RCBO's on to old wiring....HELP!!!

[sliver]

I seem to be having alot of trouble after installing anew consumer unit with 5 RCBO's I have got really high milli second readings and dont understand why I am looking at 350 x 1 and no operation on x 5. IR is fine and so is R1 + R2. Any suggestions????

 

[Mike P]

Check the size of your main MET and check your Ze if the main MET is to small or poor connection this will give you those sort of problems.

 

[sliver]

thanks for the reply mike. i've a rod which is installed beneath the lounge floor and am getting a reading of 56ohms .i've the possiblity of pme which will bring it down to 0.35,but am concerned that there may be a borrowed neutral on one of the old circuits,will this be a factor to effect newly installed circuits??

 

[shedfull]

Borrowed neutral's usually take an RCD out as soon as you power up, have you tried swapping the Rcbo's around ( where the amps are the same ) to see if it's a duff rcbo?

Lee

 

[sliver]

thanks lee,i've got a problem that when the bathroom lighting is energised the rcbo trips out,so i think that is where the neutrel problem lies,but yes i,ve swaped ,and also installed other rcbo's to double check readings from the original onesand they come up with the same reading.thanks for the input the more views i can get on this the easier to solve for me

 

[Mike P]

It probably is borrowed neutral. Some people have a habit of nicking the neutral from a shower feed to feed a light over the shower. If you have the choice of type of supply go for pme.

 

[sliver]

Cheers Mike will be looking at it monday will let you know how i get on!!!

 

[old dog]

It probably is borrowed neutral. Some people have a habit of nicking the neutral from a shower feed to feed a light over the shower. If you have the choice of type of supply go for pme.

hi do you have up and down stairs lighting this seems to be the most likely
place to find borrowed neutral