A blown ELCB - replaced with a 30mA RCD

[sparc]

Chilling out on late on Sunday afternoon when I got a call from a national home service organisation I'd never had contact with before. They asked me to attend an elderly couple who were without power - had been since noon, so they were now in the dark and cold, getting colder.

Got to house and found there was a new looking 30mA RCD after the meter, feeding a seventies vintage board with all MCBs. The RCD had tripped, taking out all the circuits. They had tried resetting just the RCD, but it wouldn't latch. So just to confirm that I flipped all the mcbs off and tried the RCD, which now latched on. Starting flipping on the mcbs one by one slowly and everything came back up. My next thought then was to let the place warm up a bit, give them some light and let them put the kettle on.

While that was going on I was digging into recent problems they'd had. The earth is TT and an old ELCB had burnt out a few weeks previously. The service company had sent someone, who replaced it with the new 30mA RCD. It had worked fine for a few weeks then tripped, taking out all the circuits.

I'd already decided I wasn't going to open the board at that point to look for which circuits were contributing to the earth leakage. Instead I wanted to leave them with the essentials for the night, then revisit in daylight. The RCD tripped again after about 15 minutes. I reset it again after disconnecting a few appliances and powering off two shower circuits and one circuit feeding the garage. It stayed on all night and is still okay 24 + hours later.

For next steps I'm thinking a) finding and fix the earth leakage/s and b) how to make the installation more resilient.

So - scene set - here are some questions I'd appreciate help on please :

In circumstance of a blown ELCB is a single 30mA RCD the best/only option? Would a 100mA S type be considered a backward step, in terms of 'By-the-Regs' protection? Yes, the 30mA gives all the circuits the required protection, but it in short term leaves the owners vulnerable to nuisance trips - not good for an elderly couple in winter. Wouldn't a 100mA S type be a better short term option - until a new board could be discussed? When the solution to a problem is considered 'ongoing' is there any defined period of time that this can take?

 

[shanky887614]

in struggling to see why there was an rcd put in at all?

if the voelcb burnt out then the problem should have been fixed not just replace by a rcd which only a cowboy would do without testing

 

[telectrix]

maybe when the RCD was fitted, the installation was fine. rain could have since got into something fitted outside or even damp in the garage. an eic from when the RCD was fitted would be useful. ( if there is one). obviously the ideal solution would be a RCBO or dual RCD board ( after the fault is rectified, of course)

 

[ImpededLoop]

^^^^ What Tel says.

A 100mA possibly wouldn't help if there is enough of a fault.

 

[sparc]

No EIC covering the installation of the new RCD was evident. There was documentation with some ELZ and RCD test results - but couldn't see any IR readings. The RCD has been in place for a few weeks before the first trip, so Tel's point about the fault being new could be relevant. Nothing to say why there was a problem with ELCB in first place, so can only speculate on whether subsequent problems with RCD are linked ....

Take point that 100mA time delay type may not have prevented a trip - if earth leak is big enough - but it could save them from repeated nuisance trips if the issues is a fridge or a bit of damp getting into a garage light.

I wonder how people feel about question of making a temporary fix while finding better long term solution - if the temp solution isn't by the book, but still gets them more comfortable and safe?

 

[telectrix]

as a temporary fix, i'd try and locate the source of the tripping fault. isolate if it's not an important part of the installation or repair if possible.

 

[Octopus]

Ah, the joys of a single, up front RCD!

 

[gnselectricals]

Hopefully my photos has attached. A job I was on earlier installing solar pv, where the old rcd unit was recently completely disconnected by an electrical 'engineer' and the tails were connector blocked together and left to dangle about in the meter cab in the hallway of an elederly couple. They were very concerned as said 'engineer' didn't accept payment and would be back to check the sockets in the week lol. Recommended full test and inspect to trace fault and a db change at the very least.

 

[davesparks]

View attachment 27260

Hopefully my photos has attached. A job I was on earlier installing solar pv, where the old rcd unit was recently completely disconnected by an electrical 'engineer' and the tails were connector blocked together and left to dangle about in the meter cab in the hallway of an elederly couple. They were very concerned as said 'engineer' didn't accept payment and would be back to check the sockets in the week lol. Recommended full test and inspect to trace fault and a db change at the very least.

Why does it need a DB change when the job is to rectify a fault?

 

[polo1]

Luvin' the windows in the meter cabinet....were these to allow an older/former meter to be read from the outside???

 

[Deleted member 26818]

Unfortunately, due to the lower disconnection times for TT installations introduced in the 17th, I doubt that you will be able to find an S type RCD which will allow compliance with the Regs.

 

[gnselectricals]

Why does it need a DB change when the job is to rectify a fault?

To make a bit of money for Xmas
The rcd unit there had been smashed to bits inside so can't reconnect that. Obviously find fault/s then recommend adding rcd protection back to installation, wouldn't fit an upfront rcd , so therefore recommend a rcbo db as that's what I mostly fit now.
However there isn't a fault to rectify in the homeowners eyes as the guy has disconnected the switch and stopped the power going off !

 

[gnselectricals]

Luvin' the windows in the meter cabinet....were these to allow an older/former meter to be read from the outside???

