PVC Duct & Static Electric Problems? - Woodworking Talk - Woodworkers Forum
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post #1 of 43 Old 02-28-2019, 07:08 PM Thread Starter
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PVC Duct & Static Electric Problems?

It seems on UTube most people use PVC for their ductwork. Was talking to the folks at Oneida looking for PVC adaptors and they said they don't recommend using PVC for the duct work? She said it creates a static electricity problem. Anyone experiencing this and is there a fix for it? Appreciate the help..
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post #2 of 43 Old 02-28-2019, 11:42 PM
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Going through the same planning.

Movement of the air and chips in pvc will create static. I will not get into the debate of whether this will cause an issue. It can definitely cause a static discharge. Some folks run wires with the PVC to ground it back to the DC just figure this into your overall cost and time.

I too am trying to plan a DC system. I like to price of PVC, but may go with the Oneida metal ducts. I have tried to layout a system with the Oneida Super Dust Deputy XL cyclone with metal duct and the ClearVue CV1800 cyclone with PVC. I am leaning toward Oneida. Part of that is the difference in cost of the cyclones. I also like the Oneida metal elbows I was looking at can vary from 90 to straight which could help with duct directions.

I might mention I have an older Grizzly 4 hp DC I am trying to make use of with my set up. If I was buying new.... I might go ClearVue PVC and wire to ground. Hard call Do the planning and math.

Good luck and let me/us know what you decide it will help us!

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post #3 of 43 Old 03-01-2019, 07:28 AM Thread Starter
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Thanks for the response. How do you run a ground wire with the PVC piping? PVC would be cheaper and I would think would provide a better sealed system. If it's just a matter of running a small metal wire through the PVC that wouldn't be expensive. If it's a special wire or size? wire I suppose it could be. I'm looking at the HF DC with the Oneida 5" Super Dust Deputy. If I go with PVC it will be 4" pipe.. If I go metal I'm leaning towards 5". Just want to ask questions and learn from people with experience instead of just buying and learning/regretting. This is suppose to be fun... :) Thanks again..
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post #4 of 43 Old 03-01-2019, 08:14 AM
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A bit different than the question here- I have a DD on a portable cart. I ran a wire from the metal mount on the DD top, soldered a washer to the wire and let it drag on the floor. No static problems.

A diamond is how coal reacts under pressure.
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post #5 of 43 Old 03-01-2019, 08:46 AM
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Static discharges/shocks are .....

The static shocks you can get from touching the DC unit while it's running are annoying, even painful, BUT not hazardous. The number of static dust explosions in home shops are miniscule, if even existent.
It takes a huge volume of airborne dust and a significant spark to make an explosion.


I have 2 Jets 1100 DCs which have a 7" plastic wire wound hose which connects the blower to the separator. While it was running, it would shock the $hit out of me. I finally figured out a solution which was to "electrically/mechanically" connect to two with a bare copper 14 GA wire. This stopped all the static shocks. Since then, I have never been concerned with any static, BUT I don't have long runs of PVC pipe either.



We need to separate the "hazard" discussion from the "annoyance' issue?

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; 03-01-2019 at 11:32 AM.
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post #6 of 43 Old 03-01-2019, 10:43 AM
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Flour mills had some horrendous explosions in the past.
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post #7 of 43 Old 03-01-2019, 11:31 AM
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Like I said above .....

Quote:
Originally Posted by johnep View Post
Flour mills had some horrendous explosions in the past.
johnep



Woodworking doesn't produce flour dust, even in small quantities.


Apples and bananas comparison. Graineries doen't deal with wood dust and woodworkers don't deal with flour dust.



http://www.home-wizard.com/article/home-explosion-risks


https://www.ccohs.ca/oshanswers/chem...ible_dust.html
read the section on "What conditions are needed for a dust explosion to happen?"

