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  1. N

    Which is the best 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...
  2. Wilko

    Domestic 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...
  3. 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
  4. 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...
  5. 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...
  6. 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
  7. 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...
  8. L

    Max Zs Permitted by BS7671 value

    Hi All, Thank you for welcoming to this forums I just want to clarify that the Value I need to enter 100% or 80% in the last column "Maximum Zs Permitted by BS7671" is it 80% from the table 41.3 from 18th Edition Regs - Page 62 or the value from Pocket Guide 18 Thank you Loges
  9. Michael J

    The maximum value for Zs on a TT system is 50/I delta. So for a 30mA RCd is 1667 ohms

    why is this not the case if the final circuits on a TN-S or TN-C-S system are protected by a RCD? Funny what you think of when you can’t sleep
  10. U

    Why I get netagive value from power meter (powerlogic pm500) for the reactive and Active Power?

    i read data every minute, and some time i get negative values, can any one explain me, i'm not an electrical engineer (i'm IT developer) so please be nice with technical terms.
  11. 1Justin

    Best value fused switch plus 2 module type 2 SPD?

    Has anyone done this yet on a budget? I'm pricing a job to run a submain off a TN-S. I'll need a fused switch incorporating SPD alongside in the same enclosure. Price sensitive. Thinking of a budget Lewden off the shelf fused switch (in 4 module enclosure), ditching the enclosure and buying 6...
  12. T

    Calculation of capacitor value for conversion from star to delta

    Hi does anyone have a notion of how to calculate the capacitance value for the above?
  13. R

    Phone calls asking if I want to sell/know value of my Business

    Hi all, I`ve been trading for the last 8 years, in the last 8ish months I`ve been getting calls from firms asking if I would be interested in selling my business. Also getting calls saying that they have clients that want to invest in the area and would I sell or when I say no they ask whether I...
  14. HumbleWorker 91RT

    Best Sockets for value and longevity?

    Just wondering which sockets you guys tend to go for, your typical plastic units for internal no brushed steel effect types, as well as your external 1 and 2 gang 13 amp. Based on price low to hi, brand perceived view (high quality through to Chinese crap) and ease of installation has good...
  15. E

    When Filling Out A N.I.C Installation Certificate Online *DEFAULT PFC VALUE*

    Why does it try to give you the value of 16KA in the drop down box for prospective fault current. Has anybody else come across this or do they know the reason why? I always put my measured value in but still would like to know the reason they try to give you the above value.
  16. polo1

    Exceeding max adjusted Zs on a board change.

    Testing during a board change, a RFC on a 32A 60898, with rcd protection, you find that the max Zs is exceeded by 0.1 ohms using the no trip setting on your mf tester On the EIC do you - A) simply record the actual measured value B) record the actual measured value and note the position under...
  17. haptism

    R1 + R2 of ring circuit

    Hi for a ring circuit, is there any need to measure and enter R1 + R2 values on a schedule of results ? Because an r2 value is already measured (together with r1 and rn). If I needed a ring R1 + R2 value to calculate ZS (although i would find ZS with a socket tester so really no need; but if I...
  18. L

    Soil resistivity

    Hi, How can I change earth resistance (R) value into soil resistivity (Rho)? Is this formula correct, ⍴ (Rho) = 2πAR (A = Distance between pegs, R = Earth resistance). Regards, L.
  19. haptism

    SWA test results

    Hi hope someone can advise; ive not done alot of testing or filling out eic's and am a bit stumped on this. I have run the usual dead tests on a 3 core swa cable used on a final circuit all tests are good. However the amour (which needs to carry the full fault current), does it not need to be...
  20. A

    Comparing heating usage Propane vs Elec

    Hi there, I do hope this is the right place to post this! I basically want to compare energy consumption in heating between two buildings. Building A has a purely electrical heating system and I can get how many kWh are consumed in one month. Building B has a gas boiler which uses 47kg...
  21. J

    Questions in power engineering interview

    I would like to seek advice from experienced guys because I have interview test for my power engineering as below. Thank you. a) For 600A switchboard, what type of device setting need to do? Can I say that I need to do setting for direct acting for MCCB since more than 100A and earth fault...
  22. A

    Ze/Zs of 3 phase supply

    Hey all, going over some testing before my final assesment. i've heard a couple of times when testing a 3 phase supply using a single phase to earth test you double the reading as your Ze/Zs, so if you test L1-E=0.07 Zs=0.14. also what i have done until now is test all three Lines to earth and...
  23. G

    mixer value on underfloor heating?

