I have an MK consumer unit with the house ring main wired into a MK 5932s MCB ( https://www.mkelectric.com/en-gb/Products/CP/sentry/MCBsinglepole/MCBsinglepoletypeb/Pages/5932s.aspx )

Occasionally when switching the MCB into the off position the switch will move toward the off position but it seems to stop half way between the two. While in this state power is still flowing to the sockets.

If I give the MCB switch a hard push down and then push it fully up again I find that it does not always reset to the on position rather moves back inbetween the on and off positions. This whole time the power remains on.

After some attempts it will reset correctly.

Initially I assumed it was a defect with the MCB but have confirmed that this isn't the case by switching the MCB over for a new one.

Any suggestions?


The handle moving to a central position is typically indicative of it having tripped and tripping when moving to Off, although not normal, is not unheard of. The part about this that is unacceptable is that it is not actually disconnecting when it does that. Regardless of whether you move the handle to Off or the breaker trips, it needs to disconnect and isolate. If your's is not doing that, it is seriously defective and needs immediate replacement.

  • As I thought, I'll give the electrician a call. Thanks! – robertmegone May 13 '19 at 19:57

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.