clueless- consumer units, and earth terminals/rods

[amandaeb]

I have read with interest many of the posts on this board, however I am still a little confused about a few things and I'm hoping someone could explain please.

I have asked a couple of electricians to give me quotes for a new consumer unit. I realise I should have asked more questions at the time, but its only since I've read up more about the whole thing that I've realised I'd rather be a bit more informed, and I'd like an unbiased view please.

What does split load mean? Is it to do with some circuits being on the rcd and some not? If not, what are the advantages of split load?

I've read about light bulbs going tripping the whole lighting circuit plunging the house into darkness, is there any way/ type of consumer unit/wiring that avoids this?

( If you don't change the bulb immediately, and you reset the switch will the other lights come back on? Or do you have to replace the bulb first?)

Also, I've been told by an NICEIC electrician that I need an earth rod, but I read in the DIY book that that's only necessary for country properties with overhead wires. I live in a city with underground cabling.

At the moment there is an earth wire running into the house from (I assume) outside, clipped to the big pipe that brings the electric supply into the house. The other electrician told me that this earth wire just needs to be permanently attached to the electric supply pipe, ie not just with the clip.

Who is right?

Also, the one electrician said they could fit the earth rod, but the other (the one who said I don't need an earth rod) said the new MEB would have to come in and do the permanent attaching of the earth wire. Apparently it looks like the moulding around the electric supply pipe has been opened previously by someone not qualified, if this is relevant?

So who can fit an earth, the new MEB or the electrician? I read somewhere that the electric work would need to be certified before the MEB would come in, is this NICEIC certification?

Lastly, is it a fire risk that the meter and existing fuse box is mounted on the wall on a wooden board and the new consumer unit would have to be fitted onto this wooden board? The one electrician told me that the wood board is the property of the former MEB! and as such they cannot take it away or alter it. There isn't space to move the unit elsewhere.

I'd be really grateful if anyone can answer any or all of these questions. I feel so vulnerable not knowing anything about it.

Thank you in advance for any help.

Amanda

 

[securespark]

Split-load refers to the consumer unit having two "sides": one where the circuits are protected by an rcd and one where circuits are not. They are both isolated by the main switch, where the rcd isolates only the protected circuits if it trips. This means you can put circuits like lights, burglar alarm etc on the non-rcd side so that if there is a trip, the lights (for example) don't go off.

Light bulbs blowing can trip the circuit mcb, but this can be reduced by using fuse-protected lamps. I swear by (not at!) Osram brand.

Usually the mcb will reset if you leave the dud lamp in situ - suck it and see (not literally!!)

I suspect that you are on a T-NS (Earth provided by sheath of cable), but double check with the supply company. They will advise whether the earth connection can be taken from the supply cable or whether you need to provide your own (rod), and maybe they will upgrade the earth connection to their cable, but they have no obligation to do so.

Talk to them nicely and see what they say.

If the engineer does call, they can look at the rest of their installation to see if all is well.

As regards the wooden board, 99% of installations are like this. In the olden days, the EB's used to say that the board their stuff is mounted on is theirs and the house CU cannot go on it, but these days they don't seem to bothered (in my experience anyway). Maybe you could ask them about that when you ring about the earth connection.

To answer your question, it is not a fire risk, as all connections are enclosed in either metal or flame-retardant plastic enclosures.

IE Switch boxes, consumer units etcetera....

Hope this helps.

 

[amandaeb]

Thank you very much for your reply Securespark

that does make things clearer. It also raised a couple more questions if you don't mind

When you ask about the earth etc do you ring your electricity supplier, if so what department would I need to speak to? Or is there a separate company that looks after the infrastructure type equipment for everyone?

I have energy saving bulbs in most fittings, do you know if these are likely to have the same effect on the circuit when they blow?

Is it more dangerous not to have the lighting protected by an RCD?

I think the electrician mentioned MCB's too. Would the lighting circuit have one of these, and if so does a bulb blowing cause all the lights to go off too?

Thank you again

Amanda

 

[securespark]

Hi Amanda

1. Don't think so. I have fluorescent lamps (low energy) everywhere and they don't seem to cause tripping.......yet!!

2. More dangerous in my opinion to have lighting on rcd cos if it trips at night, then the whole house is in darkness....

