An independent electrician and UK Power Networks, the network operator for British Gas, the electricity supplier, have both confirmed that the Earth Loop Impedance Test Ze value at the supply is 37.2 Ohms, when it should be below 0.8
In conclusion, no earth is provided to the house.
The type of earthing is by underground cable.
UK Power Netoworks can provide a Protective Permanent Earth but, to my surprise, I have to pay for it, which can be quite expensive because it implies digging up the street and the floor of the house.
Should not the electricity supplying company be responsible for this?
I will also check the price of installing an earth electrode.
Well where is the Earth usually then? I doubt if many properties have had their earths measured unless just rewired. And yes, if its part of the service, which I guess it should be if its a safely issue regarding a supply at the supply side of the CU, then there is an argument that it should be maintained by them. However in todays world of passing the buck who knows. S Stuff some earth spikes in and bond everthing to it, and I suppose the Neutral with a bit of luck their cable will blow up and they will have to fix it.. grin. Brian
It's really something which should be changed now - after all an earth is considered essential. The water companies, for example, were forced into adopting shared drains. So same sort of thing.
The background to this thread is a previous thread here,
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Basically, a washing machine engineer found an Earth Loop Impedance reading too high at the machine socket and refused to repair it.
After investigating the issue we found that the fault was the main earth as described in this thread.
Based on your inputs in that prior thread and based on the comments by the electrician that visited the property I thought that the electricity supplier was going to take care of it, but UK Power Networks says is not the case. They write:
"The new ESQC 2002 regulations require UK Power Networks to provide the facility for the customer to connect to the neutral or the protective conductor but only when installing a new electric service line or replacing an existing one, and then only when appropriate"
"The earlier regulations (1937/1988) imposed no specific requirement upon electricity supply companies to provide an earthing facility for customers' use. Therefore, where an earthing facility was provided, this was done without obligation and with no guarantee as to its performance"
UK Power Networks also said by phone that I am not required to do these works.
Am I required or not?
I have been living in the house for over 10 years without issues and have only found out about this by chance.
Would placing RCDs be a safe and legal alternative?
There were reports in the local papers some time ago, when they were digging up all of Leith St. and putting small shops out of business in preparation for tram track installation (now curtailed due to lack of funds), that the replacement of metal utility pipes by plastic meant that owners of adjacent properties should check their earth connections to see if they needed to provide their own.
Very much trying to pass the buck. But it's Edinburgh Council.
Required as in common sense making sure you and any visitors stay alive? Absolutely.
Kind of...
With a Ze (external earth impedance) of 37 ohms, then a RCD would be required for *all* circuits. However not the same RCD - you need several. The question that then remains, is that if this earth is so poor (and its supposed to be TN-S - so the likely reason for the poor earth is cable sheath damage in the supply or similar) then can you (or would it be wise to) rely on it staying in its current state of non functionality and not get any worse. The answer to which can only really be "no".
That means you need an independent earth to be certain.
Going this route you are in effect going TT. No big deal in the general sense, but you need an insulated CU (an earth fault in a metal one prior to the RCDs would never be cleared).
So in the same circumstances I would slap in an earth rod, and a new
17th edition style insulated CU with at least a couple of RCDs as a minimum. If going for a posher solution, then an all RCBO CU or possibly multiple CUs depending on how many circuits you have etc.
That's been the rule for a long time - mains gas or water pipes are not acceptable as an earth, and the utility company can change the metal pipes for plastic whenever they like.
OP should definitely fix the situation without delay. And there are legal r isks/comebacks if one fails to. Exposing people to a system you know to be dangerous could land you in very hot water if things go wrong.
But should you pay for the supplier to fix the earth? No, its not legally r equired and would not be sensible. Use your own earth rod.
No, you need RCDs covering all circuits plus an earth rod. With no rod you' re relying on an earth feed that's likely about to go o/c (the fault cause is likely to be corrosion). It might be acceptable in the 3rd world, but no t here.
Be aware that plastic (insulated) CUs are often not fireproofed and have ca used house fires. Last I heard those ones were due to be banned from sale. So pick with consideration. A split CU is best, preferably with an RCBO for each socket circuit. In an ideal world, an RCBO for every circuit.
If you actually developed a genuine earth fault which resulted in
240V across that 37 ohms, (which is dangerous because the earthed metalwork in the installation will be live) and if that 37 ohms resistance is in one place in the cable, the resulting 1.5kW generated might burn out the whole cable at the fault site quite quickly, resulting in the need to replace it, and that would probably include fixing the earthing too. Alternatively, it might just burn out what's left of the earth connection completely.
Ze is the part of the earth-fault-loop-impedance external to the installation. It's measured with the means of earthing disconnected from the installation and also from the main bonding, to remove the effect of any 'fortuitous' earthing. It's therefore meaningless to talk about the Ze at a socket.
Zs is the impedance of the complete earth-fault-loop at any particular point (such as a socket). For convenience it's conventionally measured with the main bonding connected, so benefits from the fortuitous earthing via the main bonding.
It's clear that in your case, with the Ze >30 ohms and much lower Zs readings, you are relying heavily on fortuitous earthing via the bonded service pipes - and probably back to a good metallic earth via the main bonding in other buildings. (This indicates that the bad supply earth is probably quite local to your UKPN service.)
If someone came along next week and changed those pipes to plastic you'd have no effective earthing, at least so far as any non-RCD-protected circuits are concerned. This leaves a serious electric shock risk in the event of an insulation fault in an appliance.
If UKPN won't fix the earth they provide FOC, you have two options: (i) convert your installation to TT earthing - local earth electrode and all circuits on RCDs, or (ii) pay UKPN. Ask them for a quote for a PME conversion - that has to come with a good earth!
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