SANS codes.

[Jacques#1]

The rope DB thing: We used to install the SS chain in DB's where lowering the DB is just not possible. What is safer, doing joints on the cables because they are too short or fitting the chain? As far as cost go its also just too expensive fitting seperate ciruits like a mains outside the DB (since most db's are flush mounted). I started my electrical career at an explosives and chemical manufacturing facility, where I learned the SS rope thing. Think of any electrical standard......they doubled it. If 1 Mohms is good enough for SANS, they said 10Mohms etc.

The DB in a Cupboard: The unfortunate part of the DB in cupboard as wrong as it may be, no-one will give you permission to dismantle their cupboard. The argument that I've heard more than once when telling people its not really ideal/right, is, we bought the house like this, the house was built like this.

Bonding an antenna: As the word may could possible exclude SPD's from an installtion, Page 186, 6.13.2.3 says "An antenna (including a satellite dish) shall be bonded to the installation earthing system by means of a conductor of at least 2.5mm2 copper or equivalent". This piece says SHALL.

The Space heater: The argument went around Page 199. Note 2 talks about the appliances for space heating, and 6.16.4.1.2 talks about space heater. We eventually agreed that a "Space Heater" regardless of the interpretation is actually an infra red or element heater that normally fits on a wall (thats where the out of arms reach bit comes in). And a heater that heats a space i.e. its generally doing space heating. Hope this makes sense......I don have a better way to discribe it? Why is this important you ask..... A space heater shall have its isolation in the same room/or on the appliance. If underfloor heating fell under the same category, it would have meant that installing a double pole CB in the db which is lockable and marked and under the safe principles of a fixed appliances would not have been allowed . Since I was working in the underfloor heating industry, it affected my customers that could not get a COC because there was no Isolator in the same room. Installing a 2xCB in the DB was ideal....

Fitting an E/L: If SANS relaxed a bit as far as old (1992) and new installations go we would get more done. Installing a new EL means a change to the electrical system, which in turn means the system has to comply to SANS 10142. Replacing items as I see it is not a change in the system. If SANS said.....you can install a E/L, it does not mean that the system is all of a sudden post 1992, more people would do it as its not going to cost an arm and a leg. I too inform people, but they argue that if it was only installing a new EL they would do it, because its ten other things as well once the new EL is in, no way.....?

Thats enough for one day.....

[123]

Bonding Antenna

Bonding an antenna: As the word may could possible exclude SPD's from an installtion, Page 186, 6.13.2.3 says "An antenna (including a satellite dish) shall be bonded to the installation earthing system by means of a conductor of at least 2.5mm2 copper or equivalent". This piece says SHALL.

Hi Jacques, if i thought i was confused, i was mistaken. I am confused

We have, in our area, 12 MIE's, registered. One of which marks the IE exams. Another the ecb representative. I have clarified this with some of them (incl. Mr x which marks paper 1 and 2), on numerous occasions, and the consensus was that it is not required according to SANS 10142 (1.3) (f) on page 21 of the new sans 10142 from sabs.co.za.

Their argument being that the "equivalent" part", as stated in 6.13.2.4, is preceded by 6.13, which refers to "note 2": ""NOTE 2 No external conductor is required if compliance with the requirements for continuity can be proved by the test in 8.7.2.""

Which means: 8.7.2 Continuity of bonding Amdt 4
Test the continuity of the bonding between the consumer's earth terminal
and all exposed conductive parts using a supply that has a no-load d.c. or
a.c. voltage of 4 V to 24 V, and a current of at least 0,2 A. In each case,
the resistance shall not exceed 0,2 Ω. Amdt 4

Which means, if you have tested for the values, it would have indicated if a separate earth was needed. (Cost implications)

Regards - Christo

[AndyD]

More like stepping into poo

*(nods)*

If 20-30 mA is enough, then that's always going to come down to the path the current takes. (I thought it takes about 50-100 mA, but I suppose that it will vary according to each person's own constitution).

The figure of 20_30mA you quoted is the leakage current that starts the tripping process of the earth leakage breaker or RCCD. As with any disconnect device there is a time between the start of the fault current being over the tripping threshold and the disconnection of the supply. During this window of time the fault current flows uninhibited by the disconnect device. In the case of an earth leakage current through a person receiving a shock this current would be determined by the resistance of the path to earth through the person. This resistance would very depending on a thousand and one variables such as footwear being worn, flooring surface, etc. If the person is touching an earth with the opposite hand they have contacted a live supply then this current would be large and particularly prone to causing defibrilation. The path of current flow would be across the chest.

I'd far rather have protection that's going to automatically kill the juice within a fraction of a second than get hooked up and have to wait for blind luck to take a hand, or for someone to realise there's a problem and kill the supply.

Point taken. What I'm questioning is how effective at saving live these devices are. Are they saving more lives than compulsory appliance testing would be saving. Are they giving people a false sense of security causing them to work live instead of isolating etc. I would like to see some hard figures on how much higher survival rates are with shock victims if an earth leakage breaker is installed.

Valid comment, but I think people are too blasé about electricity already. Consider the "if it works, it's fine" attitude test inspectors get from their clients. Ultimately, it's hard to see people becoming more casual about it than they are already.

I think you would be surprised at the depths of some peoples stupidity :-)

Testing an earth leakage unit is far simpler, and how often do people do that?

Good point. Appliance testing would need to be legislated. It might be more appropriate for commercial premises where people have a more 'devil may care' attitude toward the machinery and appliances.

I think extending the earth leakage protection debate to appliances is a bit tricky anyway. That takes us right into the "everthing on earth leakage regardless" scenario. Plug points are a special risk zone, I reckon, as they present a number of problems and risks you shouldn't be getting elsewhere, particularly when it comes to reliable earthing.

I think plug in appliances are more likely to suffer damage that may result in user shocks due to their mobile/portable nature. How many times have you seen a steam iron or lawn mower with a damaged trailing cable compared to a static appliance such as a geyser? These kind of faults are protected against already by the earth leakage breaker supplying the plug points.

[Jacques#1]

Which means: 8.7.2 Continuity of bonding Amdt 4
Test the continuity of the bonding between the consumer's earth terminal
and all exposed conductive parts using a supply that has a no-load d.c. or
a.c. voltage of 4 V to 24 V, and a current of at least 0,2 A. In each case,
the resistance shall not exceed 0,2 Ω. Amdt 4

Regards - Christo

I fully agree with that. The thing is, if you test the continuity by connecting one lead to the earth bar in the db, and the other on a geyser, the reading must be less than 20 Ohms (i think), so too for all continuity of bonding. If you stick the tester on the DSTV aerial and the reading is say 10 Ohms, then . I remember talking to an inspector about this. He said it is not so much the lightning, rather the voltages the decoder gives off. Have you ever touched the cable coming out of the decoder? Sometimes that thing really bites you. I haven't yet tested an aerial that passes, maybe I will get one and reduce the time I spent on site.

PS... They talk about bringing it down to the earth continuity of the system.....I don't see this as taking the cable all the way to the DB, but rather any earth point that passes less than 20Ohms, like the geyser bonding, or a junction in the roof with space for one more earth. Don't take my word on this one though, I may be wrong.

[Dave A]

I remember talking to an inspector about this. He said it is not so much the lightning, rather the voltages the decoder gives off.

That inspector might want to consider the floating earth situation that could arise in a lightning strike if the earths aren't directly connected to each other.

[AndyD]

Have you ever touched the cable coming out of the decoder? Sometimes that thing really bites you.

There may be voltages present on the inner conductor of the antenna cable but the outer braided shield should be at 0 volts (earthed). The decoder or DVD player etc that the antenna cable plugs into won't earth the braided cable shield because most of this type of appliance are of such a class that an earth isn't required and they only have a two core electrical supply cable with no earth bond to the electrical installation. If the antenna cable gives shocks from the braided shield then the decoder could have a low insulation fault.

[I need help]

I have recently done a course,and believe it is now compulsory to install an auxillary earth terminal(bar) for "others",therefore the installation does not comply without this auxillary earth bar.
To be installed and indicating it is an earth bar (earth sticker,label)

[Jacques#1]

I have recently done a course,and believe it is now compulsory to install an auxillary earth terminal(bar) for "others",therefore the installation does not comply without this auxillary earth bar.
To be installed and indicating it is an earth bar (earth sticker,label)

That earth bar is usually located at the main entry point of the house. (most new houses.....its at the ripple junction). If there is a free standing bolt and nut in the box, its an earth stud, AKA earth bar.

[Jacques#1]

That inspector might want to consider the floating earth situation that could arise in a lightning strike if the earths aren't directly connected to each other.

What I meant was....you connect the wire any other place in the earth system on the same grid, not install a new and seperate spike for this. Besides, spikes are not really recommended anymore, you are only allowed to spike if you have no other choice (as far as I know)?

[Dave A]

My turn to explain - my point was around what the real hazard is...

I've got a door handle in my office that hands out a fairly dramatic static jolt from time to time, but hasn't killed anyone yet.

[AndyD]

My turn to explain - my point was around what the real hazard is...

I've got a door handle in my office that hands out a fairly dramatic static jolt from time to time, but hasn't killed anyone yet.

This is a common problem easiest way to fix this problem is to wear high heel shoes with a pair of rubberised odour-eaters inside them :-)

[Dave A]

Sounds enticingly kinky, but I'm not sure my dodgy back could take the high heels...

[Jacques#1]

I've got a new one...Has anyone come across this before?

Overhead lines across the road, feeds down the pole and under the street to a house more than 100 years old (assuming). The cable runs up the wall and in under a galvinised roof. A makeshift connection is done at this point and a 10mm earth cable runs back down the cable to a spike about 50cm from the house. Inside the house the db sits surface mounted with one entry hole only. L+N cables comes through this hole and only 3 earth wires. The ceiling is also steel.

Without having done any faultfinding yet, here's the problem...I'll go back there in the daylight to see whats happening.

The house constantly gets hit by lightning. The lightning however fires blue flames out of all the socket outlets and the lightswitches, which are all steel. You can see the evidence by looking at the black burned coverplates and walls surrounding the S/O's and switches. Now, not having done a loop impedance and a spike test yet, i'm in 2 minds about this.

When lightning hits your house it searches for the fastest possible route down to earth, it also hits your house because it is grounded. It hits often because it is grounded, and everything is metal, but, the blackening of all the electrical equipment indicates that the lightning hits the house and rather than running down to earth (with some damage to equipment), it fires out at every end. It would seem that there is no ground on the house, and the lightning actually follows the live conductor, hoping to piggyback to an earth????? But then again, with no ground, why does it get hit so many times????? There are plenty of other houses very close?

[Dave A]

Two things come to mind on the regular strikes -

The roof of the house could be sitting at a different potential to the houses around it due to not being earthed back to the transformer, or

There's a sharp metal point somewhere on the roof which intensifies the electromagnetic field and could be atrracting the unwanted attention.

The sparks are probably because the earth is floating too far off the neutral during the strike. The loop impedance test should pick that up. You might get an interesting voltage reading between neutral and earth too.

[AndyD]

I like Dave's theory, sharp edges or acute angles etc might attract lightning.

I'm not sure if I understand the layout you're working with here. There's an earth spike close to the house, does the earth wire from the spike go directly to the DB earth bar or is it bonded with the neutral where the supply wires enter the house? Is there a meter somewhere on the premises or is it an ED?

The lack of earth wiring coming from the DB is not uncommon in old installations where the steel conduit was the earth and it was common practice to just bond all the conduits at the DB with straps and a single earth wire. I woul test the earth spike first and post the results if you feel like it. The neutral - earth bond resistance would also be nice to know as well as the neutral - earth voltage when there is a load on the system.

Is the roof steel sheet construction? If it is then maybe the roof is bonded to earth by physical contact with the steel conduiting. If it is then this might make it more attractive to lightning. If you can 'unearth' the roof so it's just at floating potential and perhaps you can install a separate earth spike far away from the electrical earth and install a lightning conductor.