Ducts... from above or from below? - Woodworking Talk - Woodworkers Forum
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post #1 of 11 Old 11-07-2017, 06:20 PM Thread Starter
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Ducts... from above or from below?

I'm about to rerun my dust collection ducts because I've built several tool carts and have added more tool stations that need dust collection drops...

I'm adding a grinder, drill and router station - sanding and miter sawing will continue to be done outside (I set up a tent for these tasks on demand) - way too messy for my small shop LOL.

I have the HF dust collector (you can see it in the corner) which has the dust ducts on the bottom.



Currently, I am running the black sewer pipe (6") from the port going up the wall and across the ceiling.

I know I should probably be using no ridge piping, but this is what I have at the moment.

I'll be installing Y connectors either way with ridge piping connecting the stations.

So my questions are:

Since the port is on the bottom of the collector should I run the duct along the floor and come up at each station or continue to run it up the wall and then come down at each station? My table saw duct will have to come down from the ceiling just because of where the saw is located, but the others are located against the wall.

Should the gates be located high or low? In other words, should the gates be located close to station (doesn't that create suction within the "Y" connector?) or should the gates be located in the 6" pipe?

This unit has 2 ports. I have one of them closed off - I read somewhere I would get better suction if the 2nd port were open. True?

I've read that using PVC is a potential fire hazard due to static electricity - if I used PVC for some of the ducting, is this something I need to be concerned with or should I avoid PVC altogether? Would I have to ground the system if I used the metal ducting?

Thanks as always in advance.

Last edited by new2woodwrk; 11-07-2017 at 06:53 PM.
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post #2 of 11 Old 11-08-2017, 08:19 AM
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My first idea was of static building up in the plastic pipe. I think that Oneida, if my memory serves me, has a deal where you can design your DC layout. Anyone else have any input? My DC system is moving the Shop Vac and Dust Deputy so the hose will reach the power tool I'm using at the moment.
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post #3 of 11 Old 11-08-2017, 10:04 AM
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Dust collection is a specific solution for each person and so it can create many myths (PVC duct fires) and confusion. I will start with your DC. The HF is a great starting point for DC, but its weakness is the undersized 10" impeller. Because of that you have the performance of a typical 1.25HP DC. So the HF is best as a mobile DC system. Trying to add lots of ducting reduces the performance even further. If I understand your setup, you are connecting to one of the 4" ports and tying 6" ridged landscape pipe? That is the probably the worst combination for two reasons; 1) as you said, never use ridged pipe for a DC. It not only catches dust in the duct but the large ridges creates turbulence in the duct greatly reducing the little flow you have. 2) You need to maintain a certain cfm/velocity in a 6" pipe to keep the dust airborne. With smooth pipe your DC can't maintain that velocity on longer runs, but you are (I believe starting from a 4" source) and trying to connect to the ridged 6". It is like trying to fill a sewer drain with a garden hose.

As far as the Y location, I have seen many people claim that it is better to put the gate close to the main line. I have not measured a setup with both gate locations, but I would guess the difference if any would be small. There is no airflow down the leg so 12" or 60" of static air doesn't seem that significant.

My advise. If you can blow dust outside then remove your blower from your DC and mount it high in your shop and blow the dust outside. This will significantly improve your performance. Run your ducts high (on the floor always seems to be in the way or take up valuable floor space). If you can't blow dust outside (neighbors, cars...) then add a separator and the dust exhaust outside will negligible. Most importantly, remove the dual 4" Y at the machine and connect 5" ducts (your machine has a 5" inlet under the Y). The standard HVAC snap lock from BORG will work fine. 6" is too big and the ridge pipe you have is a big detriment to your flow and performance.

I know this is not what you wanted to hear but with the DC and pipe you have, you will probably get better performance from a shop vac connected to each machine.

BTW: your image is no longer visible. Photobucket changed their policy this year and forum pictures are not visible.

Hope this helps, let us know what you do.

Carl
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post #4 of 11 Old 11-08-2017, 11:41 AM
where's my table saw?
 
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It just ain't all that simple ...

Dust collection is a lot like electricity, it's hard to tell what's going on inside the pipes or wires.

Once the dust and particles have fallen out of the fast moving airstream, because of insufficent flow CFMs, or not enough velocity, they will ten to pile up inside the cabinets, especially the table saw where it collects in the corners.

The best saws and machines have the dust pickup ports right at the source of the dust, cutterheads or saw blades. Trying to evacuate a 2 ft square cabinet with a shop vac or home dust collector just won't happen. Jointers and planers usually have better located port and do much better at collecting the chips partly because they are ejected with higher velocity right from the cutterhead. Older tables saws are very inefficient at collecting the saw dust. Manual labor was involved back in the day and they just scooped out the dust with a shovel.

