Can anyone offer any guidance as to what the going rate is for domestic electrians jobs? e.g. replace rewireable fuse ccu with new rcd/mcb ccu about £200 to £250? sound about right? Any guides available on the web? Many thanks.Mark
If you're lucky: sod's law is the existing cables won't reach to the positions you need in the new CU and you have to extend loads of them (crimps, please, not choc blocks!) and when you sanity-check the ring mains you find they're not rings and spend ages more tracking down where the break is and fixing it ... and so on.
Overall I'd say £200 - 300 (including materials) sounds about right.
you'd be lucky to find an NIC Inspector that would allow extending cabling with common choc blocks (reasoning - they can melt & short) porcelain maybe, j boxes or Henleys yes
You get JBs with what appears to be the same sort of material as chock blocks are made of.
I'm curious, that's all. If a chock block isn't suitable for extending wires in an easily accessible thing like a CU, then just what are they suitable for?
It's only simple if properly done using the correct size and tool.
There's a big variation in chock blocks, some manufacturers even make them in different qualities, sort of "good, better, and best". Although where safety is concerned...
In the best the plastic is nylon not polythene, and the screws don't bear directly onto the wire, there's an insert which spreads the load.
Some of the ones I bought in Halfords weren't suitable for anything. The screw heads sheared off trying to unscrew them for the first time.
"Dave Plowman" wrote | I'm curious, that's all. If a chock block isn't suitable for | extending wires in an easily accessible thing like a CU, | then just what are they suitable for?
extending twisted-twin table-lamp flexes under the bed, from what I've seen ...
I'm trying to understand what's different between them and either a socket connection or a ceiling rose etc. If used to join flex, then yes, because it won't be mechanically as strong and has exposed live bits. But none of this applies inside a CU. After all the connections to the CU themselves aren't crimped - they're a similar screw connection. I know they usually have two screws, but then you can overlap the cables in a chock block for the same effect.
Thinking about this I imagine, but don't know for certain, that there are several possible issues with choc-blocks - I'd welcome other explanations though! Guesswork follows.....
The first issue might be with the screw threads being stripped, or the screw working loose after having been tightened down. Perhaps the copper being tightened onto deforms over time to make a less secure joint? Don't forget that there are usually two screw joints per connection.
The second issue might be resistivity of the joint. I imagine that in a choc-block connection at best (and on average) only 50% of the incoming cable might make contact with the receptacle. That does nothing for current capacity, and could produce extra heat of the parts of the conductor which are actually transferring power.
A third issue might be cable protection and safety. We've all seen how some people allow the stripped part of the cable to extend beyond the protective area of the choc-block.
Any others?
PoP
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I've just had the lid off a recently installed (4 months ago) MK split load CU that upgraded a wylex unit in our local parish church- wired in that fire proof grey stuff. Alot of the circuit tails werent long enough and choc blocks adorn the inside like you wouldnt believe!
And this was done by a large electrical contractor who got the whole south west midlands "check / upgrade as necessary" contract from the Church!!!
Yes. I can understand not allowing bare chock blocks to extend TW&E etc even under the floor boards, but I've used them extensively inside steel adaptable boxes where I require more connections than a standard JB can supply. So I really don't see any difference between here and inside a CU.
To joint cables that are to be buried in plaster I can see is a different situation.
I've seen it often where Pyro has been used - because the length of sleeving supplied with some types of termination is a fixed length.
"Andrew Gabriel" wrote | >> you'd be lucky to find an NIC Inspector that would | >> allow extending cabling with common choc blocks | >> (reasoning - they can melt & short) | >> porcelain maybe, j boxes or Henleys yes | Well, that's plain bullshit. | In the other cases, the cable insulation would still melt and short. | > I've just had the lid off a recently installed (4 months ago) MK | > split load CU that upgraded a wylex unit in our local parish | > church- wired in that fire proof grey stuff. Alot of the circuit | > tails werent long enough and choc blocks adorn the inside like | > you wouldnt believe! | There's no problem with this.
Although AIUI joints must not be supported by the conductors, so the choc block should be fixed to the CU?
"Andrew Gabriel" wrote | > Although AIUI joints must not be supported by the conductors, | > so the choc block should be fixed to the CU? | I wouldn't say so. | Have you *ever* seen a choc block fixed in a BESA box?
Shouldn't need one in a BESA box if one is doing 'proper' conduit wiring.
I have seen terminal strip bolted down in an Adaptable Box though.
I think it makes for a neater job.
Mind you, I did leave the choc block floating in the wall light I put in last weekend :-)
A BESA box may have hook plates fitted for carrying a light fitting, and those have no terminals. I'm pretty certain the ceramic types of ceiling rose haven't got any either, although it's ages since I did any conduit work.
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