impedance | Page 2

impedance

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  1. 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...
  2. 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...
  3. 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...
  4. 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...
  5. 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...
  6. 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...
  7. 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...
  8. 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...
  9. 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...
  10. 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...
  11. 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...
  12. 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...
  13. Pete999

    Pete's Videos Earth loop impedance whats that then?

  14. 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...
  15. 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?
  16. Pete999

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

  17. Rocboni

    Max Zs

    Hello, Having a bit of difficulty completing the below assignment, wondered if anyone can expand on this? Explain in detail the relationship between the Protective Device and the Earth Fault Loop Impedance, Maximum Zs for the protective device and how this is calculated, Maximum disconnection...
  18. 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...
  19. N

    High earth loop impedance

    Hello all, I am studying to be an electrician but outside of the classroom I have little experience. A friend has bought a house and during the buying process had an eicr with unsatisfactory result. Reading the report it shows the ring and shower circuit to have high earth loop impedance. I...
  20. gazdkw82

    Earth fault loop impedance

    Iv been given the scenario: 6 circuit earth fault loop impedance values were recorded. Each circuit has type B cb. referring to the maximum values, show by calculation if these values are acceptable. so I can't do zs =ze+R1/R2 because they've not provided me with ze. doing some research it...

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