submain

submain

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  1. Yellowhammer

    TT sub mains and discrimination..

    Hi, Just a quick sanity check really around rcbo discrimination.. but also RCDs being used as L-E fault protection. Scenario being a garage board change. Setup is: garage sub main fed from a main house CU. Initially wired in 10mm t&e with a 10mm earth along side it, run entirely in the ceiling...
  2. 2

    Calculation submain cables

    Hi. Im looking for some advice when calculating submain cables. Basically there is a new connection of 80Amps that is to be used for a dwelling and a small workshop. I had thought taking to a feeder box with one submain and then two feeds away into the buildings. A direct run from dno to...
  3. B

    SWA to submain and NSH

    Hi guys, Can I ask you a DIY question? I'm refurbing a detached garage and adding a garden building. Garage currently has a submain supplied by 10mm T&E on catenary from the house. I want to replace this with buried cable from house to garage submain, and from garage submain to garden...
  4. T

    Submain to flats ryefield board

    Been asked to connect submains up Have a 7 way ryefield board to split with 60 amp fuses in,has red fuses fake ones in each unit and meter will be there too Do we require a main switch fuse for each sub-main or is the 60 amp fuse okay in each. Isolater will also be after the meter Cheers
  5. F

    Replacement DB to Submain RCD advice

    Morning guys, I would like some advice, currently at my workplace, I am replacing a DB and existing wiring in a warehouse. One of the ways feeds a sub-db to a small office. The sub-db is an old wylex rewireable db with 3 of the 4 ways used (Sockets,sockets,lights). My company does not want to...
  6. J

    SWA as cpc to submain-Suitability, & PC's on RCD's.

    Been looking at a CU change in a small office and would appreciate comments on the following. Office is supplied from the mains intake in the warehouse via a 2 core 16mm SWA buried under concrete with the SWA used as cpc (60A BS88 is the protection). Mains intake in the warehouse is a 3 phase...
  7. lozarus

    Melted my brain thinking about EIC for a circuit on a submain...

    Apologies if this is in the wrong section - appreciate it's more of an educational question. That said I have 2391 - but the classroom environment is very different to out there in the field and I'm only really starting out in my inspection & testing journey - so please understand if this seems...
  8. D

    Split Con Domestic SubMain

    Now we used to see a lot of this when we did new build flats etc But I think this domestic sparks is the first one on Youtube that I have seen use Split Con cable on a house board change
  9. T

    TP 100amp submain on BS88-2 fuses, but the Zs is above the Max allowed...

    I am helping a local football club who are having some issues with Zs being too high on the submain. They have the supply Henley blocked into a 100amp TP switch fuse (BS88-2) which then feeds a 35mm 4 core SWA 95m to an isolator in another building which is being built. The Ze at the incomer...
  10. J

    Submain for a cafe

    Hi everyone, A local pub is changing one of there function rooms in to a cafe, there plan was to have all gas equipment so i done the cable calcs and installed a 16mm 3 core swa as the submain cable from the main 3 phase db in the pub to what was going to be a single phase db in the cafe...
  11. S

    Overload Protection of "submain"

    Hi can someone help me with this situation please. The service head/meter is in a brick built housing box in the middle of a field, we are running power to a house some 40m away from it and im not sure of the most suitable method of protecting the 25mm SWA cable from overload. The DNO fuse is...
  12. 0

    TT Submain and switch fuse

    Another question! I'm designing for a TT system, there's going to be one 10 way Rcbo consumer unit for the house, less than 3 metres away from the DNO cutout, I'm going to swap the main switch with a 100ma Stype rcd to provide fault protection ( I'll be fitting a tails clamp inside the CU and...
  13. J

    Split con submain

    Ok I'm not a practising sparky but I'm not a clueless diy'er either. Please don't start dissecting me.. We have got a couple of barn conversions to holiday lets happening at the moment. One is a single barn that has been designed so it can be let out as one single house or two mini house. Two...
  14. K

    Parallel sub mains

    I currently have a shop which has 3 phase 6mm cable running to it but the shop is only allowed single phase, currently renovating and they need more than a 32a supply. Can I parallel 2 of the 6mm and upgrade the quicklag breaker to a 50a at the MSB and make it a 50a main switch at the shops sub...
  15. Dartlec

    How to protect existing 16mm T&E feed to CU when converting to sub main at source

    Currently quoting for a job that needs to be done next week and working out how best to proceed, so thoughts welcome. Current situation: -->PME incomer that has just been moved by UKPN within a porch (brick built permanent type) from one wall to another. -->60A main fuse -->Meter -->Large MK...
  16. J

    Has anyone come across this type of cable for a submain.

    hello I did an EICR today on a flat probably about 10 years old. everything fine except the usual C3s for non rcd protected circuits and for plastic boards etc. my question is has anyone come across the type of cable I found going from 80mcb near cut out to con unit in the flat. at first I...
  17. O

    domestic sub main question (fusing)

    Hi All, Been called to a customer property for nuisance tripping which i have resolved but when inspecting installation i have found an issue. The customer has a cabin at the back of the property with a CU inside, fed by 10mm SWA. it has 32a RM, another 32a (still locating its purpose), 16a...
  18. bigspark17

    Submain rcd fault protection

    If a 2 core swa was run for a submain to an outbuilding with no extraneous parts in it, but the zdb reading was well over the maximum earth fault loop impedance. Could an rcd time delay be installed at supply end to cover the submain ie increasing its new maximum zs reading? Hope thats clear ?
  19. Dartlec

    Judging imperial submain T&E cable

    Doing an EICR on a top floor flat recently and run into an issue I often do - which is judging imperial sizes when they are larger than the standard 1/1.5/2.5mm equivalents. In this case, the flat is fed by a Twin and Earth cable that is somewhere around the 10-16mm range equivalent, with an...
  20. 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...

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