Hi all,
New to the forum.
I have been asked to look at this for one of our guys who's had an issue onsite after some electrical works had been carried out, after some advice and potential causes and remedies please.
Long story short. Asked for a socket to be installed inside a depot only open to our workers, nothing external to be used on this. A 16amp 3-phase commando socket was installed from a local board with no RCD protection, surface wired steel wired armour. RCD could only be installed at the socket, not the board, but one wasn't.
It would appear that the wiring had been terminated incorrectly, giving one of our workers a slight belt on some metal work. The area is fenced off by metal fencing, which has no direct earth path to a board.
As you can see the diagram shows the wiring mistake, L2 into the earth terminal on the plastic box (both black cables). Now, this is a plastic box and no direct connection to the fencing. It wasn't until a capacitor testing machine was plugged into the socket that an earth fault has occurred and livened up the fence door handle.
Could anyone answer the below please?
1, the capacitor tester apparently throws out a 100v pre test volt apparently to pre-check across the 3 phases? Unsure on these testing machines.
2, if this is the case would this cause an imbalance on the star connections, forcing ampage up the L2 to the earth?
3, there is a safety switch mounted to the fencing connected to the capacitor to ensure you cannot open the door whilst the machine is live, essentially killing the power, possibly a point of contact to the fencing.
4, assuming this has back fed through the capacitor tester from the 2 phases that are correctly connected, up the earth wire to the commando socket, livening up the steel part of the SWA?
5, would an RCD at the commando socket stopped this potentially?
Any help greatly received, if any more info is needed just ask.
Not sure on how capacitor testers operate.
Thank you
John
New to the forum.
I have been asked to look at this for one of our guys who's had an issue onsite after some electrical works had been carried out, after some advice and potential causes and remedies please.
Long story short. Asked for a socket to be installed inside a depot only open to our workers, nothing external to be used on this. A 16amp 3-phase commando socket was installed from a local board with no RCD protection, surface wired steel wired armour. RCD could only be installed at the socket, not the board, but one wasn't.
It would appear that the wiring had been terminated incorrectly, giving one of our workers a slight belt on some metal work. The area is fenced off by metal fencing, which has no direct earth path to a board.
As you can see the diagram shows the wiring mistake, L2 into the earth terminal on the plastic box (both black cables). Now, this is a plastic box and no direct connection to the fencing. It wasn't until a capacitor testing machine was plugged into the socket that an earth fault has occurred and livened up the fence door handle.
Could anyone answer the below please?
1, the capacitor tester apparently throws out a 100v pre test volt apparently to pre-check across the 3 phases? Unsure on these testing machines.
2, if this is the case would this cause an imbalance on the star connections, forcing ampage up the L2 to the earth?
3, there is a safety switch mounted to the fencing connected to the capacitor to ensure you cannot open the door whilst the machine is live, essentially killing the power, possibly a point of contact to the fencing.
4, assuming this has back fed through the capacitor tester from the 2 phases that are correctly connected, up the earth wire to the commando socket, livening up the steel part of the SWA?
5, would an RCD at the commando socket stopped this potentially?
Any help greatly received, if any more info is needed just ask.
Not sure on how capacitor testers operate.
Thank you
John
