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  1. L

    Submain/RCD Selection

    Hi there, I am new to this forum and I am finding the help very useful. Could someone please advice me on the following. So If I have a 60A Cutout fuse to the property how do you size the main switch, could a 100A be used. Also how would you size the RCD’s, why would one be 63A and another 80A...
  2. H

    Short circuit bypasses mcb and trips submain mcb

    Good evening A cable was loose in a ceiling void causing a short circuit this didn't trip the 10 amp 6ka type b mcb but tripped the 50 amp type b 6ka mcb that supplied that board back at the mains. I am wondering why this occurred other than me thinking the local protection isn't very...
  3. MarkRibbands

    Augmentation of existing submain. Complicated layout. Advice please!

    Apologies for the complexity of this question, but there’s no easy way to explain it. This is a remote Norfolk house and workshops, developed over 30 years. Due to diversification, building B on the plan needs more power than originally expected, and building D is a recent addition. I’d...
  4. KeenPensioner

    No RCD in sub main

    Hi, as I've said I'm not an electrician but studying C&G in my own time and have worked as a mate. I've just had a qualified sparky upgrade my CU to a split board 10 way dual RCD. He has run a 4mm2 cable (from a 40A MCB protected by one of the RCDs) to my hut and will be coming back to wire up...
  5. HoverSPRX

    Commercial Max Demand/Diversity Query

    Hello All, Iv been asked to pick up the remedials on someone else's EICR that was done last year on a school for Deaf Children. One of the items listed on the report is the conductors leading to the sub mains from the main panel are undersized. I popped the cover off to have a look and sure...
  6. Gakure

    Summer House Submain

    Evening, may I pick you brain guys? I have wired a summer house about 30m away from the main board. I have used 32A at DB1 (not RCD protect) and 6mm² 3core SWA, where I have connected both black and sheath (sleeved) at both end as CPC. In the Summer house I have used shed consumer unit 1xRCD and...
  7. P

    Sub Main Design Calculations

    Hi all, new to here. Just designing a sub main, very long time since I have done this so just wanted some thoughts. Its to a summerhouse sort of set up that will be at the bottom of a very long garden at a later date (sockets, lighting and hot tub planned from the board). Patio is getting done...
  8. V

    ring circuit for a submain?

    trying to find answers in the reg book, but is there anything to say you can't install say a larger ring circuit for a sub main? to reduce volt drop / cable size etc. Normally you would obviously install a large enough cable, but would this be acceptable , whats our thoughts?
  9. C

    Domestic shower submain

    We are installing a new shower, electric towel rail, light and fan in a bathroom. The existing mains board is a old wylex rewirable. Gas and water is 10mm bonding from the MET in the meter cupboard. The existing mains board is litrelly inaccessiable at the back of a kitchen cupboard and would...
  10. B

    Switch fuse for tt submain

    Hi, My solution in this scenario has always been to get a Lewden switch fuse unit, and replace the 100A main switch with a wylex s-type RCD to achieve earth fault protection. With this new requirement in the 18th, am I no longer going to be able to do this? If not, does anyone know of an off...
  11. T

    Submain Supply 100a 100mA

    Installing a 25mm 3core swa to feed an exisitng consumer unit due to the SEB moving the supply. Planning to use a 100A 100mA time delayed rcd to feed the split load rcd board. Sound ok?
  12. J

    10mm t&e submain cpc

    I know there’s the adiabatic equation to work earth size but generally if you install a twin and earth cable for distribution, do you need to worry about the smaller cpc size My situation is 20 metre 10mm t and e run and not using it to provide earth bonding. Will the 4mm cpc be adequate. 50A...
  13. S

    TT submain to summerhouse

    hi all, Looking for opinions for a job I’ve been asked to do. Supply to summer house\workshop approx 8m away. TT system as out in the sticks. They want a couple of sockets and lights so going to give them a 25amp supply House cu is split load job which is full and dosen't have a 100ma main...
  14. N

    Flat Submain Supplies

    Looking for some advice on the best way to supply a 60amp submain to 12 flats which are to have their own meters within each flat (maybe) and who is responsible for doing the work. The project is a large ex club not a typical Block. I imagine the new 3 phase supply will be in to a ryeland...
  15. C

