'll be losing any wall space to the plumbing. The only draw back is the hose that will be connected to the table saw which sits in the middle of the shop. It will have to run along the ground which I hope won't cause too much of a tripping hazard.

I have seen plenty of shops where the duct work is ran along the walls, I think ceiling runs are mostly to keep it out of the way. Some of my runs are along the floor and I don't have any problems. If running it along the walls makes it shorter for you than that's better anyway, the shorter the better.

3. If I decide to the go with the 4 inch hoses will PVC help the flow of air versus the flex hoses at least for the main runs? I already have 40 feet of flex hose but am thinking of using the black pvc pipes they have at my local home depot for the main runs to the DC.

Try to use as little of the flex hose as possible, the smoother the surface is the less restriction you are going to have, ideally it is said that you should use metal duct work for DCs and PVC second.

I am no expert though, may want to read up on http://billpentz.com/woodworking/cyclone/Index.cfm

[LarryG]

Basically, +1 on JTimmons' comprehensive reply. I've just plumbed my new shop space with 4" PVC. I ran the hard pipe as close as possible to each tool and then made the final connection with a piece of 4" hose not exceeding about four feet in length. Counting all the turns and the hose, the longest run is probably upwards of 30 feet. The system is powered by the HF 2HP DC, and it works great, even for the CFM-hungry drum sander.

Not familiar with the black PVC pipe you refer to, but I would suggest the tried-and-true green sewer and drain (S&D pipe) and matching fittings. The reason is that this will give you the closest and easiest (to the best of my knowledge) match-up to standard 4" dust collection fittings. A 10' stick of the green pipe will run you $10-15 and the fittings are two to four bucks apiece, depending. Other kinds of pipe have certainly been used but to my knowledge the green S&D results in the least amount of hair-pulling when you go to make up all your connections.

Tom Miller helped me design my system and may have some additional thoughts for you, if he sees this thread.



In the photo above, you can just see the on-the-floor run that serves my cabinet saw. It's not ideal but it's not in a major traffic aisle and I've already learned to step over it when I'm in that part of the shop, so NBD.

[Garasaki]

4" circle has an area of 12.5 square inches.

5" circle has an area of 19.6 square inches.

That means going with 5" pipe gives you 57% more area.

If you understand how a fan curve works, you can imagine that a DC has a very steep fan curve - they are intended to provide lots of airflow at low static pressures. I have never actually seen a DC fan curve (although I'd love to...if someone has one they can post that'd be sweet).

A steep fan curve means that a small decrease in static pressure (think of that as the resistance of the system) results in a large increase in airflow.

If you know aerodynamics, you know airflow drag (resistance) is based on the square of the velocity of the air.

What follows is a basic run thru of the simplified calculations one might use to find a comparison of the resistance thru a 4" vs a 5" duct. It is only meant to show the trend, the order of magnitude, the general idea of what the numbers might be. PLEASE do not take the following to be concrete, 100% correct evidence. These are not real world numbers.

Velocity thru a round duct (assuming, since I am no CFD expert, uniform flow) would be based on volume / area. Assume the same volume (which really isn't true) which we can use as 1 CFM to make our math a whole lot easier, and the velocity thru the 4" is 11.52 and the 5" is 7.3 (note the decrease of 57%).

Again, resistance is based on the square of the velocity. So assuming constant values for all other inputs (not a true assumption), the resistance of the 4" duct would be 132.7, the 5" duct 53.3 (throwing units right out the window at this point).

So, looking at it from a pure percentage standpoint, and making a lot of simplifications, the resistance of a 4" duct will be 250% (2.5 times!!) that of a 5" duct. And again, because of how the fan on a DC works, even small differences in resistance create big differences in airflow.

Again, this is NOT a perfect analysis. The formula's above are simplified. Numbers are arbitrary. Regardless of that, the trend should be obvious.

I would go with the biggest duct for your horizontal runs as possible. Vertical runs are a difference story (if you believe the bill pentz thesis). I promise you can find cheaper if you look around and make some phone calls.

