Grounding a flammables cabinet?

Matt I would think that you are in pretty good shape with the cabinet on the concrete floor. It is no longer considered good practice to use interior metal water piping as an Equipment Grounding Conductor (EGC). Best practice would be to run a bare copper conductor that is not smaller than number ten American Wire Gage from the cabinets bonding terminal to the closest point on the Electrical Systems grounding electrode system. That really is likely to be overkill given that the cabinet is sitting on a conductive floor. The purpose of the bonding conductor is to limit the likelihood of static discharge during flammable liquid handling.

-- Tom H

Green or bare is the USA grounding/bonding conductor colors. You will have to go up to #4 or you will need to use a conduit to protect the wire. (per NEC). Plastic conduit is the method I would use not metal. If you use metal then you have to put bond bushings on both ends and connect the bonding wire through them. I would run a pvc conduit to the nearest electrical box and tie the bond in with the electrical system that way.

Per the NEC your bonding the metal cabinet not grounding it.

I do agree with the other poster. Bolted to concrete and away from sources of sparks and flame is usually good enough. When in doubt call your local fire marshal and ask. We have one at work. Not bolted to concrete, way from all line voltage electrical stuff. It is not bonded. The fire marshal inspects the facility about once a year. We have never had a ding for the way we did it.

I Believe : It is Illegal (Bldg.Safety Violation) to use PVC Indoors., because of the highly toxic fumes that arrise from a fire involving PVC.

It Has Been Banned for Indoor Use.

it's okay to run a length of # 10 Green or any color for that safety matter.

OR; for fun & looks attach a box with a cable or connector onto the cabinet over the screwhole and run a piece of flexible rubberized oil resistent cable use only one of the conductors or several and use crimp on tags or end connectors to attache the wire to and fro ground & screwhole/box...

I think you are better off using a screw with a bolt to attach this wire to the cabinet not sheet metal screws., if a proper bonding screw is not supplied.

I'll look up any specific codes as to where to get your earth/ground from.

Roy Q.T. ~ E.E. Tehnician

Is PVC conduit chemically different than PVC piping? PVC piping is used for all sorts of plumbing, cold water and waste lines. Or is only PVC conduit banned because the electrical wiring is more likely to ignite the stuff.

daestrom

It may be dependent on where you are. In New York City, PVC was baned for plumbing also. This may be changing with the latest building regulation changes.

Stephen

As far as the US NEC is applied were you are then PVC conduit is not banned. It is code compliant in any space that type NM cable is permitted. In some buildings and uses it must be concealed behind twenty minutes nominal of fire resistive material. It is not acceptable to most AHJs in buildings that the applicable code requires to be fire resistive or limited combustible construction. Short lengths of PVC are often accepted as physical protection for a conductor or cable were that is needed.

-- Tom H

PVC insulated wires are banned in specific places. Included in this above suppended ceilings when it is used for HVAC air return. Most network cabling is available in plenium versions with tfe insulation for this purpose.

All I am aware of is; it is banned for use in any indoor application in NYC., maybe other cities still allow it.

It's all about the toxic fumes that it produces when they are part in a fire, nothing about it causing fires as conduit in any specific application or use. These fumes are fatal to humans and they have chosen to ban it's use all together in any inclosed or indoor area where in the event of a fire the fumes may not escape easily & reach humans or animals.

Oh'., Did any one ask " The Seemingly All Knowledgeable " Bill for his opinion on my take on aluminum & it's properties ?

My Rebuttal: iI think he was very rude & judgmental., there is more to life and engineering then we all know individually.

negativity in a circuit is a good characteristic, not in a person.

if it was me....i would get a "static mat" for the front of the cabinet. the mat should come with a ground wire...usually it has a resister in series (1 megohm if i remember right). this then is wired to the cabinets ground point.

the way it works is that you the "charged" individual wearing the wool sweater stand on the mat as you grab the door handle the charge slowly bleeds off instead of a having a big static pop.

This one is Art. 500 Hazardous (Classified) Location Classes I, II and III, Divisions 1 & 2.,

I'm not sure of it's a a Class I Division I or Class 1 Div. 2 that handles flammable vapors and liquids . NEC 501.16 (A) deals with grounding directly

I think the difference being that Div. 2 involves the flammables contained & ventilated under normal conditions, that may become hazardous through abnormal operations or venting failure.

In any event I would take the anti static mat suggestion seriously too, the main idea of this Post is grounding the cabinet to prevent any static charge that may ignite vapors from accumulating, the measure should be applied through-out the shop where vapors might be present at any time by the nature of operation or accident involving noincendive circuit.

I know those shops are regulated by the state and have isolated paint booths with explosion proof fixtures, ect. they probably need to be inspected often as well.

What kind of conduit does the NYC code allow for passing through masonry (brick, concrete whatever) walls?

Thanks for all the replies! In response to a few points:

- The manufacturer-supplied "grounding screw" was simply a sheet metal screw, about #10 with a 5/16" hex head, driven into the side of the cabinet. When I tried to loosen it, it was already stripped out! I ended up drilling a hole next to it, cleaning off the paint around the hole, and installing a similar screw. I put a star washer between the wire and the cabinet, and a big flat washer between the wire and the screw head. I have seen the ground straps used on equipment racks and raceways in data centers, and that hardware is much more robust than this.

- The cabinet isn't bolted to the floor; it's just sitting on its leveling legs. There are some normal 120 V 15 A sockets about six feet away, and some 220 V sockets (20 A, 50 A) about 25 feet away. The only higher voltage than that in the building is a big three-phase panel (208/120, I think) at the other end of the building, maybe 75 feet away. In the room where the cabinet is (within 20 to 40 feet of the cabinet), welding, grinding, and cutting of metal is done.

- I like the idea of the anti-static mat. I will probably see if we can get one.

- After I set up this cabinet, I found out that we are getting another one to go next to it, which will require some shuffling around. When that happens, I will run a green ground wire and protect it with plastic conduit. There is a steel junction box (120 V and 240 V wiring, in conduit) just a few feet from the spot where I have it grounded to the water pipe, so hooking into the electrical system ground will be easy.

Again, thanks for the help!

Matt Roberds

maybe I speak for all here., Your Welcome !

as for me: the plastic molded raceway /conduit is a great idea, (wish I had thought of it };-) it'll give a nicer finish & kept look to your cabinets & shop.

good days & safety to ya.

=AEoy