RCD tripping in new build help

[Chrisbly]

I wonder if someone can shine any light on this for me...

Customer complaining of RCD tripping at random times- night/ day, everyday and sometimes only trips once every 2 months.

The rcd covers immersion, sockets and both lights which also has an alarm on one of the lighting circuits.

The lights consist of 15 spotlights and around 10 other lights.
He has a few timers around the place, no extension leads, building is around 3 years old. He has said the tripping occurred before the alarm system was installed but electrician had to come back to change 2 gang dimmer for the spotlights

Also the lights was wired without a switch wire when built so they had to come back and rip half the ceiling down to install a cable they left out. Appalling really

So the IR tests were all brilliant. Didn't want to spend too much time there and going back so wondered if anyone could shed any light.

The alarm keeps going off when the RCD trips so I was thinking of putting the alarm on the mains side so he won't have the same problem again in 10 / 15 years...

Many thanks in advance

 

[stephenf8542]

Had a similar problem at the weekend eventually found a neutral fault
Why is the alarm going off the battery should kick in when the power goes down
Steve

 

[Chrisbly]

Hi Steve,

Thanks for your speedy reply... Where was the neutral fault on yours?
Can you tell me if neutral - live is irrelevant when hunting down nuisance tripping on RCD too? I'm not the experienced of electricians :s

He / we can't turn the external alarm off when the power is done. So the alarm could go off all day while he is at work if the RCD trips so putting it on the mains should solve the issue of the alarm but not the nuisance tripping unless the fault is on that circuit

 

[EFLImpudence]

Why is the alarm going off the battery should kick in when the power goes down

It has or it wouldn't sound.

That's what they do when they detect loss of power so you can't switch them off.

 

[Chrisbly]

Just to confirm.. The alarm works perfectly and yes it goes off when the power is off. Customer problem: alarm goes off when the RCD trips and this could be at any given time (I.e at work or in the night)

 

[EFLImpudence]

As for RCD problem - as IR all good.

Only usual suspects -
Water ingress in exterior fittings, heaters or motors failing.
Could be an accumulation of smaller faults.

Can be difficult to find -
Do you have a leakage clamp meter?
If not, do a ramp test with different mcbs off and neutrals disconnected.
It may give a clue

 

[Chrisbly]

Thanks, I think I'll check the external lights and complete ramp tests and no to a clamp meter (I could of done with one just last week so will definitely get one now).

Accumulation is possible but I have heard timers are known for tripping the RCD and he has around 3 of them.

Thanks for the kind replies and I will definitely update this post once sorted.

Chris

 

[Lectrician]

The intruder alarm SHOULD NOT 'go off' when power is removed. At the most, it should beep and alert you at the keypad that power is missing, but the external siren should never sound.

If it is, the panels backup battery or charging circuit is faulty.

This should be sorted.

--

L to N faults are not going to cause an RCD to trip - You need to look for a fault between L and E or N and E. Test appliances too. Test the immersion element (do they use it?).

Asking someone where they found there neutral fault is not going to help you one bit in finding this problem. If they told you they found their neutral fault behind the lounge socket, is that where you would look? lol.

 

[Chrisbly]

I was asking to make conversation as this is my 1st post and they took the time out to reply to my question. Thanks anyway lol

 

[Chrisbly]

And I appreciate what you have said about alarms as this is not my area at all. So your telling me without knowing what the alarm is...

If someone was to pull the main fuse outside his property that they could just break in without alarming the neighbours because alarms should never go off when the power is removed?

I'm not being rude it just doesn't make sense and I presumed with any alarm if any cable was cut the alarm would sound.

 

[bernardgreen]

The fault causing the RCD to trip can be almost anywhere. It can and often is on a circuit that has had its Live isolated at the CU for testing but the Neutral still connected.

Neutral_Earth_trip

• bernardgreen
• 16 Jan 2011
• 48

For this reason the IR checks on Neutral to CPC are very important.

There is the normal near zero impedance path between the neutral bar and the incomer via the RCD meter etc and the parallel path through the fault that bypasses the RCD sensor and meter. It is the ratio of these two impedances which determines what fraction of the load current bypasses the RCD. If the impedance of the path through the fault is 100 times the impedance of the direct path then the neutral to CPC fault will only cause the RCD to trip when the load on the neutral bar is in excess of 3 amps ( 3000 mA = 100 times 30 mA )

 

[SaladFingers]

Why is the alarm going off the battery should kick in when the power goes down

It has or it wouldn't sound.

That's what they do when they detect loss of power so you can't switch them off.

Is that when they're fully set?

 

[IJWS15]

Why is the alarm going off the battery should kick in when the power goes down

It has or it wouldn't sound.

That's what they do when they detect loss of power so you can't switch them off.

Ours (Veritas fitted by ADT) doesn't go off when the power is cut, it runs off the battery until the power is restored. If the alarm goes off then the siren box is losing contact with the control box and acting as if a wire has been cut - perhaps the alarm battery needs changing or it isn't wired correctly.

 

[Chrisbly]

I see what you mean now, thank you for all your responses by the way.

I will inform the customer and he will more than likely get the whoever fitted it back as I'm quite sure this would of been installed in the last year.

Could this be the reason of the RCD tripping perhaps?

 

[markocosic]

IME most domestic alarm fitters are chimps - and everything that isn't as-built is a prime suspect.

Has the owner stuck any screws/nails between Neutral and earth?

Damp/dead spiders inside outdoor sockets/lights?