My electric shower blew the cartridge fuse in the consumer unit while I was in it the
other day, giving me a very refreshing cold shower. I replaced the fuse, and ran it
for 10 mins or so, and all seemed OK, it didn't blow the new fuse.

Is this something I should be worried about, or do cartridge fuses sometimes blow
with age? The old fuse (and shower) are probably about 12 years old.

It's a 30A fuse, I'm not sure of the power rating of the shower (it's a Heatstore
Esprite II), but I guess it must be taking pretty close to 30A. But it has been
working fine for at least 6 years.

I'm probably being over cautious, but the whole concept of a high power electrical
device which has blown a fuse in close contact with water which gets sprayed on me
has started to worry me. Would an RCD be advisable?

TIA

--
Andy

Andy Pandy said the following on 11/02/2006 17:46:
My electric shower blew the cartridge fuse in the consumer unit while I was in it the
other day, giving me a very refreshing cold shower. I replaced the fuse, and ran it
for 10 mins or so, and all seemed OK, it didn't blow the new fuse.

Is this something I should be worried about, or do cartridge fuses sometimes blow
with age? The old fuse (and shower) are probably about 12 years old.

It's a 30A fuse, I'm not sure of the power rating of the shower (it's a Heatstore
Esprite II), but I guess it must be taking pretty close to 30A. But it has been
working fine for at least 6 years.

I'm probably being over cautious, but the whole concept of a high power electrical
device which has blown a fuse in close contact with water which gets sprayed on me
has started to worry me. Would an RCD be advisable?

TIA

--
Andy



Each time you use the shower, you take the fuse from zero current to
maximum capacity (or more). This will cause the fuse wire to heat up
and expand significantly, so I expect that the fuse died of thermal
stress (i.e. old age).

You have not provided enough info. to calculate the disconnection time
of the fuse in the event of a problem with the shower itself so I can't
comment on whether you really should have an RCD regardless. Often with
the larger showers installed these days, you *need* an RCD to meet the
wiring regs requirements.

None the less, it is IMO always a good idea to protect your shower with
an RCD, since it will likely protect you from a fault in the shower
before the fuse gets close to popping. If you don't want the hassle of
upgrading your consumer unit, you should consider a separate shower
consumer unit with RCD protection.

HTH

Andy Pandy laid this down on his screen :
It's a 30A fuse, I'm not sure of the power rating of the shower (it's a
Heatstore
Esprite II), but I guess it must be taking pretty close to 30A. But it has
been
working fine for at least 6 years.

I'm probably being over cautious, but the whole concept of a high power
electrical
device which has blown a fuse in close contact with water which gets sprayed
on me
has started to worry me. Would an RCD be advisable?

If the fuse blows again soon, then I would become concerned, otherwise
it is likely that the fuse died of old age rather than an actual fault.

Irrespective of the above, an RCD would be a good idea anyway.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

In article ,
Rumble .@. wrote:

None the less, it is IMO always a good idea to protect your
shower with an RCD, since it will likely protect you from a
fault in the shower before the fuse gets close to popping. If
you don't want the hassle of upgrading your consumer unit, you
should consider a separate shower consumer unit with RCD
protection.

We looked at a house the other day, which had had 3
en-suite showers fitted. I opened the cupboard to look
at the fusebox (actual fuses), and stood staring at
it.... firstly there were not enough fuses to support
the number of en-suites, (one of them was shared!), and
then I noticed not a single RCD in sight.

--
Tony Williams.

In article ,
"Andy Pandy" writes:
My electric shower blew the cartridge fuse in the consumer unit while I was in it the
other day, giving me a very refreshing cold shower. I replaced the fuse, and ran it
for 10 mins or so, and all seemed OK, it didn't blow the new fuse.

Is this something I should be worried about, or do cartridge fuses sometimes blow
with age? The old fuse (and shower) are probably about 12 years old.

It's a 30A fuse, I'm not sure of the power rating of the shower (it's a Heatstore
Esprite II), but I guess it must be taking pretty close to 30A. But it has been
working fine for at least 6 years.

I'm probably being over cautious, but the whole concept of a high power electrical
device which has blown a fuse in close contact with water which gets sprayed on me
has started to worry me.

My hunch would be that the original shower was no more than 7kW,
and has been replaced by one which is more, and is exceeding the
fuse (and possibly wiring) rating. This will blow the fuse, but
only after some time. Check the shower's rating plate. My second
guess would be the element casing has failed.

Would an RCD be advisable?

Depends on the house wiring, type of supply, etc. It can never
do any harm, but it might be completely unnecessary. Showers
do not have to have an RCD unless the earth fault loop impedance
is too high to guarantee the fuse will blow within 5 seconds of
a short circuit to earth. If you don't have the tools to measure
the earth fault loop impedance, you should assume it's too high
to be on the safe side and fit an RCD.

What is important is to make sure all the supplementary bonding
in the bathroom is correctly fitted.

