Fault Find # 4

[Baker1988]

Will agree with Baker on that. Can't see no wires.

but looking at other RCD's on google, this one in the pic seems to be missing something on the front to tell you whether it's on/off. Like a little indicator.

If u look at the bottom of the blue switch on the rcd it has a little off mark on it which would say it is off

 

[Baker1988]

As I was saying a rcd is basically made of 3 seperate coils wrapped around a circle iron core there is a live coil which the live goes through and a neutral coil where the neutral goes through then there is a third trip coild that detects when there is a difference in voltage going through the live and returning through the neutral if there is a difference then this will create a magnetic flux round the core and that will induce a current into the trip coil which will trip the rcd, well thats what I can remember off the top of my head haha

 

[Paul.M]

Yep as you have said the rcd is not connected!!!!

The customer told me that 4 years ago an "electrician" they called out to find a fault that tripped the stand alone up front rcd. It was an old cooker with an high earth leakage that did it. Because he could not isolate that circuit away from the rcd (it is/was on the down stairs rfc, plug in oven) he just pulled the rcd cables out and left the whole house without any form of rcd protection!!!!! THIS IS A MASSIVE NO NO. Regs state that you can not leave an installation worse off then when you found it, and this chap just fooked all that up.

If that was me at the time I would give the customer the options of:-

1. Buy a new oven or get this one repaired so not to trip the rcd and in the mean time disconnect the oven (unplug it lol).

2. Upgrade the board to an integral board (dual rcd with a none rcd busbar for L + N) so the oven will not trip any rcd's as it will not be on one.

Now saying that about option 2 we are dancing around the regs a little bit. At the time of the circuit being installed it was on the 15th ed regs so rcd was not needed BUT since then they have had a new 16th ed board put in and rcd is needed. What do we do??? If the cable run is greater than 50mm from the surface of the walls, ceilings and floors OR has mechanical protection in the form of PVC or steel conduit OR SWA cable we can put that circuit on a none rcd side of a cu. The chances of this happening is none existent in my opinion so option 2 becomes redundant.


Now that we have seen all our possibilities we are only left with option 1. Get a new oven and in the mean time pull the plug out and issue a warning notice in writing to cover your arse. After all you are the Inspector and Tester of this install now and it will be you in court if any of the circuits that you have worked on causes injury, death or property damage.

 

[Baker1988]

Yep as you have said the rcd is not connected!!!!

The customer told me that 4 years ago an "electrician" they called out to find a fault that tripped the stand alone up front rcd. It was an old cooker with an high earth leakage that did it. Because he could not isolate that circuit away from the rcd (it is/was on the down stairs rfc, plug in oven) he just pulled the rcd cables out and left the whole house without any form of rcd protection!!!!! THIS IS A MASSIVE NO NO. Regs state that you can not leave an installation worse off then when you found it, and this chap just fooked all that up.

If that was me at the time I would give the customer the options of:-

1. Buy a new oven or get this one repaired so not to trip the rcd and in the mean time disconnect the oven (unplug it lol).

2. Upgrade the board to an integral board (dual rcd with a none rcd busbar for L + N) so the oven will not trip any rcd's as it will not be on one.

Now saying that about option 2 we are dancing around the regs a little bit. At the time of the circuit being installed it was on the 15th ed regs so rcd was not needed BUT since then they have had a new 16th ed board put in and rcd is needed. What do we do??? If the cable run is greater than 50mm from the surface of the walls, ceilings and floors OR has mechanical protection in the form of PVC or steel conduit OR SWA cable we can put that circuit on a none rcd side of a cu. The chances of this happening is none existent in my opinion so option 2 becomes redundant.


Now that we have seen all our possibilities we are only left with option 1. Get a new oven and in the mean time pull the plug out and issue a warning notice in writing to cover your arse. After all you are the Inspector and Tester of this install now and it will be you in court if any of the circuits that you have worked on causes injury, death or property damage.

what is/creates earth leakage? why doesnt it happen on this oven and not others?
i new the cable had too be 50mm from the surface ofthe wall to not need rcd but i didnt know it also had to be 50mm from the celing and i didnt know that pvc trunking was classed as mechanical protection i always thought that it had to be metal/steel/galv

 

[Paul.M]

what is/creates earth leakage? why doesnt it happen on this oven and not others?

Without going into too much detail its the element that deteriorates and dumps the extra current down the earth return path.

i knew the cable had too be 50mm from the surface of the wall to not need rcd but i didnt know it also had to be 50mm from the celing

The regs state "50mm from a finished surface" so any wall, ceiling and floor counts. Thats why under part P you have to drill and route cables in the middle of the joist under the floor and it will be below a ceiling. 50mm is deemed to be an adequate depth for anyone drilling a hole or hitting a nail into the "fabric of the buiding".

and i didnt know that pvc trunking was classed as mechanical protection.....

Sorry my mistake, its not unless its surface mounted in which case surface mounted super-seeds the 50mm regs. Whoops


i always thought that it had to be metal/0mm 5steel/galv

Yes mechanical protection when buried in walls etc needs to be SWA or steel conduit/galv. Sorry if I misguided you.

My reply is in blue.

 

[Baker1988]

oooo so thats the reason we alway get told to drill in the center of the joist thanks for that thats made it much clearer thanks

 

[Paul.M]

Have a read of the Part P regs on drilling joinst's. Although it skips by the reasons why, thats the reason why we have to do it to be >50mm

 

[Baker1988]

i havnt read the part p side of stuff but i have read in my college books about where to drill joists but doesnt say why we have to drill them there

 

[Paul.M]

i havnt read the part p side of stuff but i have read in my college books about where to drill joists but doesnt say why we have to drill them there

The regs state "50mm from a finished surface". What is a finished surface? Walls, ceilings and floors!

Is'nt it great how we are told how to do things through the regs without an explanation of why???

 

[Baker1988]

The regs state "50mm from a finished surface". What is a finished surface? Walls, ceilings and floors!

Is'nt it great how we are told how to do things through the regs without an explanation of why???

well i will have remember that i always thought it was just 50mm for the surface of the walls, yeah its great:banghead: