help with new consumer unit and tripping RCD

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I recently had an electrician round to replace an old fusebox with a new consumer unit. He also replaced the submain between the meter and the consumer unit. My small flat currently has all mains sockets running off a single ring main, and a separate circuit for the cooker (not a ring. A spur?). He has wired the doorbell and two lighting circuits into circuit breakers on the non-RCD side of the unit, and they work fine. He wired the cooker circuit into one of the RCD protected breakers and that's fine too.

But when he connected the ring main (with all my sockets on it) into an RCD-protected breaker, he found that it kept tripping. By plugging in one appliance at a time, he concluded that I had a faulty fridge and a faulty PC - that they both probably had neutral-to-earth leaks which were tripping the RCD. While I tried to get them fixed, he connected the ring main to the non-RCD side of the consumer unit as a temporary measure.

Now I have just had a whole new ring main installed to supply eight new mains sockets in our study. This ring is connected to one of the RCD breakers. *Any* appliance plugged into one of the new sockets causes the RCD to trip, even a mobile phone charger which has no earth (you know just a plastic earth pin). Connecting the new ring to a different RCD breaker doesn't help so I don't think it's a faulty RCD.

This made me think that the problem on the first ring main probably wasn't with the fridge and PC - maybe there's something else going on? I have tried plugging the fridge and the PC into the RCD-protected cooker circuit and they don't cause it to trip, so does that mean they're OK?

I would appreciate *any* advice here - I don't want to spend loads of money getting my appliances checked only to find there's nothing wrong with them. And if the fridge man says he's fixed the problem I can't be sure (and neither can he) that he's right until the electrician comes back again. And I don't want to call the electrician back in if he is mis-diagnosing the problem.

Are there any tests I can do (safely) using a multimeter - e.g. to see if and where there's a neutral-earth leak.

thanks for your time
 
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Sounds to me like someone has connected the neutral of the new ring to wrong neutral bar.

The RCD works by comparing the current flowing in the Phase conductor with that flowing in the Neutral condutor. A differeence of 30mA will cause it to trip.
 
You should only have 1 RCD & several mcb's, or do you mean rcbo's.
 
It sure sounds like he's got a neutral wire on the wrong busbar or not removed the link between the two busbars.

Could you turn off the power on the main switch, remove the front cover of the consumer unit and take a nice photo for us to look at?
 
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Wow, thanks for such prompt responses! Am not currently at home but I'll post a photo as soon as I have one.[/img]
 
JJ4091 said"You should only have 1 RCD & several mcb's, or do you mean rcbo's"

Having read that it has made me wonder why i have two RCD's in my Wylex CU.
A 30mA & a 100mA

This is ok isint it?

It is a council place which would explain alot. lol.
 
learner123 said:
Having read that it has made me wonder why i have two RCD's in my Wylex CU.
A 30mA & a 100mA

This is ok isint it?

It is a council place which would explain alot. lol.

Is it a TT supply i.e. an earth electrode?
 
I hope the 100mA RCD is time delayed or both RCD's will trip when you get an earth fault.
Spark123 is right, this is probably a TT supply. Probably fed overhead from a pole.
The regs require the Main incomer to be a 100mA RCD (type S is best), then the 'non' RCD protected side of the board should feed lights, cooker, immersion etc. Sockets that could supply equipment outside must be 30mA RCD protected (this is usually all sockets).
In your split load board there will be two neutral bars, one connected to the incomer and one connected to the outlet side of the RCD. If you put a circuits phase on the RCD side and neutral on the other side you will create an inbalance when you connect an appliance and trip the RCD.
 
471-08-06 says all socket outlets must be protected by RCD and then points you at 413-02-16. So, in most cases, you will need to use a 30mA RCD otherwise you'll never get Zs I^n <50V
 
martinsell said:
... This made me think that the problem on the first ring main probably wasn't with the fridge and PC - maybe there's something else going on? I have tried plugging the fridge and the PC into the RCD-protected cooker circuit and they don't cause it to trip, so does that mean they're OK?
...
Are there any tests I can do (safely) using a multimeter - e.g. to see if and where there's a neutral-earth leak.

e.g. Could I test whether there's any circuit between the neutral and earth pins on the plug (of the fridge or the PC) when it's not plugged in, just using the resistance meter on a multimeter?[/u][/b]
 

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