--
Andrew Gabriel

Andrew Gabriel wrote:

If you don't have the tools to measure the earth fault loop
impedance, you should assume it's too high to be on the safe side and
fit an RCD.

From the design point of view you can use Table 7.1 in the On-Site
Guide. If the circuit cable length doesn't exceed the maximum figure
given in the table, for the type and rating of fuse/MCB, the cable size
in use and the type of earthing, you can be reasonably confident that an
RCD won't be required. (TT installations excepted, of course.)

After installation you (somebody) must test the circuit and verify that
Zs is OK. (OSG Appendix 2 Table 2A, B, C or D as appropriate.)

What is important is to make sure all the supplementary bonding
in the bathroom is correctly fitted.

Absolutely. That's a much better step to take than unnecessarily
fitting an RCD, IMHO.

--
Andy

On Sat, 11 Feb 2006 17:46:02 -0000 someone who may be "Andy Pandy"
wrote this:-

It's a 30A fuse, I'm not sure of the power rating of the shower (it's a Heatstore
Esprite II), but I guess it must be taking pretty close to 30A. But it has been
working fine for at least 6 years.

Putting heatstore and shower into a search engine directed me very
rapidly to http://www.qualityshowers.co.uk/heatstore.htm which
reveals that the lowest rating of the current range is 7.2kW, 31.3A.
Assuming that is the rating of your shower then the overload
probably explains the eventual operation of the fuse. However, only
you can tell us what the rating of the shower is.

I suspect it is a replacement for a lower powered shower and would
wonder what the rating of the cable is.

I'm probably being over cautious, but the whole concept of a high power electrical
device which has blown a fuse in close contact with water which gets sprayed on me
has started to worry me. Would an RCD be advisable?

The most important thing with an instant electric heater is that it
is earthed properly. The innards must be solidly connected to the
water pipe and this must be solidly earthed, separate from the
"earth wire" in the cable supplying the shower.

An RCD may provide you with extra peace of mind. It will provide
extra safety, but possibly not as much as some think. Depending on
where the shower is, the electricity supply to the house and the
nature of the fault, a cartridge fuse may operate while an RCD is
still making its mind up.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

"Andrew Gabriel" wrote in message
...
In article ,
"Andy Pandy" writes:
My electric shower blew the cartridge fuse in the consumer unit while I was in it
the
other day, giving me a very refreshing cold shower. I replaced the fuse, and ran
it
for 10 mins or so, and all seemed OK, it didn't blow the new fuse.

Is this something I should be worried about, or do cartridge fuses sometimes blow
with age? The old fuse (and shower) are probably about 12 years old.

It's a 30A fuse, I'm not sure of the power rating of the shower (it's a Heatstore
Esprite II), but I guess it must be taking pretty close to 30A. But it has been
working fine for at least 6 years.

I'm probably being over cautious, but the whole concept of a high power
electrical
device which has blown a fuse in close contact with water which gets sprayed on
me
has started to worry me.

My hunch would be that the original shower was no more than 7kW,
and has been replaced by one which is more, and is exceeding the
fuse (and possibly wiring) rating.

The shower was in the house when we bought it over 6 years ago.

This will blow the fuse, but
only after some time. Check the shower's rating plate.

It's 8.5Kw! How has that been working for 6 years with a 30A fuse?

My second
guess would be the element casing has failed.

Would that not cause it to blow the new fuse pretty quick? I ran it for 10 mins after
replacing the fuse and had a shower this morning and it has been OK.

Would an RCD be advisable?

Depends on the house wiring, type of supply, etc. It can never
do any harm, but it might be completely unnecessary. Showers
do not have to have an RCD unless the earth fault loop impedance
is too high to guarantee the fuse will blow within 5 seconds of
a short circuit to earth.

5 seconds sounds like a very long time - wouldn't 240V for 5 seconds likely kill?

If you don't have the tools to measure
the earth fault loop impedance, you should assume it's too high
to be on the safe side and fit an RCD.

I might get a new consumer unit with RCD. Currently I've got 2 consumer units, one
look fairly new with cartridge fuses, the other looks ancient and has the pull out
rewireable fuses. I've got another shower that runs off the old CU.

What is important is to make sure all the supplementary bonding
in the bathroom is correctly fitted.

I don't think there is any! Would it have been the norm to do this pre 1994 (when I
think this room was converted into a bathroom)? I doubt there is in the other
bathroom either, and that's got a shower over a metal bath!

One question about bonding - I can see it would make the bathroom safe but doesn't it
increase the risk outside the bathroom (by potentially making more things outside the
bathroom, eg radiators, live)?

--
Andy

"David Hansen" wrote in message
...
It's a 30A fuse, I'm not sure of the power rating of the shower (it's a Heatstore
Esprite II), but I guess it must be taking pretty close to 30A. But it has been
working fine for at least 6 years.

Putting heatstore and shower into a search engine directed me very
rapidly to http://www.qualityshowers.co.uk/heatstore.htm which
reveals that the lowest rating of the current range is 7.2kW, 31.3A.
Assuming that is the rating of your shower then the overload
probably explains the eventual operation of the fuse. However, only
you can tell us what the rating of the shower is.

