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Installing HF 2.0 hp Dust Collector. Questioning grounding concept with unique setup. ?

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Forum topic by David Grimes posted 04-12-2011 08:41 AM 1757 views 0 times favorited 15 replies Add to Favorites Watch
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David Grimes

2078 posts in 2105 days


04-12-2011 08:41 AM

The fan/motor unit is being mounted to the wall at the time of this post. Let me quickly describe the planned setup:

The dust collector motor and fan will be about 6’ off the ground in a closet with the output pointing directly to an outside wall about 4 feet away (with no elbows, bends, etc… a straight shot to outside). This 4’ long run will utilize the HF 5” flexible duct.

The DC unit’s intake wye will be pointing down with one side blocked and the other going into the top of a separator lid and 30 gallon lidded plastic barrel below it. This approx. 2’ straight drop will also utilize Rockler 4 inch flexible duct.

The duct that feeds the separator will also be the Rockler 4 inch flexible duct (but only about 2 feet to provide a little wiggle room before it goes through the closet wall to the shop side). At this point a wye (PVC?) will occur to accept two 4” lines that will be blast-gated Rockler Dust Right flexible hose. One will remain hooked to the table saw. The other will be the portable duct for the various machines and cleanup.

What of this described system should be grounded ? Is this grounding (hanging a bare wire in the ductwork) a myth ? Is this recommended or required only for systems with many feet of pvc piping running all over a shop? There is NO WAY to bond the Dust Right 3 ft flex that stretches to 21 feet. My other sections TOTAL approximately 8 feet with no bends except at the one wye.

I believe I would feel silly installing 8 feet of bare copper in so compact a design.

I’m thinking forget it unless somebody can explain why it is necessary.

Thanks.

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia


15 replies so far

View drewnahant's profile

drewnahant

222 posts in 2555 days


#1 posted 04-12-2011 08:50 AM

There have been other posts about this, I am no expert personally, but from what I have read, I believe the concensus on here is that it is completely unnecessary. I know that my own system doesnt have any grounding, it is 4” pvc drainage pipe, about 30ft.

However, If you are uncertain in any way, especially where you will be collecting rough dust in an enclosed space which you cannot monitor, and you are shooting fine dust, which can be combustible, outdoors, you should really aire on the side of caution. Also, I would definitely recommend a smoke detector in that closet.

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David Grimes

2078 posts in 2105 days


#2 posted 04-12-2011 08:53 AM

THAT (smoke detector) is an EXCELLENT idea !!! Very cheap insurance. Thanks, drewnahant.

The fire extinguisher is already mounted 5 feet away.

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

View bubinga's profile

bubinga

861 posts in 2133 days


#3 posted 04-12-2011 09:49 AM

My plastic piping is grounded,but ,on the outside,I read an article in a woodworking Mag ,few years ago,and experts say ,any static electricity,that may occur ,Is not contained inside the piping, therefore ,the ground wire can be on the outside, and discharge, any static.

-- E J ------- Always Keep a Firm Grip on Your Tool

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Pop

427 posts in 3412 days


#4 posted 04-13-2011 05:36 AM

A smoke detector is a must. Better yet a fire sprinkler head. Better to mess up your DC than burn down your shop.

I’m not going to take sides in to do or not do grounding, but if you do the wire is on the outside of the pipe NOT inside. This is in spite of books & articles that say otherwise. Static collects on the outside of a plastic pipe. A wire running inside does nothing.

Pop

-- One who works with his hands is a laborer, his hands & head A craftsman, his hands, head & heart a artist

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David Grimes

2078 posts in 2105 days


#5 posted 04-13-2011 06:13 AM

Bubinga and Pop: Thanks for the advisement AND for the fact that you both are saying the same thing.

The smoke alarm is happening.

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

View bubinga's profile

bubinga

861 posts in 2133 days


#6 posted 04-13-2011 06:53 AM

I was playing around (About 20years ago) with a CB radio, magnet mount antenna,I figured I would stick the antenna to ,table saw for a good ground plane,.When I got within 4in of saw ,with magnet mount, a big bolt of electricity,shot between the saw and the magnet mount,wow a big loud bamm ! magnet stuck to saw ,
(my hand was holding plastic -not touching metal) ,when I pulled off the antenna,there was a small crater burned into saw top, about 1/4in dia,and 1/16 deep.
I m not sure why this happened for sure. The saw stand was open at the front and back on the bottom .so I had covered it with plastic window covering ,the kind you stick on and heat with a hair drier .
I had noticed saw dust sticking to plastic ,like static was present, but didn’t think much about it , well apparently there was a build up of static.There was no dust collector involved, the saw was on wood floor .
Again I don’t know exactly why this happened ,BUT IT DID. Scared the Sh** out of me.

-- E J ------- Always Keep a Firm Grip on Your Tool

View Les 's profile

Les

201 posts in 2156 days


#7 posted 04-19-2011 02:18 PM

I sure don’t want to get into a disagreement with anyone so will just let you know what I have experienced and how I corrected the problem.

