First little job on own house - advice

[eptesicus]

Hi,

I am currently studying/training to start a career as an electrician and i have recently finished my C&G Level 2 and currently studying for my Level 3.

In the meantime i want to do a few minor works to my house to keep my practice my practical knowledge/keep things in my head.

My MFT and other bits arrived today, so the first little job is that i want to replace a junction box outside with an outdoor double socket. The set up is:

-New build only 2 years old so everything should be new/up to code (one can hope!)
-A fused connection unit takes a spur in the kitchen of from the downstairs ring final (this ring feeds all downstairs sockets and the central heating), feeds the power to a standalone garage (which has a double socket and a light (on a fused switch)).
-Where the cable comes out of the wall on the back of the house from the fused spur it goes into a junction box attached to the wall, to link to SWA which then runs down the wall and underground, then back up to the standalone garage.

Essentially, i just want to turn this connection on the wall of the house into a double socket.

I want to do it all properly and imagine i am doing it for a customer and issue myself a minor works certificate so i wanted to know how one would go about testing this sort of small job in the real world.

Would you do all applicable tests (continuity, IR, ZS and RCD)? If so, would you do them on the whole circuit or would you do them from the fused spur , with the fuse removed (assuming it would have to be double pole to do this without touching anything in the DB?).

So far my studies haven't really covered specifically what you would do on just a small modification on a spur such as this. I am guessing that to be absolutely sure, it may be better to do the tests involving the whole circuit (though with the IR test i will have to be mindful of anything that might get damaged at 500v so will have to remove thermostats/turn off the isolation switched to the boiler and kitchen applicances etc).

Any advice would be much appreciated as it would be good to know how in the real world an electrician would go about doing the tests on something like this, as i dont want to unnecessarily risk fiddling with more stuff than i really have to.

Many thanks

 

[telectrix]

testing wise. I'd only do IR testing Land E joined and then IR test to E. A Zs reading and polarity test, together with RCD test for the RFC would suffice.

 

[Dartlec]

For the purposes of the MWC, @telectrix has covered anything you might need to do. The only additional would be to check that the fuse in the Fused spur was appropriate (13A in the this case, presumably). You could then put that as the source OPCD for the circuit you are working on.

If you wanted to be particularly thorough, you may want to test the RFC is complete at the fused spur, though that's not essential in this case since you are working only on the cabling after the reduction in fusing.

For the purposes of your work in this case, you could do all testing from the Fused Spur onwards - though RCD and Zs would obviously be testing the existing cabling from the CU.

Not sure if the existing junction box is metal, but if you're replacing it with a plastic external socket you'll need to make sure that the armour of the SWA is correct earthed with banjo clip or suitable earth nut.

 

[UNG]

testing wise. I'd only do IR testing Land E joined and then IR test to E. A Zs reading and polarity test, together with RCD test for the RFC would suffice.

I assume you mean L & N joined and IR test to E

 

[telectrix]

I assume you mean L & N joined and IR test to E

my typo.

 

[eptesicus]

For the purposes of the MWC, @telectrix has covered anything you might need to do. The only additional would be to check that the fuse in the Fused spur was appropriate (13A in the this case, presumably). You could then put that as the source OPCD for the circuit you are working on.

If you wanted to be particularly thorough, you may want to test the RFC is complete at the fused spur, though that's not essential in this case since you are working only on the cabling after the reduction in fusing.

For the purposes of your work in this case, you could do all testing from the Fused Spur onwards - though RCD and Zs would obviously be testing the existing cabling from the CU.

Not sure if the existing junction box is metal, but if you're replacing it with a plastic external socket you'll need to make sure that the armour of the SWA is correct earthed with banjo clip or suitable earth nut.

Thanks. So it would be acceptable to IR and R1 + R2 continuity on the load side of the fused spur (with fuse out), then do a ZS and RCD with everything reconnected at the new socket? I have all the intial verification figures from the installation certificate etc to use as a reference as well. That would make sense to me, as i would not be changing any of the wiring before the junction box on the spur.

The existing Junction box is plastic and the socket will be plastic, so already as the suitable connection.

 

[eptesicus]

So, I started to do this today and have hit a stumbling block already. I had assumed that with the house being only 2 years old, that everything would be done properly and up to code. However, upon opening the junction box outside, I found that there is no connection from the swa armour/nut to the CPC. That surely is not correct? I thought that the armour must be linked by a bango/piranha nut etc to the rest of the cpc (at least that is what I was taught during my level 2 unless I have misunderstood something)

Here is a picture.

