MCB tripping

[quackers]

Hi Guys

First time Ive posted , I am stuck and just wondered if anyone has an idea of what I am seeing.
Basically I have a customer (New House 4 years old) that is tripping the lights upstairs.
IR checks out and is as would be expected on a house that old. Zs is exactly the same as the original Installation Certificate.
The house has two bedrooms, one en-suite and one family bathroom.
All switches are unmolested-everything has been left as the builders left it four years ago.
All the lights upstairs are of the low voltage downlights 50W Halogen --God I hate them !!
The lights are on a 6 A Mk breaker. I have replaced the breaker as everything checks out.
However the lights still trip. On or off makes no difference, give it 20 mins and they trip.
All bathroom lights are correct in the zones-no damp.
However there is one dimmer in the bedroom. Have any of you guys come across a dimmer pulling down a 6 A MCB when off ??

Any help or direction greatly appreciated.
Cheers Steve.

 

[quackers]

Arrrhhh Saveloy good thinking..I do believe that there was a booster from memory ! Not had problems with these before , but I guess soem have

 

[mikeymoo]

Its looks like its gonna have to be trial and error, disconnect one item at a time. Time consuming i know. But maybe the only way.

 

[saveloy]

Could be faulty and would still draw current even when lights are all off.

 

[quackers]

Cheers Mikeymoo and Savely ..Will do.

 

[Wiredspark]

its an overcurrent issue. regardless of the calculated load, you Need to see whats on the circuit via a clamp meter or A meter.. You can also identify by isolation whats causing the over load. I think youll find that there will be in excess of 6a on the circuit.

Edit. You already suspect a booster, so what else is there added. Remember a MCB will not trip right away unlesss heavily overloded, ie fault current

 

[quackers]

Cheers wiredspark, Yeah I know its overloaded due to excess current. Replaced the MCB as may have been oversensitive before delving deeper. Saveloy mentioned the Booster so I think a good place to start from isolating. Unfortunately for me the whole loft has been boarded brilliantly by the builders so restricted access to trannies etc.

 

[Wiredspark]

Cheers wiredspark, Yeah I know its overloaded due to excess current. .

Cool, it was just to emphasise that its unlikely to be a fault current if it's taking 20 minuted or so dude

 

[quackers]

Cheers Wiredspark

Its just one of those issues. Poor lady only moved in yesterday and got this problem. Previous owner denied any issue ! I will try the booster route first as the fans are isolted and see how that goes.

Her budget is an issue and I dont want to be there (although she makes a nice cuppa ) and cost her lots of money.

Still Im not sure about that dimmer, may swap that at same time.
Cheers
Steve

 

[malcolmsanford]

Cheers wiredspark, Yeah I know its overloaded due to excess current. Replaced the MCB as may have been oversensitive before delving deeper. Saveloy mentioned the Booster so I think a good place to start from isolating. Unfortunately for me the whole loft has been boarded brilliantly by the builders so restricted access to trannies etc.

Is that restricted in the sense you can't test them as they are covered over with board? or just restricted as things in the way?

 

[telectrix]

suspect a nail or screw in loft boarding penetrated cable. i had similar last week on a ring final tripping MCB but not RCD. IR reading was 0.7 M ohm, so although low, not enough tom trip. fault was damaged insulation inside metal back box, intermittently tripping MCB . try shorting out L/N and bung 1000v to E.

 

[BertUK]

how many 50 watters do u have and do they exceed the rating of the dimmer?

 

[malcolmsanford]

how many 50 watters do u have and do they exceed the rating of the dimmer?

Should we also be going down the road to make sure that the TX are dimmable in the first place, but as the OP can't get access to them it might be a little difficult to confirm

 

[telectrix]

Bring back gas lighting, i say

 

[quackers]

Well still in the dark !
HAve done everything now. Disconnected dimmers, insulation resistance , both line conductors shorted and checked against earth, Booster removed from Circuit , and still trips.
Have just today found out from client that this has been happening since built 4 years ago !!

Options now are as I see 2. First as its a lot easier and less distructive to remove all 12 downlights along with transformers and replace with 230V downlights. ( I think this will work)
Option 2 and the one I dont really fancy doing is to destroy by removing all boarding in loft space and work from top down.

With everything disconnected the only thing still live will be the lighting 6A circuit looped into the trannies - These I think are the culprits !!

Cheers guys for all your help and advice any more greatly received
Ta Steve

 

[raithrovers1]

Does the breaker trip with all of the lights off?
If so, then it is nothing to do with the lights and there must be a hard fault somewhere or a load you don't know about.
A current clamp would be of great help.
If it only trips with the lights on then you should be able to switch each room light to see which one causes the trip. If you had a current clamp you could monitor the current at the MCB.