Zs and PFC

[rigby]

Hi This is my first post, I recently got 2382-10 and have started to study for my 2392. I understand there will be new qualification instead of 2392. Is this correct?

and comming to the point I changed a single socket and then used Megger 1710 to test phase to earth and phase to neutral loop.

My first problem: when I tried to find which MCB controls this socket I found it was not connected to any of the MCBs, If I turn off the main switch then it will turn off. So that means it was connected to main switch, I guess this is not allowed?

The wiring inside was one set of red-black -earth copper 6 mm2 and other set what looked like tin/aluminium wires of red-black-earth? This made me worry! it means a ring circuit and that means more sockets are connected to mains switch directly?

Any way after removing the old socket I put in new socket and started to measure
Phase to earth loop Megger 1710 showed the following: UL50V PFC 218A 1,06 Ohms
Phase to neutral loop Megger 1710 showed the following: UL50V PFC 1,25kA 0,18 Ohms

On page 49 table 41.3 gives info on type B breakers but which table do I use if it was connected to main switch?

I was already worrying about it and after these readings I need professional advice.

I take it this is dangerous situation and should change the connection from mains to a 32 A mcb.
am I right?

Your advice and analysis greatly appreciated.

Thank you

 

[EastAnglian]

If the circuit is connected directly to the main switch and is not protected by a suitably rated fuse or circuit breaker then:

1) You should not have done any work on it

2) You should have issued a safety notice to the client

3) If it is exactly as you have described then (in my opinion) you should also have disconnected the circuit as it is a potential fire risk and advised the client you had done so.

All that aside, what sort of socket are we talking about here? You won't get 2 x 6mm cables into normal 3 pin socket outlets?

 

[tony mc]

I was already worrying about it and after these readings I need professional advice.

I take it that this is your own house and you have answered your own question.

Sorry if that sounds harsh but it needs further investigation if it is as you say.

 

[cjp1]

Welcome to the forum,
Just because a socket has 2 live 2 neutral & 2 cpcs connected into it does not mean its a ring circuit all it means is its not the end of a radial circuit.
What type of consumer unit is it some more info would help?

 

[WDMDL]

Could be a ring final connected across 2 MCBs, or 2 radials interconnected.
Try again turning ALL the MCBs off, then see which TWO (OR MORE) feed this socket.
Aluminium cables need to go...oxidation at terms > high resistance > heat > fire risk.

Simon.

 

[rigby]

Hello and thank you everyone,
WDMDL- you are right, on further investigation after reading your response I found it was connected to two MCBs.
Tony MC - yes it is my house, I have lived here for 11 years with no problems in terms of electricity.
EastAnglican- I evantually was able to get 2 x 6mm cables into normal 3 pin socket outlet, yes I am now planning to re-wire this circuit or disconnect this part of the circuit this weekend, as it was only a change of socket I never this will become a big job. I do a day job (not electrician!), it is difficult to come home at 5 pm and start this in the evening. I will switch off these two MCBs connected to this section for safety.

In fact after I read your responses this evening I had a good look at my consumer unit and this weekend I will inspect it in detail to see how to rectify my CU side.

Again thanks for all responses and guidance, will keep you informed.

Thanks

 

[Octopus]

"I evantually was able to get 2 x 6mm cables into normal 3 pin socket outlet"

Cripes- that must be tight!

If you rewire the circuit make sure you involve LABC.



"""""""

 

[i=p/u]

is the rules to date no alu conductors under 16 mm, why is this

 

[Deleted member 9648]

I would advise that you get someone with experience to check this out with you...perhaps there is a forum member near by?

 

[rigby]

Hello
i=p/u You mean why the wire intalled in this circuit is aluminium < 16 mm? I dont know this is the first time I came across an aluminium wire in a circuit, and it happened to be my own "ex council" house.
wirepuller I think I can handle it, this is part of my learning and respecting electricity. The circuit is disconnected at the mo for safety reason obviously. I opened up the main distribution board this after noon and measured Ze (=0,67 ohms and PFC 344A) and PSCC (1,15 kA). I think these are safe readings. The distribution board looked a mess. I might just put a new consumer unit with RCDs, connect only one circuit to each MCB, re-wire/or remove the aluminium wires. I am going to write to building control to let them know before I start this job. May be this can become one of my assessments when I join Part P scheme.
Thank you