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Neutral-Earth Bond - Where?


Supergeek
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Hello everyone,

I recently went through every DB in and around my house in search for the Neutral-to-Earth bond, not finding it. My house is in a slightly older neighbourhood, so I am curious if anyone here know where they typically did the bonding?

I could not find any bond in my main DB (I expected it to be here), sub-db's (not expecting any here, so this is good), or the main disconnect switch that is outside my house, between my main DB and the utility source (I did find some very antique equipment in here that looks like it might have been an electricity meter at some point).

Anyone know where they did the bonding in older houses? Some pics would be nice, if available.

Thank you in advance!

 

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On 2021/06/23 at 3:56 PM, Supergeek said:

Anyone know where they did the bonding in older houses?

Is there a reason you are looking for the bonding? The bonding is done on the star point of the secondary side of the transformer at the mini-sub. It is normally not the small boxes feeding the six houses but rather the big green steel structure with 11KV or high voltage warnings on it, only your service provider will have access to that point.

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Depending on the type of earthing arrangement ... it is generally not allowed on the consumer side of the electrical installation ... however if you have an inverter/UPS/generator or the like ... there is a good chance you will have the neutral and bonded together close to the system as per the electrical regs.

This is something you need to understand before just looking for it ... if you do have it on the consumer side ... you should be concerned because there is a good chance your protective device are either not operating correctly or not installed.

 

 

 

Edited by isetech
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Maybe if OP can say what he want to do, so that he can get an accurate advice. To check if bonded, measure the voltage between your earth and neutral and you should get close to zero volts. Then you will not need to go and look for the physical connection 

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This is what the supply to my house (which is very old) and the geckos home looks like. Its a 2 core cable. The insulated centre conductor is the Live and the bare copper conductor surrounding it is the PEN (Protective Earth Neutral) Conductor. This is called a TNCS earthing system. The PEN conductor is connected to the Neutral Bar and this is earthed to the earth electrode and copper water pipes. The PEN conductor is also earthed at the transformer star point (supply point).

642765526_SupplyToHome.thumb.jpg.46c021355ee61f9dcbacbd721416d86a.jpg

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Hello everyone, 

Thank you for your replies.

@Gerrie - Thanks for the explanation and feedback. The reason I was looking for the bond was purely to get an understanding of what is being done where, and I have read some posts that this is typically done in the main DB. Thanks for clearing that up.

@isetech - Thanks for your feedback. This might be a secondary reason why I was asking. I do have an inverter, and I was wondering where this neutral - earth bonding would happen. I am trying to test my logic of what would happen in a case where you flip the main switch (which switches both L and N) and work on PV / inverter and this bond does not exist.

@hoohloc- Thanks for your feedback. It was mostly curiosity to get a better understanding of how these things are done, and where. Thanks for the information about testing the voltages. This is something I have tested before, but obviously I have not tested this for all the possible variations of switches being flipped.

@Carl- Thanks for the feedback and attached picture. I am guessing based on the other feedback that what you have in your TN-C-S earthing is slightly different from the TN-S earthing which I assume most new dwellings use.

 

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A couple of weeks ago our munisipality mains supply power dipped and spiked a couple of times and then died (Tuesdayl). Viva ELM. After that the shower taps kicked the daylights out of you when you shower or any other tap down to earth. If you had to adjust the shower taps you had to put plastic bag over the tap handles. I measured 165V AC between any tap and the shower drain. Outside my house in the municipality green box the neutral bus link (previously stolen and was replaced with 16mm² gp wire wound around the two legs of the busbars) was glowing a very nice red orange colour. In the supply box to our municipality box, the white and blue cables didn't draw any current but the red phase was pulling 270 A and was radiating quite a bit of heat. 

At my house's budgie box (where the cable enters my house from the green box) there were a lot of sparks between the earth from green box and my house earth stud, when I disconnected the live, neutral & earth between my house and green box. It still kicked like a mule.

I was advised to connect all the earth and neutral wires in my budgie box together and connect it to my own 1.8m earth rod with a 16mm² cable, as close as possible to the budgie box.

As soon as I connected the earth coming from the green box the sparks started to fly again (btw I could burn a 50w halogen globe quite bright between the municipality earth wire and my house earth or the budgie box earth stud, by that time there was 191 V between municipality earth and my earth). Even with the new earth rod connected, you still got kicked and that was happening at all the 12 houses supplied from this 1 green box. 

After three days, the municipality electrical dept arrived and replaced the burnt/burning/glowing neutral bus link and found out there is zero power to the green box. After a while they found that the supply cable to that box was burnt underground somewhere (this was friday afternoon). 

On monday a private contractor spiked the cable to locate the burnt part, their crew dug up the cable and replaced a 3m piece and by 21h00 monday we had power on again. 

My earth neutral bond, connected to my own earth rod, will stay where it is, next to my budgie box because it has happened before that the neutral bus link got stolen and then the shower shocking experience will be back, but not nearly as bad as this time when the cable burnt. 

I was advised to use a 16mm thick, at least 1.8m long earthing rod connected with at least 16mm² cable to my earth neutral bond.

After this long read: hopefully you now know where and how to do your earth neutral bond for your own safety when the municipality bond fail. This was about R200 very well spend. Just make sure that you don't hammer the rod through your supply cable, I went down about 300mm away from the street side to lessen the risk. 

Enjoy

Edited by Vaal
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