lights and Replacing old Consumer Unit With New RCD Type?


Postby greengrass » Wed Nov 23, 2016 11:27 am

Bungalow split serve on Wylex wired fuse consumer unit ie left and right side of bungalow. I know the dangers of elec so I work in strict safety.

Lights: kitchen GU10 bar with four one failed on switch on and blew the fuse with flash from switch Why flash from switch?

Changing Wylex wired plug in bayonet fuses CU.

Competent in changing but difficult to get work signed off.
open area on wall set at 4'.6" high (stand working position) believe all feeds from attic.
straightforward no clutter meter in external box same wall.
What's the rough cost of changing the Wylex wired CU to the new type RCD. (8 way) and what's possible extra under new regs: , wiring tested ok around 5yrs ago.
can't add picture or drawing
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Postby kbrownie » Wed Nov 23, 2016 5:32 pm

Normally expect the earthing to be updated.
The cost would depend how you want your circuits split.
Normally a dual RCD board would be used, but some prefer all ways to be RCBO, the latter being more expensive.

Dual RCD with earth update, probably £400.00
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Postby ericmark » Thu Nov 24, 2016 10:49 pm

There is nothing to stop you using the old Wylex fuse board even today, I have two each fed from an RCD the fire resistance may not comply, and being so old they were not type tested, but since I am skilled they don’t need to be type tested.
The problem of ionisation is odd, it can cause a massive flash across one day and nothing the next, your light switch clearly caused some ionisation of the atmosphere with in the switch on, and likely also inside the bulb of the GU10 this is why we some times get a bright flash as a bulb blows.
The MCB differs from a fuse with the disconnect times, with a fuse the loop impedance being slightly over the permitted limit will mean the disconnection time will also be slightly over the limit, but with a MCB there are two devices in one, so if the loop impedance is exceeded it can jump from 0.01 seconds to 5 seconds to disconnect so changing a plug in fuse for a plug in MCB needs the loop impedance measuring first.
The class Competent has been dropped we now only have Skilled. There is no reason why a Skilled person i.e. some one holding a City & Guilds 2391 should not sign the minor works, installation or EICR, these can be in turn used to gain the compliance or completion certificate however the method used to get the legal paperwork has to be agreed on BEFORE work starts, not after the event.
Costs vary around the country, much depends on the local DNO and their attitude to broken seals.
In 2008 there was a massive change to consumer units, then another with amendment 3, also with an EICR some non compliance with current regulations does not need reporting, so fact it passed does not mean additions will be permitted.
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