mcb keeps blowing on lighting

[Wayne Hudson]

Hello sparks
I was at a Job earlier today,the customers upstairs lights would not turn on due to the 6A mcb operating so it's a short circuit so I disconnected the supply to the first light the supply disconnected from consumer unit ,then did a insulation resistance which came out clear tried the mcb without any connection it stayed on.so connected the supply at consumer unit and left the other end not connected to anything it stayed on so connected the loop out and switch live it all come back on for 2 poxy minutes then it would come back on .I had to leave disconnected and will be returning back tommorow . Any suggestions would be extremely grateful
Thanks

 

[micknew]

Hello sparks
I was at a Job earlier today,the customers upstairs lights would not turn on due to the 6A mcb operating so it's a short circuit so I disconnected the supply to the first light the supply disconnected from consumer unit ,then did a insulation resistance which came out clear tried the mcb without any connection it stayed on.so connected the supply at consumer unit and left the other end not connected to anything it stayed on so connected the loop out and switch live it all come back on for 2 poxy minutes then it would come back on .I had to leave disconnected and will be returning back tommorow . Any suggestions would be extremely grateful
Thanks

You shouldn't have left it on for 2 poxy minutes, you should know that as a professional electrician.
It gets worst, sorry if that offends, not lol.

 

[Darkwood]

Yorkshire doesn’t exist as far as I’m concerned.

Herhmmm!!!! Its the preverbial Gods country but been an Atheist all I have as input is; 'there is Yorkshire and then there is the rest of the world'...... How very dare you :boxing_smiley:

 

[Knobhead]

 

[Geordie Spark]

I see your new medication is still at the experimental stage Tony.

Never mind though - you may win a prize at Crufts next year.

Every cloud etc. .......

 

[Wayne Hudson]

Thanks for most of the replys it ended up being a squished cable in the loft from a walk board on to and the c/u was not up to date to the 17 th edition 7671 so replaced with rcbos.tested dead and live test all performed and passed and certified and logged on to building control .so there won't be any house fires reported from Faversham .I thought I was on a site where I could talk to people in confidence without having the **** taken .I was wrong with my fault finding procedure I shouldn't of tried the mcb with a fault in the circuit but before I left I made sure it was all completely 100% safe hasn't any of yous been on a job and had to leave it and come back the next day with a clearer head obviously not cos you are all pefect.so thanks for your input keep it up north a .

 

[davesparks]

If I have a fault like that I will normally work until I have at least found it and made any temporary repairs necessary to get the lights back on. But then I am not afraid to work past 'finishing time' and will happily work as late as the client wishes me to in order to get a job done.

Also why was the 'upgrade' to RCBOs required? Did the client request this be carried out after you had carefully talked them through this? I'm sure you didn't just sell it to them as bring a necessary upgrade because the regulations say you have to, because as we all know that's not true!

 

[Geordie Spark]

Thanks for most of the replys it ended up being a squished cable in the loft from a walk board on to and the c/u was not up to date to the 17 th edition 7671 so replaced with rcbos.tested dead and live test all performed and passed and certified and logged on to building control .so there won't be any house fires reported from Faversham .I thought I was on a site where I could talk to people in confidence without having the **** taken .I was wrong with my fault finding procedure I shouldn't of tried the mcb with a fault in the circuit but before I left I made sure it was all completely 100% safe hasn't any of yous been on a job and had to leave it and come back the next day with a clearer head obviously not cos you are all pefect.so thanks for your input keep it up north a .

Good lad - well done!!

We had every faith in your ability and knew you would get there in the end!!

Now just get a towel and dry behind your ears and then grow a thicker skin.

 

[Silly Sausage]

you are all perfect.so thanks for your input keep it up north a .

It's a burden we've learnt to shoulder over many years.
Any future problems, don't hesitate to ask!

 

[SparkyJoe]

Thanks for most of the replys it ended up being a squished cable in the loft from a walk board on to and the c/u was not up to date to the 17 th edition 7671 so replaced with rcbos.tested dead and live test all performed and passed and certified and logged on to building control .so there won't be any house fires reported from Faversham .I thought I was on a site where I could talk to people in confidence without having the **** taken .I was wrong with my fault finding procedure I shouldn't of tried the mcb with a fault in the circuit but before I left I made sure it was all completely 100% safe hasn't any of yous been on a job and had to leave it and come back the next day with a clearer head obviously not cos you are all pefect.so thanks for your input keep it up north a .

Went to fix a fault, and managed to persuade customer to upgrade a perfectly fine DB to the "17th edition". well done.

 

[Badged01]

Oooooh, this forum can get so catty to the newbies .........

 

[Wayne Hudson]

I explained to the customer about the difference between rcbos and 17th edition d/b and the customer agreed on the rcbos.on the old d/b all the lighting was not protected a shed supply and cooker supply also was not protected by 30mA rcd .Any cables buried less 50mm has to be protectected by a 30mA rcd or rcbo,tt earthing arrangement zs=8.69 ohms thanks to all

 

[telectrix]

nothing wrong with explaining the advantages of upgrading the CU and letting customer make an informed decision, as long as you don't do a BG , telling them the old CU is illegal and dangerous.

 

[Wayne Hudson]

nothing wrong with explaining the advantages of upgrading the CU and letting customer make an informed decision, as long as you don't do a BG , telling them the old CU is illegal and dangerous.

So a 16 th edition c/u is perfectly safe then on a tt earth arrangement ??? What about the earth fault loop impedance being to high to provide the correct disconnection on the circuits not protected by a 30mA rcd ??

 

[Engineer54]

So a 16 th edition c/u is perfectly safe then on a tt earth arrangement ??? What about the earth fault loop impedance being to high to provide the correct disconnection on the circuits not protected by a 30mA rcd ??

Well it met compliance with the Reg's for far more years than it hasn't!!

Also, are you aware that SP RCBO's are NOT recommended for TT system earthing? They need to be either SP + N RCBO's or DP RCBO's!!

 

[Bobster]

Well it met compliance with the Reg's for far more years than it hasn't!!

Also, are you aware that SP RCBO's are NOT recommended for TT system earthing? They need to be either SP + N RCBO's or DP RCBO's!!

Schneider RCBOs explicitly state, they should not be used on TT or IT systems.