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DISTRIBUTOR CANNOT BE TRUSTED...

Former Community Member
Former Community Member
Hi folks!


This is my first forum post and hopefully and interesting topic. I am looking for some advice on where to start!

Background:
  1. 4th floor apartment tear-out in the city of Baku, Azerbaijan in a very old Soviet-era building block with unknown amounts of modifications.

  • 4 wire system (3-phase and neutral) entering and distributed throughout the building (no armoured cable / no separate earth).

  • No enforced local regulations as the general wiring in the city is a free-for-all (I am told it should be to PUE 6 standard). I could share many examples but this is not the aim of this post!

  • No building plans available from the council / no wiring / single-line diagrams available for the building or from the distributor.

  • No option available for a reliable survey - Partly being that most of the local electricians think that an earth core is a waste of money!

  • Basically the local distributor cannot be relied upon as can be seen by the photo example of the electrical panel closest to the apartment from the local government electrical company...

  • I am an electrical engineer wanting to get my hands dirty with my own project compliant to the BS 7671 wiring regs. I will design the domestic electrical installation and will have it verified by an (UK) electrician / expat before proceeding and sourcing materials.

Aim:


  1. Brand new domestic apartment electrical installation to BS 7671 18th Edition in which is in my control (full rewire, new consumer unit etc.). BS exceed the local regulations.

  • Keep politics / what-should-be for the incoming panel out of the discussion, it is what it is and there is not much I can do except wait decades for regulations and enforcements to catch up!

  • Provide the safest solution to protect my family without running away from the building / country.

Closest Panel to my Apartment:

  • Ok lets cut to the chase - this may just be the worst panel that you have ever seen however I cannot modify it as it is owned by the local government electrical company. It gets no points for compliance to any regulation (maybe 1 for being metal only!). I unfortunately has to live with this monstrosity until the building is knocked down in the future (and this is one of the newer / better panels in the building believe it or not…1 of 3 panels up to the apartment).

34853545ae5c04645e1bb134ec9267e3-img_1749.pdf


Queries:

  1. Can I assume that the incoming supply is a TN-C-S (and I know this is the distributors responsibility…) i.e. connect the MET and neutral together before the consumer panel? I know we should never assume so what is the best way to test? I am trying to source a Megger. My concern is that this could bypass some protection elsewhere in the building although it appears to have only overcurrent protection (fuses).

  • Should I have a dedicated earth run from the incoming of the building (from the neutral bar) up to the apartment consumer unit instead? My concern is that there my be a potential difference between the neutral and the earth at the apartment which could require 2P RCBOs throughout. Yes there should not be a potential difference however there is a lot of twisted wiring (junction boxes are a luxury…) and poor looking connections as well as all the apartment neutrals connected together in the block.

  • A third option would be to have an earth pit installed in the car park and run the dedicated earth to the MET in the apartment although 2P RCBOs may still be required.



Any assistance is greatly appreciated including verification / testing methods before I dive into the design of the consumer unit. Thank you in advance,


Chris
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  • 0
    Well it is not that clear which cores are lives and neutral/earth in the supply or the loop supply, or indeed which is which incoming and which is daisy chained, so the safest thing is probably to use a meter to identify the 3 phases (400V between each pair) and the neutral/earth (230V to each of the lines you think are phases.) Zooming in on  the bottom of the box is just confusing, and we cannot see if wires are crossed over in the channels where they are hidden from view.

    There is certainly scope for polarity reversal,  or being fed 2 phases instead of one phase and a neutral, and it would be hard to spot.
    826834fc7d2272d06806d81c10fc98af-original-lowerintake.png
  • 0
    In view of the rather dodgy sounding arrangements upstream of you flat, I would proceed as follows.

    Install a consumer unit with true double pole  RCBOs for each circuit.

    The RCD section gives good protection against electric shock.

    The MCB section give protection against overcurrent in EITHER pole of the supply.


    I would instal three wire circuits to grounding type socket outlets. I would earth the installation to the water pipes, this IS NOT best practice and is prohibited in the UK, but under the local conditions is in my view the least bad option.

    Even if the earth via the water pipes becomes ineffective, SOME protection is still given by class one appliances and plumbing being at the same voltage. The "earthing" has in effect become "bonding" under such conditions and still gives some protection against shock.


