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 picture:
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]
Yes. Or just silicone.
No.
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=A0pm, H. Neary wrot= e:
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.
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