A few questions on wiring practices

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peterh337

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Hi All :)

Background: electronics engineer, done tons of DIY electrics wiring including SWA stuff to outbuildings etc, and 3 phase many years ago.

Q1: We have a single phase supply. The fuse used to be 80A. One day we got a letter from Seeboard offering to upgrade it for free. So we went for it. A man came and changed the fuse for a 100A one. Just like that. What size is the incoming cable? Is is about 20mm OD which might suggest 16mm2 rather than 25mm2. The distance is about 25m. The only heavy appliance in the house is a 10kW electric shower.

I realise a fuse is for wire protection only and a 100A fuse, probably a piece of 16swg copper, will blow well before a 16mm wire.

The reason I ask is because I am getting the house ready for 3 phase (for electric car charging, one day in the distant future) and then the meter will be relocated to a box on the outside of the house, and I will need to run a cable to the existing consumer unit. Fairly obviously 25mm2 will be OK but it is awfully hard to get this cable in place so smaller the better. That run would be about 3m. (Yes I know it would be better to use the existing incoming cable (which will be disconnected at the supply when the 3ph goes in) but it is buried deep under concrete).

But then when this is done, that 100A fuse will not be there anyway, because this is all "internal". 

Q2: Do UK Power Networks ever make any allowance on their 45cm duct depth and type requirement? On the phone they say absolutely never under any circumstances whatever, but they are right jobsworths in their tone and would say that :) In the past this wasn't done and not far from me is a 33kV cable about 1ft deep in soft soil :) House supplies were often a few inches deep (in concrete) or 1ft deep (in soil). They told me they don't use SWA because it doesn't last as long.

I ask because we had a drive done in block paving. Under it is about 12" of concrete and at the bottom of that concrete is a 8cm duct (standard gutter pipe) which I got laid, all the way from the road, to our garage, in preparation for the 3ph supply. I didn't get around to checking the power company requirements for the house supply until the concrete was done... So it isn't 45cm deep but I don't see how the cable could be damaged, with a foot of concrete on top of it, and it being in an 8cm pipe.

We do have a Plan B which is to run the prescription duct through a garden, but it would be nice to use the one under the drive.

I would be looking for 3 x 80A or so.

Q3: Does the power company ever care about what is connected after the meter? They never used to. In a previous house I installed a big box with a load of 3 phase stuff (switch, RCDs, etc) and they were happy. It is possible they thought an electrician did it. Well, I tried to find one but as soon as I mentioned 3 phase and the countryside location, they all wanted £500 per half day, so I did it myself. I used a big steel cabinet.

I hear stories nowadays of electricians refusing to do any work in a house, beyond changing a bulb, unless the consumer unit etc is ripped out and replaced to comply with latest wiring regs, and wonder if the power company is similar.

Obviously, after the meter will have to be a switch and RCD (or RCBO under the new regs?) before wiring continues to the rest of the house. I can get an electrician to install a cabinet with this in, with space for the meter, but presumably he won't touch the job if there is anything else in the house he doesn't like. So maybe I should install this cabinet (like I did on the other house many years ago) and do it so it looks like it was done by an electrician.

Thank you for any feedback :)

 
To add more detail to Q3: does the power company care if the house wiring is not 18th Edition compliant? In other words, can you get 3 phase connected up without having a potentially extensive rewiring job?

 
Can I ask what level of training you have had in relation to electrical installation and the subsequent Regulations? Only if you don’t understand the principles involved in design etc then what you install may work but may be fundamentally wrong and therefore increase risk to yourself and family? 
what I can say is that as far as the supply companies are concerned they will not connect to a dangerous installation, now how they determine that is their business but they do not work to Electrcial installation regulations ie BS7671. 

 
DIY electrical wiring for about 50 years. Rewired several houses in that time. Did two when aged 13 and 14 - it's about as far from rocket science as one can get. A degree in electronics so obviously know how the stuff works but not done any electrician courses. The work is most definitely safe. 

My questions are practical ones. If someone takes the view that only an electrician can do any work in a house then that isn't going to help :)

The current house was rewired by two electricians 20 years ago. It took them weeks and cost 7k. Lots of circuits, no less than five RCDs due to some outbuildings etc. Undoubtedly not to Ed 18 now (was certainly legal 20 years ago) but then how many houses are?

It would be interesting to hear from someone working for UK Power Networks who knows their actual practice. Last time I had dealings with them on 3 phase was about 25 years ago when I installed the steel cabinet for their meter etc and I had already run about 50m of 25mm2 SWA from it to a 45kW pool heater. They didn't bat an eyelid; the work looked totally pro as far as they were concerned. That house was built c. 1960 and almost certainly didn't meet the then current regs either. So I have one very old data point on them not being bothered, presumably provided the immediately visible work isn't obviously dodgy.

