Tripping RCD

[lofty84]

One of the RCDs keeps tripping in one of the propertys we are working on. The RCD supports the ring in the kitchen, lights and doorbell from what I can remember. when we put the ring on the other rcd in the consumer unit it didnt trip, but we need to investigate this tommorow. Any ideas whats happening. I know the purpose of a rcd is to monitor the circuits it is protecting and turn its self of if it notices a difference in current going out on the line and back on the neautral of 30mA or more.

 

[Octopus]

An interesting situation, you say that the offending ring trips one RCD but when you swap it to the other it doesn't trip.

Is there much plugged in ?
Have you ramp tested the RCD's?

 

[topquark]

Try checking the main neutrals for the split load kit at the consumer unit and ensure they are all tight.

 

[lofty84]

cant say ive ramp tested the rcds mate, can u explain what this is and how to do it.

topquak can you break that down for me. new to the game and am a little conffused

I forgot to mention it seemed to trip once the fridge was pugged in and opened

 

[topquark]

In the CU, where you take the neutral to the top of the RCD device, check that it's tight both there and at it's source. Often a loose neutral can be the cause of phantom tripping. It could even be at the bottom of the main incommer.

 

[lofty84]

sourse being the load. could it be a falty cu

 

[topquark]

sourse being the load. could it be a falty cu

No source being the supply, sink is the load

 

[lofty84]

so I need to be ideally looking at the Neautrals for the kitchen ring first makeing sure they are tightly terminated in the neautral bar first. If they are then I need to check the neautral in the top of the RCD and main switch. Is that what your saying mate.

what happens if they are all sound.

should I run a rcd test with the tester

 

[telectrix]

check all neutral connections including the manufacturer's. then you need a RCD tester with ramp test faciliy. what this does is step the tripo current in increments of 5mA until the RCD trips. then it tells you what it's tripping at (in mA) . if the result is below about 22mA, then you've either got a small leakage on the circuit/s or an over sensitive RCD.

 

[topquark]

Check the neutral bar(s) for both the circuits run from that neutral, and the neutral supply to that bar. Also check the the neutral of the main incommer, I've seen folk tighten the hell out of the bus bar and leave the neutral loose before.

As Murdoch has suggested, if you are suspicious of the RCD, then ramp test it, this measures the fault current at which it will trip (which is normally around 25mA or so, very rarely is it 30mA). That will tell you at what current it's actually tripping, if it's anything less than about 22mA then bin it (or rather get the wholesaler to exchange it!). You may find that the fridge or other appliance(s) are causing enough leakage to take it over it's threashold.

 

[topquark]

Alternatively, what swift fingers said ^^^^^^^^^

 

[ipf]

Is only one RCD tripping? If so, there may be more additional leakage from different sources on one circuit than the other. An earth leakage clamp meter would shed more light.
I am presuming that this is an existing installation and CU is not a replacement.

 

[lofty84]

if its above then theres a mojor fault like a nail through one of our cables

 

[lofty84]

yep just one RCD is triping. Im fairly new to this so as u can imagine its a bit of a struggle trying to work things out

 

[Deleted member 9648]

Surely an IR test of final circuits is the first step when an RCD is tripping....??.....as far as I can see unless you establish no low IR readings, everything else...ramp tests...loose connections etc is pure guess work.