I suspect it is a replacement for a lower powered shower and would
wonder what the rating of the cable is.

The cable is 6.0 T&E (at least that what is says on the clips). The shower is 8.5Kw
so I don't understand how it works with a 30A fuse.

I'm probably being over cautious, but the whole concept of a high power electrical
device which has blown a fuse in close contact with water which gets sprayed on me
has started to worry me. Would an RCD be advisable?

The most important thing with an instant electric heater is that it
is earthed properly. The innards must be solidly connected to the
water pipe and this must be solidly earthed, separate from the
"earth wire" in the cable supplying the shower.

The cold water pipe is earthed, but I'm not sure it's earthed near the shower inlet.

An RCD may provide you with extra peace of mind. It will provide
extra safety, but possibly not as much as some think. Depending on
where the shower is, the electricity supply to the house and the
nature of the fault, a cartridge fuse may operate while an RCD is
still making its mind up.

Isn't an RCD supposed to cut the supply much quicker than a fuse?

--
Andy

In article ,
"Andy Pandy" writes:

"Andrew Gabriel" wrote in message
...
My hunch would be that the original shower was no more than 7kW,
and has been replaced by one which is more, and is exceeding the
fuse (and possibly wiring) rating.

The shower was in the house when we bought it over 6 years ago.

This will blow the fuse, but
only after some time. Check the shower's rating plate.

It's 8.5Kw! How has that been working for 6 years with a 30A fuse?

Well, it's only 35.4A.

My second
guess would be the element casing has failed.

Would that not cause it to blow the new fuse pretty quick? I ran it for 10 mins after
replacing the fuse and had a shower this morning and it has been OK.

Again, it could simply cause a little extra current draw.

Would an RCD be advisable?

Depends on the house wiring, type of supply, etc. It can never
do any harm, but it might be completely unnecessary. Showers
do not have to have an RCD unless the earth fault loop impedance
is too high to guarantee the fuse will blow within 5 seconds of
a short circuit to earth.

5 seconds sounds like a very long time - wouldn't 240V for 5 seconds likely kill?

I depends what you did with it. The time here is to limit the
amount the cables heat up, so they don't damage themselves or
cause a fire. You should not be in any danger during the fault
regardless how long it goes on for, providing your bonding is
to spec.

If you don't have the tools to measure
the earth fault loop impedance, you should assume it's too high
to be on the safe side and fit an RCD.

I might get a new consumer unit with RCD. Currently I've got 2 consumer units, one
look fairly new with cartridge fuses, the other looks ancient and has the pull out
rewireable fuses. I've got another shower that runs off the old CU.

I wonder if anyone has calculated your demand loading against your
supply. You can't normally get more than one electric shower on a
100A domestic supply.

What is important is to make sure all the supplementary bonding
in the bathroom is correctly fitted.

I don't think there is any! Would it have been the norm to do this pre 1994 (when I
think this room was converted into a bathroom)? I doubt there is in the other
bathroom either, and that's got a shower over a metal bath!

Yes it was normal before.

One question about bonding - I can see it would make the bathroom safe but doesn't it
increase the risk outside the bathroom (by potentially making more things outside the
bathroom, eg radiators, live)?

No, except that if you have plastic pipework, you shouldn't bond
radiators, baths, etc, as the plastic pipework (of at least 0.5m
length) is actually a good insulator, even with water in it.

--
Andrew Gabriel

"Gary Cavie" wrote in message
t...
The cable is 6.0 T&E (at least that what is says on the clips). The shower is
8.5Kw
so I don't understand how it works with a 30A fuse.

Fuses don't blow just above their current rating, they'll take an
overload for quite some time. Take a look at
http://www.tlc-direct.co.uk/Figures/3.13b.gif - This graph is for BS3036
rewireable fuses. Pulling 40A through it (on the bottom scale), and
follow the line up - it meets (if ever) way, way off the graph. Even a
15A fuse would take 10s according to these curves!

It's a BS1361 cartridge fuse - these blow much quicker than the rewireable ones don't
they?

An RCD may provide you with extra peace of mind. It will provide
extra safety, but possibly not as much as some think. Depending on
where the shower is, the electricity supply to the house and the
nature of the fault, a cartridge fuse may operate while an RCD is
still making its mind up.

Isn't an RCD supposed to cut the supply much quicker than a fuse?

If the fault is a hard P-N short, the RCD won't even bat an eyelid at it
- both sides are balanced.

Yes, but a hard P-N short with no earth leakage would not usually present an
electrocution danger would it?

--
Andy

In article ,
lid says...

"Gary Cavie" wrote in message
t...
The cable is 6.0 T&E (at least that what is says on the clips). The shower is
8.5Kw
so I don't understand how it works with a 30A fuse.

