Unusual electrical issue – faulty MCB?

Had a bit of strange electrical issue last night.

The power went off to the utility room sockets circuit, which also powers the central heating.

Checked the consumer unit and nothing had tripped.

I flicked the main RCD and circuit MCB off and on. Nothing happened.

Then without any further intervention, about 30 minutes later, the power came back on and stayed on.

Can MCB’s and RCD’s develop faults as they get old? Do they wear out? The consumer unit is from the the 1980’s.

I think that needs an electrician. You could in the short term check that the terminals on the MCB (particularly onto the bus bar) aren’t loose.

But from what you’ve described the problem may lie in the consumer unit, wiring, or any appliance connected to that circuit and I’d seriously consider isolating it completely via the MCB until it’s been checked since it’s clearly faulty and neither the RCD or MCB is offering protection.

I would guess a loose connection in the consumer unit.

tbh, if the consumer unit dates from the 80s it’s best replaced anyway, even if the issue is just a faulty cb. The ‘RCD’ may even be one of the old voltage operated ones (ELCB), rather than the ‘modern’ (they’ve been around for years!) current-leakage ones. If you have a loose connection, that’s one of the main causes of electrical fires in domestic installations, hence the requirement for metal enclosures in all modern CUs. You’ll also get a full PIR (insp & test) as well for reassurance that the rest of the installation is ok.
Seriously, loose connections are a real danger as there is so much current going through the CU. If there is arcing then it’ll be carbonising the contacts and making the situation worse – and arcing equals heat.

Can MCB’s and RCD’s develop faults as they get old? Do they wear out?

Yes, absolutely they do.
Did you switch any FCUs/switched fuse spurs? If they’re wired wrong and you have two on the circuit they can actually isolate the segment of the circuit bwtween them. That’s not unheard of.
As an electrician I’d recommend getting it checked and looking at updating the CU.

Had similar in my utility room .

Was a dead MCB in the end – power into MCB was ok. But nothing coming out. But could be any number of things.

replaced mcb and life was good

We had random trips of the upstairs circuit, which was eventually traced to a single wall socket for the fridge/freezer (which was wired to upstairs ring – new build). All OK once replaced.