Case studies
The importance of design
The importance of design when changing or adding electrical circuits shouldn’t be ignored. Not only is it essential to adhere to the well-established requirements for electrical installations published in BS 7671 but it might also save your property and your life. Badly installed electrical systems, or those which haven’t taken into account the correct cable sizes, earthing or protective devices can be lethal.
Ensure electrical work undertaken in your property has been done so by a competent electrician who has taken the time to perform the required calculations, is installing to the current regulations and has provided you with all of the necessary certification to evidence their work.
Fault finding
Fault finding can bring unexpected solutions. Customer had lived for 4 years with their downstairs lights tripping randomly and intermittently, they suggested when "too many" lights were on. Their consumer unit uses an RCBO for every circuit, so disruption was minimised to that circuit alone, but to make it worse they couldn’t then switch the RCBO back on for 5 minutes.
The symptoms suggested a thermal (heat) issue in the consumer unit. First step was to check the usage on the lighting circuit to see if the (approximately 40) bulbs connected to it were asking too much. Using an ammeter and all lights on (and no, it didn’t trip this time!), a current draw of 1A was measured, well below the rating of the RCBO. So not an obvious demand issue.
Next step was a quick manual (pressing the test button) and automated RCD test - no issues found. Next, the outdoor light was checked as these are common causes due to water ingress - no issues found.
Next, an insulation resistance test to see if any of the cabling had been chewed by rodents or otherwise damaged. In preparation for this, conductors need to be disconnected, and in doing so we found one of the RCBO connections was not screwed down properly. The cable was also discoloured, suggesting arcing had been taking place. This would have generated heat, which in turn would have knocked the RCBO out until it no longer detected an issue. Probably the issue.
To be certain, we finally undertook the insulation resistance test by removing all light bulbs – time consuming but worth it to ensure there were not multiple issues on this circuit – no issues found.
It’s important on installation that connections are tightened to the required torque specification to ensure the chance of loosening over time is minimised. Connections should be checked at each periodic inspection (10 years for domestic properties, 5 years for rented properties, and upon tenant change) or when work is undertaken in the consumer unit as the movement of cables can help connections work loose.
The customer reports no further issues seen!
Faulty outdoor light
Replacement of a faulty dawn/dusk switch turned into something more interesting!
With no working outdoor light, the home owner had replaced the lamp bulb but that didn't resolve the issue. A site visit quickly found that every enclosure was wet inside and that the Steinel Nightmatic 3000 dawn/dusk switch had failed.
We found SWA armoured cable coiled and unsupported, entering the IP66 enclosure via a stuffing gland and lots of silicon sealant to close the inevitable gaps. Cable entry on the top of the same enclosure was secured with more silicon, and there were no glands used to enter the Steinel unit leaving it exposed to the elements. And the "attractive" white cable was standard 13A flex, the kind you'd find on a 4-way extension.
So it was all binned and replaced with a proper external SWA gland into a new IP66 box, positioned next to a new Steinel switch to allow cable entry at the bottom on both, using seals suitable for the new cable which is rated for external use. Finally a replacement feed to an outdoor socket (behind the pillar) also correctly glanded with a drip loop.
Not only is it now weatherproof and safe, but it also looks a lot better!
Finally, when doing a general inspection we two found missing blank shields in the garage consumer unit. It's a really dangerous omission for any installer as fingers can easily touch live parts. Fitted free of charge to bring the installation up to IP2X as per BS7671:2018 A3:2024 regulation 416.2.1.