3. Not sure what kind of board you have at the mo. Mcb's tend to be more sensitive than rewireable fuses in this situation.

As for the EB, I'm not sure how the MEB arrange their services, but ask if an engineer is available to talk to. If you can't, just explain exactly the situation and they'll probably put you through to someone who can help.

 

[breezer]

i have 98% of energy saving lamps here, they never seem to "blow" but get less bright and black inside near the base, then i just change them.

as for an rcd i found this easily explains what it is for / does

 

[securespark]

Breezer


Bouht a load of 20Watters from Morrisons (look like large gls)@ £3 ea and they were great, until they started going pop, but they didn'tmake a noise or trip the mcb, just a very "electronicky" sort of niff.

Back onto my favourite brand Osram, but can't find any of theirs that look like ordinary lamps - seen any??

 

[ed998]

hi

if it helps with your enquiry - not trying to confuse anyone here , you need to ask the leccy board to come out and carry out an earth loop impedance test at your supply intake. They will know what this means and will ensure you get the correct type of earthing arrangement installed.

I have worked on houses in towns which have needed to have earth rods installed purely because the earthing from the main supply cable was not adequate - its an important thing to get right because it can affect the operation of fuses,MCBs etc... If you are thinking of getting it done - you may as well get it done right

Good luck

Ed

 

[amandaeb]

Thank you very much to securespark, Breezer and Ed. I actually feel like I'm starting to understand.

Ed- A retired electrician told me yesterday something very similar to what you said about the earth and the operation of the mcb's etc.

He said that, (if I understood correctly,) if I have an earth rod I cannot have a split load consumer unit because in this case everything has to be earthed.

He said I can only have a split load if I have an earth terminal installed. Apparently at the moment the wire clipped onto the elec supply pipe is not earthing it properly because its not directly connected to the lead inside the supply pipe. But the installation is earthed because there are connections to water and gas pipes. He talked about a ZE? reading and that it was probably ok.

Does anyone have an opinion on this?

So my question is to pass an inspection is it just the ZE?/earth reading thats important, or the way that its earthed as well?

Again, many thanks I do appreciate the time you're spending on reading and trying to understand what I've written.

Amanda

 

[ed998]

No problem

the way the system is earthed influences the earth loop reading(Ze) you will get. Basically you want this value to be as low as possible so when a fault to earth occurs there is as little resistance to earth as possible.
This will ensure that your mcbs, fuses whatever will operate within the times they are supposed to.

If the Ze is ok then the system is adequately earthed - but from what you have described it would be a VERY good idea to get this checked by someone who knows a) how to measure it and b) how to interpret the reading measured.

Hth,

Ed

 

[il78]

Amandaeb, I think you misunderstood the retired electrician or he misunderstood you.....(confusing myself)

If you have rod installed and class the system as TT then its advisable that you get a split-load board with 2x RCD's :

100mA Protecting lighting etc
30mA Protecting sockets etc

I dont think it was mentioned above but has anyone recommended that you get an inspection carried out any-way to determine the overall condition of the installation or are you just after getting the board changed?

 

[amandaeb]

Hi Il78

Thank you for your reply. After I read it I rang the electrician again and you are right, I misunderstood. Having an earth rod means I have to have 2 RCD's.

I had an inspection, by the now retired electrician, when I bought the house in 1997, and it passed apart from the upgrade to the consumer unit.

There still seems some controversy about whether the local electricity board, whatever they now call themselves, come out to do earth work. I've been told they do and they don't, but I still can't find out the name. Someone mentioned Acquilla/Aquilla, but I can't find a number for them. I'm with Virgin for my elec supply. Anyway...

Thanks to all,

I shall take on board about the light bulbs. BTW the retired electrician told me that with Crabtree boards you can get type 3 something (fuses?) which allow greater ranges of surge so if a bulb goes its less likely to trip the circuit.

Amanda

 

[Big_Spark]

Amanda, regardless of what type of supply you have from your local supplier, it IS their LEGAL responsibility to supply you with an Earth connection compliant with the Electricity Supply Act and conforming to BS7671, The IEE regs.

Don't let an electrician make you pay for something that 1: you should not pay for and 2: may not need.

As has been pointed out by others, the Earth connection is critical to the operational characteristics of protective devices, get this wrong, and they may not operate as designed which could have devastating consequences.

