Type B vs type C RCBOs - and trip warning indicators for power failure?

[Michael Kilpatrick]

I was just looking at the consumer unit (see second question further down)...but first was puzzled as to why, given that three lighting circuits in the house use type B6 RCBOs, there is a type C6 RCBO on the circuit labelled "light outside, front and hall" (an older circuit predating the extension/new CU).

Everything else is a type B RCBO with the exception of a C6 RCBO on the circuit labelled "heating & towel radiator".

What is the reason for the C6s?

And current does a C6 RCBO /actually/ trip at?

Secondly, the reason why I was looking at the consumer unit again today...

The garage circuit RCBO (a B16 going to armoured cables underground) tripped twice in the last day or so after a particularly heavy downpour. I will have to look at the garage roof soon as I know it's leaking - and there is one socket which might be near a possible leak spot. Ugh, more work.

But the question is, what is the most sensible system for fitting a warning light or buzzer so that I can tell if the garage circuit has tripped? There's a freezer in there but of course you can't tell unless you open the consumer unit or actually hear it tripping.

I observe that 'auxilary contacts' exist for some RCBOs although they seem hard to find. Good idea or not? A DIN buzzer module could be fitted, or just an external red light.

I raise that idea because it might actually be easier to mess about in the consumer unit than try to interrupt the cables to the armoured cables, in a rather tight space, in order to fit an external power failure alarm. I might soon be having some other electrical work which would warrant getting someone to help with that as well as perhaps run tests on the garage circuit.

Any handy suggestions on power failure warnings?

Michael

[ARW]

MCBs are covered in the wiki

As to an easy way to tell if the garage RCBO has tripped is to fit a 1g socket next to the CU on that circuit and plug some thing similar to this into it.

Looks like the wrong plug on that one but it gives you an idea.

Cheers

Adam

[John Walliker]

I like the sound level spec: "the alarm volume is up to 120 dB or more" which could mean anything between total silence and a nuclear explosion.

John

[Animal]

Simplest option is a relay & your chosen warning device. Next up is to add a rechargeable battery. Another option, if it's walked past, is to fit a row of neons bythe CU, Keep their current down so they last.

[John Walliker]

I recently bought some neon tubes for a similar purpose:

The ready-made ones seemed rather expensive, so I bought a bag of 100 bare neons for £9.49. I will of course be adding my own resistors.

John

[Michael Kilpatrick]

Ah. I eventually discovered, after thinking it was the dodgy old wiring to the garage lighting that was at fault, what with the leaky roof (which I think really will have to be attended to!) that actually, it's my wiring to the pond pump. Despite a lot of time, care and money when I put in the socket, junction box and cabling for the pump and the fill-valve solenoid from the rain harvester, there's a fault in the pond pump circuit.

I would have thought the IP66 box, proper PVC weatherproof cables and glands would last for decades but there's clearly something going on there.

Disconnecting the live feed from the switch back to the junction box seems to have stopped the tripping. Will replace the box with a bigger one (it's a bit cramped) and new glands etc.

The trouble with things such as the one ARW pointed us to, is that they presumably consume a bit of power. If an RCBO had auxiliary contacts to wire in a buzzer/light on tripping, it wouldn't need to consume a few milliwatts doing nothing for - hopefully! - all its life.

Michael

[Dave Plowman (News]

I would have thought a fault big enough to take a 16 amp MCB pretty easy to find?

[ARW]

Dave - it's a RCBO not a MCB:-)

[The Natural Philosopher]

Senility is advancing...

[Brian Gaff]

Yes, shovel through the cable or a very large rat. Brian