RCD nuisance tripping.

coffeehound

Condensation?  Something that gets cold overnight, then attracts condensation as the house warms up, perhaps near the bathroom.  Sorry, not much help

Ectophile

If everything in the house is on one RCD, that's probably the problem.  Houses these days are filled with electronic appliances, and each one is allowed to leak a milliamp or two and still be safe.

The RCD must trip at 30mA, but many are a bit twitchy and will trip at rather less than that.  All is requires is one more appliance to turn on in the morning and that becomes the straw that breaks the camel's back.

Replacing all the MCBs with RCBOs, and losing the RCD is one option.  Another may be to install a "split load" board with 2 or more RCDs.

Moss5

https://electricalcomponentsdirect.co.uk/acatalog/RCBO-ECD-1E-1PB32-B-curve-32A-RCBO-30mA--4.html#SID=2

https://www.electricalcomponentsdirect.co.uk/cgi-bin/sh001518.pl?WD=led's&PN=LED-INDICATOR-LAMP-AD22-22DS-GREEN-97.html#SID=13

https://electricalcomponentsdirect.co.uk/acatalog/Metal-Consumer-Unit-Details-p1.html
Don't be feint-hearted, you could do this yourself.

Moss5

To answer your earlier question, an RCD device should not follow/precede another RCD device.
So you cannot install an RCBO on an RCD protected circuit.
Why would you!

AskAsk

that must be so annoying.  as it happens between 7.30 to 8am, it must be an appliance that gets used at that time when you get up.  more likely a cooking appliance or a lamp.

Jeepers_Creepers

Thank you everyone - I really appreciate it.

Theoretica, that's what I was wondering - could it be an external trigger - a small voltage rise at that time? I'll take voltage readings day, eve and morn to see if anything shows.

Shiny - no, just standard tariff. It's not the exact same time, just in that ballpark.

Coffee - That's a thought, but I think most condensation would occur overnight, when the house cools and not as it warms up?

Ecto - thanks for the confirmation. Yes, replacing all MCBs with RCBOs would be a good thing to do in any event. Can't think of anything that's turned on that makes it trigger, tho'. I'm usually back in bed with my cuppa when it goes 'pop'. Radio on, a few lights, CH - that's it. Everyone else still in bed.

Moss - cheers.  That's about doable, although it would be £200 for just the parts. Yes, I could do this myself - I've carried out a few full rewires and CU fits in previous houses. So it's out with the RCD and in with 17 RCBOs... :-(  

AskAsk - yes, annoying because it doesn't have the decency to stay tripped, so I can try isolating circuits to track it down... It just seems to have this momentary glitch, and then it can be reset again and stay on happily. Usually it can be turned back on right away, other times it's more reluctant and takes a few attempts. Almost always once reset it stays that way. Very occasionally it'll do another pop a few minutes later. But no change in activity in that time - nothing of significance being used.

Jeepers_Creepers

The first time it happened - a couple of weeks before Christmas - it wouldn't reset right away. So I tried turning off MCBs in the order I thought they might be affected, starting with the exterior lights. Bingo! I could reset the RCD, so I thought I'd found the dodgy circuit. Later on I tried resetting that MCB, but the rear LED flood, the front LED flood and the porch CFL internal light were still not coming on.

Pretty bleedin' obvious, then - it must be a fault in the supply cable common to these three. Then I realised that a downstairs cloakroom ALSO ran from this circuit, and that light DID come on when the MCB was reset; the other three remained off (and the RCD stayed on happily). Blimey - "where's the break in the wire now?", thought I. There wasn't one - I found that all THREE lamps had failed, the rear flood being only a few weeks old. Burnt out LEDs - you could see them just about glimmer when dark. Replaced the rear flood with another LED, and that's working fine. Ditto with the porch light - LED, and working ok. (Can't be bovvered replacing the front flood - that's just left switched off)

Now, was that coincidence? Three lamps, 2XLED, 1X CFL, 'blowing' at around the same time, possibly at the same time?

FreeBear

Moss5 said: https://electricalcomponentsdirect.co.uk/acatalog/Metal-Consumer-Unit-Details-p1.html

Don't be feint-hearted, you could do this yourself.

Replacing the consumer unit is a "notifiable work" that needs to be signed off by building control or a contractor that can self certify. The average DIYer does not have access to the necessary test equipment to ensure that everything is up to the required standard.

Few installations have an isolator between the meter & consumer unit, so the main fuse will need to be pulled in order to kill the power (only a fool will try to replace a consumer unit whilst it is still live). Pulling the main fuse will entail breaking the seal, and very few people will be authorised to put a new seal on.

Jeepers_Creepers

I'd only be swapping the MCBs :-)  The actual CU is a mother of a MEM with 20 spaces. Yes, the main fuse has a seal, but there are two further connectors which are without...

Notify? Moi? Nah.

Risteard

FreeBear said:

Jeepers_Creepers said: Any other thoughts?

The RCD developing a fault ?

They don't last for ever (I've had to replace mine last year).

I can state with about 99% certainty that the RCD won't be the problem - it's the installation. It's simply doing its job.