As an aside, the house (built 1965) main feed, with the 100A fuse, is about 18mm OD cable which runs about 1ft underground in soil. The power company was happy to work on it (change the fuse 80A to 100A) despite it clearly not meeting the current regs for the depth etc.

 
Supply companies work to their own regs & rules  ,  but if they specify  anything  like  black PVC duct  ,whatever size say,  if you  use anything else they'll just walk away .    

They are not interested in whats in your house  and are not happy entering because of insurance I was told ,  breaking stuff etc ,     

They're not interested in your wiring being 18th edition  , their interest stops at at fitting double pole switch after their cut out .    Some areas they will move your meter  to save  a metering company having to turn out .

They usually want to know your estimated full load .     ( In KVA ) 

They also charge a fortune for everything. 

 
Ok so we have established that you have the relevant qualifications in electronics and I will not challenge you on your abilities to do this, providing you are prepared to accept that you will not challenge us on ours? 
whilst not rocket science there are requirements to be met with regardless. Have you the test equipment to confirm your installation is safe? Disconnection times met etc? Suitable Earthing as some older properties suffer with deteriorating earth connection? 
whether the installation was designed originally to 18th edition is irrelevant however with you requiring fundamental characteristic changes then you may well need to ensure it is. 
so with the greatest of respect putting in a box and making it work doesn’t cut it in real terms I’m sure you understand as it’s probably the same with putting in additional or alternative electronic components in a system, just because it works doesn’t mean it’s compliant nor correct. 
 

so what you will need is design load both for your tail sizing and for the supply company for their calculations to start with. 

 
Thanks Evans Electric. That makes sense; they prefer to have the meter in a box outside nowadays and I can see they don't want to go inside the house.

I have just walked past a building site where an electrician was terminating a load of 16mm2 SWA with the resin filled joints (done plenty of those too over the years, although I solder them rather than crimp) and he told me the same. They aren't interested in whether the house internals are legal.

"if you  use anything else they'll just walk away"

OK that was my other Q. Does anyone know of any cases where they can run their cable through an existing duct of a different type?

 
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DIY electrical wiring for about 50 years. Rewired several houses in that time. Did two when aged 13 and 14 - it's about as far from rocket science as one can get. A degree in electronics so obviously know how the stuff works but not done any electrician courses. The work is most definitely safe. 

My questions are practical ones. If someone takes the view that only an electrician can do any work in a house then that isn't going to help :)

The current house was rewired by two electricians 20 years ago. It took them weeks and cost 7k. Lots of circuits, no less than five RCDs due to some outbuildings etc. Undoubtedly not to Ed 18 now (was certainly legal 20 years ago) but then how many houses are?

It would be interesting to hear from someone working for UK Power Networks who knows their actual practice. Last time I had dealings with them on 3 phase was about 25 years ago when I installed the steel cabinet for their meter etc and I had already run about 50m of 25mm2 SWA from it to a 45kW pool heater. They didn't bat an eyelid; the work looked totally pro as far as they were concerned. That house was built c. 1960 and almost certainly didn't meet the then current regs either. So I have one very old data point on them not being bothered, presumably provided the immediately visible work isn't obviously dodgy.

As an aside, the house (built 1965) main feed, with the 100A fuse, is about 18mm OD cable which runs about 1ft underground in soil. The power company was happy to work on it (change the fuse 80A to 100A) despite it clearly not meeting the current regs for the depth etc.


Just to update a few points your DIY 50 years and degree in electronics hasn't manged to teach you..

BS7671 wiring regulations are NON-STATUTORY....   

so phrase about any wiring be legal or not are completely irrelevant...  

get a copy of BS7671 and read regulation 114...

If you have only got 5 RCD's and you have got more than 5 circuits it can be debated that the wiring does not comply with BS7671..

If you also read regulation 110.2  it lists the exclusions from the scope of BS7671..

which should explain to you the differences between internal wiring of an installation..

and the distribution supply to that installation..

Anyone can do electrical work..   DIY electrical work is permitted within the UK..

and as you quite rightly say any fool can join a few wires to make something work..

But BS7671 is not about making a circuit work..

It is about ensuring that it will fail safe, and disconnect the supply fast enough to protect people, property and livestock with minimal inconvenience in the event of a fault....  

Designing testing and certifying it complies with BS7671 (and if applicable Part-P building regulations) is the bit that verifies it should fail safe and not pose any danger. As at the end of the day electricity can still kill a healthy adult in less than half a second.

An up to date Electrical Installation Certificate or Electrical Installation Condition Report is the bit of paper that would confirm if your installation is still satisfactory for continued use with ref to current wiring regulations.

And would be the document to show anyone if questions were asked about the general condition of the current arrangement.

If you have suitable meters, you can download generic electrical certificates, do all the testing to complete this paperwork yourself..  If not.. 

then that's probably getting to the bit most DIY'es omit from any rewires and alterations.. and you would probably need a suitably competent person, such as a qualified electrician to do this for you?

