Old CU MCB nuisance tripping

[MattH]

The consumer unit in our house is rather old (maybe mid 90’s) and was here when we moved in.
It’s a Wickes Get/Schupa cheapo special 6 way.
In the last couple of weeks the the MCB for the sockets (one for the entire house) has started to trip randomly. The CU has not been touched for a number of years and the wiring hasn’t been disturbed lately.
The tripping seemed to be happening independent of loading.
A week or so ago I opened it up and tightened the wiring screw on the top of the sockets trip, as soon as I touched it with the screwdriver (VDE insulated) the MCB tripped and the screw was a little loose.
After tightening the screw we have not seen another occurrence until today.
As a stop gap I will buy a new (read second hand) Get MCB incase the trip has weakened because of the tripping.

But I’d like to hear from some of the experienced guys as to what I can expect if I would like the board replaced with something modern and up to spec?

As said the sockets are all on one breaker, the lighting is split upstairs and down. There are probably a few spurs around the house. All the required earths are in place, lighting, water and gas etc.

Can the board just be replaced or am I looking at a full rewire (not fun as we have solid floors downstairs).

 

[WorkshopChris]

Does it have a RCD fitted, if it does then should be a easy swap.
Well worth doing insulation resistance tests of each circuit before you start.

 

[MattH]

No RCD, it’s too old for that.
I’m not thinking of doing a swap myself at this point.
If a spark would be happy just replacing the board then I’d rather pay to get it sorted.
If it meant a complete rewire to bring the entire house up to spec then I’d be more inclined to consider swapping the Cu out myself.

I will megger out the sockets ring whilst it’s disconnected when I change the MCB though.

 

[MattH]

It was just a guess

 

[MattH]

My understanding was that as long as the earths were up to spec then installing an RCD protected CU was no issue?

16mm CSA from DNO earthing block to CU and then 10mm to utilities.

 

[dobbslc]

Megger the ring with a proper insulation resistance tester not a multimeter as you won't get a true reading otherwise.
Make sure you unplug everything and disconnect any load connected to a spur (prevents any false readings) as I think some if not all switch fused spurs only switch the live ie single pole and you want to test the neutral too.
If you get an electrician in to swap the board he / she has to carry out a full condition report of the existing wiring, its in the regs, this can unfortunately uncover a massive can of worms......

 

[MattH]

I have a Fluke resistance tester and yes I would disconnect all loads.
That’s my worry, I’m sure the internal wiring will not be up to existing regs.
Years ago when I replaced the ceiling in the living room/kitchen I pulled out at least 5 junction boxes and pulled new cable through to replace them. I’m sure there’s plenty of other hidden bodges.

 

[Robotstar5]

Megger the ring with a proper insulation resistance tester not a multimeter as you won't get a true reading otherwise.
Make sure you unplug everything and disconnect any load connected to a spur (prevents any false readings) as I think some if not all switch fused spurs only switch the live ie single pole and you want to test the neutral too.
If you get an electrician in to swap the board he / she has to carry out a full condition report of the existing wiring, its in the regs, this can unfortunately uncover a massive can of worms......

I'm a bit out of date with the regs then, I'd just check bonding, cable type and IR each circuit before a CU change, obviously any issues found would need further investigation.

 

[Robotstar5]

I have a Fluke resistance tester and yes I would disconnect all loads.
That’s my worry, I’m sure the internal wiring will not be up to existing regs.
Years ago when I replaced the ceiling in the living room/kitchen I pulled out at least 5 junction boxes and pulled new cable through to replace them. I’m sure there’s plenty of other hidden bodges.

Make sure any switched spurs (SFCU's) with neons are off as they can play havoc with an IR reading

I once smoked a TV antenna amplifier/splitter that had been spurred off the lighting circuit in the loft with an IR test

 

[HughF]

I’ve just had quotes in from two local (Trowbridge) sparks for a new cu at Tara’s, they seemed perfectly happy to quote what I asked for and didn’t mention a rewire. She had a new cu fitted about 10 yr ago and they just wrote on the eicr that there were ‘examples of very poor workmanship’, no talk of a rewire back then either,

 

[WorkshopChris]

If no RCD one thing to watch out for on a cu swap is any borrowed neutrals if you go for a new split consumer unit or neutral/earth problems that would not show up with your non rcd unit.

 

[HughF]

If no RCD one thing to watch out for on a cu swap is any borrowed neutrals if you go for a new split consumer unit or neutral/earth problems that would not show up with your non rcd unit.

very true.... my boss just had a new CU fitted and the 2 way staircase switching was making the RCD trip. They had used a combination of the downstairs live and an upstairs neutral on the original build - took a while to sort out.

 

[Nomad]

We had the CU replaced about 3 years ago - and had to upgrade the earth cable (10mm to replace 6mm ?) from CU to good earth (incoming copper water pipes). No other rewiring or chages needed.

A bonus was my sparky persuaded the elec supplier to fit an isolator between meter & CU so future maintenance can be done safely with incoming feed turned off

 

[HughF]

We had the CU replaced about 3 years ago - and had to upgrade the earth cable (10mm to replace 6mm ?) from CU to good earth (incoming copper water pipes). No other rewiring or chages needed.

A bonus was my sparky persuaded the elec supplier to fit an isolator between meter & CU so future maintenance can be done safely with incoming feed turned off

SSE (the DNO at wife's place) said that was my responsibility to have fitted - they don't do them. One of the jobs I got the sparky to quote for.

 

[dobbslc]

My view on that is if they won't install an isolator they won't be bothered by me cutting the seal to pull the fuse out either.

 

[HughF]

My view on that is if they won't install an isolator they won't be bothered by me cutting the seal to pull the fuse out either.

They weren't bothered at all, I asked if they wanted to be present to pull the cutout so my electrician could fit the isolator, they just said 'get your electrician to pull it, and he can fit one of this paper tags we issue everyone working in our area with'...

 

[Kayos]

With the rise of smart metering the DNO's have had to become more realistic when it comes to pulling cut out fuses

 

[dobbslc]

With the rise of smart metering the DNO's have had to become more realistic when it comes to pulling cut out fuses

You mean they are up to early 20th century for customer service?

 

[Kayos]

You mean they are up to early 20th century for customer service?

Not yet, maybe in a few years tho?

 

[brightspark]

any faults on the existing wiring must be put rite if u are changing the consumer unit . breaks in the ringmain incorrect size cables all

If no RCD one thing to watch out for on a cu swap is any borrowed neutrals if you go for a new split consumer unit or neutral/earth problems that would not show up with your non rcd unit.

the council and rough electricians always used a borrowed neutral on the 2 way lights to keep the 2 different lighting circuits separate u need to disconnect the live at the switch or the neutral from the light and run a separate feed cable to either one or the other. if its 2 difficult to separate them u can put both circuits on the one mcb if not 2 many lights and that will overcome it