Bill Pentz has the best site on the web for determining all the factors that go into efficient dust collection:
http://billpentz.com/woodworking/cyclone/index.cfm
Keep in mind that not every shop needs a cyclone DC and they take up more space and require more HP. Separators like a Thein and Top Hat variation and Dust Deputies work well for small shop needs. They will keep your main filters cleaner, but often have less room in the bag/bin for large amounts of chips from planing...

Both my Jet 1100 DCs are on mobile bases and I run them right up to the planer, jointer. drum sander, or table saw in use at the time with the shortest flex hoses I can live with. I have quick change couplers that make switching over just a matter of seconds.

Static in the lines can be be eliminated by grounding the motor base to the metal collector inlet with a bare copper wire. They do not have an electrical connection as factory issued, because the hose is plastic and is clamped at either end to the metal. The plastic makes no electrical contact.
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post #5 of 11 Old 11-08-2017, 02:00 PM Thread Starter
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Quote:
Originally Posted by Carl10 View Post
I know this is not what you wanted to hear but with the DC and pipe you have, you will probably get better performance from a shop vac connected to each machine.

BTW: your image is no longer visible. Photobucket changed their policy this year and forum pictures are not visible.

Hope this helps, let us know what you do.

Carl
Actually, this is EXACTLY what I wanted to know.

While I may not take all of your advise simply because I can't - such as blowing the dust outside - (not gonna happen LOL),.

However the information is greatly appreciated - removing the intake Y port for example - I didn't think that was possible so now I can look into that.

This site for some reason no longer allows me to upload pics so I uploaded them to PB - I'll find someplace else to upload images to soon.

Thanks again for your help Carl! Great stuff!
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post #6 of 11 Old 11-08-2017, 02:09 PM Thread Starter
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Quote:
Originally Posted by woodnthings View Post

Bill Pentz has the best site on the web for determining all the factors that go into efficient dust collection:
http://billpentz.com/woodworking/cyclone/index.cfm

Static in the lines can be be eliminated by grounding the motor base to the metal collector inlet with a bare copper wire. They do not have an electrical connection as factory issued, because the hose is plastic and is clamped at either end to the metal. The plastic makes no electrical contact.
Thanks woodnthings,

Yah I've been to Bill's site quite a few times - and probably will go quite a few more - his information is way above my pay grade at the moment.

But I keep learning lots and reconfiguring as needed and as I learn!
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post #7 of 11 Old 11-08-2017, 02:39 PM Thread Starter
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New image site:



The DC is in the corner and the pipe is on the ceiling:
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post #8 of 11 Old 11-08-2017, 04:42 PM
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What I learned from Pentz..

I learned that most if not all "commercial" home shop DC untis have impellers that are too small, and motors that don't have enough HP to gather up all the fines, keep them in suspension and carry them away. Most of the tech talk is over my head as well. air speed, air velocity, CFMs, pipe diamters are all simple concepts, but then start mixing in other variables and it gives me head pains.

I decided to make two DC "centers" around the 2 mobile Jet units with as short length runs of flex hose as possible, and swapping out between about 8 machines. This saves floor space and keeps bends to a minimum. I converted all my clear plastic bags to hardboard drums, easier to carry down the stairs and dump them in the compost pile. I have sloping ceilings, so overhead just didn't seem like it would work well. Gravity was fighting me with overhead as well. My design may be specific to my shop and not work for others... I donno?

The DC units with 4" flex go to the large machines, anout 4 shop vacs with 2 1/2" go to the dust ports on the bandsaw, RAS, and hand held sanders and router tables. Chip size is important and while sanding dust isn't very large, drum sanders make a ton of it. Dust even gets on the feed table causing it to slip and needs a shop vac to get it all up.

It is all a continuous experiment in my shop, especially with the table saw and over the blade covers which I found are a necessity to get it all. The blade spits up too much dust that is trapped in the gullets and it ends up in your face and on top of the work.
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The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 11-08-2017 at 04:56 PM.
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post #9 of 11 Old 11-08-2017, 05:54 PM Thread Starter
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After reading @woodnthings and @Carl10 I'm thinking of moving my DC unit out of the corner and placing it next to my Table saw which is pretty much in the center of the shop.

That way it can stay hooked up to the TS and I can run an auxiliary feed off it for the work bench as needed.

I do have a shop vac, and now I'm thinking of buying an additional shop vac just to put with the Router, Grinder, Drill press and HF Sander.

Seems kinda simple and less of a headache over all.
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post #10 of 11 Old 11-09-2017, 07:19 AM
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I've read about static electricity not being a great hazard for sawdust collection, but I wonder about grinder sparks being sucked into a cloud of sawdust. It might be better to vacuum/sweep up the grinding dust.
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post #11 of 11 Old 11-09-2017, 09:19 AM
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You should find a warning label on every DC that warns about using for wood dust only.
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