[LCHIEN]

I agree with Garasaki, going from 4" to 5" will better than halve the plumbing resistance. (resistance due to the piping) which is the principle cause of CFM reduction. If keeping the CFMs up is important, then 5" is optimal as you say. But, like you also say, 5" pipe and accessories are hard to find. Some time back I proposed running parallel pairs of 4" pipe to achieve the same thing... it was a hypothesis, someone (I can't remember who) analyzed it some more and considered it seriously.

FLex hose is definately a whole lot more lossy than straight walled PVC pipe due to the relative roughness of the wall. You would do well to minimize it's use.

[JR]

I can't add much to the excellent posts so far. I notice Larry's pic and comments about green v black, though.

I've got a backbone, similar to Larry's, made of black 4" pvc and fittings. I've also got some white S&D pipe and fittings. After noodling the 5" vs 4" theory, I then looked at fittings. IMO, the benefits of 4" connectivity outweigh the extra flow capacity in a small shop.

I believe the biggest hangup is in actually connecting tools at 4" and 2.5". There are plenty of adapters for these problems at 4" and 2.5" and not too many (none) for 5". Certainly there are none available at HD on a Sunday afternoon when you've got the time to solve the problem, DAMHIKT.

I'd think that 4" is going to work fine at 20', as Larry's pic shows. I'd go with the cheap thin-wall stuff, rather than the black, to save a few bucks. Get a HF starter kit for fittings and hose and you're in business. You won't quite be able to hook up 11 tools, but you'll have enough parts in hand to understand the intricacies of the connections.

Oh, and use wyes, not tees.

JR

[LCHIEN]

I have never actually seen a DC fan curve (although I'd love to...if someone has one they can post that'd be sweet).

A steep fan curve means that a small decrease in static pressure (think of that as the resistance of the system) results in a large increase in airflow.

Here's one from Bill Pentz's (in)famous web site covering several combinations of motors and impellors. He says you need 800 CFM or more (green) to capture all fine dust, 500 to 800 to do a fair job. Less than 500 won't pick up chips or dust adequately. Most DC's are rated with no ducting at all, real life numbers with some ducting are add static pressure drop and the resulting air flow is frequently 1/2 the manufacturer's rated values. Elsewhere on the site Bill has a spreadsheet for some estimations for duct static losses...
Static Pressure (S.P.) loss is in inches of water ( a pressure measurement).
As the small, medium large shop generally indicates, a shop with some but limited ducting will incur total losses of around 6-8" SP.

[IBBugsy]

Seems to me an alternate would be having two main 4" lines as LCHIEN mentions. If you can put the DC in a central location and run half your tools off one main and the rest off the other. The intent is to half the length of your runs. Maybe you've already planned this??

Another is to have your CFM hogs close to the DC and lighter users at the far ends.

[BT3 WOODOG]

Larry,I noticed You changed out the hose on Your D.C. I have the same one,did it help? Nice job on the ducting! Is that the Wynn filter?

[ryan.s]

Thanks for all the great info guys, really helps alot. I'm now leaning towards just going with the 4" PVC rather than trying to hunt down the 5" ducting and fittings although 2.5 times the resistance is still putting me off a bit. At least I know now that just using the flex hose is now no longer an option.

In regards to the type of ducting availalbe at Home Depot, I originally looked at the white 4" S&D pipes. I noticed that the inner diameter was slightly smaller than the black PVC and the inside of the pipe had ripples rather than being completely smooth. That's why I was planning to use the black PVC which is the only other choice at HD. Even though the walls are thicker the inner diameter is slightly larger than the S&D pipes and the cost if I remember correctly is something like $13-18 for 10 foot section.

[cgallery]

Just for fun I went to McMaster.com to check on whether they had 5" PVC (they don't). They jump from 4" to 6". I imagine the 5" stuff would be real hard to find.

[ryan.s]

So I found this site and got all excited

http://www.tlc-direct.co.uk/Main_Ind...g_1/index.html

They seem to have decent prices for 5 inch round ducting. I was mentally calculating how many 39 inch pieces I would need then I realized the .co.uk. The shipping would cost as much as the merchandise plus the prices are lbs not dollars. Oh well, that was exciting for a minute or two.

[Thom2]

I took a little different approach than some of what I've seen listed here.

One thing is that I used schedule 20 white S&D, it's smooth and only cost less than $8 per 10' section. I also used sanitary tees instead of wyes and 45 fittings. The sanitary tees have a sweep to them and should flow considerably better than a normal tee. Using these also cuts the cost of fittings since you won't need to buy wyes plus 45's.

