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This is my first post as a new member. I am a stickler for safety, in particular proving wiring and terminals are dead before starting work. Here are two instances demonstrating the importance of proving isolation before touching any electrical conductors. I found them both in one flat I bought recently.
1. Economy 7 electric storage heating. The line supply for the electric timeswitch was from the Henley block via a separate stand-alone fuse way. The neutral supply for the timeswitch was obtained from the outgoing circuits neutral bar within the Wylex/MCBs CU supplying 3 storage heaters. I was replacing the dirty FCUs with new ones.
2. Two switched supplies to an outside light. A lantern type PIR outside light by the front door had two separately switched line feeds. There were 2 FCUs side by side at the top of stairs leading down to front door. The left FCU I first thought was solely for the door intercom transformer transformer just to its left: the right FCU I thought for the lantern PIR lamp. Both FCUs spurred from a socket on the other side of the stud wall. Whilst renewing the outside lantern and replacing old dirty FCUs I discovered:
a. Both FCUs were spurred from the socket.
b. The left FCU(3 Amp fuse) did supply the intercom transformer but also the line and neutral and CPC for the outside lantern.
c. The right FCU(5 Amp fuse) supplied a line to the external switch terminal (sometimes marked with a * on the connector) of the Lantern.
I am a strong advocate for turning off Main Switches, tripping RCDs, opening CBs and pulling out fuses and testing for dead before starting work. And once covers are off studying carefully how something has been wired and not assuming anything. These two instances make me glad I do what I preach.
Hope this little ditty is of interest and a reminder that electricity is a potential killer so take care.
PS: In a previous career, following the the death of a contractor from electrocution, I was appointed into to an industrial facility to re-introduce from scratch and then enforce safe systems of work for electricity.
1. Economy 7 electric storage heating. The line supply for the electric timeswitch was from the Henley block via a separate stand-alone fuse way. The neutral supply for the timeswitch was obtained from the outgoing circuits neutral bar within the Wylex/MCBs CU supplying 3 storage heaters. I was replacing the dirty FCUs with new ones.
2. Two switched supplies to an outside light. A lantern type PIR outside light by the front door had two separately switched line feeds. There were 2 FCUs side by side at the top of stairs leading down to front door. The left FCU I first thought was solely for the door intercom transformer transformer just to its left: the right FCU I thought for the lantern PIR lamp. Both FCUs spurred from a socket on the other side of the stud wall. Whilst renewing the outside lantern and replacing old dirty FCUs I discovered:
a. Both FCUs were spurred from the socket.
b. The left FCU(3 Amp fuse) did supply the intercom transformer but also the line and neutral and CPC for the outside lantern.
c. The right FCU(5 Amp fuse) supplied a line to the external switch terminal (sometimes marked with a * on the connector) of the Lantern.
I am a strong advocate for turning off Main Switches, tripping RCDs, opening CBs and pulling out fuses and testing for dead before starting work. And once covers are off studying carefully how something has been wired and not assuming anything. These two instances make me glad I do what I preach.
Hope this little ditty is of interest and a reminder that electricity is a potential killer so take care.
PS: In a previous career, following the the death of a contractor from electrocution, I was appointed into to an industrial facility to re-introduce from scratch and then enforce safe systems of work for electricity.