Fuses don't blow just above their current rating, they'll take an
overload for quite some time. Take a look at
http://www.tlc-direct.co.uk/Figures/3.13b.gif - This graph is for BS3036
rewireable fuses. Pulling 40A through it (on the bottom scale), and
follow the line up - it meets (if ever) way, way off the graph. Even a
15A fuse would take 10s according to these curves!

It's a BS1361 cartridge fuse - these blow much quicker than the rewireable ones don't
they?

Looking at the graph for that one (3.14b.gif), yes it does, but a 30A
pulling 40A is still off the graph!


An RCD may provide you with extra peace of mind. It will provide
extra safety, but possibly not as much as some think. Depending on
where the shower is, the electricity supply to the house and the
nature of the fault, a cartridge fuse may operate while an RCD is
still making its mind up.

Isn't an RCD supposed to cut the supply much quicker than a fuse?

If the fault is a hard P-N short, the RCD won't even bat an eyelid at it
- both sides are balanced.

Yes, but a hard P-N short with no earth leakage would not usually present an
electrocution danger would it?

That scenario was in answer to the bit about RCDs blowing faster than
fuses!


--
Andy

On Sun, 12 Feb 2006 19:58:42 -0000 someone who may be "Andy Pandy"
wrote this:-

The cable is 6.0 T&E (at least that what is says on the clips).

How is it installed? Is it run through thermal insulation, clipped
to a wall, enclosed in conduit? Is it grouped with other cables?

The cold water pipe is earthed, but I'm not sure it's earthed near the shower inlet.

There should be bonding between metal pipes, metal baths and
electrical equipment in the bathroom. It can be concealed and hard
to find, but if it is not there the installation is dangerous.

If there are several earthed metal pipes running to the bathroom,
say hot/cold water and heating flow/return, and these are bonded to
the shower, then that is solid enough earthing. However, changes to
the plumbing may change this.

Isn't an RCD supposed to cut the supply much quicker than a fuse?

A common misconception. Fuses don't have mechanical parts which have
to move to open the circuit. Depending on the supply and the fault,
a fuse may disconnect a circuit far faster than an RCD.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

"Gary Cavie" wrote in message
t...
Fuses don't blow just above their current rating, they'll take an
overload for quite some time. Take a look at
http://www.tlc-direct.co.uk/Figures/3.13b.gif - This graph is for BS3036
rewireable fuses. Pulling 40A through it (on the bottom scale), and
follow the line up - it meets (if ever) way, way off the graph. Even a
15A fuse would take 10s according to these curves!

It's a BS1361 cartridge fuse - these blow much quicker than the rewireable ones
don't
they?

Looking at the graph for that one (3.14b.gif), yes it does, but a 30A
pulling 40A is still off the graph!

That would explain it! Thanks.

An RCD may provide you with extra peace of mind. It will provide
extra safety, but possibly not as much as some think. Depending on
where the shower is, the electricity supply to the house and the
nature of the fault, a cartridge fuse may operate while an RCD is
still making its mind up.

Isn't an RCD supposed to cut the supply much quicker than a fuse?

If the fault is a hard P-N short, the RCD won't even bat an eyelid at it
- both sides are balanced.

Yes, but a hard P-N short with no earth leakage would not usually present an
electrocution danger would it?

That scenario was in answer to the bit about RCDs blowing faster than
fuses!

Yes, sorry, what I meant to write was that an RCD is likely to cut the supply quicker
than a fuse in the event of electrocution (except of course in a pure P-N
electrocution, which I guess is very rare).

--
Andy

"David Hansen" wrote in message
...
The cable is 6.0 T&E (at least that what is says on the clips).

How is it installed? Is it run through thermal insulation, clipped
to a wall, enclosed in conduit? Is it grouped with other cables?

A bit of all really! As far as I can tell, it runs through an internal wall with the
cold pipe, up into the loft (insulated), then down through another internal wall and
ends up in the cellar at the CU, at that end there are a load of cables going into a
conduit.

The cold water pipe is earthed, but I'm not sure it's earthed near the shower
inlet.

There should be bonding between metal pipes, metal baths and
electrical equipment in the bathroom. It can be concealed and hard
to find, but if it is not there the installation is dangerous.

I can't find any. Rather than taking floorboards up etc - can the bonding be checked
by measuring the resistance? Are there any good on-line guides on how to do this? A
simple test confirms electrical connection between the main metal items.

If there are several earthed metal pipes running to the bathroom,
say hot/cold water and heating flow/return, and these are bonded to
the shower, then that is solid enough earthing. However, changes to
the plumbing may change this.

Indeed.

--
Andy

"Andrew Gabriel" wrote in message
...
This will blow the fuse, but
only after some time. Check the shower's rating plate.

It's 8.5Kw! How has that been working for 6 years with a 30A fuse?

Well, it's only 35.4A.

I did assume 35.4A for 10 mins through a 30A fuse would blow it...but it seems I was
wrong.

My second
guess would be the element casing has failed.

Would that not cause it to blow the new fuse pretty quick? I ran it for 10 mins
after
replacing the fuse and had a shower this morning and it has been OK.