As you state you have an underground cable, then in all likelhood you will have a TN-S supply, the steel wire armour sheath of the cable providing the Earth connection. These can and do degrade with time, however it is the suppliers responsibility to ensure you have an adequate and compliant connection.

If the Earth you have is no good, then the supply company MUST LEGALLY supply a new one, and it must NOT be an Earth electrode. The bad Earth will indicate a degraded cable, they MUST provide a new link from the supply cable in the street to your premises.

Many Electricians, innocently, believe that they can correct supply Earths by introducing an Earth Electrode, but the situation is not as simple as that. This is not a reflection on them, their abilities or honesty, it is a little known fact that it is the legal responsibility of the supplier to supply an adequate connection and replace the cable if this is not the case.

For obvious reasons the supply companies try to keep this quiet.

 

[amandaeb]

Thank you for your reply FWL, I didn't know that they were legally obliged. Can they charge for this do you know?

On yours and others recommendation I rang Virgin who gave me the number of the local company who is responsible for the supply pipes; Aquila.

Apparently I need to put in writing about having wooden floors and dpc to concrete floors, that my wiring meets current iee regulations and that the elec can provide a contractors completion certificate.

Once they receive that in writing they'll tell me if I can have a PME. Are you saying FWL that, if they come back and say they can't fit one, that I should insist they are legally obliged to? Is there an alternative to a PME or earth rod?

But as you and others have pointed out the type of fuse board I have will depend on the type of earth I get. So I can't really have the work done til Aquila tell me what sort of earth I can have. So should I have Aquila come before I have the new consumer unit? The retired elec mentioned that the certificate was just concerned with the earth bonding.

So it seems that they will deal with the earth issue, I wonder why the one elec told me they don't do it anymore... He was the one that wanted to fit an earth rod.

Is an earth rod not as good as an earth connection to the supply pipe? Or is it a matter of principle about who supplies what and pays for it?

I will be very pleased if your advice saves me money!

Thank you again
Amanda

 

[Big_Spark]

Amanda, let me correct one thing...you not have a pipe bringing electricity into your home, it is a cable. If you state you have a pipe to the muppets in the call centre you will simply confuse them more than they are already.


Regarding your Supply. They are talking shiite. They are LEGALLY abliged to supply you with a cable that meets all current (pardon the pun) regulations under the Electricity Supply Act.

You must demand in writing that they come out and test you supply for compliance and that your earth connection is adequate, and that if it is not they must replace it. When you contact these poeple by phone, get the address of their engineering department, and find out the name of their Director of Engineering or whatever they call them. Address the letter to them personally, and send it by SPECIAL DELIVERY so you have a record of it.

If they refuse, then I suggest you seek legal advise.

The one thing I will say is that you do not need a split load board and the main switch need not be an RCD.

Example:

Main Switch: 100A Double Pole Isolator
Circuit 1: Cooker: 40A 100mA RCBO (RCD/MCB Combined)
Circuit 2: Downstairs Ring (Sockets) 32A Type B MCB
Circuit 3: External Use Sockets 20A 30mA RCBO (These will be sockets used to power garden tools)
Circuit 4: Kitchen Sockets (Ring) 32A 100mA RCBO
Circuit 5: Upstairs Ring (Sockets). 32A Type B MCB
Circuit 6: Immersion Heater or Boiler 16A Type B MCB
Circuit 7: Downstairs Lights. 6A Type B MCB
Circuit 8: Upstairs Lights. 6A Type B MCB

This may be seen as a typical installation that will overcome any of the problems connected to your type of situation.

I would strongly urge your to change your consumer unit, then insist that they issue a full Inspection and Test certificate once the work in completed, they should anyway.

Regarding the Earth Rod, the effectiveness of the rod will depend on the soil conditions into which it is installed. Dry ground has a higher resistance than damp ground. If the soil is susceptable to drying out or flooding during the year, this will seriously effect the operational characteristics of the electrode. Before any electrode can be installed there must be a proper investigation of the soil completed to determine it's characteristics.

It is not as simple as hammering a copper rod into the ground, connecting a cable to it and walking away.

 

[il78]

Do you not consider downstairs / kitchen sockets to be expected to power equipment outdoors, I know you have stated external sockets protected.....but not everyone has these....