Yeah iv seen these windows quite a bit, my mates got one where meter cab is inside and has the glass outside , the meter is on a hinged board so can be read from outside and then swung back to work on it. Only problem is that it's a metal cab with the tails goin through a razor sharp hole to the meter which went bang last Sunday night @ 12.30 lol

 

[shanky887614]

Yeah iv seen these windows quite a bit, my mates got one where meter cab is inside and has the glass outside , the meter is on a hinged board so can be read from outside and then swung back to work on it. Only problem is that it's a metal cab with the tails goin through a razor sharp hole to the meter which went bang last Sunday night @ 12.30 lol

lol no grommit strip? bad luck but not unexpected

 

[UNG]

Why ask this

So - scene set - here are some questions I'd appreciate help on please :

In circumstance of a blown ELCB is a single 30mA RCD the best/only option? Would a 100mA S type be considered a backward step, in terms of 'By-the-Regs' protection? Yes, the 30mA gives all the circuits the required protection, but it in short term leaves the owners vulnerable to nuisance trips - not good for an elderly couple in winter. Wouldn't a 100mA S type be a better short term option - until a new board could be discussed? When the solution to a problem is considered 'ongoing' is there any defined period of time that this can take?

When you appear to have already decided to do this

To make a bit of money for Xmas
The rcd unit there had been smashed to bits inside so can't reconnect that. Obviously find fault/s then recommend adding rcd protection back to installation, wouldn't fit an upfront rcd , so therefore recommend a rcbo db as that's what I mostly fit now.
However there isn't a fault to rectify in the homeowners eyes as the guy has disconnected the switch and stopped the power going off !

Can't understand why these days every mole hill has to be turned into a mountain when all you have to do is find and fix the fault not quite sure how or why the inside of the RCD has been smashed to bits may be you could enlighten us

 

[gnselectricals]

Why ask this



When you appear to have already decided to do this



Can't understand why these days every mole hill has to be turned into a mountain when all you have to do is find and fix the fault not quite sure how or why the inside of the RCD has been smashed to bits may be you could enlighten us

Think you maybe confusing the op and myself 2 differnt jobs just thought I'd crash the thread.
Don't see why I'm making a mountain out of a molehill ? I want called into fix the fault etc I was there to undertake other installation work, they had what they stated was a power cut due to what I assume is a fault which tripped the rcd and wouldn't reset. They called an electrician out who promptly disconnected the rcd, with a hammer by the look of it as the terminals were chewed to F***. They then connector blocked the tails live as the seals were stil in place. They then left without payment promising to return to test the 'plugs '.
So when I arrived I thought it was slightly rough and was a bit concerned that a life saving device had been disconnected.
Hope that's clear enough

Regards

 

[Engineer54]

Unfortunately, due to the lower disconnection times for TT installations introduced in the 17th, I doubt that you will be able to find an S type RCD which will allow compliance with the Regs.

If the time delay S type RCD was the only RCD protection in place your right, but i think were talking here about providing a front end back-up means to downstream 30mA RCD's on a TT system that fail to operate at say a 5 X fault condition....

I'd be quite happy with an operating time on a backup device of between 130 to 500 mS on a TT or TN system, regardless of what BS7671 say's. It will also bring to notice that the primary downstream 30mA RCD is not functioning correctly.

 

[Knobhead]

To make a bit of money for Xmas
The rcd unit there had been smashed to bits inside so can't reconnect that. Obviously find fault/s then recommend adding rcd protection back to installation, wouldn't fit an upfront rcd , so therefore recommend a rcbo db as that's what I mostly fit now.
However there isn't a fault to rectify in the homeowners eyes as the guy has disconnected the switch and stopped the power going off !

That s patently obvious!

If the installation has been on a single up front VOELCB or RCD for years who the hell are you to say I won't fit a RCD as a replacement?


The customer should ask for a 2[SUP]nd[/SUP] opinion from a reputable electrician.

Out of interest, if you’ve never been in contact with this national home service company before why does it seem you were so quick off the mark with this job?
I’d be very dubious of a national home service company that just phoned me on spec.

They could be rip off merchants!

 

[gnselectricals]

That s patently obvious
Which was a bit tongue in cheek with included smiley face.

If the installation has been on a single up front VOELCB or RCD for years who the hell are you to say I won't fit a RCD as a replacement?
The whole problem as I was told by the client was that there was a fault that was taking out the rcd. The guy came and disconnected the rcd without finding the fault. Why would I put back one rcd when in the event of a fault they loose all power again ? Obviously I realise the fault should be found first, then reinstate rcd protection. I would tell the client the pros and cons of an upfront rcd and a dual rcd or rcbo board and leave them make a decision after recommending an rcbo db as that's what I would prefer to fit.


[/COLOR]
The customer should ask for a 2[SUP]nd[/SUP] opinion from a reputable electrician.

If that's aimed at me I would take offence at that insinuation that I'm not reputable based on some banter on an electricians forum.

 

[Knobhead]

You can take your fence wherever you like. You’re trying to boost the price and therefore your profit by insisting on unnecessary work.

 

[gnselectricals]

Fair enough although I'm hardly going to rot in hell for making ppls electrical installs safer. Peace out