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hi did a IR on a shed board L-N was 0.11Mohms so took out the radial circiut and light circuit did them separately and was fine 299Mohms so why low when they are connected to the shed board????? dont do much testing so help be nice cheers
 
IR tests should be carried out with L and N dissed from the board, so that low reading is irrelevant.
 
IR tests should be carried out with L and N dissed from the board, so that low reading is irrelevant.
Hi Tel don't normally question your replies, but looking at table 10.3.3 in the OSG it says.
"For an installation operating at 400/230V , although the IR value of 1Mohm complies with BS7671, where the IR reading is less than 2Mohm the possibility of a latent defect exists. in these circumstances each circuit should be tested separately" The original test was obviously a global test at the board.
 
hi did a IR on a shed board L-N was 0.11Mohms so took out the radial circiut and light circuit did them separately and was fine 299Mohms so why low when they are connected to the shed board????? dont do much testing so help be nice cheers

Why were you testing the shed?
 
Surely you must have seen a difference at some point!

Does the shed have a cu and if so what type? What is at the house end of the circuit? How many circuits in the shed?
 
Well it shouldn't be, have you got the switch off at the board.
 
I take it the board has a rcd main switch it could be reading across that. Switch off the MCBs and take the supply neutral from the neutral bar.
 

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