    EIC for submain db rewire

    Part Rewire to do, small shop on a large premesis 4 lights, 2 sockets, 2 spurs...The existing DB(DB4) which is staying, is fed via 32A mcb from a sub main DB3. Fed by 63 A mcb in another DB2 which then goes to DB1 which is connected to origin. Took a while to chase through as all DBs are in...
  16. B

    NICEIC Certification Scheme Certifying Submain using niceiconline

    Hi, trying to work out how to put in figures to certify a sub-main install from origin to consumer unit using niceic online software...Tests all done but can't figure out how to make it look sensible for the certs! Thanks
  17. S

    Amendment 3 and Upfront RCD/Overcurrent protection for TT Submain

    Hi all, Currently looking for something to protect a Sub Main in a house. Supply is TT and consumer unit is to be located aprox 10m away from the incoming service. Sub main will be 25mm armoured, and all final circuits will have RCD protection. As far as I can see, I will still need an up...
  18. T

    Extending sub main cables?

    Hi everyome We're refurbing our lower ground flat within a Victorian terraced house, and there are 2 flats above. Contractor has knocked out all relevant walls and found services running through what is to be open plan living room. So we need to relocate the service run to the flats above. Gas...
  19. T

    Shed submain SWA RCD protection

    Hi all, Went to a house on friday due to sub-main to shed not energising. This was simply due to the MCB playing up. I flicked it on and off a few times and it works fine now. However im not happy with the way the submain has been installed poorly. The sub-main is in the form of a 3 core SWA...
  20. G

    no rcd circuit on 5x5 splitload board

    HI all curently have a 6x6 split board, submain on circuit 1 to another split board, is there a way i can get this off the rcd or make it a high integraty board, need the submain off the rcd, 50mm everywhere so no isssues photo below DSC 0054 - cheers Grand
  21. V

    30mA rcd trips at 17mA when submain connected mcb is on...ok when submain mcb is off

    Hi all Ok...been to a job today with a random tripping 30mA rcd its a bit of a full on a undertakers.... 3p cutout feeds 3 main switches...1 for a workshop db...for a flat over the undertakers...1 for the undertakers.... from the undertakers mainswitch...we have a swa submain to a...
  22. V

    Earthing on a domestic TT supply system with submain, advice needed please

    advice needed please , what is the correct thing to do. The scenario: -meter position and switch fuse @ front of house , with 100mA time delay protecting submain (TT SYSTEM) -the above submain supplies a 17th ED split load DB at back of house (2 x 30mA rcds etc etc) -submain is only 10mm T+E...
  23. S

    rules and info on running a pv system on a sub main board

    i have been asked to quote a pv system, the easiest board is a submain which is fed by a 16mm cable which is big enough for the pv system i want to install, but does the pv installation still work the same through a sub main, the main consumer board has no spare, and the sub main has lots of...
  24. P

    Out Building Has No Earth

    Hi guys, working on a pir yesterday, 2 buildings, readings in main building fine. 10m away there is an out building getting feed from an isolator "in main building" earth reading 50ohms. Can i supply a new earth via a earth rod for the out building and put a rcd on the main switch at the...
  25. F

    Ipfc/Ipsc measurement at 2nd distribution board

    Hi, My first post - hope someone can help. I need to test the prospective fault current at a garage consumer unit. The unit is supplied from an RCBO in the main consumer unit. I intend to carry out the test at the incoming terminals of the garage consumer unit switch with everything switched...
  26. R

    Domestic RCD Question!

    Hi new to the forum so Hi again. Quick background of myself, I am a time served electrican but still new only 22 I have the 17th and 2391 however my background is industrial hence havent done much with houses in the past anyway.... Im looking to put a 2 way garage RCD consumer unit into my...
  27. L

    very low pfc on submain board

    hi all hoprfully someone here can answer this question for me: i tested a sub mains today and i only got 0.35 KA is this normal for a submains as at the main mainsboard the pfc is 3.3 KA the main fuseboard has a rcd main switch so at the submain i had to use no trip pfc not sure is this makes...
  28. T

    PUB... Cooker Circuit ?

    Well, its not actual a cooker circuit but didnt know how to title it. Its a circuit to a long plate warmer thing.. being used for a sunday carvery. Its 6.3 kw There is a Submain in the pub kitchen, with few sockets, lights and extractor. it looks like the submain is fed by 10mm swa, 125a...
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