    I can not recomend earthing to the suppliers neutral, too much risk of an upstream open neutral in view of the questionable standards observed.
  • Former Community Member
    0 Former Community Member
    UPDATES   (to Pandora's box)


    Busy period now finished - heavy renovation works well underway. An electrician also opened the main and sub main panels. 

    A picture is worth a thousand words... (and is also a good excuse to learn some AutoCAD!):
     




     

    Main Building DB

    1.jpeg
    2.jpeg
    3.jpeg   The neutral bar is not looking healthy at all. First time I have seen DB conductors just wrapped around each other, obviously not a good connection from the melted insulation.
    4.jpeg   The yellow core of this old 4 core cable looks like it could go out to an earth electrode however this is just an assumption.




    Sub-Main DB


    5.jpeg
    6.jpeg   More twisted together neutral connections.
    7.jpeg   The neutrals connect to the DB earth boss.




    In summary, a broken neutral is very possible at multiple points in the building or at least with a bad connection.


     


    1. To make it more interesting, there is a ground-level water pump, only for the flat in question (one pump per flat). I am considering to isolate the pipework prior to the pump to make a TT earth system from the earth electrode only i.e. isolate all extraneous pipework via isolation flanges and converting to plastic prior to entering the apartment.   8.jpeg

    • Another reason for this is that the metal gas main that runs around the outside of the building to a lot of flats is connecting to a lot of combi boilers. This is basically their only earth connection.

    • Rebar could be connected to within the building concrete works / last electrical panel. I doubt there is any deliberate electrical continuity during the building construction such as copper rods in the foundation piles / clamps to maintain electrical continuity throughout. There is only the steel ties between the rebar which would still form a connection of sorts. Interestingly though that the local electricians would appear to connect to it on the last panel as previously highlighted.   9.jpeg



    Queries
    1. Can rebar encased in concrete be used as the sole earth electrode for the flat? I am trying to get a loop tester in country so I can check it first. I guess the rebar (assuming it is electrically continuous) would be classed as an extraneous conductor. Just curious as this could avoid the issues below.

    • It will be near impossible to install a new TT earth electrode in the car park / yard away from underground metalwork. I need to continue my homework on rebar electrodes and distances away from other buried services. Would it be such an issue in a flat with no extraneous connections for the TT earth electrode to be in close proximity to buried metal work? If a fault from another system were to raise the ground potential then all the exposed metalwork in the flat should also raise to the same potential i.e. no potential difference between exposed metalwork within the flat.


    Thank you in advance,


    Chris
  • 0
    Yes, rebar can provide a good earth electrode and I would use this after testing, possibly in conjunction with metal water pipes.

    I would not consider any arrangement that uses any part of the neutral system as an earth, far too much risk of an open neutral.


  • 0
    well the photos once again show that those who think electrical installations in the UK are in a bad way should go abroad a bit further,  the gap in 'professional' behaviour when you have no-one setting any standards at all can be very wide indeed,and yet the accident rate remains acceptable it seems.

    You could take a low wattage lamp and see if you can light it between the live and the rebar - way back in the dark ages of pipe smoke and coal dust when 3 pin sockets were a new thing, a test lamp of a few tens of watts was a quick way to verify if a proposed  earth electrode or water pipe was any good at taking current to ground or not.

    In a refinement to the test, you could measure the line to rebar voltage with the lamp on and off and estimate an effective electrode impedance.

    Of course if it does not light, then remove it PDQ, as for the duration of the test you have made it live, and there may be some poor sod dancing about in the basement...

    Mike.
  • 0
    It will be near impossible to install a new TT earth electrode in the car park / yard away from underground metalwork. I need to continue my homework on rebar electrodes and distances away from other buried services. Would it be such an issue in a flat with no extraneous connections for the TT earth electrode to be in close proximity to buried metal work? If a fault from another system were to raise the ground potential then all the exposed metalwork in the flat should also raise to the same potential i.e. no potential difference between exposed metalwork within the flat.

    The idea of keeping a TT earth separate from other earthing systems generally only applies where there's something about the other earthing system you wish to avoid - e,g. avoiding the dangers of PME earths when supplying caravans or EV charge points.


    If the other hand you're only using a TT system because a supplier's earth terminal isn't available (otherwise PME would have been fine) then there's little need to worry about segregating your earthing arrangements. Indeed it's quite common to have rural TT installations that have TN-like Zs values because there's a path via bonding to metallic water or gas pipes to a TN neighbour.


