Replacing old consumer unit

[mikealig]

I have a old flush-mounted consumer unit with fuse wire plug-in sockets installed when the house was build around 1970. In the twenty odd years I've lived there, the house has had 4 extensions and, apart from the most recent, everything hangs off this consumer unit. I've never had any problems but would like to upgrade the unit. I'm concerned that once I embark on this, I'm committed to unlimited costs if problems are encountered and need to be fixed. I was considering replacing the plug-in sockets with ones that have MCBs (Wylex). Would this be a valid test of my electrics i.e if I didn't have any of these flip-out I could be confident that a new consumer unit would be OK to be fitted?

Thanks

 

[JBPElectrics]

Somewhere I read recently about a spark who fits a standalone 30ma rcd main switch for a couple of days to just such instalations, I thought what a good idea!

Fitting MCBs will tell you nothing you dont allready know! (save your money!)

In theory the sparks that quote should carry out some basic checks first, I do but not as comprehensive as a pir. This enables me to give a 'fixed' quote, which whilst often more than some sparks is never renegotiated, perhaps you could get someone to quote on that basis?

If you have a periodic inspection done it could cost a couple of hundred quid, hence I like this rcd idea!

 

[electronicsuk]

If you have a periodic inspection done it could cost a couple of hundred quid, hence I like this rcd idea!

That doesn't really prove a lot in terms of installing a new CU. If you provide a fixed quote then that's your call, but it leaves you open to a world of problems with borrowed neutrals, broken ring finals, insufficient bonding, and all the other things you'd expect from an installation that has been played about with for so many years.

A full PIR upfront on an installation this age really is the only way to go. If you don't like the results, only get the most urgent items attended to and save until you can afford to have all the work done. If the results are good and there is no major work to be undertaken, you may have needlessly spent a couple of hundred quid, but at least you have some peace of mind and don't leave yourself the open-ended cost of whatever remedial works MUST be done after fitting the new CU. Once you fit it, there's no going back.

 

[JBPElectrics]

Mathew, I agree with everything you have said, however i would guess your a little like me and for the sake of an hour and a GOOD quote will check end to end and test for borrowed Ns, it takes no time for a quick Ze and a snout at bonding.

'touch wood' Ive not been majorly caught out YET!

What gets me is spendig £200 on the PIR when the total cost of the CU change may be £4-500......

 

[electronicsuk]

Mathew, I agree with everything you have said, however i would guess your a little like me and for the sake of an hour and a GOOD quote will check end to end and test for borrowed Ns, it takes no time for a quick Ze and a snout at bonding.

Hypothetically perhaps, although I'm not really a domestic spark

 

[chapeau]

JBPElectrics is my kinda sparky!

 

[Taylortwocities]

Somewhere I read recently about a spark who fits a standalone 30ma rcd main switch for a couple of days to just such instalations, I thought what a good idea!

That may tell you that the combined earth leakage is less than 20ish mA but is no guarantee of anything else, as outlined above - borrowed neutrals, broken rings, spurs off spurs, undersized conductors, missing earths.
None of these will trip an RCD fitted on the whole circuit.

A basic live&neutral to earth Insulation Resistance test would be much more useful. IMO.

 

[JBPElectrics]

I completaly agree and thats what I do now, but I cant help thinking if your likely to get the work, do the tests, stick an old rcd on the lot and see what happens for a couple of days, will highlight dodgy emersion heaters, cookers freezers, nail through a wire and enable me to make a decission on how/what/where!

Havnt done it yet but have a couple of old rcd main switches kicking around.

 

[Steve]

I was considering replacing the plug-in sockets with ones that have MCBs (Wylex). Would this be a valid test of my electrics i.e if I didn't have any of these flip-out I could be confident that a new consumer unit would be OK to be fitted?

Thanks

No, since your installation will not only be protected by MCBs, but RCDs as well. They do different jobs, and an RCD is far more likely to show up hidden problems on an old installation.