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values

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  1. kkkkk

    High continuity resistance on ring final circuit

    Hi peeps I have continuity measurements on a ring final circuit of: L/L 1.4, N/N 0.78, E/E 1.7 Loose connections somewhere? There is a new CU with RCD. Insulation resistance measurements are good. There is a boiler added into the circuit as a spur. Any suggestions or comments? THANKS!! :) :) :)
  2. D

    RCDs raising zs values

    Was at a property toady which I've done previous work before including fuseboard change. All i did today was change a few socket plates over for new ones. Took some Zs readings and noticed they were very near the limit of being acceptable ie: 0.92, 0.98 etc. Took a Ze at the board with main...
  3. SJD

    Testing MCBs

    Much though I don't like it, once in a while I use a second hand MCB - for one that has long since gone obsolete and new ones are unavailable. What about testing used MCBs before reusing them, does anyone actually do this? I just tested a 5A MCB at a couple of values of loading, it seemed to...
  4. M

    Earth Faulth Loop Impedance HELP!!!

    Hi can somebody shed some light upon correction factors for earth fault loop impedance. I know that the vales of zs in bs 7671 are if the conductors are running at max temp ie worst case scenario , am I right in believing that if you get a measured result you apply 0.8 to it?
  5. L

    High measured Zs values

    I have some remedial works to do on a fairly large commercial installation. The majority of the submains from the main panels are protected by 63 and 100A MCCBs, and as a results of a high Ze (0.24), a lot of the submains Zs’s don’t meet the regs figure. Replacing the cables is not an option...
  6. S

    Origin of Ze Values...

    Where did the nominal/limit values of Ze for TNS and TNC/PME originate from? I mean the values that are listed in OSG and various other publications, but why? Does it really matter? As long as your Zs for a cct falls within the max for the protective device...
  7. S

    Max Zs Values

    Anybody know where I can find Max Zs values for BS88-2 fuses over 200A please? The regs only go up 200A. I know I can contact manufacturers and ask them, but wondered if there is a quick reference anywhere? Thanks
  8. P

    bs7671 15th ,16th Zs values

    Can any one be kind enough to post the old Zs values fir fuses from the 15 and 16 edition thanks
  9. K

    ZS values on TT system

    I did a periodic and got some strange zs values. Can anybody explain these readings for me. Ze 14.1 Ring main r1 0.53 rn 0.53 r2 0.80 so r1+r2 = 0.33 measured zs came up with 30.3 Another ring main with very similar readings Lighting circuit ZS was 14.4 which is more like what I would expect to...
  10. J

    Will a reading higher than given in 7671 for Zs values be okay if protected by RCD

    I might be COMPLETELY wrong.... but I have recently finished my level 3 in college and I'm sure I was told that if a Zs value is higher than the max reading in BS7671 it's okay if it's protected by a 30mA RCD, so it passes. I sort of remember writing 'satisfactory' on the test form next to Zs...
  11. P

    max zs of large fuses

    BS7671 tables only go to certain size fuses eg how can I find max ZS of 400 amp BS88 - 2 on niceic test sheets they ask for a max value out of regs table I have only managed to find a busman fuse chart which differs been told by employer to use these values on sheets any input would help thanks
  12. S

    Zs on rcbo

    Hi guys had a conversation with the boss in the office after work today about a zs I got on a 32A c type rcbo bs 61009, the earthing system is TN-C-S, he said he wasn't worried I got a zs reading of 0.90 even though a type c 32A rcbo has a max zs of 0.72 his words were "it's just like a TT...
  13. oxford 12

    Neutral current values

    Been to a flat today to investigate why the neutral at the meter was carrying more current than the phase.This was spotted when a smart meter was clamped to the tails at the meter.Done some load checks myself with a clamp meter,did find some differences between phase and neutral when different...
  14. S

    MCB Energy Let Through Values

    I know that MCB's are grade with an energy let through rating of 1, 2 or 3 and 3 being the highest. I also know that it relates to the sizing of the cpc. However that is about where my understanding ends, I have read a few threads and documents, but still having trouble getting my head around...
  15. sparkymalarky

    MCB's 230V/110V Zs Earth fault loop impedance values

    I give these out to some of our younger electricians in the aim to get them familiar with such values. Probably old news to most of you fellas but sure it won't do any harm. Calculations from BS7671 anyway, just handy to have a hard copy other than BGB. Cheers John
  16. K

    ZS for Push button Wylex 3871 Type B fuses

    Hi, I have old style Wylex push button breakers at CU, and these are labelled as BS 3871, Type B and are 5 & 30 amps. I can not find any ZS values in the regs for these, but see these labelled as N/A. Any help apprecriated. Thanks
  17. F

    Question about Insulation Resistance values

    Job is to extend a kitchen ring circuit, and have a question about Insulation Resistance values. Tests on existing ring (2.5/1.5 t&e) carried out and results as follows - Ring continuity (end to end) R1-R1 = .38W RN-RN = .42W R2-R2 = .64W Continuity W R1-R2 = .34W Insulation Resistance MW...
  18. M

    EICR coding

    Hi guys After advice doing EICR report on a welfare set up on a building site I am after advice on my coding welfare set up is on a tn-s protected by 100ma main rcd tripping out at 42.3ms at x1 I have some covector heating circuits on a c16 mcb but zs is to high for the c16 what code would...
  19. N6rul

    2394 past paper scenario need help please anyone.

    Scenario The building has its own supply and forms part of a 230 v TT System. Ze and PFC have not been measured. All circuits are wired in 70 degree Celsius thermoplastic single core cables, with copper conductors, in surface mounted, galvanized steel trunking and conduit. All accessories...
  20. SibertSolar

    Section 2.1.2 on DTI Guide - Voc/Isc mulitpliers

    Guys, As we know, for switches/cables/isolators etc, you need to multiply your Voc values by 1.15 and Isc values by 1.25 to calculate the relevant max values for suitable protection. However, does this apply to MPPT or Max DC voltage/current input values on inverters? Any thoughts? Thanks Andy

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