    As you say, if you can create an equipotential zone, the actual potential it is at is far less of a worry. In practice you can never create a perfect equipotential zone (especially if bits of the installation go outside!) But it seems you're in a far from ideal starting position so I think the best you can go is find some kind of reliable Earthing facility (local electrode or re-bar) and then bond everything within reach - including things that might be connected the dodgy supply 'Earth' if needs be. As far as possible using Class II equipment outdoors at ground level - or protected by insulating enclosures - can mitigate the risks there. Or you might consider a separated circuit for things like the water pump (i.e. unearthed, fed via an isolating transformer) - although if the pipework is metallic, it's probably pointless.


    Just bare in mind that if yours is the only installation in the area that does have proper bonds and the supply N/PEN does go faulty, you might end up carrying the return currents for most of the neighbourhood through your bonds - so generous oversizing might be the order of the day. Plastic plumbing can certainly help.


       - Andy.
  • Former Community Member
    0 Former Community Member
    RESPONSES:


    mapj1:

    I assume the unmetered GY from phase 1 is a sub-main to another similar board.



    Simon Barker:
    Somebody seems to have tapped in an extra un-metered live, in green-and-yellow, from the incoming breaker, and fed it out the bottom of the panel alongside two earth wires.  Is this a sneaky way to hide abstraction?

    So the unmetered GY from L1 is a 63 A supply... to the door bell! And has also been tapped into another panel which is where the trail goes cold. Let’s just say I am very cautious to press the plastic door bell button now and not touch the surrounding metal!   1.jpeg

     
    mapj1:
    An example of the better earth problem - not quite in the UK, but almost, as Lyle works in Ireland, and it certainly is could happen here. 

    Very interesting case! As long as a L-E fault at my end is disconnected within the required time period as per the regulations then I do not see an issue with my new earth electrode potentially being better (lower resistance) than the one in the substation. It sounds as if this is not unusual for customer TT installations.

     
    mapj1:
    An all pole breaking RCD at the incomer is a good start, good, along with some sort of external earth connection- which at the FOB may be associated with comms antennas /equipment. Either a direct N-E bond or via a capacitor after the RCD will trip the RCD if the neutral voltage is too far off earth or if the LN are reversed - which you have to assume can happen at any time as other things may be severed and reconnected outside.  Then under-voltage and over-voltage trips will guard against the worst errors such as being fed 2 phases instead of one phase and a neutral, though if possible small electronics equipment is designed to work OK from less than 100V to over 400V so that we do not really care to much. Note that there are situations where driving an earth electrode is not desirable,  the most extreme example would be suspected buried ordnance, but in a more domestic setting,  to buried strike water and gas pipes could be almost  as disappointing. 

    Also very interesting - I will add it to my homework! The earth electrode will be tricky however a job for the local workmen so I do not cause chaos!

     
    AJJewsbury:
    So generally any new CU installed in the UK in the last 5 years or so will be steel cased.

    Thanks Andy, I was leaning towards metal anyway and is what I’m used to!

     
    mapj1:
    In an installation with such an iffy earthing culture and random taped joints, I suspect the metal vs plastic argument may swing the other way - you cannot get a shock off a plastic box  !!


    Hmm… I am now unsure whether plastic piping / plastic consumer unit or bonding all extraneous metal pipe work & exposed metal surfaces is the way to go… food for thought!

     
    AJJewsbury:
    I'm confused. There appear to be 3 outgoing C32 MCBs and three meters. However the top left meter seem to be connected directly to one of the apartments without going through a C32 (dark blue wire) - could it be that the highlighted single pole C32 MCB is actually in the N?

    Correct - 3 outgoing C32 MCBs and three meters. The dark blue wire you mention is the outgoing neutral from the top left meter (Also see the relevant page from the meter manual with the order of the terminals here). The light blue cable from terminal 2 (second from the left) is the outgoing live. This goes to the right of the panel and up to the left side MCB. It is difficult to see because of the blue trunking which I have only ever seen used on intrinsically safe cabling systems. Also I’ve had a voltmeter in the panel so the MCBs are in fact connected to the live wires.

     
    mapj1:
    Well it is not that clear which cores are lives and neutral/earth in the supply or the loop supply, or indeed which is which incoming and which is daisy chained, so the safest thing is probably to use a meter to identify the 3 phases (400V between each pair) and the neutral/earth (230V to each of the lines you think are phases.) Zooming in on  the bottom of the box is just confusing, and we cannot see if wires are crossed over in the channels where they are hidden from view.

