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  1. M

    Max Earth Fault Loop Impedance for OverCurrent Devices Before Amendment 3 and Now???

    Maximum Earth Fault Loop Impedance for OverCurrent Device was calculated 230/(MCB Rating*5) * Rule of Thumb is that correct? And how are they worked out now after Amendment 3?
  2. M

    Loop Impedance tester electrical circuit

    Hi A quick one I was wondering if anyone knows how a multifunction tester performs a loop impedance test. I understand how to perform a test and what the results of a loop impedance test give you in working out your PSCC and earth fault current. I use my Fluke multifunction tester every day at...
  3. R

    Testing Loop Impedance through RCD.

    Hi, installed some circuits in a factory. The circuits were tapped off of a busbar that goes straight to the main switchgear. From this I installed a Chint RCD, which then goes to 2x Chint TP MCB and 1x Chint SP RCD. One of the TP MCB´s goes to red commando sockets and the SP MCB goes to blue...
  4. J

    RCD impedance

    Hi everyone, I appreciate this is probably a really silly question. I’ve come across the below test question and although I know how to find the answer, I don’t understand why we would need to know what the max permissible earth fault loop impedance is in relation to a 30mA RCD? I hope someone...
  5. A

    Earth Fault Loop Impedance Test for lighting circuits

    Hello guys, Do you do Earth fault loop impedance test for lighting circuits during periodic inspection ? do you measure it at the lighting point? what is the percentage of lights you test? Thanks alot in advance
  6. D

    Megger loop impedance irregularity

    Hi, I have a Megger mft1720 and the low current loop test isn’t working properly. Just wondering if anyone else has had issues? Readings are stupidly high compared to the high current test, and this can be made even worse if there’s an rcd in line......
  7. M

    Industrial Excessive earth fault loop impedance

    I work for a hotel chain and recently we’ve had our 5 yearly test they have 8 circuits from our LV panel with excessive loop impedance readings !! So apart from either introducing an rcd or dropping mcb ratings or type is there any other way of achieving satisfactory readings ?? Also if I have a...
  8. LewisM

    6A MCB Tripping on Earth Fault Loop Impedance Test

    Hi, just finished a partial rewire at my sisters house and when testing the two lighting circuits (up&down) the 6AMCB trips for both circuits individually, I thought the MCBs might just be sensitive to the test but the smoke alarm circuit also 6A is fine when testing, R1+R2 and IR test all fine...
  9. Gary Tollison

    Earth fault loop impedance, initial verification, multiple DB

    Hello. Not sure if this is the correct forum to post this in (still trying to work out where the trainee section is). Just been doing some practice fault-finding online. Found this scenario: After doing initial verification on an outbuilding with its own DB, which is supplied from the main DB...
  10. N

    earth fault loop impedance calculation

    hello all could anyone help me i am doing my 2392 and i am a little stuck i have been asked a question which is using the following measured value of loop impedance 0.5 (40amp bs en 60898 type b mcb) ferfering to the maxium tabulated value given 1.15 show by calculation if the measured value is...
  11. T

    Potential earth loop impedance issues for second floor flat

    Hello! After years of renting I'm currently in the process of purchasing our first property. We've had an offer accepted on a 1 bedroom flat in Surrey. However there are questions over the electrics, and knowing little about electrical wiring I'm a bit stumped on how bad the electrics are and...
  12. Gary Tollison

    Earth fault loop impedance - textbook values vs BS7671

    Hello. I'm in the final stages of completing my electrician course, and I find myself confused (again) by EFLI. In the textbook provided is this: Uo 230V see below for each circuit. Calculate the maximum Zs for each circuit: Complete the table. The answers given in the textbook are said to...
  13. C

    Refurb works In offices

    Just your thoughts on this one,doing a part refurb on existing offices,no initial verification or certs found anywhere. Premises rewired bout 1990,adding sockets here & there in each room. The DB is a Crabtree Tpn polestar,just finished some loop readings ,& not good,1.49 the highest,there is...
  14. Midwest

    Loop Impedance Testing - Strange fault code

    Being doing a domestic bathroom refurb', lighting, altering shower circuit (have a Megger 1730 MFT). History, property has no RCD protection, but as it was a Hager CU, had contemplating using RCBO's (TN-C-S supply). Before doing any work, I decided to clamp the meter tails, as the property has...
  15. soms

    Earth loop impedance measurement affected by dimmer switch

    Working on a job today which included a very simple new lighting circuit. The lighting circuit a very short run from a distribution board to a single switch position, which then supplies a single luminaire. The customer wanted a dimmer switch to control the fitting. To crack on and perform the...
  16. Gary Tollison

    loop impedance, temperature, cable factor....

    Hello I'm not sure if this is the correct forum area to post this in, apologies if it isn't... I've been working through some mock questions on-line, and found myself confused by this: The measured value of loop impedance for a circuit is 0.83ohm. If the temperature at the time of the test was...
  17. Gary Tollison

    earth fault loop impedance

    Hello :) I'm confused about EFLI which I am guessing should be relatively straight-forward. I can't get my tired brain to figure out how to calculate the value for EFLI on system-side circuits? eg: what should the actual calculated value be for a 40A circuit, and how do I get that figure...
  18. LeeH

    Resistance of a transformer windings.

