Electronics > Projects, Designs, and Technical Stuff

Emergency stop switch for study/lab (UK wiring question)

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Docara:
Hi Slin,

I'm a UK sparks.
Obvious disclaimer - Make sure you get your own independent advice only use what I say as a discussion with you own electrician.

I've written, rewritten amended this so many times I hope it stall makes some sense - sorry if it doesn't.

First off, any additional circuit or change to an existing circuit and you'll get clobbered by Part 'P'. Basically, in a domestic installation, you are only allowed to change 'like for like' anything else required a minimum of a 'Minor Works Certificate'. Sorry Bud testing is required no matter what you do. I'm a tester I've signed off major installations but I can't install a socket in my own house. I don't do enough private (domestic) work to justify the Part 'P' registration. I do infrequent full house major jobs and just pay £100 to the local council to rubber stamp my certification. Anyway I digress!!!

Get a friendly electrician in and have chat on your pre-plastered installation. I'm thinking about cable zoning and verification of your houses earth bonding. Then see if they will be happy for you to do the work under their direction - beers might be needed leading up to certification.

First off, ring final circuits terminate at a breaker in the fuseboard - nowhere else apart from rare occasions using contactors, so this answers your question about the cooker switch ;)

My assumptions are you want to isolate your lab at one location on leaving, that you have a dedicated ring circuit to your lab and that it is a new/convert build so you don't want it to look like a dogs dinner.

When you start doing what you want to do, ring circuits start to become a right royal PITA so avoid them unless used conventionally.

Right, the easiest way to achieve what you want is to convert your lab ring sockets into 2x radials. So the ring enters your lab at a convenient location then radial 'loads' splits off. SO ring in, 2x radials out. Where the ring and two radials meet install 2x Switched Fused Connection Units (switched spurs) with 13A fuses installed. Keep adding FCU and Radials to your hearts desire - remember on a ring there is no limit to points fed. There would be nothing wrong if you wanted 1 FCU per socket. I would change the 32A main MCB to a 20A (though consider length of run and Earth Fault Loop (Zs) implications). The important part is the 13A fuse in the FCU. You are limiting each 2.5mm2 leg to 13A from a 20-32A  supply. I don't like 32A on anything other than a kitchen ring to be honest. If the ring breaks then 32A protecting a 2.5mm leg is too much - 20A protecting a 2.5mm leg is fine. I think 24A capacity for 2.5mm2 T&E.

If you REALLY want to keep your lab ring and have remote off I would suggest you go down the small consumer unit route (think garage supply £40 - cheapest DIN rail box with lid) local to you lab, and get a suitably rated contactor (ideally DP). Bear in mind to verify the number of ways needed in the consumer unit/garage supply before purchase - from memory they are 6 ways - 2 main switch, 2 RCD 1x32A MCB 1x6A MCB. The coil circuit could then be controlled by an external switch using a 1 or 3A MCB in series with the contactor coil or connected to an emergency switch (also in local consumer unit/garage supply). As you can appreciate when do you stop adding control circuits and MCB's? Things can get messy/fiddly very quickly.

Another option could be installing a contactor in your existing consumer unit if there's room and run a remote switch to you lab or RF switcher etc etc

But on balance I think I would do the first option have two or more conveniently positioned Switched FCU feeding 13A radials from the existing 20-32A ring supply. Remember discrimination of circuits, you are not expecting all sockets to be pulling 13A each.
Strictly speaking these radials are not part of the fixed installation but an 'accessory', though it's hard not make that argument when buried in walls with T&E supplying flush sockets in a wall - down to the guy certifying. Remember to protect your cables with capping before plastering. Obviously RCD protection on sockets.

Lastly, apart from it possibly looking like shit if you could work out a nice way to have the two radials on a 2.5mm flex on plugs, plugged into switched sockets you are guaranteed not to need certification after the sockets. The 'Point of Isolation' is removable (plug).
If your installation would lend itself to perhaps having a couple of surface back boxes mounted about 150-200mm apart, with the lower box having a blanking plate and 2x stuffing glands in the top, flexes coming out with plugs and plugged straight into the sockets. If all white it should look OK. You could always terminate the flex into the back of 2x FCU's instead of plugs and sockets so again it is obvious what is going on.
All your electrician would need to do is cert for a double socket/FCU on a ring (cheap) and leave you alone to you installing the sockets in your lab where and when you want them.

