We have a newly installed RCD that trips in a very puzzling way. Let me
explain.

We have two separate consumer units. One has a split load RCD and supplies
the back of the house - it has never tripped. The other is an older "fuse
wire" consumer unit with 16 circuits supplying the front of the house. It is
protected by an RCD on its incoming feed and it is this RCD that trips
several times per day.

There is no single cause that trips it - sometimes it is a light, sometimes
the computer, etc. What is really puzzling is that the TV can trip it. The
TV is in the back of the house fed from the other consumer unit and
therefore is not even supplied through the troublesome RCD.

The RCD has been checked with an RCD tester and it passed OK.

Any ideas? Our electricians are baffled.

Thanks

"Hzatph" wrote in message
...
We have a newly installed RCD that trips in a very puzzling way. Let me
explain.

We have two separate consumer units. One has a split load RCD and supplies
the back of the house - it has never tripped. The other is an older "fuse
wire" consumer unit with 16 circuits supplying the front of the house. It
is protected by an RCD on its incoming feed and it is this RCD that trips
several times per day.

There is no single cause that trips it - sometimes it is a light,
sometimes the computer, etc. What is really puzzling is that the TV can
trip it. The TV is in the back of the house fed from the other consumer
unit and therefore is not even supplied through the troublesome RCD.

The RCD has been checked with an RCD tester and it passed OK.

Any ideas? Our electricians are baffled.

Thanks


Check that the RCD is not too sensitive,
check the insualtion been the tv ariel cable and N as well as E. Check there
is no N / E reversal

Hzatph wrote:

We have two separate consumer units. One has a split load RCD and supplies
the back of the house - it has never tripped. The other is an older "fuse
wire" consumer unit with 16 circuits supplying the front of the house. It is
protected by an RCD on its incoming feed and it is this RCD that trips
several times per day.

16 circuits is quite alot to have on one RCD. It would be interesting to
carry out RCD test while on load to see how much extra leakage is
required to trip it.

There is no single cause that trips it - sometimes it is a light, sometimes
the computer, etc. What is really puzzling is that the TV can trip it. The
TV is in the back of the house fed from the other consumer unit and
therefore is not even supplied through the troublesome RCD.

The RCD has been checked with an RCD tester and it passed OK.

That does not mean that it is not pre sensitied by cumulative leakage
from all the circuits it is feeding to the point where it right at the
point of tripping with little provocation. You could try to isoate if
there is a circuit that is doing the bulk of the leaking by
disconnecting each in turn for a day and seeing if that reduces the trip
rate.

You did not mention what sort of supply you had, or the trip current of
the RCDs. Also what sort of circuits are fed from the re-wireable
consumer unit?



--
Cheers,

John.

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| Internode Ltd - http://www.internode.co.uk |
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\================================================= ================/

In article ,
Hzatph wrote:
We have a newly installed RCD that trips in a very puzzling way. Let me
explain.

We have two separate consumer units. One has a split load RCD and
supplies the back of the house - it has never tripped. The other is an
older "fuse wire" consumer unit with 16 circuits supplying the front of
the house. It is protected by an RCD on its incoming feed and it is
this RCD that trips several times per day.

There is no single cause that trips it - sometimes it is a light,
sometimes the computer, etc. What is really puzzling is that the TV can
trip it. The TV is in the back of the house fed from the other consumer
unit and therefore is not even supplied through the troublesome RCD.

Is there any equipment which could cause the earth from one CU at some
point to to be shared with the earth for the other somewhere else? I
realise both CUs will share an earthing point.

Perhaps an aerial lead from a DA? Hi-Fi equipment interconnection?

--
*Nothing is foolproof to a sufficiently talented fool.

Dave Plowman London SW
To e-mail, change noise into sound.

To answer some of the questions.

Both RCDs are 30mA.

The 16 circuits have:

4 ring mains
2 power spurs (cooker, immersion heater)
The rest are lighting circuits as far as I know.

The only connection we can think between the consumer units is the aerial on
the TV - we have TVs on both parts of the house. We tried disconnecting this
but we still got a trip. The aerial has a masthead amplifier powered by a
transformer on a normal socket fed by the main fused consumer unit.

As Dave says both consumer units connect to an earth which I think is
connected to the neutral in the incoming supply. There is a cable from there
to ground on the Manweb side of our supply about 30m from the house.

Hope that helps.

Thanks for all the suggestions.

Hzatph wrote:

The 16 circuits have:

4 ring mains
2 power spurs (cooker, immersion heater)

^^^^^^^^^^^^^^^^
Prone to high leakage!

Try turning off / pulling the fuse for this and see if it helps.

If that does not find it then you are going to need to start testing the
wiring for each circuit with a megger.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article , John
Rumm writes
Hzatph wrote:

The 16 circuits have:

4 ring mains
2 power spurs (cooker, immersion heater)

^^^^^^^^^^^^^^^^
Prone to high leakage!

Try turning off / pulling the fuse for this and see if it helps.

If that does not find it then you are going to need to start testing the
wiring for each circuit with a megger.


Also look for Nutral/Earth shorts or leakage, these are often overlooked
and don't usually show up until some current is flowing through the
system.....
--
Tony Sayer

I would suspect that, but both these items are switched off. We have kept a
log of things that trip the RCD and it is a long list - there is no regular
pattern.
"John Rumm" wrote in message
...
Hzatph wrote:

The 16 circuits have:

4 ring mains
2 power spurs (cooker, immersion heater)

^^^^^^^^^^^^^^^^
Prone to high leakage!

Try turning off / pulling the fuse for this and see if it helps.

If that does not find it then you are going to need to start testing the
wiring for each circuit with a megger.

I would suspect that, but both these items are switched off. We have kept a
log of things that trip the RCD and it is a long list - there is no regular
pattern.

On Sat, 20 Aug 2005 21:45:49 +0000 (UTC), "Hzatph"
wrote:

I would suspect that, but both these items are switched off. We have kept a
log of things that trip the RCD and it is a long list - there is no regular
pattern.

Hi,

I wonder if the neutrals on the the two consumer units are connected
somewhere, maybe on a lighting circuit.

Does the TV trip the RCD on switch on? If so it's probably the large
current draw from the degauss circuit.

A good way to track down the fault would be isolate each L-N circuit
in turn by disconnecting the neutral as well as just pulling the fuse.

Be very careful though, no responsibility accepted if you fry
yourself! :^)

cheers,
Pete.

Hzatph wrote:

We have a newly installed RCD that trips in a very puzzling way. Let me
explain.

We have two separate consumer units. One has a split load RCD and supplies
the back of the house - it has never tripped. The other is an older "fuse
wire" consumer unit with 16 circuits supplying the front of the house. It is
protected by an RCD on its incoming feed and it is this RCD that trips
several times per day.

There is no single cause that trips it - sometimes it is a light, sometimes
the computer, etc. What is really puzzling is that the TV can trip it. The
TV is in the back of the house fed from the other consumer unit and
therefore is not even supplied through the troublesome RCD.

The RCD has been checked with an RCD tester and it passed OK.

Any ideas? Our electricians are baffled.

Thanks


Neutral earth leakage somewhere.