Live bath taps

[Lectrician]

DID the rec bloke disconnect your earth from the CU to the head while he did the loop test from L to N(pme)?? If not - then that was a pointless test.

PME can do some weird and wonderful things. If your bonding is providing a lower resistance path than the elec boards corroding joints, current will flow through your earthing system/pipes. This then creates a PD.

You need to get this sorted asap - installing a rod could actually make things worse.

 

[Panjandrum]

You need to get this sorted asap - installing a rod could actually make things worse.

I don't understand how it might make things worse - could you explain?

 

[gazza30]

Good news chaps
problem sorted nedl bloke is a wast of space (to be nice) the problem was with the pme earth it had a nick in the earth wire case and so did the live meter tail
one was touching the other hence live in the house .
The nedl bloke would have noticed this if he had done his test with the main fuse in.
had new 16mm earth and new meter tails fitted and all is fine now.
Thanks to everyone for all the great help and good advice.
Now going for a nice hot bath ha ha.

thanks again

Gary

 

[Lectrician]

Circulating network currents.

The returning neutral from the neighbourhood can travel through the neutral, and any parallel earths. The voltage dropped due to these currents can cause fairly heafty PD's. I am not saying a rod would make it more dangerous - just could.

 

[mapj1]

very, very pleased to hear a definite fault has been found and clearerd up - worth sticking with it.. enjoy the bath

PS for those unsure of the risk's of the addition of an extre earth but one without adequate current handling capability - read the RSGB paper I referred to earlier, for good diagrams of wherer the currents can go
(for radio earth read "extra earth path")

 

[Panjandrum]

OK thanks - it was a genuine question, not an interrogation
Actual explanation sounds a bit scary to me. I kind of assume that stuff is OK and has been tested.
I'd have expected much more dramatic effects from the features Gary has described - ought to have been live-earth drama
If there was no such drama that suggests that the incoming earth just isn't.

 

[plugwash]

I imagine the same could apply to water and gas pipes especially on larger PME supplies

am i the only one who things a slightly leaky gas pipe a badly fitted earth clamp and a PME fault could be seriously troublesome?

 

[mapj1]

There are certainly those of us who think if you have 2 wire feed overhead and the choice is "PME or TT?", in many cases TT is the lesser of the two evils.... (and for the gas pipe the upper bound on the fault current is much lower...)
But what do I know - I've only seen and heard of it going wrong, not seen the cost saving of not having all those earth rods.
I agree there can occasionally be a problem with sticky RCDs, but I don't know if that is actually a more common fault - and if it was you could square the risk term (in the way that 1 in 1000 becomes 1in 1 million) by having two in series..

 

[plugwash]

afaict the main issue with TT is if the RCD fails....

i've never known any homeowner who tests thier rcds regularlly and indeed the standard arrangements in homes makes this a PITA to do

a system with two rcds in sequence (as is common in uk TT setups) will mitiage this to some degree but its still not brilliant

personally i think TN-S should be mandatory for all new installation except where they must be joined to existing wiring that can't support it

 

[Lectrician]

PME is not allowed in petrol fourcourts for the very reason your mention re-gas plug.

Also gas filling wharehouses (to fill 'calor gas' tanks) etc.

PME does have serious consequences when it fails, as does TN-S and TT. TT for the rcd issue plug has raised, and TN-S can be deadly on large current installs. A short from N to E close to the origin can see upto half of the neutral current flow through the fault - if this is a fault in a light fitting really close to the origin, the 1mm can burn out.

All three are evils, but my choice is always TN-S , TNC-S , TT.

 

[HDRW]

nedl bloke is a wast of space

Well seeing what you said about him earlier:

(i think he wanted to go home as his wife was in his case).

it looks like he won't be working much longer and we can expect to see the headline: "Electrician arrested for suitcase murder"


Cheers,

Howard

 

[gazza30]

howard

That was to say that his wife was on his case not in it

 

[HDRW]

howard

That was to say that his wife was on his case not in it

That's OK, one of my hobbies is "Deliberately misunderstanding for comic effect"

Cheers,

Howard

 

[Damocles]

So the result was a direct short live to N/E before the meter? This had sufficient current flowing to raise the voltage on the n/E to 50V? Is it just me, or is that a steady short to earth of at least 50-100A? Did anything get warm?

 

[HDRW]

So the result was a direct short live to N/E before the meter? This had sufficient current flowing to raise the voltage on the n/E to 50V? Is it just me, or is that a steady short to earth of at least 50-100A?

All of that, I'd have thought... (how would you calculate that, not knowing any of the Rs involved?)

Did anything get warm?

I was wondering about that - in fact howcome the service fuse didn't blow? And failing that why wasn't there a sizzling sound under the stairs?

A number of years ago my late father was a shop manager, and one day an unoccupied shop next door was giving off hot smoky smells. He investigated and got the landlord to open up the premises, where they discovered the incoming main cable glowing brightly and giving off smoke (below the service fuse). They said "Blimey!" They didn't want to touch it. They called the fire brigade, in case the place went up.

They arrived, and the bloke in charge said "Blimey!!" and wouldn't touch it.

They called the electricity board (it was a while ago!) and along came the neat, clean-shaven man in a small van, who said "Blimey!!!" He wouldn't touch it.

There was then the succession of increasingly rough men and larger vans as elewhere described, and they dug up the road to disconnect it from there, while the fire brigade stood by, just in case. (I imagine they replaced the cable thereafter).

I always wondered, how do you get a short in a main cable like that, presumably without interference? There was no sign of break-in or kids messing with it or anything - although the glowingness of the cable might have obscured that...

Cheers,

Howard