Discuss earth loop impedance in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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palmerelectrcal

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client had washing machine eng. called out....who tested the single switced socket??? (w/machine drum fault) and on his rport indicated a higher than acceptable earth loop impedance (254 ohms) as a result im sent to check installation...theres nothing wrong with the installation however a subsequent measurement confirms the figure of 250 ohms...the seperate rccb doesnt trip on an applied fault condition.!! any advice? ps probably going to seek to get the old wired fuse board up graded to a new c/u..:clap:
 

telectrix

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get a Ze reading either side of the rccb. if say, you get 0.2 ohms on the supply side, and 240 ohms on the load side, it's the rccb . then again, you may have a TT or no earth at all, installation relying on the water/gas bonding. too many variables yet.
 

oldtimer

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More info needed mate.

A bit of advise here as above more info but at the same time when you go to look at a job like this you need to get as many readings as possible not just for us but for you let me explain you test the socket yep high reading then you need to test some random sockets and even the cooker outlet socket as well then get a Ze,PFC,PSSC and so on . I was called to a job because british gas said there was a problem turns out it was a faulty socket the rest of the house was fine so you need to treat this like a doctor does do the standard tests then you get the diagnoses
 

Blowcat

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Sounds like a case of fingers crossed when the new DB is installed, because if that fault is still there it wont look good, especially if you then charge the client further money to fault find and fix the fault.
Best to do a full test from the incoming supply then to that circuit. Also worth doing an additional Zs test using the low ohms setting (you use for RCD testing) cos there might be a fault with the incoming earthing that is not picked up with getting a conventional Ze
 

needasparks

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I'm going to agree with blow on this. How come you did not do any further testing to confirm what the cause of the fault was, how much longer does it take to carry out deduction testing to a circuit. Did you try another socket, take a Ze ?
From you OP you say you rechecked the socket and said its a mains change because the rccb did not trip but surely your test should have told you the actual problem for the high reading setting aside the no-trip issue. Or have i miss read the OP.
 

Guitarist

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A week has passed and no more info was forthcoming....
Guessing he either sorted it, or has booked himself on a fault-finding course.
 

oldtimer

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or as always they come on the forum and dont tell us the outcome leaving us all bewildered so me thinks there should be a report button so the next time time they come on they are warned that if they dont comply then struck off
 
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palmerelectrcal

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thankyou for the above. sorry i didnt give much info..there is no distributers earth ..the higher than accptable impedance is only acheived from the bonding to i/c water main/gas pipe. is this something thats common bcause on another job...a victorian terrace refurb...the c/u
and wiring has been updated but again thers no distributers eth provided. referring back to the above.... i did in fact tst other sockets/other ccts. and the installation otherwise is fine, rgards a p.
 
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palmerelectrcal

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i wasnt intending to upgrade the board to eradicate the fault it was just extra info,
 
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