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- Dec 25, 2011
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Testing my kitchen ring today and looks like I need a new RCD!
A TT system installed in 1987. Stand alone "Keyswitch Varley" 80A, 30mA RCD in it's own enclosure fitted between the meter and DP switch in the CU. CU is a metal clad Crabtree with a line of C50 Type 2 breakers so yes, all circuits on the one RCD. Excuse the photo angles the CU is mounted against the ceiling in the porch with 2'6" between walls.
View attachment 2867
View attachment 2866
Anyway, I did the 3 step dead tests all ok then moved onto the IR tests again no problems. Polarity OK. Moving on and earth loop tests at the sockets just show up the need for a working RCD with circa 50A only for L-PE.
Then doing the RCD test and 1/2x no trip. On 1x it just read >299ms and on 5x >40ms. It tripped "eventually" but was noticeably slow. I appreciate a new RCD is needed ASAP but what was odd was that even pressing the test button it took a good while for it to trip? Out of interest before I bin it does that suggest a mechanical fault within the RCD. Don't worry, not thinking I can repair it but what makes them go wrong? Appreciate it is nearly 30 years old! I know the theory from college as to how they work but again what makes them "go slow"?
(By the way the meters used were a Megger BM221 Insulation Tester and a Megger RCD & Loop Tester LCB2500/2).
Straight down to TLC tomorrow! Any best make to get? MK, Hager?
Thanks
A TT system installed in 1987. Stand alone "Keyswitch Varley" 80A, 30mA RCD in it's own enclosure fitted between the meter and DP switch in the CU. CU is a metal clad Crabtree with a line of C50 Type 2 breakers so yes, all circuits on the one RCD. Excuse the photo angles the CU is mounted against the ceiling in the porch with 2'6" between walls.
View attachment 2867
View attachment 2866
Anyway, I did the 3 step dead tests all ok then moved onto the IR tests again no problems. Polarity OK. Moving on and earth loop tests at the sockets just show up the need for a working RCD with circa 50A only for L-PE.
Then doing the RCD test and 1/2x no trip. On 1x it just read >299ms and on 5x >40ms. It tripped "eventually" but was noticeably slow. I appreciate a new RCD is needed ASAP but what was odd was that even pressing the test button it took a good while for it to trip? Out of interest before I bin it does that suggest a mechanical fault within the RCD. Don't worry, not thinking I can repair it but what makes them go wrong? Appreciate it is nearly 30 years old! I know the theory from college as to how they work but again what makes them "go slow"?
(By the way the meters used were a Megger BM221 Insulation Tester and a Megger RCD & Loop Tester LCB2500/2).
Straight down to TLC tomorrow! Any best make to get? MK, Hager?
Thanks