I don't think I've cocked up with the above let me know if there are any glaring errors

Monkeh:

--- Quote from: Docara on December 02, 2019, 08:42:52 pm ---First off, any additional circuit or change to an existing circuit and you'll get clobbered by Part 'P'. Basically, in a domestic installation, you are only allowed to change 'like for like' anything else required a minimum of a 'Minor Works Certificate'. Sorry Bud testing is required no matter what you do. I'm a tester I've signed off major installations but I can't install a socket in my own house. I don't do enough private (domestic) work to justify the Part 'P' registration. I do infrequent full house major jobs and just pay £100 to the local council to rubber stamp my certification. Anyway I digress!!!
--- End quote ---

I'm not entirely sure you're correct - the regulations, I believe, still contain regulation 12(6A), which requires notification only for new circuits, replacement of the consumer unit, or addition or alteration to circuits in a special location. Outside that, no notification is required.

Yes, a minor works certificate is required, but this is not notification and has nothing to do with Part P, but BS7671:

--- Quote ---644.4.201 Where electrical installation work does not include the provision of a new circuit or replacement of
a distribution board or consumer unit, a Minor Electrical Installation Works Certificate, based on the model given
in Appendix 6, may be provided for each circuit that has been added to or altered as an alternative to an Electrical
Installation Certificate.
--- End quote ---

Now, I'm not a sparky by trade and I don't know the various regulations backwards, and it's entirely possible I've missed something (keeping track of amendments to legislation is nigh impossible as the government is incapable of presenting them correctly), but assuming you perform the appropriate testing and do the paperwork, it seems perfectly permissable for work to be performed without invoking any expensive processes. Of course, there is 644.5 requiring a 'competent person', ie. one who's forked out a great deal of money for some paper, and probably been taught a lot of bad habits and nonsense in the process. Not at all attempting to put down properly competent electricians, but there's a lot of 'competent' cowboys and a lot of not 'competent' DIYers who know what they're doing.

Obviously, filling out that certificate correctly requires a range of tests most people, even here, simply do not have the equipment to carry out - but in practical terms nothing is going to be made worse by the provision of a few additional sockets, if the workmanship is adequate.

All the annoying legal bollocks aside, assuming there's no intention to supply more than 3kW, I see no problem with a single FCU supplying as many sockets as desired.


--- Quote ---If your installation would lend itself to perhaps having a couple of surface back boxes mounted about 150-200mm apart, with the lower box having a blanking plate and 2x stuffing glands in the top, flexes coming out with plugs and plugged straight into the sockets. If all white it should look OK. You could always terminate the flex into the back of 2x FCU's instead of plugs and sockets so again it is obvious what is going on.
All your electrician would need to do is cert for a double socket/FCU on a ring (cheap) and leave you alone to you installing the sockets in your lab where and when you want them.
--- End quote ---

This is a fixed installation, no matter how unpluggable it may be, and all the requirements of BS7671 and the building regs apply.

artag:
Doesn't it only require certification when you sell the house ?
You could collect the changes (and 'repairs' .. I think you're allowed those) and do them all at once.
 

Monkeh:

--- Quote from: artag on December 02, 2019, 10:16:36 pm ---Doesn't it only require certification when you sell the house ?
--- End quote ---

Certification is from the wiring regulations (not law) and is required for any substantial work.


--- Quote ---644.1 Except where Regulation 644.4.201 applies, upon completion of the verification of a new
installation or an addition or alteration to an existing installation, including the replacement of a distribution board
or consumer unit, an Electrical Installation Certificate based on the model given in Appendix 6 shall be issued to
the person ordering the work.
--- End quote ---

This is not the same as notification, which is to do with the building regulations (law).

Docara:
Ha! Ha! Aren't our regs great !!!!!!

So many good points, right not in any particular order

Slightly picky answer and a play on the English language - You do not 'require' a certification 'when' you sell your house, you should already be living in a certified and tested house and have either an Electrical Installation Certificate (EIC) or Periodic Inspection Report (PIR) in place to cover the installation. If this is under 10 years old you're covered, however it 'looks' better if your house has just passed a Periodic because it gives the buyer the impression the electrics are safe. A domestic dwelling should be tested every 10 years (max), 5 years if commercial or even less if the installation is in a harsh environment or liable to change or abuse (farm yards is the classic example - those farmer boys love nails for fuses :-DD and have never seen a rodent eating a cable.
You are correct for rental properties a new full Periodic test isneeded when vacated and before new people move in.

