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  1. The apprentice

    max volt drop to sub board

    max volt drop to sub board 3 core swa 137 meters ?
  2. 1

    Max Zs @ 80% TN-C-S System

    Morning all, I'm currently finishing off my Lvl 3 C+G and I just need to finish off my design spreadsheet then I'll have completed it. I've one last column to fill in "Max Zs @80%" the design is based on a hotel using a TN-C-S supply. I'm just wanting to know where I can find this information...
  3. Ruairi Hansen

    Max zs readings for TT

    Hi just wondering what people are noting as there max permitted zs reading on test results sheet for TT systems? 200ohms or 1667ohms?
  4. P

    Domestic 45A breaker max Zs values

    Hi all, Why is there no max Zs value for a 45A type B breaker in table 41.3 of 18th edition? What value should be used as max value on schedule of test results? Cheers.
  5. happyhippydad

    Working on electrics with 2 supplies.

    I have little knowledge of PV. When working on circuits supplied by a domestic CU, is it fine to just have the main switch off in the CU or should you be isolating the PV as well? The stickers all over the CU's in this example all say to disconnect both supplies.
  6. 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...
  7. J

    Max Permitted Zs for 3036 semi enclosed rewirable fuse...

    I'm just hoping I can cross reference my knowledge or be corrected by someone on a quick query. It's a test question I'm doing but I'm querying the answer I've been given. I want to find the Max permitted Zs on a 3036 45A fuse. I was under the impression that I should reference table 41.2 in...
  8. C

    Commercial Max disconection times

    Having a debate on site as to disconection times on a TN system, does the 18 addition say 0.4 up to 32amp and 5 after and 5 for distribution circuits?
  9. B

    Max Zdb TNS system help

    TNS system Ze is 0.3 ohms all good now sub mains is fed from this but I’m getting 3.15 ohms still should be under 0.8 ohms? Thanks
  10. C

    Diversity applied, max load well over.

    Seen a couple of threads on diversity and excessive max loads recently. Just had a design from a clients for their house. Applied diversity is 196A. Having 2 9kW showers install, A 4kW instant water heater, a cinema room, ring main per floor, lighting circuit per floor and ring main for...
  11. M

    60A Fuse box - is (typical) over 60A max load OK?

    This relates to one of those old 60A Wylex Fuse boxes that has been upgraded with MCBs - I know it would be a very good idea to upgrade, but the question is, how does the "Max 60A" rating moulded on the box apply? The main fuse is 60A and the load after diversity calcs is 89A. I am aware that...
  12. B

    Max Demand for mixed use commercial units

    Hi, Looking at a potential job. Agricultural buildings being divided into 10 mixed use units of around 1000 sq ft each. Present supply is a 100A TPN incomer. Future use of units is unknown at this stage, but planning is for B1 B2 so uses could be anything from a warehouse with a bit of lighting...
  13. C

    Max zs on double pole mcb

    I am filling out test sheets and have a merlin gerin D32 C60 HD double.pole mcb. The rating on the mcb says 415V feeding 2 feeds to a canalis busbar. BS7671 States max zs for D32 0.4 secs is 0.34. Is this just for single pole MCB? I have also check my max zs value from manufacture stating...
  14. B

    BS 7671 max surface temperature under fault condition ???

    Can anyone give me some clarification on the following. I am installing some Osram Planon Plus led light panels into a temporary building and have been told the transformers need to housed in an enclosure as they do not have the correct markings for BS7671 "max surface temperature under fault...
  15. jackhammerJIM

    Commercial sub mains exceed max zs of mccbs

    Thoughts required on todays scenario . Commercial premises fed from 100 amp 3 phase TNS supply ZE 0.40 feeds 80 amp 3 phase switch fuse (max zs 0.57) feeds 400 amp mainswitch protek panel in 35mm swa 16mm earth 125 amp mccb (0.24 max zs) submain exceeds max zs at 0.57 Had this down as a...
  16. spud1

    What if a circuits Max Zs is exceeded but the circuit is protected by an RCD?

    Just processing an EICR and noticed a couple of final circuits measured Zs values (fed from a sub distribution board) slightly exceed the Max permitted Zs values for the OCPDs that protect them. Obviously I will note this as a design flaw in the observations, but I just wondered, from the...
  17. S

    Industrial max zs for 1492 and 1489 allen bradley breakers

    Hi we are using allen Bradley 1489 and 1492 range of circuit breakers, and I cant find the max zs values on any of the data sheets, does anyone have a list of them? Many thanks
  18. gazdkw82

    Maximum Zs values for BS3871

    Where can I find the max Z's value for a BS3871, type 3, 32A MCB? Iv had a look through BS7671 and done some searching online but I cannot find it. IV found some tables with listed Zs values for a 3871 but I have no idea where they originate from or how old
  19. Lekky1

    Exceeded max demand questions

    Hi guys, I have been asked to fit a ring main in a utility room currently being built with a outside socket and a lighting circuit with 4 led lamps and a outdoor light, this much I am comfortable with. My issue is with the max demand, The current consumer unit is loaded to the max with 212amp...
  20. haptism

    Varilight Dimmer max loading

    Hi, hope someone can advise. Ive just called Varilight helpline in regards to max loadings on their 300w trailing edge LED single gang dimmer. They tell me that I can have a maximum of x30 10w leds on the dimmer. Most info out there regarding dimming LED suggests to divide the dimmers wattage...