In regards to EddieM, another reason I wanted my own MFT is so I can ensure that my wiring is electrically sound and everything is as it should be.
I am rather grateful for having it now, as without it I would not have discovered that I have a higher than permitted Zs for my kitchen radial socket circuit. My kitchens socket circuit is a radial circuit protected by a 32A type B MCB that is wired in about 20M of 4mm² T&E and has a system loop impedance (Zs) of 1.23Ω even though the PSCC was 187A. On a another circuit what is a 20A Radial wired in 2.5mm² T&E, I got a system loop impedance (Zs) of 1.16Ω on a socket what was about the same distance from the DB as the socket in the kitchen with the high Zs value.
I suspect the high loop impedance reading in the kitchen is down to where the first item/s on the circuit are 5 FCU's for the fixed kitchen appliances (4mm² T&E loops in and out of each FCU). I remember my electrician having a hard time installing the FCU's while at a awkward angle, plus we had settlement in that area of the house where the floor dropped by about 40mm few years ago. All is nice and tight in the DB/CU.
Reference for permitted Zs values: https://www.niceic.com/Niceic.com/media/Pocket-Guides/Pocket-Guide-18.pdf
Also, is this outdated as it has different Zs values than the above link: http://www.electricalsafetyfirst.org.uk/mediafile/100106752/master_EARTHFAULTLOOPtable.pdf
Can anyone scan and attach the page of permitted Zs values from Amendment 3 of BS7671:2008.
Regards: Elliott.
I am rather grateful for having it now, as without it I would not have discovered that I have a higher than permitted Zs for my kitchen radial socket circuit. My kitchens socket circuit is a radial circuit protected by a 32A type B MCB that is wired in about 20M of 4mm² T&E and has a system loop impedance (Zs) of 1.23Ω even though the PSCC was 187A. On a another circuit what is a 20A Radial wired in 2.5mm² T&E, I got a system loop impedance (Zs) of 1.16Ω on a socket what was about the same distance from the DB as the socket in the kitchen with the high Zs value.
I suspect the high loop impedance reading in the kitchen is down to where the first item/s on the circuit are 5 FCU's for the fixed kitchen appliances (4mm² T&E loops in and out of each FCU). I remember my electrician having a hard time installing the FCU's while at a awkward angle, plus we had settlement in that area of the house where the floor dropped by about 40mm few years ago. All is nice and tight in the DB/CU.
Reference for permitted Zs values: https://www.niceic.com/Niceic.com/media/Pocket-Guides/Pocket-Guide-18.pdf
Also, is this outdated as it has different Zs values than the above link: http://www.electricalsafetyfirst.org.uk/mediafile/100106752/master_EARTHFAULTLOOPtable.pdf
Can anyone scan and attach the page of permitted Zs values from Amendment 3 of BS7671:2008.
Regards: Elliott.