    Does any of you clever chaps know what the resistance of a 5kVA transformer should be? It's a 240-110 CTE. I have a resistance of 0.16 Ohms (1400A) If I recall what little transformer theory I covered years ago the impedance will increase when energised but how much I have no idea...
  19. B


    Zs=Ze+R1+R2 if you have R1+R2 and the Ze of cu through dead testing what is the need of doing an earth fault loop impedance test once you've energised the cu?
  20. C

    Fault Current Distribution

    Hello All, 1.Star connected earthed neutral Source to Star connected earthed neutral load? Say if a L-G fault occurs between the source and load, How does the fault current gets distributed? To the source side neutral or load side neutral? 2.Star- Star Transformer. Neutral earthed on both the...
  21. S

    Spanish Earth Road installation

    Hi, Quick question, does anyone know if there is a different spec to the U.K. for earth rods? I'm told in Spain they are longer but not sure if that is correct? Also are there any regs in Spain relating to the positioning of the rods etc (i.e. distance fro property)? Any advice greatly...
  22. G

    Earth fault loop impedance

    How does earth fault loop impedance and disconnect time requirements change for 3phase 3 wire 230 volt systems where the phase to earth voltage is 133 volts instead of 230 volts?
  23. S

    Battery Storage And Uk Regulatory Compliance

    Hello all, I am thinking of adding battery storage to my existing setup to increase self-consumption and provide backup for power cuts. Currently I have 16 x 230W panels feeding 2 + 2 kW StecaGrid inverters installed in 2011. If I were to add for example a Victron MultiPlus 48/3000/35-50 in...
  24. 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...
  25. B

    For Sale Megger LTW 425

    http://www.test-mete...dcXmBoChmzw_wcB Same as the above, it's a year old but has only been used 3-4 times tops. I don't think it's in calibration still, but I can arrange to have it calibrated for anyone interested. Key specs below: Will post some photos when I get home later. I think...
  26. T

    Can you work out the value of the resistor?

    Hi guys, Just wondering if you can help me on this one, I have a RLC series circuit the values are as below; R = unknown L = 800mH C = 300uF from there I have calculated; the resonant frequency to be 10.3Hz the capacitive reactance 51.50 ohms The reason I need to know is I need to work...
  27. S

    trouble with 2394/2395 revision queston

    hey guys.... ive downloaded some revision questions for my 2394/95 course i have booked for august and ive come across a question im a little unsure about......even when i have used the regs and GN3 to help. a little help would be greatly appreciated as there is no answer sheet for the...
  28. F

    Fault current

    Can someone explain why fault current is higher when your zs is lower trying to write down reason but struggling on what to put
  29. H

    Suitable testing instruments

    Hey guys, I need help finding out which tester you'd need to test for: continuity of circuit protective conductors, earth fault loop impedance and prospective fault current. I'm pretty sure you'd use a low reading ohmmeter for continuity but I don't know the other two. Also, any requirements...
  30. P

    1st Generator install

    I have been installing a 3 phase 60KvA generator connected to a MDU with a 100A 0.1A RCD, when I test the earth electrode resistance (Ra) using the earth fault loop impedance tester I get a reading of 1845 ohms, as this does not meet the Ra x Ia less than or equal to 50v, 1845 * 0.1 = 184.5 , it...
  31. K

    Earth Fault Loop Impedence question

    hello, i got this qustion and would like someone to show me the working out of it please. the measured value of loop impedance for a circuit is 0.83 ohms. if the temperature at the time of the test was 20c and the cable is 70c (factor1.2), what is the correct value. ze = 0.4 ohms
  32. S

    KEWTECH KT64 loop testing..

    hi guys when measuring loop empedans with kt 64 it gives me 2 option by chosing with f1 L-n l-pe which one shoul be used?? Thank you very much..
  33. S

    AC Circuit Theory Maximum Power Transfer

    Hello All, I am currently hitting a barrier with regards to the basics of this question. It is for a HND so I may have put this in entirely the wrong forum. Apologies if so. A 50HZ supply is connected to various given impedance's connected in series and parallel. Calculate the value of the...
  34. M

    Domestic Prospective fault current ?

    Can somebody please clear up for me what is prospective fault current? Am i right in thinking its the value of overcurrent you get through fault conditions like short circuits and live conductors and exposed conductive parts ? Thanks
  35. E

    Earth Loop Impedance testing

    I have a standard KT71 pat tester and have been offered a job testing cash registers. The problem is I will be expected to also carry out an Earth Loop Impedance test and I do not possess the kit or the knowledge to do it. I am considering sub-contracting the Earth Loop Impedance testing part...
  36. T

    Line to earth fault but MCBs will not trip..Why?

    I was called to a single phase installation in a pub as the staff were receiving shocks when touching equipment such as fridges water pipes etc. I located a damaged cable where line and PE conductors were touching and causing 240 volts on the entire earthing system at the installation. In other...
  37. J

    PFC Testing

    Hi all. Just a question which seems to get me a bit confused about PFC testing. I understand that the value of PFC you put on a EIC or any other form is the highest value of either the PSCC or the PEFC. Now when you get the reading on your meter (which is sometimes displayed with the Zs value)...
  38. E

    ZS on final sub circuit

    Lads Have measured R1 + R2 and get a total of .45 ohms, when I test the ring with my tester I get 2.1ohms, the unit was calibrated last week, any ideas?
  39. J

    Measuring earth loop imopedance Ze using FLUKE meter - settings??

    Guys (n' girls of course) I have just started using a 1653B FLUKE and when testing earth loop impedance Ze (ie. impedance of supply - tested at supply origin), I presume I use the 'LOOP IMPEDANCE' setting (line to protective Earth L-PE) using the Z1 Hi current setting, and NOT the 'Earth...
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