Kirk and Crane's Electric Blog.

  • Matt

This week's call outs

We don't do a lot of domestic call outs - but this week has seen quite a few, some include:

RCD Tripping (1)

Customer said that everything had been working when they left for work but on their return there was no power and lighting to downstairs.

We quickly diagnosed a problem with the lighting circuit and soon found that a kitchen fitting was full of water causing a dead short.

Although we diagnosed,found and repaired the problem quickly luckily they had a split load board, and so with 2 RCD units splitting the circuits most of the house's power remained on during the process.

RCD Tripping (2)

With only one master RCD remote from the flat this tenant was loosing all power at what appeared to be random intervals.

We diagnosed the cause as a faulty water heater element - though frustratingly when cold it tested out OK, only creating a fault once it reached a certain temperature , and being thermostatically controlled created the "random" tripping pattern for the tenant.

Circuit Breaker Tripping on Overload.

A simple find , an shower unit had been exchanged for much larger unit causing the circuit to trip.

We carefully explained to the customer that in terms of circuit design and load carrying capacity:

Cable capacity > Circuit Protection > Load.

ie the cable should be able to carry more than the load can give it, and that the circuit protection should not nuisance trip until it sees a fault or overload.

Unfortunately they had created

Load > Circuit Protection > Cable Capacity

and so if they want to keep that shower unit the circuit needs rewiring and the protection upgrading.

Easter Egg.

Changing light fittings we found , in the loft space, some poor cabling practice by previous electricians, but the worst was the cable in the photo below.

Now, that cable was dead when we checked it, not that we could readily identify where the other end was but:

a) I might have been a switched feed , or a time-clock outside lighting feed , or an immersion feed , or a circuit just switched off, and therefore could be live at other times.

b) It was millimeters from a metallic lighting fitting that had it become live could have become live, caused a spark, caused a short , or even an nuisance RCD trip*

c) Now it could have been old dead cable, but other end disappeared into the building fabric so we could potentially have been hours tracing it to prove it could never become live.

We fitted a joint box. Screwfix, for example, will sell you a joint box for under £2.

Isn't it worth it?

We might be the cheapest electrical contractor, but as Red Adair said

" If you think it's expensive to hire a professional to do the job, wait until you hire an amateur"

(* An RCD sits like an electrical sea-saw looking for an imbalance between the live and neutral current. This obviously assumes that live and neutral on a circuit follow the same path. A potential downside is that if you create a "better" path for the neutral back to earth then the current will flow along that path rather than the original circuit . The RCD sees this as a fault and trips. In this case, had the cables touched, or touched the light fittings, they could have created shorter paths, and caused and RCD trip - and boy, unlike the ones at the top of this page, would that have been difficult to find!)

© 2018 Kirk & Crane Electrical Co Ltd.  If its on your to-do list, phone 01476 590707 and cross it off, we'll sort it.

Kirk & Crane Electrical. Co. Ltd

69-73 London Road



NG31 6HW

Privacy Policy.