Again, it could simply cause a little extra current draw.

Would an RCD be advisable?

Depends on the house wiring, type of supply, etc. It can never
do any harm, but it might be completely unnecessary. Showers
do not have to have an RCD unless the earth fault loop impedance
is too high to guarantee the fuse will blow within 5 seconds of
a short circuit to earth.

5 seconds sounds like a very long time - wouldn't 240V for 5 seconds likely kill?

I depends what you did with it. The time here is to limit the
amount the cables heat up, so they don't damage themselves or
cause a fire. You should not be in any danger during the fault
regardless how long it goes on for, providing your bonding is
to spec.

Yes - I need to check this. Is this something fairly easy to do? Are there any good
online guides?

If you don't have the tools to measure
the earth fault loop impedance, you should assume it's too high
to be on the safe side and fit an RCD.

I might get a new consumer unit with RCD. Currently I've got 2 consumer units,
one
look fairly new with cartridge fuses, the other looks ancient and has the pull
out
rewireable fuses. I've got another shower that runs off the old CU.

I wonder if anyone has calculated your demand loading against your
supply. You can't normally get more than one electric shower on a
100A domestic supply.

Good point - I don't think the two showers have ever been used together. Put the oven
on and boil a kettle and I guess that's pretty close to 100A.

What is important is to make sure all the supplementary bonding
in the bathroom is correctly fitted.

I don't think there is any! Would it have been the norm to do this pre 1994 (when
I
think this room was converted into a bathroom)? I doubt there is in the other
bathroom either, and that's got a shower over a metal bath!

Yes it was normal before.

One question about bonding - I can see it would make the bathroom safe but
doesn't it
increase the risk outside the bathroom (by potentially making more things outside
the
bathroom, eg radiators, live)?

No, except that if you have plastic pipework, you shouldn't bond
radiators, baths, etc, as the plastic pipework (of at least 0.5m
length) is actually a good insulator, even with water in it.

The pipework is mostly copper, with a bit of lead.

--
Andy

There should be bonding between metal pipes, metal baths and
electrical equipment in the bathroom. It can be concealed and hard
to find, but if it is not there the installation is dangerous.

Thats a bit over the top and a very sweeping statement.Have you seen the
bathroom in question ?.The potential is there for it to be dangerous under
certain circumstances true, but there are thousands of bathrooms up and
down the country which have no bonding. And I have been to some where the
bonding is infact incorrect. I don't think it was very wise to put the
fear of god into people that they are taking their lives in their hands
just having a shower.

Dave

On Sun, 12 Feb 2006 20:45:17 +0000, Andrew Gabriel wrote:

In article ,
"Andy Pandy" writes:



No, except that if you have plastic pipework, you shouldn't bond
radiators, baths, etc, as the plastic pipework (of at least 0.5m
length) is actually a good insulator, even with water in it.

I may have missed something here. I thought the reg was that
supplementary bonding could be omitted if there was less than 0.5m of
copper pipe?


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

On Mon, 13 Feb 2006 05:57:08 +0000 someone who may be Dave Stanton
wrote this:-

There should be bonding between metal pipes, metal baths and
electrical equipment in the bathroom. It can be concealed and hard
to find, but if it is not there the installation is dangerous.

Thats a bit over the top and a very sweeping statement.

It is a correct statement, when there is a shower in the bathroom
where water passes over an uninsulated heating element and one is
relying on there not being a large amount of leakage.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On Sun, 12 Feb 2006 22:32:38 -0000 someone who may be "Andy Pandy"
wrote this:-

How is it installed? Is it run through thermal insulation, clipped
to a wall, enclosed in conduit? Is it grouped with other cables?

A bit of all really! As far as I can tell, it runs through an internal wall with the
cold pipe, up into the loft (insulated),

Is it above the insulation, below it, or in the middle of it?

then down through another internal wall and
ends up in the cellar at the CU, at that end there are a load of cables going into a
conduit.

How long is this conduit?

I can't find any. Rather than taking floorboards up etc - can the bonding be checked
by measuring the resistance?

Not really, unless you wish to disconnect them from the rest of the
house:-)

Is the shower above a metal bath? If so is there a green and yellow
wire going to that? Is there any low level electrical equipment in
the room, such as a towel rail, if so is there a similar wire going
to the equipment or the box from which it is fed.

I suspect this is something in the FAQ, but if not there is probably
much information available. Look for supplementary bonding in a
search engine.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

"David Hansen" wrote in message
...
How is it installed? Is it run through thermal insulation, clipped
to a wall, enclosed in conduit? Is it grouped with other cables?

A bit of all really! As far as I can tell, it runs through an internal wall with
the
cold pipe, up into the loft (insulated),

Is it above the insulation, below it, or in the middle of it?

Below - but this is only a short run (maybe 3-4 foot).

then down through another internal wall and
ends up in the cellar at the CU, at that end there are a load of cables going into
a
conduit.

How long is this conduit?

