RCD

[romchik]

Hi guys. Happy easter to you! I have more trouble know and need your help .
My RCD on the CU is keep tripping. When i take everthing from all plugs it is Working but when i put fridge or computor or TV and RCD is down again. I am positive that fridge and rest of them is working properly. I have tried to connect my kitchen ring to MCB on the not RCD protected side of CU and is working but when i put it back to RCD protected side it is down again. Any ideas what could it be? (All wiring was done by profesional electrician)Thank you
CU is Wylex Split load
RCD is 80 A 30mA

 

[andy]

it could be that all the appliances in question are leaking to earth, and when combined are going over the 30mA of the RCD tripping it

does it trip when all 3 are connected are just 1? naturally, a computer leaks to earth, but unless you have a room full of computers it shouldnt be a problem. does the RCD trip when the T or test button is pressed?

 

[Lectrician]

Usually a case of a neutral to earth fault. Not a flat down fault, but the more appliances you plug in, the more load is taken, the more will leak from N to E......30mA.....POP.

You need to test the insulation of every circuit fed from the RCD. Disconnect the neutrals of these circuits from the CU when testing. Use an insulation tester for this (a multimeter will not usually find a fault of this type).

I trust you know how dangerous it is inside a CU (I remember you from previous posts), but obviously remember what is live and whats not!

 

[Big_Spark]

Lec's advice is good, but depending on the age of the fridge, it is likely this is the guilty party..they are notorious for tripping RCD's if they are more than a few years old..

 

[DanE]

It I were a betting man, which I am , I would put money on the fridge either drawing too much current for the RCD, or when the compressor kicks in, it spikes enough to trip the RCD.

 

[theshogun]

Are your rcd circuit neutrals connected to the rcd protected neutral bar?

 

[romchik]

So many replies.... Thank you guys
The RCD trips if i put any of appliances. I have three circuits.
I have tried all three .The same problem.RCD circuit neutrals connected to the rcd protected neutral bar. .Is it possible- the same problem with all three circuits?Could it be a faulty RCD? (it did work for about month) I do not have insulation tester
Thank you

 

[Big_Spark]

The Neutrals are a red herring, don't worry about that, they are common regardless.

If the RCD is popping no matter what else is plugged in, then the RCD is likely faulty, if it was the circuit, it would trip even with nothing plugged in.

Have you tried to unplug everything, then plug in a lamp or something similar? If it trips then that basiclly confirms the RCD has had it.

What make is it, and what rating is it? 63A/30mA - 80A/mA...what?

And how large is the ring connected to it, and what is usually plugged into this ring??

 

[romchik]

The RCD is Wylex 80A 30mA (WRS 80/2)
I switched all three MCB off and i can not switch RCD on it does not stay in on position.
On this ring i have dishwasher ,washing machine,cooker hood, and boiler. cooker hood was working (i did not try to switch fan.i tried only lamp)and it is on the ring (Switch with neon)
but if i put even small radio the RCD is down-strange. But like i said the other two ring are with about 17 sockets between them and they do the same with RCD when i plug something there. Sorry for my bad English but i bet it is better than your Russian
Happy Easter.

 

[theshogun]

The Neutrals are a red herring, don't worry about that, they are common regardless.

He has split load cu.
_________________
Moderator

edited to correct quote

 

[Lectrician]

A fault from N to E, even high resistance, wouldn't trip the RCD without anyload on either of the circuits.

Disconnect the neutrals after the RCD, and replace them one at a time until you find the one that causes it to trip with an appliances plugged in.

 

[romchik]

I have disconnected all three circuits (i meen i disconnected live cables from MCBs on the RCD side and i can not switch it on,it is does not stay in the switched position) I do not think it is a fault with circuits.

 

[Lectrician]

You need to disconec the neutrals aswell to prove it isn't the circuit.

If there is another path for curent to flow, it will.

Turn n appliance on, and some current will return to the supply transformer via a neutral to earth fault. If this is after an RCD, it will trip. This N to E fault could be on one circuit, while an appliance plugged into the other causes it to trip.

 

[Damocles]

If there is a n-E short on any of the RCD circuits then it could trip the RCD if there is any load irrespective of which circuit. It is also possible that with all rcd breakers turned off, a load on the non-rcd side could cause the rcd to trip.

The breakers only disconnect the LIVE. The RCD trips if there is a difference in current through the RCD betweeen live and neutral. So if the load in the non-rcd side causes voltage to rise on N, then some of that current might flow through the RCD and back to earth.

As someone said, try disconnecting the neutrals as well as switching off the breakers. Then reconnect one by one and load the circuit to see if it trips.

 

[plugwash]

If there is a n-E short on any of the RCD circuits then it could trip the RCD if there is any load irrespective of which circuit. It is also possible that with all rcd breakers turned off, a load on the non-rcd side could cause the rcd to trip.

indeed if your system is TN-S or TT its possible the trip could be caused by a load change in another property.

if there is a NE fault anywhere on the rcd side of your system then the RCD will trip if the NE voltage rises above a certain level (how high depends on the nature of the fault) the NE voltage can be effected by numerous factors not all of which will be inside your install.