Please suggest method to solve intermittent lighting fault.

[GR8DAN]

Have upstairs lights which completely lose power for a period of time (a few minutes to an hour or more). Fuse box does not trip.

More info: Had an extension built four years ago. The electricians replaced the fuse box with a modern unit with breakers (previous one required fuse wire). The extension lighting comes off one breaker. All other house lighting (upstairs and downstairs) comes off another breaker. When upstairs lighting loses power the downstairs lighting stays on, so must be two circuits. The upstairs lighting didn't use to flicker but does now when about to lose power. The breaker is quite sensitive, a blown bulb will cause it to trip, but its not tripping when the upstairs lights lose power. Can't confirm yet but loss of power may be occurring when bathroom lights turned on and other upstairs lights are also on. There have been no changes to the lighting since the extension was built. Problem has occurred several times since last Thursday. Usual items on the lighting circuit: normal bulbs, energy savers, spots, switches, dimmers, extractor fans.

If it was a lose connection wouldn't that trip the breaker? And it's been fine for years until this week.
Is a component in the circuit about to fail? Hence the intermittency.
Is something overheating? Hence the power returns after a period, again a component on borderline failure.
What could be failing in the circuit that causes lose of power but not trip the breaker?

Am usually good at fixing simple faults but this has me stumped. How would I best tackle this? Any fault finding suggestions would be appreciated.

Thanks for your time.
DAN

 

[THRIPSTER]

Loose connection between breaker and lighting. Try isolating CU and tightening breaker screws - if not that then is likely to be a junction box somewhere - probably in roof space. A loose connection would not necessarily cause the breaker to trip. As it is a loose connection would be prudent to find the fault quickly as it is probably accompanied by arcing.

Regards

 

[jj4091]

Loose connection between breaker and lighting. Try isolating CU and tightening breaker screws - if not that then is likely to be a junction box somewhere - probably in roof space. A loose connection would not necessarily cause the breaker to trip. As it is a loose connection would be prudent to find the fault quickly as it is probably accompanied by arcing.

Regards

Or the first ceiling rose if wired loop in/out

 

[Taylortwocities]

Look closely at the the connection at the bottom of the MCB, where the busbar goes in.

ONLY DO THIS WITH THE MAIN SWITCH OFF AND EVRYTHING CONFIRMED AS OFF. See section on safe isolation

It is possble that the busbar isnt properly clamped onto the MCB.

 

[RF Lighting]

Wouldn't that affect downstairs too, as the OP says they are bath on the same breaker?

There will be a loose connection somewhere along the line.

Might be at a light fitting, maybe a switch, maybe a hidden joint.

Unfortunately no one will be able to tell you exactly where.