12v downlights trip mcb when switched off

[dan.]

not everytime but sometimes they trip it. why would switching them OFF trip a fuse?

 

[Apache]

loose connection?

 

[electrizion]

As Apache says,

Switching off under load creating overload current across bad connection

 

[Evans Electric]

not everytime but sometimes they trip it. why would switching them OFF trip a fuse?

I take it you mean " tripping an MCB" . Is it the old style wire wound transformer, which are often quite large and feed 4 or 6 fittings.

These can be a nightmare for tripping MCBs but usually switching ON not off. Its the inrush of current when the tranny powers up that trips when switching ON and are best backed up with a type C or a HRC fuse.

Switching OFF can cause a rise in current and it may be that. ( Breakdown of magnetic fluxes like the old points on a car) Is it a 6amp MCB ? could try a 10amp or a Type C .

Or it could just be that the circuit amps are close to the MCB rating.

Deke

 

[dan.]

been back to have another look.3 spots in the ceiling and 2 over a vanity unit.they used to be on different switches but were put into one.if wired into 2 different switches they dont trip anything.it is quiet random doesnt happen everytime,but can be made to trip if turned on and off a few times.all the fittings are about 15 yrs old and acces is bad as the fittings were fitted b4 the loft conversion was done and are now inaccesable without major damage to the ceiling.i disconneted the 2 vanity lights at the switch as this seems to cure(or mask) the problem.MCB is a 6amp type b.with every light on in the house it doesnt trip,just this bathroom.

 

[green-hornet]

I would think this is a problem with age of the circuits involved and loose connections.

Every connection through the circuit would require inspection, you now have to remember the regulations especially with the new 17th as regards to any junction box that is inaccessable for inspection, they should be terminated into maintenance free connectors like the push fit type mentioned on this forum.

I fear you have your hands full with this problem, however it was primarily caused by bad working practice from previous electricians and not you.

Basically you would have to tell the customer you can fix the problem, but it would involve some remedial repairs after you have done so, I bet they saved some money on the initial install and are now paying for the cheap job that was done.

 

[dan.]

thats what ive told them.i think theyll just leave the 2 vanity lights disconected,i really cant see them wanting the room wrecked.

 

[batty]

been back to have another look.3 spots in the ceiling and 2 over a vanity unit.they used to be on different switches but were put into one.if wired into 2 different switches they dont trip anything.it is quiet random doesnt happen everytime,but can be made to trip if turned on and off a few times.all the fittings are about 15 yrs old and acces is bad as the fittings were fitted b4 the loft conversion was done and are now inaccesable without major damage to the ceiling.i disconneted the 2 vanity lights at the switch as this seems to cure(or mask) the problem.MCB is a 6amp type b.with every light on in the house it doesnt trip,just this bathroom.

Dan are you saying all lighting is on one circuit.

Batty

 

[green-hornet]

Dan are you saying all lighting is on one circuit.Batty

Hey good point two circuits cojoined neutrals an all that headache

 

[dan.]

yup whole house lights are on 1 circuit.its a small bungalow thar been converted in to a medium sized house

 

[ianmacd]

When the lost was converted they should have put new circuits in. Are you able to split the lighting now?

Ian.

 

[dan.]

not without it needing some serious decorating after ; -)

 

[batty]

Sounds to me like circuit is on the verge of being overloaded hence tripping out. As said on previous thread makes me mad when builders do these conversions without upgrading electrics ******s want shooting.

Batty

 

[D Brennan]

I would think this is a problem with age of the circuits involved and loose connections.Every connection through the circuit would require inspection, you now have to remember the regulations especially with the new 17th as regards to any junction box that is inaccessable for inspection, they should be terminated into maintenance free connectors like the push fit type mentioned on this forum.I fear you have your hands full with this problem, however it was primarily caused by bad working practice from previous electricians and not you.

Basically you would have to tell the customer you can fix the problem, but it would involve some remedial repairs after you have done so, I bet they saved some money on the initial install and are now paying for the cheap job that was done.

Whats classed as inaccessable??

if you can pull the spot light down and the jointboc/chocbox comes down is this classed as inaccessable or accessable, only asking because i fitted some smokes in a house today, smokes didnt come with a base so connections will be going into a jointbox and pushed into ceiling.. is this wrong now??

 

[Apache]

Whats classed as inaccessable??if you can pull the spot light down and the jointboc/chocbox comes down is this classed as inaccessable or accessable, only asking because i fitted some smokes in a house today, smokes didnt come with a base so connections will be going into a jointbox and pushed into ceiling.. is this wrong now??

nah that can be accessed without damage to d

 

[The Godfather]

Whats classed as inaccessable??if you can pull the spot light down and the jointboc/chocbox comes down is this classed as inaccessable or accessable, only asking because i fitted some smokes in a house today, smokes didnt come with a base so connections will be going into a jointbox and pushed into ceiling.. is this wrong now??

Accessible:

Without the use of tools or keys.

The Godfather

 

[green-hornet]

Whats classed as inaccessable??if you can pull the spot light down and the jointboc/chocbox comes down is this classed as inaccessable or accessable, only asking because i fitted some smokes in a house today, smokes didnt come with a base so connections will be going into a jointbox and pushed into ceiling.. is this wrong now??

No what you describe is accessable, you have a means of getting to the fitting by removal or otherwise.

Any junction box in a loft is classed as accessable, because there is reasonable access to inspect, however akward this is.

Main situations where maintenance free jb come to their own are

In a wall, ie extending a lighting circuit or ring main.

Under a tiled or laminate floor.

Problem with most house designs are that the two main tiled floor areas are the bathroom and kitchen, and behold the wrath of any woman faced with distruption of these hallowed surfaces to get cables in.

Remember any thing you connect by way of a screw connection has to be available for inspection and service,

Any connection that is maintenance free does not and can be ignored on any pir report.

 

[SPECIAL LOCATION]

Remember any thing you connect by way of a screw connection has to be available for inspection and service,Any connection that is maintenance free does not and can be ignored on any pir report.

Quite so Mr Hornet!Applaud Smiley:x

Just for the benefit of t'others reading..

maintenance free would include..

Crimp joints.

Solder joints.

Cold Resin sealed joins.

Push fit connections, a'la Wagos et al.

basically.. NON screw driver terminals!!!!Guiness Drink

 

[green-hornet]

Yep I agree and well pointed out.

I sometimes forget others may read the posts and do not include all the other solutions.

Thanks special for pointing this out.

 

[Evans Electric]

I take it you mean " tripping an MCB" . Is it the old style wire wound transformer, which are often quite large and feed 4 or 6 fittings. These can be a nightmare for tripping MCBs but usually switching ON not off. Its the inrush of current when the tranny powers up that trips when switching ON and are best backed up with a type C or a HRC fuse.

Switching OFF can cause a rise in current and it may be that. ( Breakdown of magnetic fluxes like the old points on a car) Is it a 6amp MCB ? could try a 10amp or a Type C .

Or it could just be that the circuit amps are close to the MCB rating.

Deke

So, have you checked the current with all those lights on. ? May be looking at a 10amp MCB