Polarity Reversing At Will

[securespark]

Cheers! Happy drinkings!

 

[Spark123]

Daft as it may seem, there isn't a fault on a non-rcd protected circuit (very naughty as its TT) - even possibly in a neighbouring house or supply cable - which is causing the earth to become live to 240v hence showing reversal as the neutral-earth voltage is now 240v.

 

[ricicle]

Changeover switch wired up incorrectly?(Regarding the Genset idea)

 

[ricicle]

Forget my last post - that would cause permenant rev polarity.I'm off to bed

 

[viewer]

How about the other houses?

 

[securespark]

Simply don't know!

Was unable to access any other properties...

 

[securespark]

Daft as it may seem, there isn't a fault on a non-rcd protected circuit (very naughty as its TT) - even possibly in a neighbouring house or supply cable - which is causing the earth to become live to 240v hence showing reversal as the neutral-earth voltage is now 240v.

Finally got it!! And S123, you win the prize for getting nearest!

The reward is a pair of my socks, worn for 2 weeks.... What do you mean you don't want them? A child in Africa would die for those socks. Hmmm, they probably would, actually...

Another engineer went round recently (as several engineers had been & the managers were getting miffed that no-one had cottoned on to the problem yet!)

He pinned it down to a fault on a two way light switch.

I believe the supply is mock PME. It looks like PME in that A. Muppet had fitted an illegal link from cut-out to board, but it was actually TT with no earth other than that supplied by the water main.

It appears the lighting had such a high EFLI it was not tripping any protective devices.

Further, the two way switches had a twin & earth using the cpc as a strapper.

The resulting effect was as follows:

When the two way switch was in one position, the polarity was sound. In the other position, Hey Presto! it was reversed!

Who'd have thought it hey?

 

[RF Lighting]

I'll have to store that in the back of my mind and impress the youngsters at work in 20 odd years time

The earth that was used as a strapper, was it still connected to earth at one end, or just uninsulated and shorting to the back box?

Did the pile of dead bodies under the landing lightswitch not give you a clue as to where the fault lay?

 

[EddieCurrent]

Hello,

Just trying to understand this,(please help),
I would have expected (wrongly ) the RCD to trip when the lightswitch caused the reversal, this would not cause any 'imbalance', even if only for a split second at all ?????

Thanks.

 

[jj4091]

missed page 2

 

[securespark]

The earth that was used as a strapper, was it still connected to earth at one end, or just uninsulated and shorting to the back box?

Not sure, wasn't there.

Did the pile of dead bodies under the landing lightswitch not give you a clue as to where the fault lay?

 

[bernardgreen]

One lesson to learn from this is NOT to trust the conductors that are claimed to be earth. Especially in ANY situation where the earth is "local" and not supplied from the incoming supply.

In the old days the metal water pipe gave a very reliable reference from which to check the quality of the electrical earth.

How many earth rod earths become useless during a dry summer ? When party line telephones used an earth rod and it iwent dry the call exchange button didn't work so you watered the earth rod until it did work. How do you know when to water your electrical earth to make it effective again.

Bernard
Sharnbrook

 

[EddieCurrent]

Hello,

Bernard, you seem well up on RCD's ( and more), can you help with my post above please ?

 

[bernardgreen]

Hello,

Bernard, you seem well up on RCD's ( and more), can you help with my post above please ?

Kompliments always wake me up.

In this scenario there is probably no leakage current as there is no effective earth to the the ground so a return current to the network supply transformer is not possible. With out that the currents in the two wires through the RCD are equal and opposite and therefore no un-balance exists.

The "earth wiring" in the switch was not an earth but a conductor that only connected to either live or neutral depending on the switch setting. As it had no other conductive route to earth, live, neutral or other potential it was impossible for any significant current to flow along it. Some very small current due to capacitive effects with adjacent wires would flow but this would not be enough to trip the RCD. So it didn't matter which way the switch was the RCD would not trip.

Bernard
Sharnbrook

 

[EddieCurrent]

Thank you Bernard,

I still cant get my head around the fact that when the 'offending' switch is actually switched physically, for that split second, there is no imbalance.

I will get the books out, and read your post again properly and go through it slowly till its clear..

I do thank you for your time taken helping me.