Bus bars and MCBs
- Thread starter WillMu
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We used a local electrician who previously certified and PAT tested our other house when we rented it out.
We did ask the council but their process seemed like overkill (plans on paper plus two visits) and was four times more expensive (apparently the rules have changed, and they are now allowed to charge thru the nose for this).
The electrician inspected the layout when it was "wired" but exposed in trunking, wiring to socket backs, routing thru joists, the resistance of the conductors from end to end and end to socket, and also took readings for break times for various load and phase combinations for the MCB and the RCD. And he did the final connections and then sent me a certificate.
He also said that 4mm was massive overkill and that I'd misinterpreted the additional restriction given how short the run thru insulation and the depth of insulation (But I did know I was erring on the side of caution)
We did ask the council but their process seemed like overkill (plans on paper plus two visits) and was four times more expensive (apparently the rules have changed, and they are now allowed to charge thru the nose for this).
The electrician inspected the layout when it was "wired" but exposed in trunking, wiring to socket backs, routing thru joists, the resistance of the conductors from end to end and end to socket, and also took readings for break times for various load and phase combinations for the MCB and the RCD. And he did the final connections and then sent me a certificate.
He also said that 4mm was massive overkill and that I'd misinterpreted the additional restriction given how short the run thru insulation and the depth of insulation (But I did know I was erring on the side of caution)
What sort of certificate did he give you?
I don't have it in front of me, I asked him to provide me with certification that the work complied with Part P (implication - and was tested as safe).
What exactly are you trying to get at?
Are you implying that because he didn't pull the cables thru the holes in the joists himself that they couldn't possibly be done within the bands of an acceptable installation?
What exactly are you trying to get at?
Are you implying that because he didn't pull the cables thru the holes in the joists himself that they couldn't possibly be done within the bands of an acceptable installation?
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Then anyone competent will not be willing to sign to say it meets regulations and is safe.
I'm pretty sure you don't!
There are two ways to comply with Part P, and this isn't one of them.
You should either:
Have all the work done by someone who can self-certify the work
or:
Go through that "overkill" process with the council.
>Then anyone competent will not be willing to sign to say it meets regulations and is safe.
Not all the hacks are electrical - I doubt that the electrician would case that where the the old sockets had been was filled in with concrete, or that the laminate flooring doesn't fit right, or that the where they have been lifted the floorboards have been replaced with ones 4mm thinner and then covered with newspaper and the edges smoothed with masking tape, or that the damp was fixed with damp proof paint rather than new guttering, or that the conservatory drains into a bucket which fills up and floods the patio (and god knows what else) whenever it rains.
And as to the unsafe hacks - these were removed before I did any work - I didn't fancy a live flowerbed or 32 amps running across the wall in underrated cable.
>I'm pretty sure you don't!
Please go on.
>There are two ways to comply with Part P, and this isn't one of them.
Where does the line get drawn between a lackey pulling wires for an electrician who is there and a lacky pulling wires and having an electrician connect them after testing them as safe?
Does the electrician taking a T break make your house not comply with part-p?? how about a phone call??
The council process seemed much more applicable for someone wire a whole house and consumer unit, not someone doing a relatively simple, easy to review and small amount of work
Not all the hacks are electrical - I doubt that the electrician would case that where the the old sockets had been was filled in with concrete, or that the laminate flooring doesn't fit right, or that the where they have been lifted the floorboards have been replaced with ones 4mm thinner and then covered with newspaper and the edges smoothed with masking tape, or that the damp was fixed with damp proof paint rather than new guttering, or that the conservatory drains into a bucket which fills up and floods the patio (and god knows what else) whenever it rains.
And as to the unsafe hacks - these were removed before I did any work - I didn't fancy a live flowerbed or 32 amps running across the wall in underrated cable.
>I'm pretty sure you don't!
Please go on.
>There are two ways to comply with Part P, and this isn't one of them.
Where does the line get drawn between a lackey pulling wires for an electrician who is there and a lacky pulling wires and having an electrician connect them after testing them as safe?