I am therefore assuming that to do this properly, I will need to get a piranha nut, some crimps and a bit of green and yellow cable so I can link the armour properly (I assumed that would all already be there for me to just link it all up in the earth terminal on the socket!)?

 

[telectrix]

yous correctin that the steel armour needs to be earthedusing a fly lead ( i would fit a bit of 6.0mm).also, looking at that connector block, there's enough exposed copper conductor to short a bus out.sure you can rectify that. personally I'd use wagos.

 

[Dustydazzler]

I come across a lot of swa nowadays with no bango or earthing nut on the armour

are the new breed no longer bothering earthing the armour

 

[eptesicus]

yous correctin that the steel armour needs to be earthedusing a fly lead ( i would fit a bit of 6.0mm).also, looking at that connector block, there's enough exposed copper conductor to short a bus out.sure you can rectify that. personally I'd use wagos.

Thanks

Any particular reason why the fly lead csa would have to be so large? The csa of the line conductors to the supply of the junction box is 2.5mm, and then the swa from that is 1.5mm.

I was going to use 2.5mm for the fly.

 

[eptesicus]

I come across a lot of swa nowadays with no bango or earthing nut on the armour

are the new breed no longer bothering earthing the armour

I'm surprised that something like that would have got passed initial verification on something only two years old. I thought that was a pretty big requirement for swa that goes out and underground (ie for the armour to have continuity back to the MET).

 

[Robson689]

I'm surprised that something like that would have got passed initial verification on something only two years old. I thought that was a pretty big requirement for swa that goes out and underground (ie for the armour to have continuity back to the MET).

Is it not earthed at the other end of cable?

 

[telectrix]

Thanks

Any particular reason why the fly lead csa would have to be so large? The csa of the line conductors to the supply of the junction box is 2.5mm, and then the swa from that is 1.5mm.

I was going to use 2.5mm for the fly.

you're right. it's just that i always have 6mm Gn/Y on the van but not always 2.5.

 

[eptesicus]

Is it not earthed at the other end of cable?

Not as far as I can see. This is the other end:

So there is nothing linking the armour OR the metal clad switch box to the cpc...

 

[loz2754]

SWA is only required to have the armour connected at one end (if the armour is not being used as a CPC), as already mentioned, so it may well comply.
However, I always connect the armour at both ends and at every joint, where applicable, just to be sure. I believe most sparks would do the same.

 

[Dustydazzler]

No fly lead to the box either , talk about rough as a badgers

 

[pc1966]

SWA is only required to have the armour connected at one end (if the armour is not being used as a CPC), as already mentioned, so it may well comply.
However, I always connect the armour at both ends and at every joint, where applicable, just to be sure. I believe most sparks would do the same.

If it is going to be earthed at one end I would always say it must be the supply end, lower Zs on the armour and less risk of something stupid being done at the load/accessory end.

Like the above example! If the armour is earthed, it is fortuitous by means of the back box and not by any acceptable connection.

To add: I would agree that it should be earthed at both ends if practical, exception usually is a feed to a TT'd building/caravan where the cable is TN and the end is a plastic gland as you are using only L & N and putting in a local rod for the RCD/onwards installation.

 

[pc1966]

I think what your 1st home exercise has shown is a Golden Rule you should apply on jobs - test and inspect first before you make any changes.

It might well be the installation broken/unsafe to begin with, and that is a whole extra set of donkey balls to suck when you go to test your own work and find something amiss.

 

[Dustydazzler]

I tend to only earth (bango) the supply end , just how I do it…

sometimes I banjo both ends but only when the wind is blowing east

 

[eptesicus]

Yeh, it is a bit poor isnt it. I thought my criticism may have been unjustified as i thought both ends had to be connected to the cpc. However, then i check the termination at the other end and A. it isnt connected there either and B. the metal back box isnt connected either.

I think what your 1st home exercise has shown is a Golden Rule you should apply on jobs - test and inspect first before you make any changes.

It might well be the installation broken/unsafe to begin with, and that is a whole extra set of donkey balls to suck when you go to test your own work and find something amiss.

You are absolutely right. I shouldn't have assumed that just because it was almost brand new/done a few years ago by a big firm that it was done correctly.

I am glad i took the time to inspect it/ask these questions first.