    There is certainly scope for polarity reversal,  or being fed 2 phases instead of one phase and a neutral, and it would be hard to spot.

    Andy / Mike - Hopefully this clears things up now (confusing I know - cannot trust the cable colours).   2.jpeg

    Another point is that the national voltage is not quite to IEC 60038 and is not expected to migrate as the country is not in the EU. I realised this when installing 660 V switchgear instead of 690 V (non-domestic installation).

     
    broadgage:
    Install a consumer unit with true double pole  RCBOs for each circuit.

    The RCD section gives good protection against electric shock.

    The MCB section give protection against overcurrent in EITHER pole of the supply.


    I would instal three wire circuits to grounding type socket outlets. I would earth the installation to the water pipes, this IS NOT best practice and is prohibited in the UK, but under the local conditions is in my view the least bad option.

    Even if the earth via the water pipes becomes ineffective, SOME protection is still given by class one appliances and plumbing being at the same voltage. The "earthing" has in effect become "bonding" under such conditions and still gives some protection against shock.

    Thanks broadgage. Agreed - I had decided on 2P outgoing RCBOs to isolate any dodgy neutrals in the event of a fault plus for peace of mind with a baby in the flat. My understanding is that, if the circuit is off, any external backfeed via a N-E fault within the flat on the same circuit through the RCD would also trip it. I also plan to install a 300 mA time delayed S type 2P RCD on the incoming side, purely as a backup and for good practice (especially if my new earth electrode is better (lower resistance) than the distributors! - thanks Mike for the example).


    Sockets - Agreed 3-wire grounding type. I am still leaning towards UK type to avoid polarity reversal. I am now sure that I need a new earth electrode down in the carpark which the metal pipework could also be bonded too. Ok so another tally for bonded metalwork instead of plastic...

     
    broadgage:
    I can not recomend earthing to the suppliers neutral, too much risk of an upstream open neutral in view of the questionable standards observed.

    Agreed, the TN-C-S route is dead. TN-S is not available from the distributor (no separate earth conductor). So my only option is TT.



  • Former Community Member
    0 Former Community Member
    RESPONSES (Continued):

     


    broadgage:

    Yes, rebar can provide a good earth electrode and I would use this after testing, possibly in conjunction with metal water pipes.

    I would not consider any arrangement that uses any part of the neutral system as an earth, far too much risk of an open neutral.


    The other point I meant to mention is that, from an oil and gas background, I am used to designing redundancy into everything so bonding extraneous metal pipework for me would be preferable to relying on a single earth electrode connection (i.e. single point of failure).

     



    mapj1:

    You could take a low wattage lamp and see if you can light it between the live and the rebar - way back in the dark ages of pipe smoke and coal dust when 3 pin sockets were a new thing, a test lamp of a few tens of watts was a quick way to verify if a proposed  earth electrode or water pipe was any good at taking current to ground or not.



    In a refinement to the test, you could measure the line to rebar voltage with the lamp on and off and estimate an effective electrode impedance.



    Of course if it does not light, then remove it PDQ, as for the duration of the test you have made it live, and there may be some poor sod dancing about in the basement...




    Thanks Mike, I love to learn the good old ways! Go easy on my setup, it is difficult to source items when you don’t have Amazon or B&Q! So… it would appear that the rebar has a very poor / no electrical connection to earth at all from the lamp test (I am trying my hardest to get a loop tester in country):



    3.jpeg
    4.jpeg   The brightness of the lamp is the same as the image 3, just the camera used makes it seem less in this shot. 
    5.jpeg
    6.jpeg
    7.jpeg
    8.jpeg



     



    AJJewsbury:

    The idea of keeping a TT earth separate from other earthing systems generally only applies where there's something about the other earthing system you wish to avoid - e,g. avoiding the dangers of PME earths when supplying caravans or EV charge points.



    If the other hand you're only using a TT system because a supplier's earth terminal isn't available (otherwise PME would have been fine) then there's little need to worry about segregating your earthing arrangements. Indeed it's quite common to have rural TT installations that have TN-like Zs values because there's a path via bonding to metallic water or gas pipes to a TN neighbour.