Does the electrician taking a T break make your house not comply with part-p?? how about a phone call??
The council process seemed much more applicable for someone wire a whole house and consumer unit, not someone doing a relatively simple, easy to review and small amount of work
The electrician has to sign to say three aspects of the install have been done correctly:
(1) Design
(2) Installation
(3) Inspection and Testing
He might get a labourer to help with (2), but will be checking numerous things as the work progresses. This forms part of the inspection element of (3)
In your case, you are doing the design. This can be checked retrospectively, but will cost if it was wrong. You are also doing most of the installation, without any ongoing inspection. Some inspection cannot be done at the end.
Sorry, but I don't think you are competent to do the design. If you where you would know what PSCC was, and what bearing it had on the safety of your proposed solution.
(1) Design
(2) Installation
(3) Inspection and Testing
He might get a labourer to help with (2), but will be checking numerous things as the work progresses. This forms part of the inspection element of (3)
In your case, you are doing the design. This can be checked retrospectively, but will cost if it was wrong. You are also doing most of the installation, without any ongoing inspection. Some inspection cannot be done at the end.
Sorry, but I don't think you are competent to do the design. If you where you would know what PSCC was, and what bearing it had on the safety of your proposed solution.
>Sorry, but I don't think you are competent to do the design.
Well, it's not a surprise, you know nothing about me.
You might just as easily assert that I can't weld to a standard that would pass an MOT. Of course that can be tested after the fact too.
>If you where you would know what PSCC was
Where I work we use acronyms which baffle and confuse people too, it doesn't mean that the people who don't know what the acronym stands for don't understand the implications, it's just deliberately obtuse.
>This can be checked retrospectively, but will cost if it was wrong.
Which is why I am here asking a question in advance to committing to a course of action and finding I am wrong when it will cost me to fix it.
>Some inspection cannot be done at the end.
Such as?
Well, it's not a surprise, you know nothing about me.
You might just as easily assert that I can't weld to a standard that would pass an MOT. Of course that can be tested after the fact too.
>If you where you would know what PSCC was
Where I work we use acronyms which baffle and confuse people too, it doesn't mean that the people who don't know what the acronym stands for don't understand the implications, it's just deliberately obtuse.
>This can be checked retrospectively, but will cost if it was wrong.
Which is why I am here asking a question in advance to committing to a course of action and finding I am wrong when it will cost me to fix it.
>Some inspection cannot be done at the end.
Such as?
The cable that was pulled across a sharp edge of a hole in a 400 year old joist ( hard as iron ) under a floor board and has had the insulation abraided down to expose bare copper.
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I'm fitting a new circuit for a kitchen as I found that all sockets in the whole house were on a ring of 32Amp on cable that measures just less than 2mm
What method are you using to get a CSA of 2mm?
I know what you where considering doing to a type tested consumer unit.
A fair point. If I tell you that it stands for "Prospective Short Circuit Current" would that help?
To name 3:
Cable routes.
Erection methods to minimise the spread of fire.
Accessibility of joints.
We know that you don't know what Ze is.
We know that you don't know what PSSC is.
We know that you buy inappropriate components due to ignorance of their characteristics.
We know that you have a number of hare-brained ideas about modifying the internals of consumer units.
What else do we need to know to judge your competence?
>The cable that was pulled across a sharp edge of a hole in a 400 year old joist
OK, but you can do damage to cable which has been installed for 20 years by doing something stupid with plumbing - surely the regs can't be expected to catch that!
And you can see everywhere the cable has been pulled thru and pretty much 100% of the cable run
>What method are you using to get a CSA of 2mm?
Vernier calipers on the copper conductor which is single core - not tinned.
I assumed that it must have been some imperial measurement but can't find anything that would match this description online (what I found said that imperial cable should be multi-stranded for this capacity)
I have yet to inspect everything - some part of the house have obviously been rewired and I'm removing a lot of copper that isn't connected either end. There is disconnected twin for lighting still in the walls in some places, alongside twin and earth that I assume went in at the same time as the CU.