I also did all ceiling runs with hose drops from the tees, I did not want to deal with hard pipe being in the way and all my drops will eventually be quick disconnect so that I'll be able to knock the hoses off if they are in the way (or if I need a longer section to reach somewhere).

Something I learned along the way is that there are 2 different type of blast gates, (http://www.ptreeusa.com/blastgates.htm) one is labeled as a "Quick Disconnect Blast Gate", one side of these fits very nicely right into the S&D fittings (I also think this will fit right into the schedule 20 pipe as well). The other fitting is a normal blast gate. The normal gates fit very nicely into the green S&D (I think the green stuff is schedule 35) but don't fit fer crap with schedule 20 or the S&D fittings. I ended up with a few of the normal gates and used 3" pieces of the green stuff to make adapters from the gate to the fittings.

One thing you may want to consider is a 2 1/2" drop in the center of the shop. I had installed one for the shark guard, but have found it a lot handier than I originally planned. I keep a 10' piece of shop vac with a coupler to hook to the 7' hose that feeds the shark. This setup makes general cleanup around the shop a breeze. I seriously underestimated this drop when I planned out the shop.

Good luck, have fun and show us some pics of what you come up with!

[ryan.s]

What are the differences between schedule 20 and schedule 35 pipe? I've never seen the green pipe in my local HD. Thanks!

[LarryG]

Woodog: The stock 5" hose on my DC had slowly developed a permanent, flattened kink in it that reduced its free area to maybe a quarter of what it should have been. The replacement you see was fashioned from one two-foot length of straight 5" stove pipe and two adjustable elbows, with the seams sealed with a few wraps of electrical tape (not yet applied, when this picture was taken). Total cost: around $10. I can't really say how much this single mod helps since I added the canister filter and went to the PVC ducting system all at the same time. And yes, that's Wynn's spun-bond polyester filter.

Ryan: I don't doubt Garasaki's numbers ... I really don't. That's a road we've been down many times here on this forum. The decision comes down to, as JR and a couple others have mentioned, the cost and availability of 5" pipe and fittings.

The pipe portion of the problem is actually not that hard. HD has 5" galvanized stove pipe for around $8 for a 5' piece. That's more than 4" S&D but for the relatively small quantities a small shop would need, the total cost would still not be too bad. The fittings are another matter. The 5" x 5" x 4" metal wyes that I found cost $30 each. IIRC my system has 11 wyes, for which I paid ~$4.50 each ... fifty bucks total. The same thing in metal would have cost me over $350 by the time shipping was factored in. And that's just the wyes; I also needed a number of ells and 45s.

The green pipe I have is dead smooth inside; I'm not familiar with the rippled variety you mention. Nor, again, am I familiar with the black stuff. It may well work fine. My point was and is to carefully scope out the inside and outside diameters of EVERYTHING in your system -- pipe, hose, fittings, dust ports on the machines -- and make sure you're not giving yourself major heartburn by choosing a certain kind of pipe based on price or availability. When you go shopping for pipe and fittings, take some of your DC fittings with you. That's what Tom Miller advised me to do, and I found (as he knew I would) that a little trial-and-error in the store can be a real eye-opener as to what all will be involved in getting all these pieces to peacefully coexist.

My local HD doesn't have the green pipe, either. Lowe's, however, does.

+1 on Thom's suggestion for a 2-1/2" drop somewhere. I have two (CMS, spindle sander) and by plugging in a shop vac hose, I now use my DC to vacuum the shop. Consider a floor sweep drop, too.

To get back to the 4" vs 5" question ... again, I cannot argue with the numbers, but what I *can* tell you is that my current system is soooooooo much better than the hose-based system I had before that it's almost like I bought a new, bigger DC unit. I'm getting a lot less fine dust on everything in the shop, and the "visible" dust collection efficiency at my jointer, planer, router table, and even the drum sander is a solid 98% or better. Understand, this is NOT to say some fines are not escaping into the air; I know some are, and the increased CFM from the lessened resistance of 5" pipe would no doubt help with that. But as a practical matter ... for what I paid ... I'm thrilled with my 4" system's performance.