Well it drops 2 stories from the loft to the cellar. The only other cables coming out
at the loft end are lighting cables by the looks of it.

I can't find any. Rather than taking floorboards up etc - can the bonding be
checked
by measuring the resistance?

Not really, unless you wish to disconnect them from the rest of the
house:-)

Is the shower above a metal bath?

The shower referred to in my OP isn't, it's in a shower cubicle. My other shower,
however, is over a metal bath.

If so is there a green and yellow
wire going to that?

I can't find any earth cables anywhere in either bathroom, but I've not had a proper
look under the floorboards. Would you expect the hot & cold pipes feeding the sink to
be connected above the floor level - because they certainly aren't in either
bathroom.

Is there any low level electrical equipment in
the room, such as a towel rail, if so is there a similar wire going
to the equipment or the box from which it is fed.

Nope - no low level electrical equipement unless you count the immersion heater which
is in the airing cupboard in the bathroom.

I suspect this is something in the FAQ, but if not there is probably
much information available. Look for supplementary bonding in a
search engine.

Have done.

http://www.tlc-direct.co.uk/Book/5.4.3.htm

looks like a pretty good guide.

Thanks.

--
Andy

"Andy Pandy" wrote in message
...
I wonder if anyone has calculated your demand loading against your
supply. You can't normally get more than one electric shower on a
100A domestic supply.

Good point - I don't think the two showers have ever been used together. Put the
oven
on and boil a kettle and I guess that's pretty close to 100A.

In fact it would appear that the supplier fuse is only 60A, and the meter is only
40A! Yet there are 2 8.5Kw electric showers! I don't think we've ever used both
together.

How easy/expensive is it to get the supply & meter upgraded to 100A?

--
Andy

On Tue, 14 Feb 2006 22:33:42 -0000 someone who may be "Andy Pandy"
wrote this:-

Is it above the insulation, below it, or in the middle of it?

Below - but this is only a short run (maybe 3-4 foot).

Then the insulation will need to be considered in your cable sizing
calculations. If a cable passes through an insulated wall, such as a
cavity insulated wall, then the heat can escape at either end of the
insulation, but in this case the distance is too great.

then down through another internal wall and
ends up in the cellar at the CU, at that end there are a load of cables going into
a conduit.

How long is this conduit?

Well it drops 2 stories from the loft to the cellar. The only other cables coming out
at the loft end are lighting cables by the looks of it.

The question is how many cables go into it at the bottom and how
heavily loaded they are. It sounds like you will need to take the
grouping into consideration in your calculations. Lighting cables
can often be ignored in such calculations, if they are lightly
loaded.

The shower referred to in my OP isn't, it's in a shower cubicle. My other shower,
however, is over a metal bath.

The book you mention below is a good guide to what needs doing in
both cases.

I can't find any earth cables anywhere in either bathroom, but I've not had a proper
look under the floorboards.

Then you have two options. The first option is to take up the
floorboards and have a proper look, with all that this entails. The
second option is to add some supplementary bonding yourself. Only
you can decide which course to take.

There is a third option, do nothing, but I wouldn't recommend it.

Would you expect the hot & cold pipes feeding the sink to
be connected above the floor level

Not necessarily. If it was done then it might well have been done
out of sight, which is neater but gives doubts to people who come
along later. However, it may not have been done. I don't know the
history of the house and its services.

Bonding can be done neatly, by hiding the cables behind pipes and
putting the clamps up behind fittings.

One clue would be if you have a metal sink in the kitchen. Is this
bonded? If it is then that implies that at some time someone who
knew what they were doing was involved with the electrics.

The bonding should have been checked when the showers were
installed. At the very least I would expect a green and yellow wire
going from the shower unit to the metal bath. If it does not have an
earth tab then a bolt can be screwed into one of the feet.

http://www.tlc-direct.co.uk/Book/5.4.3.htm

I see from the bottom that it was, "Extracted from The Electricians
Guide Fifth Edition by John Whitfield". This is an excellent book
that I recommend to anyone who is thinking of doing electrical work
themselves. Buy or borrow a copy. The actual Wiring Regulations are
in a "harmonised" format, which makes them difficult to follow until
one knows them well and so not suitable for many people.

The diagram tells you more than a thousand words. Note that the
bonding to the shower tray assumes a metal waste pipe, there is no
need to bond little bits of metal such as the strainers in the
bottom of shower trays.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

"David Hansen" wrote in message
...
Is it above the insulation, below it, or in the middle of it?

Below - but this is only a short run (maybe 3-4 foot).

Then the insulation will need to be considered in your cable sizing
calculations. If a cable passes through an insulated wall, such as a
cavity insulated wall, then the heat can escape at either end of the
insulation, but in this case the distance is too great.

It doesn't go through an insulated wall (it's an internal wall).

then down through another internal wall and
ends up in the cellar at the CU, at that end there are a load of cables going
into
a conduit.

How long is this conduit?