If you want to know what the local DNO's working practices are it may be best to actually contact them direct..

https://www.ofgem.gov.uk/key-term-explained/map-who-operates-electricity-distribution-network

As several of us could give our opinions about what they want or not...

But the bottom line its the bods who deal with your area that call the shots on how they want to their cables installed.

They may or not be bothered about your internal installation..

It really depends on how big a "More-Than-My-Jobs-Worth" hat they wear!

:C

 
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@peterh337 if people say they won't do anything apart from changing a bulb of the installation isn't up to the 18th edition they aren't worth using.

This situation is about to get worse due to the I'll thought out legislation regarding electrical inspections for rental properties.

Where are you in the UK? England and Wales would need compliance of part P undertaken

 
Thanks everyone.

Yes I am well aware that DIY wiring is legal etc and noncompliance with current regs does not make the house "illegal" in any way. You might get a funny survey if you want to sell it :)

Didn't they change the wire colour from white to grey to make DIY wiring obvious? There was then a run on the white wire and it remained available for years afterwards.

What I was getting at is that if you want an electrician to do any work on a house (for example install an extra socket) he won't touch it unless he converts the consumer unit to the latest regulations. I've just had a mandatory 5 yearly check at the office and they said an RCD must now be an RCBO and the (metal) box was not right (there was a 2mm gap around the CBs etc, which is pretty usual) so that was 1k to put that right but we had no choice as we needed the report for the landlord. It is well possible these people are not being truthful but if I press for evidence they say they will walk away. Finding electricians is really hard nowadays.

Re the # of RCDs, we have one non-RCD circuit for a fridge/freezer, as was customary for decades for well known reasons. I have read this is now illegal for new work. What I don't know is whether an electrician can legitimately  insist on this if say installing a new socket; if he does then chucking out a freezer which occassionally leaks 31mA (which is harmless if it is properly earthed) is gonna cost somebody. Obviously this is "not right", appliances should not leak anywhere near 30mA, the ones most likely to leak are ones with common humidity issues like fridges and washing machines, not to mention electric showers, and they are the very ones most likely to give you a shock, and half the time the problem is a duff RCD; I have often fixed nuisance tripping by changing the RCD. In other cases I've seen e.g. fluorescent lights this proved to be a real b*gger (the lights seem to have significant capacitive leakage L-E; 0.4uF at 50Hz will leak 30mA) if you have say 10 of them, and I solved that with a 1kVA isolating transformer, which is a great solution but would horrify an electrician :)

I will look up regulation 110.2 but I've been told that the power company works to its own special rules which are not online.

I am in England.

 
Well lads it seems we should have done an electronics degree to understand electrical install requirements. Clearly a nuisance tripping rcd is solved by changing the rcd - who knew :C  clearly wasn’t an issue within the circuit otherwise we’d have seen or heard of the results of the tests that had been carried out :C  

 
OK, fair enough, feel free to attack a new poster. I know the scene well; it's no problem. In the meantime, someone might post some useful info.

 
OK, fair enough, feel free to attack a new poster. I know the scene well; it's no problem. In the meantime, someone might post some useful info.


Well, this forum is really for light DIY and sparks earning a living to share information.

Your view is that you don't want to pay and want everything on a plate for free 

Time to get my coat

As for the EICR, my advice would be to get other sparks to review and quote 

 
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OK, fair enough, feel free to attack a new poster. I know the scene well; it's no problem. In the meantime, someone might post some useful info.
this is not a personal attack it is about highlighting the knowledge you are missing. I’m sure you’d do the same in your field. If you are taking this as an attack it says more about you than me. 

 
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This is not my bouncy castle but the general idea is to play the ball not the man.

 
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Help me out here, to be clear, what you want is all the answers with no idea of safety or would you like one of us to pop round and test it for you? 

 
Thanks everyone.

Yes I am well aware that DIY wiring is legal etc and noncompliance with current regs does not make the house "illegal" in any way. You might get a funny survey if you want to sell it :)

Didn't they change the wire colour from white to grey to make DIY wiring obvious? There was then a run on the white wire and it remained available for years afterwards.

What I was getting at is that if you want an electrician to do any work on a house (for example install an extra socket) he won't touch it unless he converts the consumer unit to the latest regulations. I've just had a mandatory 5 yearly check at the office and they said an RCD must now be an RCBO and the (metal) box was not right (there was a 2mm gap around the CBs etc, which is pretty usual) so that was 1k to put that right but we had no choice as we needed the report for the landlord. It is well possible these people are not being truthful but if I press for evidence they say they will walk away. Finding electricians is really hard nowadays.

