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  1. P

    Do you test the suppliers earth conductor for continuity??? (Initial verification)

    Hi guys, QUESTION: Do you test the suppliers earth conductor for continuity??? The guidance note 3 2.6.5 refers to regulation 643.2.11 which requires a continuity check be carried out on all protective conductors including: EARTHING CONDUCTOR, CPC's and bonding conductors. I am aware of the...
  2. N

    size of earthing conductor from switched isolator to CU

    Domestic single phase supply, TNCS, 25mm tails. From supply to Fused switched isolator : Earthing conductor is 16mm. From isolator to CU : Earthing conductor downgraded to 6mm for what ever reason I don't know. Is there something in the regs that says after an isolator the conductor can be...
  3. I

    Use of Singles for Main Earth Conductor and Incoming Neutral?

    Hi folks, Limited experience here and never come across this before. Whilst I can appreciate the conductors may be the appropriate CSA combined, (I haven't measured them) terminating the Main Earth Conductor in the MET like this with what looks like 4 x 4mm2 doesn't allow for the conductors to...
  4. I

    Need to understand the neutral conductor

    Appreciate there are a lot or questions about this already but I just can't seem to grasp it so hopefully asking the question in my way will help. Background: UK 240v AC domestic system. As I understand it, if everything is wired correctly and there are no faults, I can touch the neutral...
  5. B

    Conductor insulation breakdown

    I’m currently problem solving a lighting circuit issue on a retail park. newish install (12months old) IR of 12M Ohms across all three conductors, getting some very odd IR readings overall, I got a low reading between two separate disconnected cables, sent my meter off to be calibrated and came...
  6. KeenPensioner

    Insulation resistance with broken line conductor

    Hi, I'm not an electrician but I'm studying the material required for the C&G 2394/5 just for the sake of it. I think I understand the theory behind insulation resistance testing (but maybe not!) and the reason the test is performed at 500V (insulation condition, fault finding) and that loads...
  7. P

    duplicate protective conductor question

    Is there a requirement stipulating a final circuit supplying only one socket outlet should incorporate a duplicate protective conductor?
  8. L

    Gas Bonding Conductor in 20mm conduit

    The scenario, Property has no bonding to gas meter. There is a 4mm T+E radial from the DB to an outside socket which is located 300mm from the gas meter (external meter). The 4mm T+E is housed in 20mm plastic conduit running along the external wall. To prevent things looking a complete mess...
  9. G

    Regulation 434.5.2 - Time a conductor can withstand fault current

    Can anyone help me clarify the formula in regulation 434.5.2, the time a conductor can withstand a fault current without sustaining damage. t=k2 x S2 / I2 The regulation states I is the effective fault current. Does effective fault current mean the prospective short circuit current/...
  10. marconi


    Over the last few days I have been stuck indoors because of the rainy weather. To pass the time I cobbled together my simple idea for a FRC live conductor break detector, ie break in L or N. I also have a working demonstrator for detecting a break in the cpc but I will/may post that another...
  11. S

    Industrial Questionable Conductor Size

    I am in the process of installing a 5 core 70mm feeder cable for a DB. 70mm cable lugs are too large for the cores but 50mm fit perfectly. I have taken this up with the cable supplier. Their response was that 50mm lugs are often used om 70mm cores? Having been in the trade for 41 years I have...
  12. S

    Broken PEN conductor

    Attended a seminar today based on EV charging points. The broken PEN conductor was mentioned and converting to TT. 2 things. 1. How often does a PEN conductor go down?? My understanding was that they use PME to reduce this risk further. 2. I asked the question as to should we be installing...
  13. Strima

    Main Earthing Conductor Termination with SPDs

    Here's a question that I was asked earlier. If you have SPDs installed in a DB is it permissible to terminate the main earthing conductor into the SPD first then the DB earth bar? Or must it be terminated in the DB earth bar first then the SPD?
  14. C

    Conductor Operating Temperature H07RN-F

    Hi All, I'm trying to calculate CCC & VD for H07RN-F Single core cable. Used for event powerlock runs. TPN AC - Ref Method C - Flat & Touching Table 4E1A/B covers Single Core 90*C thermosetting insulated cables, which I have used correction factors to convert these values to flexible cable but...
  15. S

    Main Protective Bonding Conductor question

    Hi guys Would appreciate your comments on the following.. I am currently involved in the refurbishment of a building with 2 service heads (both in use) but only one gas intake and one water intake. What are the main bonding requirements in this situation? I am assuming both MET's require a...
  16. V

    SWA cable , TT, do i need an earth conductor in the cable?

    At the origin the installation is TT. Plan is to install a submain to a new db. Not carried out all the calcs yet, but my question is does the swa require an earth conductor in the cable. Basically planning on running a phase and neutral or perhaps even 2 x phases and neutral.(the cable will be...
  17. B

    Commercial Defining what equipment has protective conductor current

    Hi all, I have an engineer who has failed a wall mounted data cabinet because the PDU is hard wired into a switched fused spur, the spur is spurred off a ring main in 2.5/1.5 twin and earth. He has failed it under regulation: 543.7.203 The wiring of every final circuit and distribution...
  18. T

    Main earthing Conductor also bonds water

    Domestic TNCS, main earthing conductor runs to water pipe, bonds via clamp with label, cable is continuous, then runs on to MET in DB. Seems wrong, but cant find specific reg to say so....any thoughts? Thanks, Timotei
  19. P

    High Zs on SWA Armour / New Earthing Conductor

    Hi all I am after some help/Advice if possible please A SWA sub main Distribution circuit has been given a Code 2 Rating on a recent EICR due to a high Zs of 2.8 ohms. The cable is 180 metres long and runs underground in ducting. The Install is from a few years ago when a new Substation was put...
  20. D

    confirmation of earthing conductor size

    Hi Guys just a quick question but what the hell do I put in confirmation of earthing conductor size when the earth is the swa
  21. leep82

