Conducting concrete

[F Murtz]

Is there an echo in here?

[trader_4]

On Wednesday, January 4, 2017 at 8:24:20 PM UTC-5, James Wilkinson Sword wr ote:

oncrete is a porous material which may or may not contain water. The floor of your house should never contain water, or you have BIG problems, way ab ove a possibility of shock.

n the introduction of VAT on April Fool's Day in 1973.

/

Ufer Ground or Concrete Encased Electrodes

Originally, Ufer grounds were copper electrodes encased in the concrete sur rounding ammunition bunkers. In today?s terminology, Ufer grounds c onsist of any concrete-encased electrode, such as the rebar in a building f oundation, when used for grounding, or a wire or wire mesh in concrete.

Concrete Encased Electrode

The National Electric Code requires that Concrete Encased Electrodes use a minimum No. 4 AWG copper wire at least 20 feet in length and encased in at least 2 inches of concrete. The advantages of concrete encased electrodes a re that they dramatically increase the surface area and degree of contact w ith the surrounding soil. However, the zone of influence is not increased, therefore the resistance to ground is typically only slightly lower than th e wire would be without the concrete.

Concrete encased electrodes also have some significant disadvantages. When an electrical fault occurs, the electric current must flow through the conc rete into the earth. Concrete, by nature retains a lot of water, which rise s in temperature as the electricity flows through the concrete. If the exte nt of the electrode is not sufficiently great for the total current flowing , the boiling point of the water may be reached, resulting in an explosive conversion of water into steam. Many concrete encased electrodes have been destroyed after receiving relatively small electrical faults. Once the conc rete cracks apart and falls away from the conductor, the concrete pieces ac t as a shield preventing the copper wire from contacting the surrounding so il, resulting in a dramatic increase in the resistance-to-ground of the ele ctrode.

Ufer Ground or Building Foundations

Ufer Grounds or building foundations may be used provided that the concrete is in direct contact with the earth (no plastic moisture barriers), that r ebar is at least 0.500 inches in diameter and that there is a direct metall ic connection from the service ground to the rebar buried inside the concre te.

If you bothered to look at your own country's codes, you'd see that Ufers are one of the allowed types of grounding in the UK.

se

"Handbook of the Wiring Regulations" (UK) Based on BS 7671 2001 edition

It's page C2/15, they show 7 types of allowed earth grounds, two of the 7 are metal electrodes embedded in concrete.

But then you say codes don't matter and you've demonstrated that you're one of the village idiot trolls, so I'm sure that won't change anything either.

[DerbyDad03]

Concrete is a porous material which may or may not contain water. The flo or of your house should never contain water, or you have BIG problems, way above a possibility of shock.

on the introduction of VAT on April Fool's Day in 1973.

urrounding ammunition bunkers. In today?s terminology, Ufer grounds consist of any concrete-encased electrode, such as the rebar in a building foundation, when used for grounding, or a wire or wire mesh in concrete.

a minimum No. 4 AWG copper wire at least 20 feet in length and encased in a t least 2 inches of concrete. The advantages of concrete encased electrodes are that they dramatically increase the surface area and degree of contact with the surrounding soil. However, the zone of influence is not increased , therefore the resistance to ground is typically only slightly lower than the wire would be without the concrete.

n an electrical fault occurs, the electric current must flow through the co ncrete into the earth. Concrete, by nature retains a lot of water, which ri ses in temperature as the electricity flows through the concrete. If the ex tent of the electrode is not sufficiently great for the total current flowi ng, the boiling point of the water may be reached, resulting in an explosiv e conversion of water into steam. Many concrete encased electrodes have bee n destroyed after receiving relatively small electrical faults. Once the co ncrete cracks apart and falls away from the conductor, the concrete pieces act as a shield preventing the copper wire from contacting the surrounding soil, resulting in a dramatic increase in the resistance-to-ground of the e lectrode.

te is in direct contact with the earth (no plastic moisture barriers), that rebar is at least 0.500 inches in diameter and that there is a direct meta llic connection from the service ground to the rebar buried inside the conc rete.

false

It's not just that he believes that "codes" don't apply to the owner of the building, there is another problem with your explanation:

"Concrete, by nature retains a lot of water..."

The only time the water in concrete is an issue is if it rains a lot. Go ahead, ask him. ;-)

"Only if the concrete stays wet. Which won't happen unless it rains a lot. "

See? He said it. It must be true.

[trader_4]

There is something wrong with the bonding and/or grounding, and it shouldn't be hard to identify and correct. I'd get it fixed before something bad happens.

[gfretwell]

Check, or have an electrician your grounding electrode system. Also be sure metal piping is bonded around any plastic sections, water softener and the water heater.

[TimR]

Two separate ideas being debated here.