Competent Person - horrific term - in the electrical sense this does not mean someone 'who is competent'. It means someone who can prove their competency (with qualifications eg City and Guild 2391). How could you stand up in court and show that you knew what you were doing, you would have no defence.
As an aside - when I did my 2391, I was told that I would be considered guilty in a court of law unless I could prove myself innocent by issuing a test certificate for any work I did or I was the last electrician to touch an installation and someone was hurt - even if it had nothing to do with me. e.g I change a downstairs socket for a drink for my mate down the pub and his daughter was electrocuted using the upstairs shower some months later, I could be on a manslaughter charge with no defence because I couldn't prove what I did or didn't do.

Wiring Regulations and the Law, I don't fully understand this, but basically it goes something like this. The wiring regs are not law but they are incorporated into the building regulations and I think the Health and Safety legislation which ARE law therefore they are a legal requirement. - Something like that.


--- Quote ---I'm not entirely sure you're correct - the regulations, I believe, still contain regulation 12(6A), which requires notification only for new circuits, replacement of the consumer unit, or addition or alteration to circuits in a special location. Outside that, no notification is required.
 
--- End quote ---

Yes you are correct with this one however it is a difficult one in this context and is ultimately down to the person doing the test. Effectively it is a new circuit - but it's not. In context to the OP I do not know the background of the installation he was talking about. For his house insurance, selling his house in the future and local authority purposes notification from a Part 'P' registered spark would only pay what £1.50 online to ensure his customer (and himself) was covered from all angles. The circuit sounded like it was massively f**ked around with adding many more points on it than it originally had and the functionality had changed. Earth leakage implications, tripping characteristic would need to be addressed which would be fundamentally different to what was there before. The only original part of it was two legs back to the CU. To be fair you are probably correct with a minor works but I am not standing in a guys house with a coffee having a chat but on a pubic forum not knowing who might read this in the future  and takes things literally.
I would still prefer to tick all boxes in this application. Label up the CU with Lab Supply and notify. If the guys house burned down from an unrelated fault the new lab's electrics 'would' be blamed - no cert - no insurance pay out.
I'm not 18th Edition, but I believe there is now a provision for a spark to 'sign off' other peoples installation which was what I was getting at in the post. To me it's a no brainer.


--- Quote ---All the annoying legal bollocks aside, assuming there's no intention to supply more than 3kW, I see no problem with a single FCU supplying as many sockets as desired.
--- End quote ---


I agree, but again were not chatting personally in his house, its some things to for him to consider and discount as necessary with his sparks.


--- Quote ---This is a fixed installation, no matter how unpluggable it may be, and all the requirements of BS7671 and the building regs apply.
--- End quote ---

I disagree - though there's no way in hell I would install this in walls on a professional level, it would allow a DIYer to do his own install and comply with regs. If this was an extension lead screwed to the wall what's the difference? If this was in flex feeding sockets via a stuffing in the end of some dado trunking or any trunking come to that, what's the difference? I don't have my (17th Ed Amend 3) regs to hand but I can't think of anywhere where it states you can't. You don't test extensions cables do you. They rely on the protection offered by upstream devices RCD's, MCB, Fuses as applicable. What if you have a flush FCU, back feeding a boiler with a cable buried in a wall is the boiler part of the fixed installation - No, it' is an accessory. You would disconnect it when carrying out out an Installation Resistance Test! How about a 240V thermostat with cables buried in the wall - again we don't test. There are many instances like these which are not part of the fixed installation.

If you know of a specific section dealing with buried cables in this context I would be very grateful if you would let me know.

Remember the regs are not written to be verbatim they are a written as a guide to professional electricians enabling them to use their judgement to comply with the law on their installation given certain criteria. And for the record I am uncomfortable and REALLY squirming writing all of this bit :palm:


--- Quote ---You could collect the changes (and 'repairs' .. I think you're allowed those) and do them all at once.
--- End quote ---

ish!!! Other than replacing like for like, Every piece of electrical work needs or should have had certification of some sort when installed. The killer is the change in colour codes to 'harmonise' with F**cking Europe so this dates your installation. Any new Brown and Blue core cable with Grey outer sheath cables is post requirement for certification and notification. The government has done an absolutely piss poor legislation job with no notification to the public - unlike Gas Safe and Corgi before them.
You ask the average man in the street about Part 'P'. If you do get a positive response they think it is a qualification not a £750 odd/year club with the government tracking how much work you notify online to estimate your tax returns.

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