    Great! Thanks for the confirmation Andy.



    AJJewsbury:

    As you say, if you can create an equipotential zone, the actual potential it is at is far less of a worry. In practice you can never create a perfect equipotential zone (especially if bits of the installation go outside!) But it seems you're in a far from ideal starting position so I think the best you can go is find some kind of reliable Earthing facility (local electrode or re-bar) and then bond everything within reach - including things that might be connected the dodgy supply 'Earth' if needs be. As far as possible using Class II equipment outdoors at ground level - or protected by insulating enclosures - can mitigate the risks there. Or you might consider a separated circuit for things like the water pump (i.e. unearthed, fed via an isolating transformer) - although if the pipework is metallic, it's probably pointless.


    Just bare in mind that if yours is the only installation in the area that does have proper bonds and the supply N/PEN does go faulty, you might end up carrying the return currents for most of the neighbourhood through your bonds - so generous oversizing might be the order of the day. Plastic plumbing can certainly help.



    So it is possible to install a new earth electrode immediately next to the water pump casing at ground level and bond the local metallic pipework (water + drainage) to it. The only place I can bond the gas pipe would be on the 4th floor (the gas pipe is tucked away in a locked location at ground level and loops around the building horizontally to each flat).

    I can’t see any immediate issue with the parallel earth path between the TT earth electrode - consumer unit MET & the MET through the water pump cable armour to ground, it would help for the oversizing aspect.

    I know there is no easy answer to this but what would you suggest for generous oversizing? I guess 16 mm2 won’t cut it. I fear you will say as large as possible…$$$

    The plastic water and drainage is typically what would be used locally anyway into the flat. Here is another proposal utilising as much bonding as possible:



    CG Project Rev02.pdf



    Chris


  • Former Community Member
    0 Former Community Member
    UPDATE #2


    Further testing today revealed extraneous conductors in the stairwell which is where the new combi boiler will be situated. There is a neighbours combi boiler and neighbours lead drain pipe close by the metering panel on the same mezzanine level. I repeated the rebar test to make sure the clamp connections were good. The values in the photos are as when using two hands (maybe the new Fluke Connect function could come in handy in this instance…):
    9.jpeg     Apologies for the bad quality, this is the only photo I have to hand at the moment of the stairwell.


    10.jpeg   Checking the clamp connection to the rebar.
    11.jpeg   276 kilo Ohm between the top of the stair rebar and the mezzanine level rebar connection to the earth boss.
    12.jpeg   1.15 Mega Ohm between the top of the stair rebar and the extraneous metal gas pipe. Similar results for all nearby stairwell rebar connections.
    13.jpeg & 14.jpeg   Illumination achieved from clamping onto the incoming gas supply and between the outgoing live.
    15.jpeg & 16.jpeg   Illumination achieved from clamping onto the neighbours lead drainage pipe and between the outgoing live (don’t worry they weren’t home).




    It would appear that the buildings rebar was not intended to be electrically continuous throughout. Interestingly, it would seem that the regs require that the exposed metallic structural parts of the building are bonded which would include the rebar...

  • 0
    I know there is no easy answer to this but what would you suggest for generous oversizing? I guess 16 mm2 won’t cut it. I fear you will say as large as possible

    How big is the N into the building? - no need to go larger than that I guess. In the UK we'd apply table 54.8 to the size of the supply N (e.g. 10mm² bonding for up to a 35mm² supply N, 16mm² for up to 50mm² etc up to 50mm² for over 150mm²) - so that would be my minimum (I'm presuming the main services aren't bonded where the enter the overall building) - so maybe somewhere between the two depending how the numbers worked out.


    The problem is really just bonding to extraneous-conductive-parts that have a low impedance back to the source - which it looks like the gas pipes for one have. Things simply stuck in the soil - such as a TT earth electrode will have a resistance (due to the soil around it) of many Ohms - which will naturally limit the current to something relatively modest. So some care with the placement on bonds might reduce the costs a bit.
    neighbours lead drainage pipe

    That looks small for drainage - given that lead pipes (at least UK ones) usually have quite thick walls it looks like it would have a pretty small bore - much like a 1/2" water supply pipe.


      - Andy.
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