Well it drops 2 stories from the loft to the cellar. The only other cables coming
out
at the loft end are lighting cables by the looks of it.

The question is how many cables go into it at the bottom and how
heavily loaded they are. It sounds like you will need to take the
grouping into consideration in your calculations. Lighting cables
can often be ignored in such calculations, if they are lightly
loaded.

It looks like the cooker cable and a few light cables go in at the bottom. The cooker
is almost directly above the CU so the cable won't go very far till it branches out
of the conduit.

Would you expect the hot & cold pipes feeding the sink to
be connected above the floor level

Not necessarily. If it was done then it might well have been done
out of sight, which is neater but gives doubts to people who come
along later. However, it may not have been done. I don't know the
history of the house and its services.

Bonding can be done neatly, by hiding the cables behind pipes and
putting the clamps up behind fittings.

One clue would be if you have a metal sink in the kitchen. Is this
bonded? If it is then that implies that at some time someone who
knew what they were doing was involved with the electrics.

The kitchen and utility rooms are bonded - there is bonding between the hot & cold
pipes and the sink, and the bonding cable then goes into the plaster so it presumably
bonds with the earth wire of the electrical socket ring.

I guess (as per fig 5.15 in the link below), this means that bonding the metal cases
of appliances like the washing machine and the dishwasher is not required.

These rooms are in an extended part of the house (built c1994), but the bathroom is
ancient (I think it's the original 1930's cast iron bath!). The shower room (en
suite) is in the old part of the house but is a converted bedroom.

I would imagine the wiring was done correctly for the extension, but the conversion
of the en suite and installation of the showers was a separate project. The fact that
two electric showers are installed when the supply fuse is only 60A and the meter is
only 40A does not inspire confidence.

The bonding should have been checked when the showers were
installed. At the very least I would expect a green and yellow wire
going from the shower unit to the metal bath. If it does not have an
earth tab then a bolt can be screwed into one of the feet.

Nope - there appears to be none unless it is very strangely routed.

Of course it may be that the resistance of the bath to earth is greater than
50kOhms - thus not requiring bonding as per the link below. The pipes entering the
bath are actually lead - about 2 foot of lead connects the copper pipes of the cold
and hot water supplies.

http://www.tlc-direct.co.uk/Book/5.4.3.htm

I see from the bottom that it was, "Extracted from The Electricians
Guide Fifth Edition by John Whitfield". This is an excellent book
that I recommend to anyone who is thinking of doing electrical work
themselves. Buy or borrow a copy.

Yes, will do. Thanks.

The actual Wiring Regulations are
in a "harmonised" format, which makes them difficult to follow until
one knows them well and so not suitable for many people.

The diagram tells you more than a thousand words. Note that the
bonding to the shower tray assumes a metal waste pipe, there is no
need to bond little bits of metal such as the strainers in the
bottom of shower trays.

Is bonding the copper pipe just as it enters the shower sufficient, or should the
bonding be attached to the actual shower metalwork/earth terminal?

--
Andy

On Wed, 15 Feb 2006 17:25:13 -0000 someone who may be "Andy Pandy"
wrote this:-

It doesn't go through an insulated wall (it's an internal wall).

It was just an illustration. You will need to consider the rating of
the cable when it has thermal insulation on one side.

It looks like the cooker cable and a few light cables go in at the bottom. The cooker
is almost directly above the CU so the cable won't go very far till it branches out
of the conduit.

Unless it is somewhat less than a metre you will need to consider
the grouping factor, assuming that the cooker cable feeds an
electric cooker.

I guess (as per fig 5.15 in the link below), this means that bonding the metal cases
of appliances like the washing machine and the dishwasher is not required.

It is not required. Where equipment is connected by short cables
this is enough.

I would imagine the wiring was done correctly for the extension, but the conversion
of the en suite and installation of the showers was a separate project.

Quite possibly.

The fact that
two electric showers are installed when the supply fuse is only 60A and the meter is
only 40A does not inspire confidence.

That depends on the assessed maximum demand and diversity, but it is
certainly not ideal. Do you have an overhead line or cable supplying
the house?

Is bonding the copper pipe just as it enters the shower sufficient, or should the
bonding be attached to the actual shower metalwork/earth terminal?

That depends:-)

With bonding one needs to understand what is required and what is
not. People not understanding come up with horrors from time to
time; such as metal window frames, radiators and the metal in a sink
strainer all being bonded with little green and yellow wires that
will soon be broken off. Fortunately such things are pointless
anyway.

If pipes are made out of metal and there is reliable metal to metal
contact between pipes and fittings then little is gained by bonding.
The pipes and fittings are more conductive than any bonding cable
one will see in a house anyway.

One reason for supplementary bonding is to ensure that things people
are liable to be in contact with are at the same potential. Taps are
turned off with wet hands, lowering the insulation resistance of dry
hands. People touch towel rails with wet hands to get a towel. If
the metalwork of a shower was to become live then it is a good idea
if the bath is at the same potential.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

In article ,
"Andy Pandy" writes:
How easy/expensive is it to get the supply & meter upgraded to 100A?

