resolved: MCB on but no power

[rp9]

Evening.

Our downstairs socket ring tripped the mcb on Sunday. Despite resetting it and the RCD several times (the switches are on, they don't flick back off) there was still no power.
I've unplugged and switched off every socket, still nothing.
I've swapped the downstairs and the upstairs MCB's (both same rating) but still nothing (ie, the upstairs ring works whichever MCB is in place so not a faulty MCB.)
I've unscrewed several of the sockets (not all) and found nothing out of place.

Is there anything else I can check easily? (ish). Want to do as much donkey work as I can before calling someone out.
The downstairs ring is on a seperate RCD to the rest of the house, could the RCD be faulty?

Thanks,
RP.

 

[sparkydude]

Not an MEM RCD by any chance is it ????? Some RCDs need to have their switch pushed right down before being pushed right up to reset them. If you push it down you should hear a click , the up and voila all power should be restored.

Nick

 

[rp9]

It's an mk one (at least the mcb was so I assume it is.)
Alas I've tried that...many times!

Thanks,
Rich

 

[sparkydude]

Does the RCD have a test button ? Does it trip when pressed ? does the RCD control any other MCBs apart from the ground floor ring main ? if so are they working ?

Nick

 

[rp9]

It does have a button and it does trip.
Unfortunately it's the only MCB on the circuit.

 

[ban-all-sheds]

Is the circuit a ring or a radial?

 

[sparkydude]

Do you have a multimeter or means of testing voltage ???? (not a neon screwdriver !!!)

If so you need to prove that the MCB is working correctly and you actually have power leaving the RCD and entering the MCB and leaving the MCB to the circuit.
What happened to cause the power to trip or did it just occurr randomly ??

Nick

 

[rp9]

I haven't got a multimeter...yet. If I can't borrow one I'm off to buy one on my way home, along with a long cable to try and split the ring if I can (the wiring seems a little 'abstract' (to be polite!)

What's the best way to test the RCD/MCB?

This time the trip seemed to be random (ie, no heavy loads on.) Before it's tripped if the dishwasher and washing machine/tumble dyer have been on at the same time.

I did have power briefly for about 15 seconds yesterday before it went off again, though neither the MCB or RCD appeared to have tripped.

 

[rp9]

Just an update. I've done a continuity check and Live and Earth are all ok. Neutral however wasn't.

I loosened, reset and tightened the bottom of the RCD. Voila, the power was back on......for about 10 minutes (I boiled a kettle ok whilst it was on.)

It then went off. Turning it back on I can hear a crackling type noise around the RCD/MCB area and the power slowly trips off.(ie, a lamp slowly fades out) although neither the RCD or MCB had switched off.

(it's an MK 40A RCD which doesn't appear to be available at screwfix if that is the problem.)

 

[ban-all-sheds]

Did you check the connections for signs of heat damage, strip cables back to clean copper etc?

 

[sparkydude]

A 40A RCD in a domestic consumer unit is not right, should be a minimum of 63A or preferably 80A. Can you post us a pic of your consumer unit as something does not sound right to me.

Nick

 

[rp9]

Apologies, it is 80A, not quite with it at the moment (11 week old baby keeping us busy!)

There are no signs of heat damage, copper looks clean.
As I type, power been on for 15 minutes.

Two photos at:
//www.diynot.com/network/rp9/albums/6208

, it's the right hand side (the taped switch is a cable to a shower which is no longer attached.)

We had the CU fitted when we moved in 4 years ago, a days job for one man turned into 2 days for 2 as they struggled with the odd wiring (one room above the garage has 3 different trip switches.)

 

[rp9]

Latest: I put a kettle on whilst the power was still on.
Came back and watched the RCD crackle and occaisionally spark. It then really started spitting out sparks so I hit the reset button.

I assume from this it's a faulty RCD? Or could there be other problems elsewhere causing this?

Edit: The video clip of the RCD can be seen here:
http://www.youtube.com/watch?v=Got6usda8Qg

This is sideways on, the sparks are actually coming out of the bottom of the right hand RCD.

It's staying off, but I'm suprised it didn't trip. Show's how easily fires start!

 

[1john]

Have you got the cable in the terminal securely, perhaps the conductor is jammed either side of the terminal or it is not tight, are you certain that the terminal and the copper are clean and not burnt / carbonised??

 

[rp9]

I'm not certain no. Everything appears very tight.

I assume if I hit the left hand RCD that will remove power to the right hand one so I can remove it? (there isn't any other switch to turn off all electric from what I can see....and certainly want to be sure!)