The main switch in my consumer unit seems to have failed-
the trip button makes a click and turns the switch off,
but theres no power at the output
feeding the MCBs to the circuits.

What can have happened?
(Its quite dusty where the CU is.)

Legrand 100A switch 100ma RCD 602711
Its like the one on the right in this pictu
http://edmundson-electrical.voltilin...&catalogType=P

Luckily half the house lights are off another consumer unit,


[george]

In article ,
"george [dicegeorge]" writes:
The main switch in my consumer unit seems to have failed-
the trip button makes a click and turns the switch off,
but theres no power at the output
feeding the MCBs to the circuits.

What can have happened?
(Its quite dusty where the CU is.)

Consumer unit components (MCBs, Switches, RCDs, etc) hate dust
(particularly brick/plaster dust - it gets inside and wrecks
them. The installation instructions often contain grave warnings
against fitting them whilst there's risk of dust contamination.
So it could be that dust has got inside your main switch/RCD and
written it off. It might be some other problem with it.

In any event, if your diagnosis is correct that there's no power
available at its output when switched on, it needs replacing - you
mustn't try to repair it nor continue using it even if it seems
to start working - next time it might fail to switch off.

Also with the power off, you (somehow) need to vacuum all the
dust out of the CU, and make sure it's well enough sealed to
stop it getting inside again. Don't blow or brush it out.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 19/04/12 22:48, Andrew Gabriel wrote:
In ,
"george writes:
The main switch in my consumer unit seems to have failed-
the trip button makes a click and turns the switch off,
but theres no power at the output
feeding the MCBs to the circuits.

What can have happened?
(Its quite dusty where the CU is.)

Consumer unit components (MCBs, Switches, RCDs, etc) hate dust
(particularly brick/plaster dust - it gets inside and wrecks
them. The installation instructions often contain grave warnings
against fitting them whilst there's risk of dust contamination.
So it could be that dust has got inside your main switch/RCD and
written it off. It might be some other problem with it.

In any event, if your diagnosis is correct that there's no power
available at its output when switched on, it needs replacing - you
mustn't try to repair it nor continue using it even if it seems
to start working - next time it might fail to switch off.

Also with the power off, you (somehow) need to vacuum all the
dust out of the CU, and make sure it's well enough sealed to
stop it getting inside again. Don't blow or brush it out.

Seal it with flexible frame filler from a gun thing?
Does it need any ventilation?

[george]

george [dicegeorge] wrote:
On 19/04/12 22:48, Andrew Gabriel wrote:
In ,
"george writes:
The main switch in my consumer unit seems to have failed-
the trip button makes a click and turns the switch off,
but theres no power at the output
feeding the MCBs to the circuits.

What can have happened?
(Its quite dusty where the CU is.)

Consumer unit components (MCBs, Switches, RCDs, etc) hate dust
(particularly brick/plaster dust - it gets inside and wrecks
them. The installation instructions often contain grave warnings
against fitting them whilst there's risk of dust contamination.
So it could be that dust has got inside your main switch/RCD and
written it off. It might be some other problem with it.

In any event, if your diagnosis is correct that there's no power
available at its output when switched on, it needs replacing - you
mustn't try to repair it nor continue using it even if it seems
to start working - next time it might fail to switch off.

Also with the power off, you (somehow) need to vacuum all the
dust out of the CU, and make sure it's well enough sealed to
stop it getting inside again. Don't blow or brush it out.

Seal it with flexible frame filler from a gun thing?

Yes. Or just silicone.

Does it need any ventilation?

No.

--
Adam

On Thu, 19 Apr 2012 22:20:30 +0100, "george [dicegeorge]"
wrote:

The main switch in my consumer unit seems to have failed-
the trip button makes a click and turns the switch off,
but theres no power at the output
feeding the MCBs to the circuits.

What can have happened?
(Its quite dusty where the CU is.)

Legrand 100A switch 100ma RCD 602711
Its like the one on the right in this pictu
http://edmundson-electrical.voltilin...&catalogType=P

Luckily half the house lights are off another consumer unit,


[george]


Dust shouldn't be a problem. These devices must be enclosed.

Why does it "seem to have failed"? Check the output at the terminals
after removal of all loads. Switch in the loads one by one and see
what happens.

regards

HN

On Apr 19, 11:47*pm, H. Neary wrote:
Dust shouldn't be a problem. These devices must be enclosed.

Unfortunately ERA research into RCD reliability found dust (&
humidity) is a problem in that it causes stiction. The RCD trip time
can increase unless tested regularly. I think failure is circa 7%, but
that did not specify time span (probably very long, but realise people
could have 4-19 RCBO in a domestic CU these days so change of *a*
failure is higher).

They are enclosed but not sealed against dust, and yes plaster/brick
dust particularly from diamond cutting will stuff them. It is a very
"paste" like dust which is both penetrative and obstructive. Stuffed
the smooth switch operation of an IP66 Clipsal 56SW20 from 150mm
diamond bit dust fallout... found all the gaps in the draught sealer
too :-(

On 20/04/12 19:11, js.b1 wrote:
On Apr 19, 11:47 pm, H. wrote:
Dust shouldn't be a problem. These devices must be enclosed.

Unfortunately ERA research into RCD reliability found dust (&
humidity) is a problem in that it causes stiction. The RCD trip time
can increase unless tested regularly. I think failure is circa 7%, but
that did not specify time span (probably very long, but realise people
could have 4-19 RCBO in a domestic CU these days so change of *a*
failure is higher).

They are enclosed but not sealed against dust, and yes plaster/brick
dust particularly from diamond cutting will stuff them. It is a very
"paste" like dust which is both penetrative and obstructive. Stuffed
the smooth switch operation of an IP66 Clipsal 56SW20 from 150mm
diamond bit dust fallout... found all the gaps in the draught sealer
too :-(
There was a lot of plaster dust came out when I tipped the old switch
upside down,

I have demolished some old plaster walls above it.

So now all the other components are suspect.

drat.

[g]