1. Ufer grounding as an appropriate or legal method of grounding your system.

1. Concrete floors considered to be at ground potential.

For the latter, I have always been told that you must consider a concrete floor to be at ground, and therefore refrain from touching any hot wires.

I have not attempted to measure that myself and don't know the source of the claim. But I've seen it in a number of electrical safety classes, so if it is an urban legend it is a well distributed one.

[James Wilkinson Sword]

I thought the general idea in America was to make them NOT wind proof, but easy and cheap to rebuild?

[James Wilkinson Sword]

I never said pure water :-)

[James Wilkinson Sword]

It's very good. Which is why people get shock in swimming pools and baths.

[Tekkie®]

James Wilkinson Sword posted for all of us...

Negative, if one looks at an AM radio station the tower is used as the antenna. Note a big ceramic insulator between the tower and the foundation. the is a spark gap on the insulator for lighting. If the transmitter is active then a non conductive ladder to climb the tower. That is why maintenance is performed at night because they are off the air.

[James Wilkinson Sword]

On Thu, 05 Jan 2017 14:37:55 -0000, trader_4 wro= te:

. Concrete is a porous material which may or may not contain water. Th= e floor of your house should never contain water, or you have BIG proble= ms, way above a possibility of shock.

er on the introduction of VAT on April Fool's Day in 1973.

e surrounding ammunition bunkers. In today=E2=80=99s terminology, Ufer g= rounds consist of any concrete-encased electrode, such as the rebar in a= building foundation, when used for grounding, or a wire or wire mesh in= concrete.

se a minimum No. 4 AWG copper wire at least 20 feet in length and encase= d in at least 2 inches of concrete. The advantages of concrete encased e= lectrodes are that they dramatically increase the surface area and degre= e of contact with the surrounding soil. However, the zone of influence i= s not increased, therefore the resistance to ground is typically only sl= ightly lower than the wire would be without the concrete.

When an electrical fault occurs, the electric current must flow through = the concrete into the earth. Concrete, by nature retains a lot of water,= which rises in temperature as the electricity flows through the concret= e. If the extent of the electrode is not sufficiently great for the tota= l current flowing, the boiling point of the water may be reached, result= ing in an explosive conversion of water into steam. Many concrete encase= d electrodes have been destroyed after receiving relatively small electr= ical faults. Once the concrete cracks apart and falls away from the cond= uctor, the concrete pieces act as a shield preventing the copper wire fr= om contacting the surrounding soil, resulting in a dramatic increase in = the resistance-to-ground of the electrode.

crete is in direct contact with the earth (no plastic moisture barriers)= , that rebar is at least 0.500 inches in diameter and that there is a di= rect metallic connection from the service ground to the rebar buried ins= ide the concrete.

-02-01&f=3Dfalse

20 feet deep. How deep is the concrete in your floor? 6 inches?

-- =

I know you believe you understand what you think I said, but I'm not sure you realize that what you heard is not what I meant.

[James Wilkinson Sword]

Yes, 5V can be very very nasty....

[Rod Speed]

So is mine.

I don't. What's the detail on the plumbing ? Mine is soldered copper, mostly but not entirely yorkshire fittings.

Very unlikely. I know mine isnt because I did the mesh and slab myself and I don't get that effect.

Gotta cite on that ?

What are you doing hot water wise ?

[gfretwell]

The 20 feet is horizontal.

[James Wilkinson Sword]

On Thu, 05 Jan 2017 20:57:15 -0000, Tekkie=AE wrote= :

ed house means you're earthed. Concrete is a bloody good insulator!

The base can get wet.

-- =

Hipatitis (n): Terminal coolness.

[James Wilkinson Sword]

If it's not below the water table, no conduction.

[FromTheRafters]

All materials conduct, some better than others.

[makolber]

If you touch a hot 120 V wire while standing in socks on your concrete basement floor or on a deck outside, you WILL get a shock.

It's up to you if you want to call that __conducting__ or not.

m

[trader_4]

With regard to the initial claim, that concrete does not conduct, it's the same issue with both. If concrete did not conduct, a concrete encased electrode for an earth ground would be useless and you would not get shocked standing on a concrete floor.

[TimR]

I found a reply from OSHA to a question from a corporate safety officer:

Question 2: Would you consider an ungrounded fan, on a dry concrete floor, on grade, in an industrial setting a violation of this specific standard?

Reply: The use of an ungrounded fan situated on a dry concrete floor on gra de in an industrial setting will be a violation of the OSHA rule at 1910.30

4(f)(5)(v)(C)(5), if the fan has exposed non-current-carrying metal parts t hat can be contacted by employees. Concrete on grade level, because it will absorb moisture from the earth and be a good conductor in direct contact w ith the earth, is always considered to be at ground potential.