consumer unit mixed messages

[dogmadmum]

hi guys i am after some clarification with regards to my consumer unit.

MY home is 30 years old and has the original consumer unit with the fuse wire blocks, although i am having no problems with that unit i would like it changed it to the trip switch type. I have had two qualified electricians out for quotes with two completely conflicting reports. One says the earth cable to my cold water tap and gas/electric box's are fine and that i just need the consumer box changing at a cost of £250 plus vat, the other saying my earthing is 6mm and will need updating to 10mm at a cost of 400 plus vat can i ask how would i know if my earthing is OK or indeed needs replacing.
thank you in advance

 

[telectrix]

the only way to tell if the bonding is adequate is by measurement of fault current and calculation. some electricians will blindly upgrade it without testing. get the guy who quoted £250 to explain if he's going to determine if it is OK at 6mm and if he gives you satisfactory answers then £250 is a good price. however, if he finds that it needs upgrading, then his price will be around £400 as well.

 

[RexT]

Hi dogmadmum,

Personally I would say the electrician who installs has to sign off paperwork to say that it is safe and complies with the current regulations.
I know that the first quote seems 'cheap' and reasonable however the electrician who has 'surveyed the property prior to the works is giving his professional opinion.
For me I would choose the latter as I would like compliance with the latest regulations.
I know the regulations are not retrospective in the case of enforcement but the change of a consumer unit is a fairly big job and you should consider that you would like the full package rather than the conusmer unit but not the earthing.
I will probably be disagreed with but this is an opinion.
I would also suggest that you check out the qualifications of your electrician and what he is going to give you after the works in the way of proof for safety / paperwork.
Hope this helps.
best wishes
Rex

 

[Des 56]

To give reasonable advise,it would help to know the earth system type
Do you know? or can you post a picture of the service fuse/meter position


Edit to say
Some good advise from RexT and well worth considering

 

[Guest123]

The 6mm protective bonding conductors may well be fine for continued service but an examination would need to be made to ensure this.

Also the earthing system within the property has a bearing on wether or not upgrade is needed.

 

[telectrix]

as rex says. the work is notifiable, so you will need to check if whichever spark you use is a member of elecsa, napit or niceic. don't just go by a logo on his van. ask him for his membership number and verify by checking with the body he is with or your local area building control (LABC)

 

[dogmadmum]

hi dec 56 i will post a picture for you as i really dont know what you mean by earth system type, are you wanting a picture of the consumer unit or the electric metre postion which is outside in a plastic box?
sorry but i can only just manage to change a plug (blush)

 

[telectrix]

there are 3 basic types of earthing. TT which is you own earth rod. TN-S where the earth is taken from the metallic sheath of the supply cable. TNC-S where there will be a brass terminal block on the side of the cut-out ( supplier's fuse). however, this can only be accurately determined by a qualified sparks with the necessary test gear to verify.

 

[SW1970]

hi dec 56 i will post a picture for you as i really dont know what you mean by earth system type, are you wanting a picture of the consumer unit or the electric metre postion which is outside in a plastic box?
sorry but i can only just manage to change a plug (blush)

Try to get a picture encompassing these items...

and this ...

This is the electricity company fuse and the bottom of the electricity meter (but both items might look a bit different at your place, e.g. a different colour and size).

 

[lamb]

If the supply is outside in a plastic box and an underground service (not overhead supply) it will be TNC-S and in this case the main bonding should be upgraded to 10mm and the earthing conductor to 16mm.
BS7671 - "before any alteration or addition can be made to an existing installation it shall be acertained that" ..... "the earthing and bonding arrangements are adequate."
TNC-S minimum adequate bonding size = 10mm. Replacement of consumer unit = alteration to an installation.
Both prices sound pretty cheap to me anyway.

 

[Octopus]

hi guys i am after some clarification with regards to my consumer unit.

MY home is 30 years old and has the original consumer unit with the fuse wire blocks, although i am having no problems with that unit i would like it changed it to the trip switch type. I have had two qualified electricians out for quotes with two completely conflicting reports. One says the earth cable to my cold water tap and gas/electric box's are fine and that i just need the consumer box changing at a cost of £250 plus vat, the other saying my earthing is 6mm and will need updating to 10mm at a cost of 400 plus vat can i ask how would i know if my earthing is OK or indeed needs replacing.
thank you in advance

You don't say where you are but £250+ VAT for a board change seems a little on the light side and how the sparky can say its OK without testing the continuity beats me.

I'd say £400 is more on the money.

 

[Amp David]

If the supply is outside in a plastic box and an underground service (not overhead supply) it will be TNC-S and in this case the main bonding should be upgraded to 10mm and the earthing conductor to 16mm.

Is that so, well our house must be one of a kind then! Outside in a plastice box but TNS? Why will it beTNC-S and nothing else?

 

[lamb]

Because by the time cavity wall boxes came in all new underground services were PME, paper insulated cable was out and plastic concentric cable was in (well in my area anyway).
I have never seen a TNS supply in an outside box but i'm sure it is possible (wouldn't leave much room to terminate the lead covered cable though)

 

[Andyfm]

I`ve seen a few round here which are TT

 

[Amp David]

Those pics have to show TNS, clamp on the sheath