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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> Circuit breaker question and possible damage https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1434389119 Message started by Oldman on Jun 15^th, 2015, 6:25pm

Title: Circuit breaker question and possible damage
Post by Oldman on Jun 15^th, 2015, 6:25pm

While I was testing a power outlet, the live wire side of the outlet touched the metal boxing and some sparks flew and knocked out the power for the entire house. Both the breaker for the outlet and the main breaker were tripped. After resetting both the breakers I got the power back up.

I would like to know if that could of caused any potential damage to the electronics in the house that are on different circuit breakers in the breaker panel. All the rooms in my house have properly grounded outlets except for one I just discovered where the grounding wasn't working properly. That one room has two desktop computers, computer networking equipment that are all plugged into a surge protector. So far all my electronics turn on fine. Since the room isn't grounded properly I am concerned if outlet accident would have caused any damage to the equipment in that room. I have no electrical background so if any certified electrician could answer my questions I would greatly appreciate it.

Title: Re: Circuit breaker question and possible damage
Post by Lectrician on Jun 16^th, 2015, 7:47am

Grounded is an American term, not UK. Is this UK?

No damage will occur to your items, but an unearthed socket is dangerous as should anything plugged into in become faulty, the fuse, MCB, RCD etc will be unable to trip and clear the fault. An Earth is required for safety reasons, not to protect your equipment.

Title: Re: Circuit breaker question and possible damage
Post by Oldman on Jun 16^th, 2015, 3:36pm

I'm not from the UK but not American either, I'm from Canada.

Can you please explain in more detail what you mean by unable to trip and clear the fault?

I turned off the power to the room with the malfunctioning grounding before checking the outlets and the grounding wires for outlets were connected tightly and the ground wire was attached to the breaker panel as well.

Would the grounding not work if the live and neutral wire were reversed? That's the only other possibility I have not checked yet.

Title: Re: Circuit breaker question and possible damage
Post by CWatters on Jun 16^th, 2015, 7:02pm

Hope Lectrician doesn't mind me contributing...

MCB and RDC work in different ways but for the purposes of this discussion you can assume they work by detecting current incorrectly flowing to earth - as you found out.

Suppose the back box you worked on had been on the circuit with a faulty earth. When the live wire touched the back box the breaker would not have operated. This would have two effects:

1) the back box would still be live waiting for you to touch it.

2) depending on where the earth fault was, all other back boxes and face plates connected to it by the faulty "earth" wire would also have been live. That could also include the metal case to a washing machine, fridge or computer (Any metal cased machine that needs an earth).

Important you get the faulty earth fixed as it can be very dangerous.

Title: Re: Circuit breaker question and possible damage
Post by Oldman on Jun 16^th, 2015, 8:36pm

So without the earth wire the breaker won't trip to stop the electricity from flowing?

After I found out the grounding wasn't working I relocated my surge protector to another room with working grounding via power extension cord. Currently all the outlets in that room are not in use.

The room has 5 outlets which are all connected to one circuit that goes directly to the breaker panel with nothing else connected to it. Even the lighting in the room is on a separate circuit which has working grounding. I turned off the power to that room and checked the earth wire for all outlets and they are connected tightly to the right connector. The wiring on the breaker panel looks good too so I am baffled why it's not working.

Title: Re: Circuit breaker question and possible damage
Post by Oldman on Jun 18^th, 2015, 2:51pm

I figured out why the surge protector was displaying no ground for my outlets. The contractor that finished that room a few weeks ago apparently reversed the live and neutral wires in the original outlet while adding the additional 4 outlets. After correcting the wires in the original outlet, all of them are working fine now, I bought an outlet tester and tested all the outlets just in case.

Title: Re: Circuit breaker question and possible damage
Post by CWatters on Jun 21^st, 2015, 9:20am

I'd still get an electrician to check the earth/ground arrangement. The earth must be "good enough" not just "connected".