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  1. T

    UK Maximum Zs Value Exceeded

    Hi I have recently done some testing on an installation. A submain is fed from a B50 mcb and has a zs of 1.10ohms. The maximum for this is 0.87. The cable supplying the submain is a 25mm 2 core swa with the armourings used as the cpc and is roughly a 70m run. Both glands and earth leads have...
  2. J

    What equation can be used here to find the value of the capacitor?

    Hi all, I'm struggling with these questions for this circuit as the equations I have in order to work out impedance etc all seem to need the value of the capacitor so I'm at a loss now and was wondering if there was a way to work out the capacitor value or if there was another equation I could...
  3. J

    2396 - Calculated Zs value

    Hi All, Any help would be greatly appreciated. When calculating the Zs for a circuit specifically for 2396 do you have to incorporate the on site guide multiplier tables I2 and I3? It seems to be dependant on what training material you use.
  4. F

    Zs values recorded results.

    Evening everyone, I was taught when carrying out Zs testing to test both L-PE and L-N and record the highest result of the two tests for my Zs column. However, speaking with a friend he informed me that this is wrong as Zs = Ze + (R1+R2) and not (R1 + RN) which is right and never crossed my...
  5. Gaz92552

    Max Zs value for AFDD

    Does anyone know where I can find the maximum Zs values for AFDD's? Table 41.3 refers to 60898 and 61009-1 but AFDD's are BS 62606
  6. newfutile

    Which value to record on EICR?

    I work for a housing association where i have to conduct EICR‘s then conduct remedial repairs until a satisfactory report can be issued. while inspecting bin store lights (fed by 1.5 3 core SWA) 1.56 was the ZS on initial inspection. The swa outer was not earthed at either end. now i have...
  7. gmdaly

    meaning of 'design' value for max Zs?

    Hi all, I have an assessment exam question that asks for the design value for a 32A 60898 MCB max Zs. By 'design' value is this the regs tabulated value (working temp) or the lower value 80% for testing in ambient?. With no other information the word design is throwing me as it seems like it...
  8. Anthony Deakin

    How to work out no value of Zs to Ze being 0.35 ohm

    Hi all, ive been asked this question A direct measurement of Zs cannot be carried out. The supplier gives a Ze value of 0.35 ohm and the line and cpc resistance as 36.24 milliohm/m. If the circuit is 31metres in length the earth fault loop impedance will be? What is the formula please? Thank you
  9. A

    Low End to End R2 value Help

    Hi I’m still learning so forgive my stupid question. I’ve been testing a ring main off 4mm/1.5mm singles in metal trunking and conduit. My reading are: L-L 0.91 N-N 0.90 E-E 0.80 I was expecting my R2 value to be 2.66 x 0.91=2.42 I this purely parallel path related?? many thanks
  10. H

    would anyone know the actual value of the negative rail (-Vcc) for the ICL7660?

    i have been ficking through the datasheet but i cant seem to find it :(
  11. R

    The measured value of loop Impedance for a circuit is 2.4 Ohms

    Hello trainee forum thank you very much for letting me in here and as a consequence hopefully helping me to develop my skills and knowledge. I'm currently focusing on the 2391 and have enrolled myself on a course with no previous Inspection and testing experience or Knowledge so I do feel kind...
  12. O

    Best value fire rated downlights

    Hi everyone, Been fitting the cosmos eco from Screwfix, but more time-consuming as yiu can't loop in / out. What's you're best push in easy fit alternative...under 72 quid?
  13. J?OLsinner

    GRANDFATHERS old-style scooped forced air torpedo heater sentimental value!

    Recently had this part burnt out . I have tried to contact numerous parts people, companies, and diffthat didn't
  14. N

    earthing scheme suitable for worst/large value of soil resistivity in order to get earth resistance value below 5 ohm?

    i don't the exact value of the soil resistivity as no survey of soil sample is carried out at the site .However Copper earthing electrode 50mm diameter of 2.5 m is driven where its circumference were filled with chemical compound power to the height of rod and earth resistance was found to be...
  15. Wilko

    Properly priced EICR is good value

    Evening All I’m doing a few EIRCs for the rental market and I thought I’d share my recent experience. I was asked to inspect a 2 BR flat, just on 5 yrs old. The flat is in excellent condition, it has always been rented and has the original EIC and the most recent gas safety cert. Both...
  16. C

    Ohm value of transformer

    For those of you who work with onsite MV-LV transformers, does anyone know the line to earth ohm value of a transformer? I'd like to include that in the loop impedance path. Similarly when stepping down LV to LV. View: https://Upload the image directly to the thread.com/a/PIsy0nt View: https://Upload the image directly to the thread.com/JwUM0fv
  17. Zdb

    Computer earth leakage value (mA)

    I know every computer/equipment type will have a slighty different earth leakage stated by the manufacturer, however I was wondering what people use as a "rule of thumb" value when designing ring final circuits in offices intended to be used for computers. I was thinking 1.5mA per computer inc...
  18. S

    IR value on ring

    Carried out an EICR on an older installation at the start of the week prior to a mains board swap over. I had a low reading on one of the ring main IR tests, between live & neutral 0.02MOhms. I couldn’t see anything plugged in or switched on anywhere on the circuit & at that point I couldn’t...
  19. H

    need a capacitor across relay contacts to arrest arcing. wondering about type and value ?

    wondering what capacitor type and value across relay contacts at 7amp ac load to avoid arcing
  20. A

    Max Zs value for MCCBs

    Hi Guys, in an installation with one main Distribution board and several submain-DBs, do when you measure Zdb on a submain-DB incomer? and do we need to verify the Zdb value with the upstream protection device?( for example, a 250A, MCCB on the MDB outgoing). If yes, how can I get the max Zs...

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