Water mains and earthing
 

Sorry if this is mildly OT, but I'm not sure where else to ask.

Three Valleys Waters has just very kindly relaid the mains outside my
house with spiffing new plastic ones. Among the notices they dished out
were warnings that if my electrical system was earthed to the old metal
mains, this would no longer work.

Neither Powergen not...er, whatever 24-7 is called now...seem terribly
interested or knowledgeable. Any idea how to establish whether it is
worth calling an electrician in?

* The house (a 1950s ex-council house) was last rewired c1989 by the
council.

* Obviously the Water Co only replaced up to my street side stop cock.
From there to my house is still the old iron mains feed.

* My shower has an earth wire connected to the cold water tap of the
sink basin. I ran it slightly absent-mindedly and didn't get
electrocuted.

* In my meter cupboard there are a couple of whacking great earth wires
near the meter, running from the circuit breaker box. One is attached to
a metal poll apparently drilled into the wall, another to a copper pipe
coming from (or to) the gas meter (!).

Am I just being paranoid?

Off to boil some water....

--
Oh, as usual, dear

Ian Cundell wrote:

Three Valleys Waters has just very kindly relaid the mains outside my
house with spiffing new plastic ones. Among the notices they dished out
were warnings that if my electrical system was earthed to the old metal
mains, this would no longer work.

They do that to cover themselves.

Neither Powergen not...er, whatever 24-7 is called now...

....EDF Networks.

* The house (a 1950s ex-council house) was last rewired c1989 by the
council.

If it was competently re-wired at that time you should have no worries,
and nothing should need changing.

* My shower has an earth wire connected to the cold water tap of the
sink basin. I ran it slightly absent-mindedly and didn't get
electrocuted.

That's bathroom supplementary bonding, only part of the overall earthing
and bonding scheme.

* In my meter cupboard there are a couple of whacking great earth wires
near the meter, running from the circuit breaker box. One is attached to
a metal poll apparently drilled into the wall, another to a copper pipe
coming from (or to) the gas meter (!).

See the FAQ at
http://www.diyfaq.org.uk/electrical/....html#earthing

If you're still unsure, post a photograph of your electrical intake,
meter and consumer unit location on the Web somewhere and further
comment will doubtless be offered...

--
Andy

Andy Wade wrote:

Neither Powergen not...er, whatever 24-7 is called now...

...EDF Networks.

Andy - aren't the b*ggers - however sliced-n-diced-n-microprivatised -
still under a legal obligation to tell you what your earthing
arrangements are, and what the maximum supplier's earth loop impedance
is (even if the latter will almost always be the Conventional answer of
'0.35/0.8/yourproblem' respectively for TN-C-S, TN-S, and TT ;-) ?

Stefek Zaba wrote:

Andy - aren't the b*ggers - however sliced-n-diced-n-microprivatised -
still under a legal obligation to tell you what your earthing
arrangements are, and what the maximum supplier's earth loop impedance
is (even if the latter will almost always be the Conventional answer of
'0.35/0.8/yourproblem' respectively for TN-C-S, TN-S, and TT ;-) ?

Yes, there's a list of data they are obliged to provide in the BS 7671
Amendment 2 which I've just mentioned in another thread. Here's a quick
cut'n'paste. I've added the usual answers (for LV supplies) and some
comments in square brackets:

quote
Regulation 28 of the Electricity Safety, Quality and Continuity
Regulations 2002 requires distributors to provide the following
information to relevant persons free of charge:

- The maximum prospective short-circuit current at the supply terminals
[1-ph: 16 kA; 3-ph 25 kA; can be higher in the former LEB area]

- The maximum earth loop impedance of the earth fault path outside the
installation (Ze)
[TN-S: 0.8 ohm; TN-C-S: 0.35 ohm, TT: 21 ohm]

- The type and rating of the distributor’s protective device or devices
nearest to the supply terminals
[usually BS 1361 Type 2, 100A, or whatever records show for older stuff]

- The type of earthing system applicable to the connection
[TN-S, TN-C-S or TT, but their records may be inaccurate - consumers can
to some extent change the means of earthing without reference to the
distributor]

- The number of phases of the supply
[this tends to be either 1 or 3 ;-)]

- The frequency of the supply and the extent of the permitted variations
[50 Hz ±1%]

- The voltage of the supply and the extent of the permitted variations.
[230/400 V -6%/+10%; -10% after 2008, perhaps]
/quote

--
Andy

In article ,
Andy Wade wrote:

Stefek Zaba wrote:

Andy - aren't the b*ggers - however sliced-n-diced-n-microprivatised -
still under a legal obligation to tell you what your earthing
arrangements are, and what the maximum supplier's earth loop impedance
is (even if the latter will almost always be the Conventional answer of
'0.35/0.8/yourproblem' respectively for TN-C-S, TN-S, and TT ;-) ?

Yes, there's a list of data they are obliged to provide in the BS 7671
Amendment 2 which I've just mentioned in another thread. Here's a quick
cut'n'paste. I've added the usual answers (for LV supplies) and some
comments in square brackets:

quote
Regulation 28 of the Electricity Safety, Quality and Continuity
Regulations 2002 requires distributors to provide the following
information to relevant persons free of charge:

- The maximum prospective short-circuit current at the supply terminals
[1-ph: 16 kA; 3-ph 25 kA; can be higher in the former LEB area]

- The maximum earth loop impedance of the earth fault path outside the
installation (Ze)
[TN-S: 0.8 ohm; TN-C-S: 0.35 ohm, TT: 21 ohm]

- The type and rating of the distributor¹s protective device or devices
nearest to the supply terminals
[usually BS 1361 Type 2, 100A, or whatever records show for older stuff]

- The type of earthing system applicable to the connection
[TN-S, TN-C-S or TT, but their records may be inaccurate - consumers can
to some extent change the means of earthing without reference to the
distributor]

- The number of phases of the supply
[this tends to be either 1 or 3 ;-)]

- The frequency of the supply and the extent of the permitted variations
[50 Hz ±1%]

- The voltage of the supply and the extent of the permitted variations.
[230/400 V -6%/+10%; -10% after 2008, perhaps]
/quote

Thanks for the feedback chaps.

On a related question, presumably as a consequence of detritus getting
in the mains feed (?), my electric shower keeps overheating and cutting
out. Is there an easy way to clean one of these things out?

--
Oh, as usual, dear