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)
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post #8 of 43 Old 03-01-2019, 12:35 PM
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True. But both produce static and flour dust is highly inflammable. Sawdust usually coarser but sanding wood produce similar particle size. It was these small particles that were breathed in by wood workers and could produce cancers. Did so in the UK furniture industry.

https://www.google.com/search?q=fire...hrome&ie=UTF-8

https://www.woodshopnews.com/feature...s-of-wood-dust


johnep

Last edited by johnep; 03-01-2019 at 12:47 PM.
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post #9 of 43 Old 03-01-2019, 05:48 PM
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Quote:
Originally Posted by johnep View Post
Flour mills had some horrendous explosions in the past.
johnep
A college friend worked in a feed mill where smoking or any type of open flame was forbidden due to the explosive nature of the fine dust. So...he learned to chew tobacco. Example- I had a small bucket of sawdust that I tossed on a burn pile. Flashed like a quart of gasoline! In the future, I will dump the sawdust BEFORE lighting the burn pile. I learn real fast!

A diamond is how coal reacts under pressure.
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post #10 of 43 Old 03-01-2019, 09:12 PM
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Great topic. Getting ready to build a small PVC Dust Collection system. I will use some copper wire and run it to ground to be safe.

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post #11 of 43 Old 03-02-2019, 12:17 AM
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I have an all-plastic Craftsman shop vac, connected to a plastic dust separator. They share a movable cart. I take a plastic hose from the dust separator and attach it the the tool in use. The hoses are those black plastic "accordion" hoses. On dry days, I can see the sawdust fingers around the hose that is plugged into the tool. (In case you are thinking about leaving a wire touching the ground, I operate my tools mostly on paving stones set in sand on hard dirt, but I work on the concrete slab in the garage on rare occasions.)

Here is my question:

-> How would you ground the hoses, the dust separator, and the shop vac? There is nothing but plastic, plastic, plastic on the outside of this contraption. My goal is to prevent static discharge between the "final" hose and the tool itself.
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post #12 of 43 Old 03-02-2019, 07:54 AM Thread Starter
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Thanks for the replies. My mind was in a totally different place on this topic. I thought the static charge would cause the dust to stick to the insides of the pipe. Sort of like when you cut PVC and the dust sticks to the pipe. After reading I'm not too concerned about an explosion or fire but that static electric shock would drive me nuts. Do you need to run a wire inside the entire length of PVC tube or can you attach/tape a wire to the outside near the blower and ground it there? I'll have about 30' in total PVC before connecting the flex hoses. Started thinking about using the 5" light weight metal duct piping from Home Depot. Cost would be about the same as the 4" PVC, a little bigger diameter pipe, but since I'll be feeding that into a plastic DD I'll still have to run a ground wire somewhere.
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post #13 of 43 Old 03-02-2019, 10:53 AM
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Mine will be a small PVC Dust Collection System and it will pretty much be all plastic. I plan on running a small non coated wood screw into one of the pipes, not so long that it would catch debris. I will run a wire to ground from that.

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post #14 of 43 Old 03-02-2019, 01:12 PM
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Deciding whether to use 5" or 4", metal VS plastic. There is a big difference in the air volume that the two can carry. Cross sectional area = pie x r squared so the ratio is 25 to 16. So the 5" duct can carry 50% more air! That said, if your fan is only capable of enough air movement for a 4" duct, use the plastic. Many of the small (cheap) dust collection systems use a "free air" cfm rating. That # is totally worthless for use in calculations for your system. If yours has a CFM rating at a specified suction measured in water column then you can use that for your calculations. Usually machines need a minimum of a 4"wc at the hood. There are multiple loses before that. Each foot of pipe, elbow, flex duct, and especially the filter bag. The typical cheap system doesn't have enough filter to move its rated air volume. Especially once the filter has some dust load. There are lots of system calculators on line. Watch out for the recommendations to use an increasing trunk line size for each additional tool. As a one man shop you won't be using multiple tools at once. So trunk line calculations don't apply. You need to keep your duct velocity above 3500'/min. Or the duct will fill with chips. Chips increase friction and reduce flow even more.
You can increase the performance of your small system by adding filter area. I've used American Fabric Filter Co. They can help you.
The mini cyclones available will reduce the filter plugging but they also add to the lose of flow. A planer makes a lot of chips and will quickly fill a 55 gallon drum.
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post #15 of 43 Old 03-03-2019, 08:09 AM
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I just made this comment in another thread, but it also applies here:

