Static electricity

[ryan_618]

I got a complaint yesterday (I'm an inspector) from someone that was shopping at a grocery store and got shocked. I went to the store and found that it was static electricity. Anytime you touch a shopping cart and touch a shelf, you get a static shock. Now, its not like i had fuzzy slippers on and was rubbing a balloon on my head, I mean you walk two feet and get shocked again and again. The manager says it is the shopping carts causing the problems. The customer also said he got an arc from his hand to the cart about 8" long. This sounds like an exaggeration to me, but I have to take it seriously and investigate it. Could this be because of improper bonding of the structural steel? Is there anything in the NEC that I can use to enforce here? I just don't need some 80 year shopper with a pace-maker laying on the ground here! Please help if you have any suggestions. Thanks in advance.

 

[don_resqcapt19]

Re: Static electricity

Have the carts been changed? Has the floor treatment been changed? This appears to be a static build up caused by the friction between the cart wheels and the floor. I don't see where the steel bonding or lack there of would play any part in this problem. I think that the floor treatment or the cart wheels will have to be changes to solve this problem.
Don

 

[karl riley]

Re: Static electricity

You say you found it was static electricity. Did you also test for AC?
Karl

 

[bennie]

Re: Static electricity

Karl makes a good point. I would read the EMF in the area, with a Gaussmeter

 

[bphgravity]

Re: Static electricity

I would simply hand out rubber gloves to the customers as they walk in the store!

 

[bennie]

Re: Static electricity

Bryan: I still have my leg shackles from my days of working high voltage. I made them from copper sheet material and a braided jumper with a
c-clamp.

When repairing live power lines, I would connect the shackle to the faraday cage in the bucket. When I noticed a blue and red streak jumping from my fingers, I knew the jumper had come loose.

This was from the energy field, it was uncomfortable but not lethal.

 

[don_resqcapt19]

Re: Static electricity

It would be highly unlikely that a problem with the building electrical system could cause visible arcs to a person without also causing injury to that person.
Don

 

[caj1962]

Re: Static electricity

Just curious but do the offending shelves have power ran to them? I know at several of our large chain stores here they have ran EMT from a jbox in the ceiling down (about 15 feet unsecured)to an outlet that they power up everything from hotplates to cash registers. I always wondered what was going to happen when that unsecured emt comes loose and starts rubbing the conductors.

 

[iwire]

Re: Static electricity

Don has the answer, this will continue until something changes with the floor or carts, something conductive dragged from the carts would work.

Many times when we drive scissor lifts on VCT flooring they build up a static charge which is quite annoying when you get a shock to your ear or neck from the ceiling grid.

If this is happening we will attach a few inches of jack chain on the lift to drag on the floor and that stops it.

This is a real problem for electronics makers and they can buy special carts to prevent this, notice the drag chain on this one.

ESD Utility Cart

 

[ryan_618]

Re: Static electricity

Thanks for all of your replies. I couldn't see that the shelves had any power to them, and no, I have not checked for AC. This building is about 9 months old, and my thoughts were that I might have the electrical contractor and/or electrical engineer take a look at the store. My biggest concern is really a legal one, which is, does the city have any jurisdiction over static electricity? I would like to be able to force them to remedy the problem, but legally I'm not sure if I can. Does any code that you guys are aware of address this?

 

[bennie]

Re: Static electricity

The risk management official, for the company should be made aware of this situation. Also the cart manufacturer will be exposed to a degree of liability if someone in injured.

The cart manufacturer may want to look at other types of wheels. Automobile tires have carbon added for static prevention.

 

[tom baker]

Re: Static electricity

Static electricty can be minimized with more humidity in the air. Here in the puget sound area we rarely have static. In alaska, you learn to touch your car with the key held between your fingers.

Is there a way to increase the humidity?

 

[hurk27]

Re: Static electricity

Ryan

does the city have any jurisdiction over static electricity?

can we totaly control lightning?
dont think so.
I think this would fall under "act of god"
as far as liability goes.

 

[ryan_618]

Re: Static electricity

I think I agree with Wayne. I am concerned for the liability of the store, however; it is beyond my scope. Thanks very much for all of your replies, I will share some of them with the owner and let them figure out how seriously they want to take it. Thanks again

 

[fsak]

Re: Static electricity

Static electricity problems will be a problem with low humidity and shiny waxed floors. The wheels on the carts could be a factor as well as the type of shoes and clothes.

Get a static electricity meter to verify the static voltage. Or just increase the humidity, use anti-static floor wax, drag a ground wire from the shopping carts, change the shopping cart wheels to ones that are conductive, make everyone wear natural fiber clothes, underware and leather sole shoes, move the store to Hawaii OR just DON'T WAX the floor. Dust and dirt will dissapate the static charge.

 

[pierre]

Re: Static electricity

Hello Ryan,

FYI The local inspection agency is involved in a 256 million dollar law suit as we speak, their attorney says they should be cleared, but so far it has cost them more than $ 25,000.00 in fees. Their deductable is $ 25,000.00. This is why we 'cross our T's and dot our I's!!
A good attitude goes a long way.

Pierre

Pierre

 

[ryan_618]

Re: Static electricity

Pierre, thanks very much for your reply. I have a hard time determining if my enforcing something that is not a requirement is malicious prosecution or if me closing my eyes on something is negligent malfeasance! I have expressed my concern to the store manager and they seemed to understand, but I also made it clear that I could not require them to do anything. Thanks again