    C.P.C in T&E as a live conductor

    I know the thread title sounds bad but hear me out. I have wired an intermediate switch set up with feed at one switch, switch wire at another and twin and earth as my strappers between to an intermediate switch. My customer wishes to use lightwave switches for the three posistions mentioned...
  22. C

    protective bonding conductor size

    Hi guys, I've questioned something at my workplace and after receiving my answer I'm not overly convinced and would like some other experienced gods to chime in :) On a new install in an existing property today I went to bond the Water and noticed it was already done, clearly many moons ago...
  23. GBDamo

    High integrity earthing.

    i understand the need, as I see it any circuit with a likelihood of more than 10 mA earth leakage should be subject to high integrity earthing. This requirement can be achieved by many methods and I can see the sense in some. Using RFCs instead of radials gives two paths so in the event of a...
  24. R

    Coordination between conductor and oveload devices

    A good memory trick for exam conditions for coordination Ib In Iz (Alphabet) the earlier letters are always lower in value than the earlier ones, saves remembering Ib < In In < Iz Ib < Iz
  25. kingeri

    Extraneous conductive part as bonding conductor

    Been nosying about at my brother's new house this week and fixing a few bits and bobs. The electrical installation mainly dates back to the early 80's at a guess and apart from a few broken accessories and a lack of RCD protection (now fixed) it has all checked out okay. PME earthing. Today...
  26. Andy78

    EICR - Undersized earthing conductor

    Doing inspections today and found a couple of properties with under sized earthing and bonding conductors. Earthing system is TNC-S and features 6mm earthing conductor and 6mm bonding conductors. I normally code 6mm bonding conductors as C3 and am happy to do so here too, but should I be coding...
  27. J

    Supply conductor size for 8 bedroom Victorian house

    Hi folks, I've recently visited a large 8 bedroom Victorian house. It has a three phase supply. One of the phases feeds the main house, its wired through a 100 amp main switch/ isolator. The Suppliers Side is 25mm tails but the customers side to the main house consumer unit appears to be 16mm...
  28. J

    What code? bonding conductor

    A connector block has been used to extend a 10mm water bond, what code would you recommend? Thanks
  29. Michaelwgroves

    Can you join Main Protective bonding conductor

    I have a 6mm main protective bonding conductor from a 1981 install; adiabatic equation says this is sufficient and no signs of thermal damage. (Discussed in separate thread). Gas was not bonded, it's a big job to run new cable so I've used redundant water bonding as now all plastic to bond gas...
  30. Marcus Vaughan

    6.0mm earthing conductor to MET on TNS

    Hello. I am carrying out an inspection on a domestic TN-S system. First observation is that I can see 16.0mm earthing conductor fro CU to MET - but then is steps down to 6.0mm connecting to the supply cable. This should be 16.0mm - shouldn't it? I am going by table 54.7 in the big yellow book...
  31. happyhippydad

    Finding a broken line conductor in a ring?

    Hello all. I haven't been posting for a while but I have been 'lurking' as Rpa put it :). Life gets in the way of things! I rarely come across a broken ring, but I now have a broken line conductor on a ring (or rather a poor connection somewhere) R1=1000ohms, R2=0.61ohms, can't member On but...
  32. PLW

    Cables with thermosetting insulation (XLPE cables)

    I understand that XLPE cables operate at a maximum temperature of 90c compared with 70c for PVC insulation. What I don't understand is why the increased temperature permits a reduction in conductor size if XLPE insulated cables are used in preference to cables having PVC insulation. If the...
  33. C

    Main bonding Conductor

    Just your thoughts on this one,recently did a bit of work at a factory unit,there are several units being used by a company. The electrics are really pretty bad,my concern is main bonding of structural metal work,can't really see any Earth conductors to these. In the one area there are steels...
  34. M

    Electrical installation design guide

    Have been sizeing up the size of armour on diffent SWA cables to make sure they are suitable to be protective conductors. Come across table 8.8 page 100 .on this table it says maximum bs88 fuse size (for example) 120mm 4core is 500a, when it also says current carrying capacity is 335 method c...
  35. N

    EICR recommendations

    Just a quick one. Testing a house that's install is about 20 year old. Obviously hasn't got a metal clad DB, earthing is only 10mm. Would you put these down in the reccomendations? Even though these items were perfectly fine when it was installed? Lee
  36. L

    Does it need it?

    hi everyone, I have got a job to do in a local hairdresser to change a consumer unit fed off an economy 7 meter. My question is do you need to test and notify the works like you would in a domestic dwelling? Also is it mandatory that the incoming services of water/gas are bonded with 10mm...
  37. Rocboni

    Earthing and bonding

    Copied this from trainee section to see if I can get an answer, it is talked about a lot on the forum but reading through the old posts I can't determine whether I'm right or wrong. What I'm looking to understand is sub main earthing conductors. Is what I am saying right? So a sub main to an...
  38. M

    Adiabatic equation on distribution circuits

    Now I know this has probably been covered a few times but I'm struggling to come to terms with my own calculations. I would appreciate it if someone could tell me if my calculations are correct. So basically I've done a periodic and some of the CPC sizes for sub mains are less than half the...
  39. haptism

    Earth marshalling point

    Hi all, have a question about an earth marshaling point. Just looked at a building where there is no bonding present at the incoming water stop cock (although a bond has been made somewhere, from a sub CU). If i put a clamp on the incoming water is it acceptable to run a cable to earth bar of a...
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