Bizzare fault(s)

[RF Lighting]

Got called out to a friends house last Tuesday around lunch time.

The circuit breaker for the sockets had tripped and would not reset. 30A plug in MCB in an old wylex CU.

I got there and tried to reset the circuit breaker. It went with a real pop. A quick IR test of the circuit showed it was a dead short L>E.

I spent a couple of hours breaking the circuit down and found where the fault was.

Here's the odd bit.

Fault was in an attic conversion. Wiring up there is about 4 years old. There is a spur somewhere from the RFC, presumably via an inaccessible junction box. This enters the attic straight into an RCD FCU, then supplies the lights and sockets from here.

The FCU had not tripped, and the 13A was still intact.

I disconnected the faulty part of the attic radial, and IR showed about 40MΩ. I was happy enough with this. Powered back up no problems. Assuming the FCU hadn't tripped as it was faulty, did an RCD test, and it tripped out perfectly. About 40ms and 19ms.

Fast forward to friday night. Got a call at about 8pm, and got there for about 10. Circuit had tripped and wouldn't reset again. It was another L>E dead short. Went straight to the attic and and another part of the radial had gone down. Disconnected this too, and IR showed 40MΩ again.

Powered up and left.

Got a call 30 mins later to say the FCU was growling and then set on fire

Found this:

God knows whats been going on. I think I could be there a while sorting everything out

 

[333rocky333]

What sort of load was being used prior to all the problems , would it have been in excess of the 13 amp rating.

I will asume your insulation tests wernt via the rcd

Ive had a couple of there rcd sockets blow up internally just by operating one of the buttons which was a bit scary

 

[Lectrician]

I was going to say the same - You didn't meggar it did ya?

I too have had one of these go with a bang at the press of it's integral switch. Nasty. (Not as bad as the main RCD which went pop when I turned it on, blowing the main DNO fuse!).

 

[RF Lighting]

All that was running through it was your typical teenagers bedroom laoding. TV, xbox, etc. and a couple of lights via a 3A FCU. No heating or heavy loads.

It was meggered L&N>E at 250V as the very first test before I started removing everything off the circuit, but I would hope it could cope with that.

I've had an RCBO go bang when pressing the test button. Scared the crap out of me

 

[Lectrician]

Should have been fine at 250v I guess, although perhaps DC can upset them? They make a big deal over not IR testing them.

 

[RF Lighting]

I don't think it was the IR testing. It operated fine for 3 days after the IR test.

I'll be getting rid of the FCUs arrangement when I go back to sort out the initial fault anyway.

 

[studentspark]

I've heard an RCD FCU make a most unusual noise and blow when the load and supply get cross connected.

 

[securespark]

Rob: You are NOT alone!!!

I have a love/hate relationship with Greenbrook Powerbreaker RCD spurs.

I used to think they were the best of the bunch, but I hate them because they fail on me.

I used to think it was just the ones I bought from WF, so I bought some from other wholesalers. They failed too, so I thought it was because I bought them.

I genuinely thought they had something against me. Well, you would, wouldn't you? ALL the Powerbreaker RCD spurs I have EVER installed have gone wrong, eventually. They all ended up either:

Not tripping when the test button is pressed.

Buzzing when the test button is pressed.

Buzzing when the test button isn't pressed.

Exploding when the test button is pressed.

Exploding when the test button isn't pressed.

So I gave them up. Then I started working in my current job. And I started meeting my old friends again. And yes, they started dying again.

Now I am installing Kensington. So far they seem to be Simon-proof. Touch wood.

Send it back to Greenwood and complain most vociferously. The only way they'll do anything about this shockingly poor rate of failure is for sparks to send 'em back EVERY time.

I have sent so many back, the guy joked he'd have to start sending me a stash of pre-paid jiffy bags!

 

[Spark123]

I have noticed Greenbrook Powerbreaker sockets make a buzzing noise when the test button is pressed even after they have tripped off.

 

[RF Lighting]

I have a power breaker RCD socket in my garage. Once you plug something in, you often have to whack it to make it work. I'm beginning to think this might not be a coincidence...

 

[AdrianUK]

TEST Button jammed/shorted resulting in test unbalancing resistor in circuit all the time & cooking?

Adrian

 

[securespark]

I have a power breaker RCD socket in my garage. Once you plug something in, you often have to whack it to make it work. I'm beginning to think this might not be a coincidence...

Better believe it, bro!!

 

[Scoby_Beasley]

Can I take it that Greenbrook are not really up to the job in hand then?

Any ideas on who else makes an RCD FCU that is 'pretty enough' to be installed in a house?

 

[333rocky333]

Timeguard do a white one, although look a bit more bland than the greenbrook ones
I particurly like there rcd sockets as they have proper switches, unlike the powerbreakers that use the test/ reset button and dont give the option of turning one outlet off, then again I think powerbreaker now do one with switches,
In fact spirit pub group specified them for all there cellers in the london area.
I dont recall ever replacing a timeguard socket one either, and seen them used in harsh coldroom enviroments running industrial beer coolers and ice machines, as for there spurs, they are relatively new so no experiance of them.

 

[ban-all-sheds]