    HI all, installed a s plan, well i say s plan, heating up stairs and underfloor down, there is a 3 way manifold for the underfloor heating, a couple of question regarding that pls 1 actuator came , but there is a value i open with that stat so i assume i dont need the actuator ?? also i...
  24. S

    Checking loop tester readings from a sample socket.

    After calibration of my loop tester,I am considering using a socket in the house for future calibration checks and to connect various low resistances in series with earth via a rotary switch to give a range of readings,and if so what value of resistors?Thanks for any advice...
  25. G


    Q, The earth fault loop impendence measured for a circuit is L1.1 0.61 determine showing all calculations weather it complies with Bs7671 what do I need to do
  26. A

    Max permissible ZS for rcbo 61009

    So, when I did my 2391 I&t course I was told to use to values in table 41.3 of the regs for max ZS value for rcbo which provide earth fault, and over load protection. Recently a colleague of mine said you should use the value in table 41.5 which states a max permissible ZS of 1667 ohms. I don't...
  27. E

    Twin and earth testing

    Hi, A quick question, maybe a stupid one .... but it baffles me ,and I cannot find any info on the net. If you do the continuity test on a lighting circuit to get your resistance values, wired in twin and earth, how do you the the value for the earth ? Obviously you link the earth and phase or...
  28. F

    rcd tripping times

    just a quick one doing some rcd tests today, and at x1 value the tripping time was 46mseconds and at x5 29mseconds now i no that as long as at x5 value is under 40mseconds all is ok just thought the x1 value was a bit high so my question is there a max value for times 1 as i must admit not had...
  29. D

    high pfc domestic property

    hi, fitted new consumer in a domestic house. testing. ze 0.16 zs at origin 0.04 pfc 6.2ka the pfc is my problem, ohms law would make the pfc work out around 5.7Ka (using 0.04 as your resistance) (with all paths in place) using megger 1553 two lead test, high current, pefc and pscc are the...
  30. L

    2394 question

    Hi I am due to start the city and guilds 2394 course next month. I thought that I would have a look at some past questions to see what to expect. I am having trouble with one of the questions and was wondering if anyone could explain the theory to me. 16) The measured value of loop...
  31. A

    RCD tripping times at 1x and 5x

    I understand that when carrying out RCD testing an RCD should trip within 300ms at 1x and 40ms at 5x but is it common that on occasions for the RCD to trip quicker at 1x than 5x. I never had it occur personally. I am just looking at some old certs and on some circuits the RCD is tripping...
  32. P

    Earth Fault Loop Impedance

    Hi all, I am hoping someone can clarify if my understanding on earth fault loop impedance testing is correct. A low efli is needed so a protective decive can operate in the required time, the lower the z the quicker it will operate. ZE= External resistance from borad to supply, board...
  33. N

    Megger mft1710 multifunction tester - nottingham

    Megger MFT1710 electrical tester Very Good Condition Received in part exchange when i sold my old phone. I have no use for it and i'm only interested in getting the cash it owes me. Comes as pictures with ***no box***. I've browsed through eBay and know the value of these tester's so no silly...
  34. S

    R1+R2 of a ring circuit

    I know you take the highest reading, though not sure if you take the highest reading on the ring circuit or a spur off the ring circuit? cheers
  35. 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?
  36. T

    AC Circuit Theory Maximum Power Transfer

    Hi Everyone, I'm trying to determine, for the network shown below the value of the load Impedance that will dissipate the maximum power and the value of this power.I already calculated the Rth , but I'm stuck on P=I2R.Can someone help please? Thank you.
  37. J

    Wylex main switch

    Hi , could someone help me please , I did an eicr yesterday. Few questions now the ccu is the old Wylex board with push in type mcb's 3871 type , what is the main switch bs en number ? Can I say its a limitation as it's not evident ? the Ze I recorded is 0.63 ohms it's a tncs , is this a c2 or...
  38. matt1386

    Trainee - Advice please

    Hi all, sorry if this is in the wrong section, wasnt too sure where to post it Basically ive started college a few weeks late so im having to play catch up at home to get to where the rest of the class are at Ive come across a question on my work sheet which im not sure how to work out and...
  39. M

    Testing question

    hi all I am currently working as a mate the contractor I'm working for which I shall not name does the following test. he only measures zs doesn't do continuity r1 r2 he says that there is a good earth return if these results are within those permitted, he takes his ze from his zs to obtain his...
  40. S

    Industrial stand alone generator system

    any help on this one very much appreciated. We have a stand alone 3 phase workshop any generator installation. The supply is TN-S, seperate PE back to the generator, which has its own earth electrode. Ze for the system is in effect the short circuit impedance at the generator between a live...
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