Help with RCD's tripping

[heavyhands]

hi ive been getting my house rewired recently and the sparkie has went on his holidays before he had time to finish properly (everything was wired up and earthed except for the loft) and ive been having some problems with my rcd's tripping, not sure if its a fault on my consumer unit and something i could sort out by just getting some new breakers or rcd. my consumer unit has 2 rcd's and my bedroom socket is on the first rcd which works fine when the second rcd is switched off but if both are on and i plug something in upstairs they both trip but the breaker my bedroom ring is in doesnt trip. my consumer unit was second hand but "practically new" is what the sparkie said and ive checked all the wires through the floor and everything seems connected fine, right thickness cables and in a sufficient breaker. any clues to whether i need a new rcd or two or if its something else? any help is appreciated, thanks.

 

[1john]

Your sparky has made a really really silly mistake. When is he back from his holidays??

 

[londonboy]

Second hand cu doesn't inspire me with confidence either.

 

[1john]

bloody sparkies eh, going on holidays, half way through a job, and so close to Christmas, especially after fitting a 2nd hand consumer unit.

Sometimes people try and fit consumer units themselves and because they don't understand how things work they install them incorrectly or cant test things to ensure they aren't faulty. Of course an electrician has the knowledge and equipment to know how to install the units and test them properly.

 

[ricicle]

Sounds like you picked the wrong Electrician !

 

[riveralt]

Put the r1, r2, rn, R1+R2, IR, Earth loop impedance figures and RCD test data for each of the ring final circuits up on the site and we will have a look at them. They will be marked on the Electrical Installation Certificate Test result page.

 

[bernardgreen]

works fine when the second rcd is switched off but if both are on and i plug something in upstairs they both trip

Suggests that the neutral ends of these rings are not in the correct neutral bars.

 

[Chri5]

Did you really use a spark, or was it a DIY job ?

Unfortunately the "gone on holiday" excuse as to why you have posted its commonly used as a cloak.

Shared neutrals and neutrals terminated incorrectly (as Bernard mentioned) are likely to be the problem. Replacing RCD's are unlikely to resolve the issue.

A fully populated 17th board with 10 x mcb's on 2 x rcd rails is under £100 for supply, why would anyone use a 2nd hand one that has the potential to be duff (ask yourself why a nearly new 2nd hand item was removed from it's last installation).

Check the board, if the board is 2 or 3 way (direct, rcd 1 and rcd 2) then the neutrals need to go to the correct bar.

Obviously the neutrals out to the circuits on rcd 1 would terminate on the neutral rail for that rcd unit ONLY.

 

[mikhailfaradayski]

how often is the tripping occurring?

Can you post the information asked about above? - It may help.

As your electrician is on holiday so close to xmas, i would imagine that you can't get him back until the new year? ( or will he then be going skiing, so you might not see him til easter? )

so far, its all a bit of a mystery. More information required, please

 

[tonyelectric]

hmm. don't like the sound of the "second hand" CU, there is in theory nothing wrong with using second hand items if they are in good working order, trouble is how do you know it all works to spec, the RCD is easy to check, but the MCBs?.

I do keep a few second hand items on the van like imperial conduit fittings we can't get anymore, old porcelain fuse carriers and a few old type MCBs but only "to get someone out of trouble", not to fit as the heart of a new install - hope he didn't charge you for it, that would be cheeky

 

[heavyhands]

the sparkie didnt test the wiring yet because he wanted to finish the loft aswell dont know how long or much work it takes to test properly but he didnt seem to inspired to do it twice so i dont have any of the test certificate info you required, sorry. i did get the neighbour to look at it tho he runs a home improvement and extension company so hes done bits and pieces with electrics but hasnt a clue whats wrong. the neutrals are both in the same bar and any socket in the bedrooms are tripping both rcd's as soon as anything is plugged in (tried a few different things to make sure) it was running off the first rcd which is an 80amp one and he tried on a breaker on the second rcb and nothing tripped except one of the live wires wasnt long enough to reach safely so it couldnt be left like that. he tried switching the rcds over and running the bedrooms from the same breaker on the left side through the second rcd and this time only the 1 rcd tripped (the one on the right side which didnt have the bedroom ring on or any other power running through it) but nothing trips for any other socket rings or lights in the house. he thinks its probably the rcd thats ruined even tho nothing else trips it but not sure so ive phoned another sparkie up recommended from a friend this time and just gonna let him sort it out next week and ill let you all know how it goes if your wanting to know what happened. thanks for your help!

 

[ban-all-sheds]

hmm. don't like the sound of the "second hand" CU, there is in theory nothing wrong with using second hand items if they are in good working order, trouble is how do you know it all works to spec, the RCD is easy to check, but the MCBs?

Nearly all of the 10's of millions of people living in houses which weren't brand new builds when they moved in have got 2nd hand CUs...

 

[1john]

There is probably nothing wrong with the RCD, the circuit has been connected incorrectly. Your sparky thats coming round will sort this very quick for you, and hopefully do some testing so you knwo everything functions as it should. Good luck.

 

[tonyelectric]

hmm. don't like the sound of the "second hand" CU, there is in theory nothing wrong with using second hand items if they are in good working order, trouble is how do you know it all works to spec, the RCD is easy to check, but the MCBs?

Nearly all of the 10's of millions of people living in houses which weren't brand new builds when they moved in have got 2nd hand CUs...

Totally agree with your statement BAS, my house still has a wooden backed Wylex with rewirable fuses, (which as a spark I should have replaced, but it works and ain't going to make me any money so i've not done it yet)

My point was that i've never heard of a CU being recycled and dumped off on another customer, this could be totally legit for example it could have spent 6 months in a temporary installation and been removed almost good as new, but i've got at least 20 CUs stacked up out the back of the garage that have been removed from places for various reasons, some work fine, most are pre 17th, but i'm not going to dump them off on a paying customer when new equipment is not that dear.

That coupled with the seeming lack of tests, fault, dash off on holiday makes me think this might, and I stress might be a rogue operator

 

[Taylortwocities]

(Confession)

When I started out there were a couple of times when I thought that I could make a few bob by putting a reclaimed item from one customer into another customer.
I only did this twice as both times I had to go back and change the item as it had failed.

So it cost me.