Metal dust collection Grounding ??

[jay st clair]

The local fire marshall wants to see documentation that a metal dust collection system doesn't require a ground. Does anyone know where i could get that info .Thanks Jay

[Matt Tawes]

The local fire marshall wants to see documentation that a metal dust collection system doesn't require a ground. Does anyone know where i could get that info .Thanks Jay

Dont know where its specifically stated but I'm sure you could get the info. in print from the units mfr.
Sound like your local fire marshal is a fool, I mean come on its metal duct hooked to a metal cyclone with a metal housed motor in which the motor's power supply is grounded in the outlet.

[Stephen Musial]

If he's the fire marshall, shouldn't he show you the documentation that it does require a ground?

[Myk Rian]

Ground it anyway. A 12" length of wire from the fan to the base structure.
He must be one of them yunguns.

[Dan Friedrichs]

So...the reason to ground PVC ducting is because of the static generated by the dust running across the PVC. Metal, of course, does not generate the static, so even though it would be VERY easy to ground, what exactly is the reason for doing so???

I doubt you'll find something saying what you're looking for. You could:
1. Get a professional engineer to draw a rudimentary plan of your ducts and include a note to the effect that the ducts don't need to be grounded. His seal should satisfy the fire marshall.

2. Since it's metal, grounding it would be very easy, and you might just do it to make the fire marshal happy, even though it's not necessary. You may actually already be grounded through the 3rd prong on the DC outlet.

3. As Stephen said, make him show you something that says it's required. He can't arbitrarily make up rules, and he won't be able to find something that says grounding is required.

[Thomas Syrotchen]

It is humerous since its the National Fire Protection Assoc that is the source for most of these requirements.

I beleive that NFPA 664 section 7.9 should cover that area as it addresses static electricity requirements. 7.9.1 requires the hoses be conductive to prevent static buildup. 7.9.2 requires machines to be grounded or bonded if they accumulate static electricity. It doesn't require the hose to be grounded but I think it then becomes a matter of interpretation. The simple argument is the 7.9.1 requires that the hose be conductive to prevent static buildup and therefore it would not be subject to the requirements of 7.9.2.

The other issue is there might be another area of the code that is more open to interpertation that might be used as an argument requiring it.
The bigger question what is the cost of grounding the system and what is the harm versus what is the harm of challenging the Fire Marshall.

[John McClanahan]

I would ground it. For protection from line voltage as well as static charge buildup. I have a small book titled "Dust Collection Basics" that has a chapter on proper duct grounding, both plastic as well as metal.

John

[jay st clair]

Thanks for the replies, this is just the latest in the long list of issues the fire marshall has came up with ,he also needed to know the cfm needs of each piece of equipment along with a dust control blue print. He wasn't sure if our 15 hp 3phase motor would do the job, on the plus side I know alot more about fire codes than I used too. Jay

[John McClanahan]

Sounds like he doesn't have any knowledge of dust collection safety and is making you do all the leg work.

John

[Ken Fitzgerald]

Jay,

I don't know where you are located but it was reported here recently that there are fire codes regarding this but only in industrial/commercial applications. The code applied to certain systems above a certain CFM which the levels would only apply to commericial applications.

[Frank Hagan]

I wonder if he's requiring a bonding connection rather than a ground? On some appliances, the metal cabinet has to be bonded, as well as the motor grounded. Pool equipment is this way; you have to run a separate bonding wire back to the ground bus or to a separate rod pounded into the ground.

It should be easy to show a ground connection on the metal duct, unless you have plastic joiners or something like that isolating sections. Test continuity between ground at the blower and the duct.

Local codes can trump the NEC, and sometimes local codes give great latitude to the inspector. Its usually futile to try and fight them if they have a local code on their side.

[Rollie Meyers]

I wonder if he's requiring a bonding connection rather than a ground? On some appliances, the metal cabinet has to be bonded, as well as the motor grounded. Pool equipment is this way; you have to run a separate bonding wire back to the ground bus or to a separate rod pounded into the ground.

It should be easy to show a ground connection on the metal duct, unless you have plastic joiners or something like that isolating sections. Test continuity between ground at the blower and the duct.

Local codes can trump the NEC, and sometimes local codes give great latitude to the inspector. Its usually futile to try and fight them if they have a local code on their side.

That is a good way to get someone killed, the earth is a poor conductor & unless it's bonded together (NEC does require that) the rod is useless & unsafe, there is more that needs to be written about this.......

[Frank Hagan]

That is a good way to get someone killed, the earth is a poor conductor & unless it's bonded together (NEC does require that) the rod is useless & unsafe, there is more that needs to be written about this.......

You could be right; I simply don't know. At the time I worked in that industry, either method was acceptable (ground rod or a run back to the main service ground rod).

The "local agency having jurisdiction" usually has more authority than the NEC, and trying to argue against local codes is an exercise in frustration. Generally, to get an exemption you have to go before whatever the rule making committee is (City Council, City Manager's Office, etc.) and argue your case.

For the OP, I was just pointing out that it might not be a concern about static from wood dust at all. It could be a general bonding requirement based on the material of the vent, the voltage of the equipment in a residential setting, etc. In this case, attaching a ground wire and making sure you have continuity to ground along the length of ducting is probably easier than the proverbial "fighting city hall".

[Steve Chandler]

The local fire marshall wants to see documentation that a metal dust collection system doesn't require a ground. Does anyone know where i could get that info .Thanks Jay

. although you'll have to ground it so it will pass. It all depends on the area and what the local inspectors deem necessary unfortunately. I've seen this a few times and the problem was solved by installing duct from Nordfab, (they attached welding lugs on the different pieces). Not sure if there's any information about it on their website, but there is a lot to see: www.nordfab.com. Good luck!

[Mark Norman]

If he's the fire marshall, shouldn't he show you the documentation that it does require a ground?

^^+1

Thats hogwash for him to require that of you Jay.