Re the # of RCDs, we have one non-RCD circuit for a fridge/freezer, as was customary for decades for well known reasons. I have read this is now illegal for new work. What I don't know is whether an electrician can legitimately  insist on this if say installing a new socket; if he does then chucking out a freezer which occassionally leaks 31mA (which is harmless if it is properly earthed) is gonna cost somebody. Obviously this is "not right", appliances should not leak anywhere near 30mA, the ones most likely to leak are ones with common humidity issues like fridges and washing machines, not to mention electric showers, and they are the very ones most likely to give you a shock, and half the time the problem is a duff RCD; I have often fixed nuisance tripping by changing the RCD. In other cases I've seen e.g. fluorescent lights this proved to be a real b*gger (the lights seem to have significant capacitive leakage L-E; 0.4uF at 50Hz will leak 30mA) if you have say 10 of them, and I solved that with a 1kVA isolating transformer, which is a great solution but would horrify an electrician :)

I will look up regulation 110.2 but I've been told that the power company works to its own special rules which are not online.

I am in England.


erm…..  Nope...    BS7671 wiring regulation is STILL non statutory....  :shakehead

There is no requirement to upgrade a fuse box to add an additional socket..

You are probably reading the wrong books.. or websites if you have been reading about certain items being illegal for new work..   

Your concept of nuisance tripping..  and method of "fixing" is a bit comical to say the least...  :huh:

It may be wise to have a google about the effects of electric shock current passing through the human body to see if 31ma can be harmful...   :wacko:

If you have been replacing numerous supposed "Duff RCD's".. I would suggest your Cause & Effect logic could well be reversed...

(Almost on a par with.. My car wont start so I will replace the engine, rather than investigating the real cause!)

Unfortunately... we sometimes get people asking question, who think they already know the answers they want to hear..

And if they don't hear the answer they want..  and/or are told that some of their knowledge or understanding is inaccurate/incorrect/wrong/ or just plain daft...  Then for some strange reason, they think they are being "attacked"!?   :C

Irrespective of what you know or don't know, or what qualifications or practical experience you have,

There are a fair few years of industry standard practice around what qualifications are required for electrical installation & testing..

No doubt there are some areas of overlap with the underlying science of required qualifications for an electronics engineer..

But there are also a lot of significant differences, especially around how easily it is for a fault to be fatal compared to just a bit of damaged kit..

Back to your opening point:-

Obviously, after the meter will have to be a switch and RCD (or RCBO under the new regs?) before wiring continues to the rest of the house. I can get an electrician to install a cabinet with this in, with space for the meter, but presumably he won't touch the job if there is anything else in the house he doesn't like. So maybe I should install this cabinet (like I did on the other house many years ago) and do it so it looks like it was done by an electrician.
Have you consulted a couple of electricians to get some actual answers from someone who has physically seen your installation?

As it sounds like a lot of guess work and assumptions based on your perception of what the wiring regs require...

which from earlier comments are flawed in a few areas...

It will help if you realise the fact that forum help sites such as this are a two-way process..   and just as you asked...  

If someone takes the view that only an electrician can do any work in a house then that isn't going to help


It is also important to remember,  if someone takes a view that formal electrical qualifications, experience and knowledge of multiple historic editions of BS7671 wiring regulations up to the current edition, has negligible relevance compared to 50yrs DIY and some electronics qualifications, Then that certainly isn't going to help either....

:popcorn  

 
Thank you all again.

My comments above on trade practice are from actual experience. Somebody I know has a 2nd house which is rented out. I don't know if this makes a difference (an EICR may or may not be needed depending on # of occupants perhaps) but every electrician has flatly refused to do anything unless they upgrade the whole house wiring to latest Ed 18. Plus we had the comical experience here with the 2mm gap around the CBs. Yes one should get multiple quotes but there is a risk in getting someone new in that they might find other stuff... the building is at least 60 years old. The last firm said that all wiring above the false ceiling has to be re-done because it is lying loose; they eventually admitted this is not a legal requirement. There is a lot of stuff online about Ed 18 being statutory; maybe it is posted by trade people, which would not surprise me as I see the same in my business (the electronics rags are packed with scary compliance articles).

The idea of an RCD replacement in nuisance tripping came from an electrician, in cases where the leakage was measured well within spec. An RCD is quite simple (basically a transformer with 2 windings with some other bits) but they can develop faults after many years.

But anyway that is just a background for why I prefer DIY and why I have been looking for pointers. I am asking on a forum because it is easier than getting electricians round and pretending they will get work out of it. They might (as I said I paid 7k for the rewiring 20 years ago) but they might not.

I might get the power company to do a site survey. It would still be handy to know if anybody has ever come across a case where they didn't insist on the 45cm deep specific-type duct. Logically a tube in 30cm of solid concrete should be more than good enough.

 
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I have never known a supply company to use anything other than the correct duct both colour and size nor have I known them to lay a cable at less than 450mm. 

 
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