RCD unit keeps tripping!

[scrootmum]

Hello - I've just registered with this forum to see if anyone has any ideas about what could be going on with the electrics in our place

We have two RCDs, one in the main house and another seperate one for the conservatory that services the garage and the garden. For a while, the ring main in the conservatory has on occasion been known to make the RCD in the house trip but it has always been a random isolated incident. Since last week however, the RCD in the house is now tripping at random times. We isolated the ring main in the conservatory, and put a new ring main breaker in the rcd for the house up from 32 to 40 amp thinking it could be due to overload - after all, the ring main in the house is carrying all the sockets.

Now, the RCD in the house keeps tripping, seemingly randomly but I have noticed it tends to go at times when the boiler is firing up for the first time, morning and evening. However, it could just as easily go when you're turning over the tv or pluging things in or taking them out.

As it doesn't seem to be any one particular gadget or socket that's causing the problem we're stumped. Does anyone have any idea about what might be going on?

Ta

Rx

 

[ColJack]

firstly, change the breaker back to 32A.. it is not acceptible to put a ring main on a 40A breaker..

now.. the main reason for RCD trips is usially damage to a cable, or water in something..

check your outside lights ( yes the lights.. trust us. ) see if they have any condensation in them..
same goes for any outside electrics..

do a search for RCD and you'll find many many many topics dealing with this often asked question, with diagnosis tips in almost every one..

your best bet is to get a decent electrician in to track it down for you if it's none of the above.. it may need rectification work..

 

[dannyboi2003]

Change the ring main breaker back to the 32amp one NOW! A ring main should be protected by a 32amp breaker maximum. As for why the RCD is tripping it could be anything or a combination of things. I'll let the pro's advise you on that one.

 

[Taylortwocities]

Agreed.
That breaker must be put back.

RCDs do not trip as the result of overloading. They trip due to an earth fault on the circuit. The earth fault could be on the live or the neutral leg so isolating the fault is often a long drawn out process of elimination.

An electrician could narrow it down by doing an insulation test. That will check out the fixed wiring but not what is plugged in to it.

Have you recently bought a new appliance? eg Some of the new TVs can pust RCDs into tripping if the installation is one the edge.

 

[ColJack]

wouldn't a live - earth fault be a short though? causing overload of a breaker every time you tried to reset it?

a neutral / earth fault is the tricky one to find since it won't trip until a certain amperage is flowing somewhere downstream of the RCD?

 

[RF Lighting]

wouldn't a live - earth fault be a short though? causing overload of a breaker every time you tried to reset it?

It would depend on the resistance of the fault

 

[securespark]

And therefore the amount of fault current flowing.

 

[RF Lighting]

Often referred to as Ohms law

 

[securespark]

Thanks. I couldn't remember the geezer's name...

 

[RF Lighting]

 

[ColJack]

yes but what I was getting at is that a nail through a cable that shorts neutral and earth wouldn't necesarily trip an MCB ( on a TN-C-S since they're connected at the cutout ) but a nail that shorts Live and earth would..

 

[Pengwyn]

Why have 2 RCD's in series anyway ?

If they are both 30mA RCD's then there is no discrimination.

Anyway I doubt a forum is going to solve this problem, sounds like it needs a spark with some testing equipment.