I have about 100’ of 4” PVC in my DC system that handles the whole shop. I only have static problems where ever I collect fine dust. The 26” drum sander being the worst offender. When I hooked up the unit to the system it created major static on the outside of the pipe, to the point that it would stand up the hair on your arm from 6” away.

To correct the problem I ran the wire inside the pipe from the sander to the point where it connects to the main line. The wire is grounded to the machine on one end and to the electrical ground ( green lug ) on the other. All hint of static disappeared.

If you go to image 5 in my shop pictures you can see the sander and the dust line I am talking about.

If you have any questions let me know.

Les

-- Stay busy....Stay young

View Pop's profile

Pop

427 posts in 3412 days


#8 posted 04-19-2011 04:31 PM

Well Lee, It seems I may be wrong. Wire inside the pipe is not logical, but if it works it works. The physics of the thing would move the static from it’s source to the point of furthest distance to be dissipated. That would put the static collection at the outside of the pipe. Hence, the wire looped around the outside of the pipe.

Pop

-- One who works with his hands is a laborer, his hands & head A craftsman, his hands, head & heart a artist

View ClayandNancy's profile

ClayandNancy

511 posts in 2481 days


#9 posted 04-19-2011 04:44 PM

My last shop was in the basement and I had maybe 30’ of 4” duct in the entire system. I drilled 1/8” holes every six inches or so and stuck a pop rivet in the hole. I ran bare copper wire, I think it was 22 gauge, from the metal frame on the DC and then to a pop rivet. Wrapped it once around the rivet then on to the next etc. etc. Then I went back and compressed all the rivets. Grounds the outside and puts a grounding point on the inside. Probably over kill but it worked, never had any static at all. Pop rivet sealed the holes.

View Les 's profile

Les

201 posts in 2156 days


#10 posted 04-19-2011 05:33 PM

Hey Pop,

I don’t disagree with you at all and the outside was the original plan as well, but I thought I would give the inside a try and it worked for me. Not sure why, but I guess it doesn’t matter.

Les

-- Stay busy....Stay young

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Pop

427 posts in 3412 days


#11 posted 04-20-2011 06:29 AM

Les. There an old saying. If something works DON’T try to improvement it. Just LEAVE IT BE, and hope it keeps working.

Pop

-- One who works with his hands is a laborer, his hands & head A craftsman, his hands, head & heart a artist

View ChrisK's profile

ChrisK

1809 posts in 2547 days


#12 posted 04-20-2011 03:35 PM

The current topic is of interest and I did a quick Google search for grounding DC systems. I am a mechanical engineer with some experience in getting sparks to ignite vapors and smoke. Static electricity can pose a very real problem in a system with combustibles. The following link goes into a lot of detail and real world experience.

Stay safe! Use a smoke detector that is wired into the house 120 VAC system and has a battery back up.

It goes with out saying that the DC motor and metal frame must be grounded!

http://home.comcast.net/~rodec/woodworking/articles/DC_myths.html

Chris

-- Chris K

View Pop's profile

Pop

427 posts in 3412 days


#13 posted 04-20-2011 07:15 PM

I have quoted Rod Cole’s paper a good many times. I agree with most of his observations. I have a presentation I do on designing a shop. When it comes to dust collection and PVC pipe I take the approach given to me by an old dust collection engineer. OK ! It’s a one in a million chance. What if your number comes up and it’s the millionth. Wire is cheap and I will loop that wire around my pipes and err on the side of caution.

I still maintain that a wire on the inside of a PVC pipe just catches dust and clogs up pipes. The “pop” I get is on the “OUTSIDE” of the pipe and that’s were I’m going to put my wire. Rod can do whatever he wishes in “his” shop, and I’ll do what I wish to do in “my” shop.

I also think that in spite of Rod’s scientific approach to this discussion and his resulting paper on the subject this debate will continue forward for time immemorial.

I also am convinced that the most dangerous thing in a wood shop from a fire causing source is a floor sweep. any metal that you sweep into that hole is going to go through the impeller of the dust collector and spark. Or worse yet fall in the dust bend and smolder for an hour or so until it starts a fire. Most likely after work. When you’re in bed, and not in your shop with fire extinguisher in hand. That’ll put you in the market for a new shop, and if it’s attached a new home.

Pop

-- One who works with his hands is a laborer, his hands & head A craftsman, his hands, head & heart a artist

View TheDane's profile

TheDane

4997 posts in 3129 days


#14 posted 04-21-2011 01:59 AM

I’m with Pop on this one … I’ve never been convinced that there is a great danger of fire, but why take the chance?

Plus, if you are using any solid-state devices (e.g. computers, CD player, etc.) that little shock you get can cause major damage to your electronics.

—Gerry

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

View bigike's profile

bigike

4050 posts in 2754 days


#15 posted 04-21-2011 02:05 AM

The hose I bought for mine has a metal wire in it and the company said I can ground it useing that.

-- Ike, Big Daddies Woodshop, http://www.icombadaniels@yahoo.com

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