pulsing lamps

[chloebear]

Hi all,

Got a bit of a strange one - just been to a house that has had a new CU fitted and they are having problems with one of the ring circuits - if you plug in a standard lamp it pulses fast, not enough juice to run the TV if you plug it in either????????
anyone got any good ideas???????

 

[nickblake]

Check your voltage / Zs the circuit could be a neutral fault make sure nothings plugged into the circuit , also do a Ze test as this could be a fault on the neutral of the supply TNCS ,When loading the voltage is dropping ,

 

[Sintra]

Agree check voltage on circuit and Zs.

 

[chloebear]

all other circuits in the house seem to be Ok, I will be returning in the morning to continue the investigation, just looking for pointers & if anyone has come accross this before. Could a mixed leg & leg on the line conductor cause this??

 

[chloebear]

standard bayonet fitting, tried three table lamps and all doing the same thing

 

[nickblake]

do a full test as you would with a ring continuity L to L N to N cpc To CPC ,and R1 R2 insulation and Zs

 

[Sintra]

Does sound like you have low voltage on that circuit. Keep us posted with your findings.

 

[chloebear]

turns out that the cause of the problem with pulsing standard lamps on the ring cct was due to the line conductor being connected to a breaker on the main switch side of the board and the neutrals being connected to the RCD side of the board. MK board with dual RCD protection, the RCD had tripped into its mid way state and was causing this effect. Solution for the time being was to re-connect the neutrals to the non rcd protected side of the board and hey presto no problems. I also discovered why the ring cct was places on its own breaker on the non RCD side - there is quite a large leakage cpc/Line on this cct, so I guess it was causing a lot of nucance tripping. Next stage is to find out the cause of this problem.

 

[Guest123]

Well at least you're going to sort it all out for them, unlike the clown who left it like that!!!

 

[SimpleSimon]

turns out that the cause of the problem with pulsing standard lamps on the ring cct was due to the line conductor being connected to a breaker on the main switch side of the board and the neutrals being connected to the RCD side of the board. MK board with dual RCD protection, the RCD had tripped into its mid way state and was causing this effect. Solution for the time being was to re-connect the neutrals to the non rcd protected side of the board and hey presto no problems. I also discovered why the ring cct was places on its own breaker on the non RCD side - there is quite a large leakage cpc/Line on this cct, so I guess it was causing a lot of nucance tripping. Next stage is to find out the cause of this problem.

But if the RCD was tripping in it's 'mid-way' state, shouldn't you be a bit concerned as to why it's not completely tripping out?

 

[Guest123]

MK ones dont go all the way down when they trip, they stop at half way. To reset you need to push the switch all the way down and then back up.

 

[SimpleSimon]

Didn't know that. Why is that? Doesnt cut off supply properly by the sounds of it?

 

[chloebear]

MK rcds have 3 states of operation (or not) fully up is in normal operation mode, tripped halfway is standard trip mode & to reset the trip you have to toggle the switch into the down position and then reset to the fully up position.
Dont know why - just a standrd of the MK rcds.