"If you design your system with runs of pipe, be sure you include a way to clean them out from time to time. Sawdust will settle in them, even with the best of dust collectors, let alone a shop vac. With time, temperature, and humidity changes, the sawdust can accumulate and harden inside the pipes like arteriosclerosis."
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post #16 of 43 Old 03-03-2019, 09:02 AM Thread Starter
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Appreciate all the help..

Larry42: I'm getting the HF DC and the 5" DD from Oneida. I also ordered the Wynn 35BA filter. The lady at Oneida said the HF DC comes with a 5" inlet which is why I felt it would be good to run the entire system with 5" metal piping. After looking at the HF DC again it states a 4" inlet.. Not sure a 4" inlet connected to a 5" pipe run will produce the best results. I don't have the mindset to understand the physics behind all this. Thought to ask the people who have actual hands on experience what they found to work and not work. I do appreciate the help!
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post #17 of 43 Old 03-03-2019, 09:26 AM
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All that's good, but .....

You should also replace the impeller:






OTHER modifications that are popular include mounting the motor/blower on the wall .....
https://www.google.com/search?q=harb...w=1536&bih=750


Understanding dust collection basics is spelled out here:
http://billpentz.com/woodworking/cyc...nerscorner.cfm


Look at the header that runs across the top and you will find:
http://billpentz.com/woodworking/cyclone/blower.cfm


and:
http://billpentz.com/woodworking/cyc...mpeller_sizing

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; 03-03-2019 at 10:22 AM.
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post #18 of 43 Old 03-03-2019, 09:41 AM
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Wood magazine had a tip a while ago where one guy took HVAC foil tape and wrapped it around like a barber pole. He then terminated it with a bare wire underneath and grounded that wire.
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post #19 of 43 Old 03-03-2019, 10:30 AM
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Static electricity and dust collection ......

This section from the Pentz web site deals with static in the home shop system:
http://billpentz.com/woodworking/cyc...ic_electricity


He also ran an aluminum sticky tape (HVAC tape) inside and outside the pipe, but there were issues. his falls into the difference between "annoyance" and hazardous" issue that I mentioned a few posts above. One solution I've read is to run a bare copper wire inside the pipe with a connection to ground at both ends, being careful not to interrupt the continuity at the joints. That seems like a real pain and may induce clogs if it's not kept perfectly smooth and flat. Not for me .....


Pentz references this article which says;
Dr. Rod Cole wrote an excellent article in Fine Woodworking that debunked the static myth with PVC pipe.

http://www.woodcentral.com/articles/...cles_221.shtml

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; 03-03-2019 at 10:35 AM.
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post #20 of 43 Old 03-03-2019, 11:09 AM
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Quote:
Originally Posted by SteveKoz View Post
Appreciate all the help..



Larry42: I'm getting the HF DC and the 5" DD from Oneida. I also ordered the Wynn 35BA filter. The lady at Oneida said the HF DC comes with a 5" inlet which is why I felt it would be good to run the entire system with 5" metal piping. After looking at the HF DC again it states a 4" inlet.. Not sure a 4" inlet connected to a 5" pipe run will produce the best results. I don't have the mindset to understand the physics behind all this. Thought to ask the people who have actual hands on experience what they found to work and not work. I do appreciate the help!


My HF collector has a 5” inlet with a removable 5” to 4” Y. It allows for 2 4” runs. Remove the Y & you have the single 5” inlet.


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