impedance

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  1. 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...
  2. 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
  3. J

    Earth Fault Loop Impedance...

    Hi there, I’m just hoping someone could clear something up for me at all. I’m just working my way through some test questions and I’ve come across one in which isn’t making sense to me. Q. Calculate the maximum earth fault loop impedance permissible for a 30mA RCD used to protect a circuit...
  4. 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......
  5. M

    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...
  6. S

    Earth fault loop impedance

    Morning all. So just trying to refresh my grey matter but having a biff moment. Earth fault loop impedance with circuits protected by BS EN60898 type B circuit breakers. I know the tabulated values are in table 41.3, but for the life of me I’ve forgotten how to calculate if acceptable or not. So...
    • Sean McD
    • Thread
    • earth earth fault loop impedance fault impedance loop loop impedance
    • Replies: 4
    • Forum: UK Electrical Forum
  7. 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...
    • LewisM
    • Thread
    • earth earth fault loop impedance fault impedance loop loop impedance mcb test tripping
    • Replies: 6
    • Forum: UK Electrical Forum
  8. 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...
  9. 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...
    • nathanm1982
    • Thread
    • calculation earth earth fault loop impedance fault impedance loop loop impedance
    • Replies: 3
    • Forum: UK Electrical Forum
  10. 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...
    • TeeCK
    • Thread
    • earth flat floor impedance issues loop loop impedance potential second
    • Replies: 27
    • Forum: UK Electrical Forum
  11. 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...
  12. cliffed

    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...
  13. 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...
  14. 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...
    • soms
    • Thread
    • dimmer dimmer switch earth impedance loop loop impedance measurement switch
    • Replies: 8
    • Forum: UK Electrical Forum
  15. 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...
  16. 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...
  17. Pete999

    Pete's Videos Earth loop impedance whats that then?

  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

    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. Pete999

    Pete's Videos Earth Fault Loop Impedance, who needs it?

    • Pete999
    • Thread
    • always earth earth fault loop impedance fault impedance loop loop impedance media needs sparky stuck
    • Replies: 4
    • Forum: UK Electrical Forum

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