OK, but you can do damage to cable which has been installed for 20 years by doing something stupid with plumbing - surely the regs can't be expected to catch that!
And you can see everywhere the cable has been pulled thru and pretty much 100% of the cable run
>What method are you using to get a CSA of 2mm?
Vernier calipers on the copper conductor which is single core - not tinned.
I assumed that it must have been some imperial measurement but can't find anything that would match this description online (what I found said that imperial cable should be multi-stranded for this capacity)
I have yet to inspect everything - some part of the house have obviously been rewired and I'm removing a lot of copper that isn't connected either end. There is disconnected twin for lighting still in the walls in some places, alongside twin and earth that I assume went in at the same time as the CU.
What diameter did you measure the conductor to be?
>I know what you where considering doing to a type tested consumer unit.
You know what I was asking /could be/ certified.
Given that the the clamps are clearly not designed to be only used with a busbar I don't think that is such a massive jump.
Also, given that the internals of the CU appear to be 90% designed to a standard (the clip rail, the size and position of the front, the incomer coming in thru the bottom etc. etc.), with the busbar being the only part which appears to be incompatible it isn't a massive surprise that I assumed that there was a recommended way to mix and match.
I can't be the first person to think this - I doubt that I am alone even in the company of certified installers.
There isn't a certified way to do this, and so I won't be doing it.
>A fair point. If I tell you that it stands for "Prospective Short Circuit Current" would that help?
Yes, it would explain an awful lot, and I would hazard a guess that inside the CU there is an option to pull -for a moment- what, 800+Amps thru the 100Amp fuse. Doesn't really change the design of the ring though, except for knowing the difference between a B C and D rated MCB (which I am getting fitted by someone qualified - so even if I didn't it wouldn't matter much. BTW the only inductive load on this circuit is the fridge).
The internals of the CU are deliberately designed to minimize the chances of a short between the Pre-MCB and earth or neutral and happening, with the neutral and earth bars above the outcoming side of the MCBs so even if you were foolish enough to let an incoming wire dangle before it hits an MCB, it should fall only on the plastic, and all wires are solid core, so to dangle at one end it would have to be free from the other as well.
>Cable routes.
very obvious as you can see all the cable (of course it will be covered, but not before testing)
>Erection methods to minimise the spread of fire.
very obvious as you can see all the cable
>Accessibility of joints.
very obvious as you can see all the cable, and even then, the only joints are in the sockets
You know what I was asking /could be/ certified.
Given that the the clamps are clearly not designed to be only used with a busbar I don't think that is such a massive jump.
Also, given that the internals of the CU appear to be 90% designed to a standard (the clip rail, the size and position of the front, the incomer coming in thru the bottom etc. etc.), with the busbar being the only part which appears to be incompatible it isn't a massive surprise that I assumed that there was a recommended way to mix and match.
I can't be the first person to think this - I doubt that I am alone even in the company of certified installers.
There isn't a certified way to do this, and so I won't be doing it.
>A fair point. If I tell you that it stands for "Prospective Short Circuit Current" would that help?
Yes, it would explain an awful lot, and I would hazard a guess that inside the CU there is an option to pull -for a moment- what, 800+Amps thru the 100Amp fuse. Doesn't really change the design of the ring though, except for knowing the difference between a B C and D rated MCB (which I am getting fitted by someone qualified - so even if I didn't it wouldn't matter much. BTW the only inductive load on this circuit is the fridge).
The internals of the CU are deliberately designed to minimize the chances of a short between the Pre-MCB and earth or neutral and happening, with the neutral and earth bars above the outcoming side of the MCBs so even if you were foolish enough to let an incoming wire dangle before it hits an MCB, it should fall only on the plastic, and all wires are solid core, so to dangle at one end it would have to be free from the other as well.
>Cable routes.
very obvious as you can see all the cable (of course it will be covered, but not before testing)
>Erection methods to minimise the spread of fire.
very obvious as you can see all the cable
>Accessibility of joints.
very obvious as you can see all the cable, and even then, the only joints are in the sockets
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