It used to be free, when your supplier owned the network.
I haven't needed to get it done since the businesses were
split up. No one seems to worry about 40A meters -- they
are commonly used on 100A supplies.

Your own CU and wiring had to be already suitable for 100A,
main earthing up to spec, etc. or I suspect they would
refuse the upgrade.

--
Andrew Gabriel

"David Hansen" wrote in message
...
The fact that
two electric showers are installed when the supply fuse is only 60A and the meter
is
only 40A does not inspire confidence.

That depends on the assessed maximum demand and diversity, but it is
certainly not ideal. Do you have an overhead line or cable supplying
the house?

A cable. The main earth terminal is a clamp around the incoming cable - so if I've
understood the FAQ correctly it's a TN-S system.

Is bonding the copper pipe just as it enters the shower sufficient, or should the
bonding be attached to the actual shower metalwork/earth terminal?

That depends:-)

With bonding one needs to understand what is required and what is
not. People not understanding come up with horrors from time to
time; such as metal window frames, radiators and the metal in a sink
strainer all being bonded with little green and yellow wires that
will soon be broken off. Fortunately such things are pointless
anyway.

Bonding metal window frames can be dangerous AIUI, as a fault could electrocute a
window cleaner outside.

Radiators surely need bonding? (assuming the resistance to earth is less than 50
kOhms).

If pipes are made out of metal and there is reliable metal to metal
contact between pipes and fittings then little is gained by bonding.
The pipes and fittings are more conductive than any bonding cable
one will see in a house anyway.

Exactly. I'd have thought a test would be to measure the impedance between metal
objects which are connected via pipes, and if this is greater than a certain value
bonding is required. After all bonding simply reduces that impedance. Obviously this
would need to be redone after any plumbing work is carried out.

What am I missing here?

--
Andy

"Andrew Gabriel" wrote in message
...
How easy/expensive is it to get the supply & meter upgraded to 100A?

It used to be free, when your supplier owned the network.

I phoned them - it's still free.

I haven't needed to get it done since the businesses were
split up. No one seems to worry about 40A meters -- they
are commonly used on 100A supplies.

That's good because they told me I'd have to arrange a meter change with the company
I pay the bills to, who then need to arrange it with them.

Your own CU and wiring had to be already suitable for 100A,
main earthing up to spec, etc. or I suspect they would
refuse the upgrade.

I have 2 CU's, one is old and probably isn't suitable, but the other supports 100A.
Would this be OK, provided the new one takes most of the load? The earthing is TN-S.

--
Andy

On Fri, 17 Feb 2006 09:38:14 -0000 someone who may be "Andy Pandy"
wrote this:-

Do you have an overhead line or cable supplying the house?

A cable.

I'm surprised there is only a 60A fuse on it then. Perhaps it is
fairly elderly.

The electricity supply system assumes what seems to those who do not
know about it a remarkably high level of diversity, but it still
works most of the time. Even if both showers were running together
they would only be on for a relatively short period of time.

The main earth terminal is a clamp around the incoming cable - so if I've
understood the FAQ correctly it's a TN-S system.

That's likely.

Radiators surely need bonding?

Consider water taps. Are they bonded? Assuming metal pipes, there is
reliable metal to metal contact at the joint between the bonded pipe
and the tap. If such joints were not reliable then every length of
pipe and tap would need to be bonded.

A radiator is a similar consideration. In a bathroom if the central
heating pipes are bonded in the bathroom (and they should also be
bonded by main bonding conductors elsewhere) does adding another
bonding cable to the radiator achieve anything?


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

"David Hansen" wrote in message
...
Do you have an overhead line or cable supplying the house?

A cable.

I'm surprised there is only a 60A fuse on it then. Perhaps it is
fairly elderly.

Well it's in a bakelite box with 60A written on it - unless the fuse was upgraded but
the box not changed/labelled? Are such things known?

Radiators surely need bonding?

Consider water taps. Are they bonded? Assuming metal pipes, there is
reliable metal to metal contact at the joint between the bonded pipe
and the tap. If such joints were not reliable then every length of
pipe and tap would need to be bonded.

A radiator is a similar consideration. In a bathroom if the central
heating pipes are bonded in the bathroom

Sorry - that's what I meant - I didn't mean the radiator itself necessarily needs
bonding, but the pipes to it.

--
Andy

On Fri, 17 Feb 2006 12:53:54 -0000 someone who may be "Andy Pandy"
wrote this:-

Well it's in a bakelite box with 60A written on it - unless the fuse was upgraded but
the box not changed/labelled? Are such things known?

No. One might be able to fit a fuse of a smaller rating, as it is
physically smaller, but not a fuse of larger rating.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On Fri, 17 Feb 2006 09:38:14 +0000, Andy Pandy wrote:


Radiators surely need bonding? (assuming the resistance to earth is less than 50
kOhms).

No but their supply pipes do if they are more than 0.5m of metal pipe.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html