One for the sparks - 'Those that can, do...
Discussion
...and those that can't, teach.'
I was doing a survey of a secondary school yesterday (M&E condition survey - not hanging about the railings in an old Volvo with an SLR and telephoto lens before you get the wrong idea
). Like many schools they now offer NVQs and this one had a construction college attached. The following has been rigged up by a City & Guilds Electrical Installation lecturer.
I spot at least five howlers and a couple of things that aren't exactly to C&G standard!
I was doing a survey of a secondary school yesterday (M&E condition survey - not hanging about the railings in an old Volvo with an SLR and telephoto lens before you get the wrong idea
). Like many schools they now offer NVQs and this one had a construction college attached. The following has been rigged up by a City & Guilds Electrical Installation lecturer.I spot at least five howlers and a couple of things that aren't exactly to C&G standard!
I know little about electrics and nothing about C & G standards. I'll take a stab:
Too much insulation stripped off.
Wires not secured
Earth wire not full covered with insualtion
The connectors have two groups of three surely all the blue wires should be together and all the brown wires.
Am I close?
Too much insulation stripped off.
Wires not secured
Earth wire not full covered with insualtion
The connectors have two groups of three surely all the blue wires should be together and all the brown wires.
Am I close?
ts at college pulling it all apart Hmm I'm going to say:
Live and neutral wires to the lamp should be reversed
Live and neutral wires for the horizontal twin and earth reversed
No brown sleeve for the switched live
Built-in cable hooks for the lamp wires not being used
Exposed wires where they enter the terminals
I'd also have the two earth wires entering the terminal from opposite directions, but not sure if that's just a habit I've picked up or if it's recommended.
Live and neutral wires to the lamp should be reversed
Live and neutral wires for the horizontal twin and earth reversed
No brown sleeve for the switched live
Built-in cable hooks for the lamp wires not being used
Exposed wires where they enter the terminals
I'd also have the two earth wires entering the terminal from opposite directions, but not sure if that's just a habit I've picked up or if it's recommended.
Nothing would shock (as in surprise rather than bzzzz!) me much if I saw it on an actual installation, but the fact a C&G lecturer has done this is quite worrying to me. I picked up the following:
- There is insufficient spare for re-termination - if that neutral snaps in the terminal there is insufficient length to reconnect it. The proper way is to fold the cable away from the terminals and then back, creating a little loop.
- Too much copper exposed on the circuit protective conductors.
- Too much copper exposed on the neutral conductor.
- The phase and neutral connections are the wrong way round. The neutrals should be in the top three terminals as it gives more room for any cable feeding another ceiling rose.
- Cable ends are not doubled over - single cables in individual terminals should be folded back to make the connection more mechanically sound.
- The permanent live to the switch is not sleeved brown to identify it as a phase conductor.
- The cord grips for the flex have not been used.
- The outer sheathing of the twin and earth cables should extend approximately 10mm into the ceiling rose to ensure adequate mechanical protection.
- The twin and earth appears to have been stripped by pulling the CPC. C&G say this is wrong as it can stretch the cable and reduce the cross sectional area. When I was at college, we put this to the test with a micrometer and demonstrated there was no recordable reduction in CSA. I do it this way myself but C&G teach you to cut into the cable end with a penknife and push it down the length of the cable with slight twisting pressure so the blade pushes into the bare CPC cable.
- The flex looks like it has been cut lengthways with a Stanley knife. The C&G way is to score the circumference of the cable and manipulate it until you can snap through the last bit of sheathing. I use this method myself as it is neat but I wouldn't criticise any method that doesn't damage the insulation.
Wow, a bit of a mess really! Whilst the current config would work in isolation it’s wrong on just about every level.
Where to start:
Ok
1. Flex to lamp holder - outer insulation stripped incorrectly - needs to expose enough inner cable to allow cable to be wrapped around retainers on backplate.
2. L and N in lamp holder flex incorrect. N should be in top N bank. L in bottom Line bank.
3. Top (unclipped) T&E is loop in. Cable should be clipped although may be just out of shot. Also, L is ok but N should be in top N bank (although would work as-is).
4. Bottom (clipped) T&E is switch. No sleeving on s/live. Should be 1 core to loop bank and other core to line bank (sleeved appropriately). As noted, line bank has been reversed with top N bank.
5. Earth sleeving cut a little short leaving exposed wire.
6. Probably lots more too!
I assume that was someone’s homework that was left as a ‘how not to’ example.
jeff
Edit: Gaah.. I see the boss has already beaten me too it. Damn my typing is slooow!
Where to start:
Ok
1. Flex to lamp holder - outer insulation stripped incorrectly - needs to expose enough inner cable to allow cable to be wrapped around retainers on backplate.
2. L and N in lamp holder flex incorrect. N should be in top N bank. L in bottom Line bank.
3. Top (unclipped) T&E is loop in. Cable should be clipped although may be just out of shot. Also, L is ok but N should be in top N bank (although would work as-is).
4. Bottom (clipped) T&E is switch. No sleeving on s/live. Should be 1 core to loop bank and other core to line bank (sleeved appropriately). As noted, line bank has been reversed with top N bank.
5. Earth sleeving cut a little short leaving exposed wire.
6. Probably lots more too!
I assume that was someone’s homework that was left as a ‘how not to’ example.
jeff
Edit: Gaah.. I see the boss has already beaten me too it. Damn my typing is slooow!
Edited by no eye deer on Wednesday 28th September 12:31
no eye deer said:
I assume that was someone’s homework that was left as a ‘how not to’ example.
I was hoping that myself. 
The caretaker (or maintenance manager as they call them now) noticed me looking at it. He told me he believed there are about four things wrong with it and several sparks who have been there with their kids on open nights have pulled him up on it. Apparently he refuses to see any fault in it and gets quite annoyed if anybody suggests there are any. Ganglandboss said:
*The flex looks like it has been cut lengthways with a Stanley knife. The C&G way is to score the circumference of the cable and manipulate it until you can snap through the last bit of sheathing.
Would that not weaken/potentially damage the wires? (and possibly also cut through into the wire insulation if you accidentally cut too deep?)
MH said:
944fan said:
The connectors have two groups of three surely all the blue wires should be together and all the brown wires.
For your own safety stay away from electrics.Mike
Can you explain (in laymans terms) what the middle brown and middle blue cable are doing in that circuit? (I assume that they are joined if that is a common terminal they are connected to?)
ETA, whilst we've got so many experts demonstrating their knowledge, what are the two 'supply' (grey) cables for? Is that a multi-switch setup?
monthefish said:
Ganglandboss said:
*The flex looks like it has been cut lengthways with a Stanley knife. The C&G way is to score the circumference of the cable and manipulate it until you can snap through the last bit of sheathing.
Would that not weaken/potentially damage the wires? (and possibly also cut through into the wire insulation if you accidentally cut too deep?)Bill said:
Talking of sparks wot do....
SWMBO has bought a new light fitting for the bathroom that has an earth connection, is this standard for all bathroom fittings now or just because it's mostly made of metal? The current wiring doesn't have an earth.
It has to have an earth connection so the protective device (fuse or breaker) operates if a live conductor touches against the metal case. Once upon a time light fittings didn't have to have an earth so your wiring is either old or just rough. I would recommend you get a spark in - get him to put the fitting up and ask him his opinion on the general condition. He may need do a full periodic inspection and test (which will cost you) or it may be blindingly obvious a rewire is needed (which will cost you even more and make a mess). SWMBO has bought a new light fitting for the bathroom that has an earth connection, is this standard for all bathroom fittings now or just because it's mostly made of metal? The current wiring doesn't have an earth.
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