Am I right in assuming that when T + E cable is referred to as 2.5mm that is
the diameter of the bare conductor?

Is there a chart anywhere that gives the outside dimensions including all
the insulation?


--
Dave
The Medway Handyman
www.medwayhandyman.co.uk
01634 717930
07850 597257

Am I right in assuming that when T + E cable is referred to as 2.5mm that is
the diameter of the bare conductor?

It's the cross-sectional area of the conductor...

"The Medway Handyman" wrote in message
...
Am I right in assuming that when T + E cable is referred to as 2.5mm that
is the diameter of the bare conductor?

Bugger me. You're one of the last people I'd expect to be asking that
question. Surely you've seen enough 2.5 T+E over the past few years, even if
you're not doing electrical bits, for the answer to be obvious?

(area, as Colin said, coz that's the relevant bit for resistance/current
carrying capacity)

cheers,
clive

On Mon, 3 Sep 2007 23:28:09 UTC, Colin Wilson
o.uk wrote:

Am I right in assuming that when T + E cable is referred to as 2.5mm that is
the diameter of the bare conductor?

It's the cross-sectional area of the conductor...

pedant
It's the cross sectional area of the main conductors, but probably not
the CPC ('earth').
/pedant
--
The information contained in this post is copyright the
poster, and specifically may not be published in, or used by
http://www.diybanter.com

"The Medway Handyman" wrote in message
...
Am I right in assuming that when T + E cable is referred to as 2.5mm that
is the diameter of the bare conductor?

No. It is the cross-sectional area. Single strand 2.5mm^2 conductors will be
about 1.8mm diameter.

Is there a chart anywhere that gives the outside dimensions including all
the insulation?

The cable manufacturers used to do data books giving that information, but I
usually just get a bit and measure it, if I need to know.

Colin Bignell.

Clive George wrote:
"The Medway Handyman" wrote in
message ...
Am I right in assuming that when T + E cable is referred to as 2.5mm
that is the diameter of the bare conductor?

Bugger me.

I'd rather not, if its all the same to you :-)

You're one of the last people I'd expect to be asking that
question. Surely you've seen enough 2.5 T+E over the past few years,
even if you're not doing electrical bits, for the answer to be
obvious?

Indeed I have, but I hadn't ever thought of it before.

(area, as Colin said, coz that's the relevant bit for
resistance/current carrying capacity)

Obvious now I think about it.

I was just after a quick rule of thumb guide so I could measure to outside
of the insulation & tell if it was 4mm or 6mm without having to disconnect
things & get a vernier out. 2.5mm was just used as an example.


--
Dave
The Medway Handyman
www.medwayhandyman.co.uk
01634 717930
07850 597257

"The Medway Handyman" wrote in message
...
Am I right in assuming that when T + E cable is referred to as 2.5mm that
is the diameter of the bare conductor?

Is there a chart anywhere that gives the outside dimensions including all
the insulation?

PLEASE tell us all that you no longer do any electrical work (even making an
allowance for Part P sillyness!). THIS is one of the very first things you
are taught in 'electrical college' after "DO NOT put the screwdriver in
there!!!"

HTH

John

The Medway Handyman wrote:

I was just after a quick rule of thumb guide so I could measure to outside
of the insulation & tell if it was 4mm or 6mm without having to disconnect
things & get a vernier out. 2.5mm was just used as an example.

I've posted this befo

CSA (CPC) Strands Overall
mm^2 No./dia. mm approx.
--------- ------- ----------
1.0 (1.0) 1/1.13 4.5 x 8.2
1.5 (1.0) 1/1.38 4.7 x 8.2
2.5 (1.5) 1/1.78* 5.3 x 9.9
4.0 (1.5) 7/0.85 6.1 x 11.4
6.0 (2.5) 7/1.04 6.8 x 13.1
10 (4.0) 7/1.35 8.4 x 16.8
16 (6.0) 7/1.71 9.6 x 19.5

* or 7/0.67

--
Andy

It's the cross-sectional area of the conductor...
pedant
It's the cross sectional area of the main conductors, but probably not
the CPC ('earth').
/pedant

I never said which conductor :-p

I've posted this befo

CSA (CPC) Strands Overall
mm^2 No./dia. mm approx.
--------- ------- ----------
1.0 (1.0) 1/1.13 4.5 x 8.2
1.5 (1.0) 1/1.38 4.7 x 8.2
2.5 (1.5) 1/1.78* 5.3 x 9.9
4.0 (1.5) 7/0.85 6.1 x 11.4
6.0 (2.5) 7/1.04 6.8 x 13.1
10 (4.0) 7/1.35 8.4 x 16.8
16 (6.0) 7/1.71 9.6 x 19.5

* or 7/0.67

You, sir, are a god :-p

John wrote:
"The Medway Handyman" wrote in
message ...
Am I right in assuming that when T + E cable is referred to as 2.5mm
that is the diameter of the bare conductor?

Is there a chart anywhere that gives the outside dimensions
including all the insulation?

PLEASE tell us all that you no longer do any electrical work (even
making an allowance for Part P sillyness!). THIS is one of the very
first things you are taught in 'electrical college' after "DO NOT put
the screwdriver in there!!!"

The reason I want to spot the difference quickly & easily is so I don't get
into problem situations. I've been asked to remove an old electric cooker
and install a new one. The new one is 9kw. Before I get involved I want to
check that the cable is big enough. If not I will turn the job down.

Its called "if you are not sure check it out". Basic common sense.

And don't talk to me about 'qualified electricians' - I've seen more bodge
ups & sloppy work from them than anything else.


--
Dave
The Medway Handyman
www.medwayhandyman.co.uk
01634 717930
07850 597257

On Tue, 04 Sep 2007 00:23:11 GMT, "The Medway Handyman"
mused:

John wrote:
"The Medway Handyman" wrote in
message ...
Am I right in assuming that when T + E cable is referred to as 2.5mm
that is the diameter of the bare conductor?

Is there a chart anywhere that gives the outside dimensions
including all the insulation?

PLEASE tell us all that you no longer do any electrical work (even
making an allowance for Part P sillyness!). THIS is one of the very
first things you are taught in 'electrical college' after "DO NOT put
the screwdriver in there!!!"

The reason I want to spot the difference quickly & easily is so I don't get
into problem situations. I've been asked to remove an old electric cooker
and install a new one. The new one is 9kw. Before I get involved I want to
check that the cable is big enough. If not I will turn the job down.

Be aware that insulation thickness can vary wildly.
--
Regards,
Stuart.

The Medway Handyman wrote:
Am I right in assuming that when T + E cable is referred to as 2.5mm that is
the diameter of the bare conductor?

CSA of phase/neutral

Is there a chart anywhere that gives the outside dimensions including all
the insulation?

http://wiki.diyfaq.org.uk/index.php?title=Cables


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John wrote:

PLEASE tell us all that you no longer do any electrical work (even making an
allowance for Part P sillyness!). THIS is one of the very first things you
are taught in 'electrical college' after "DO NOT put the screwdriver in
there!!!"

In the grand scheme of things, it makes little difference. As long as
you know what size cable you should be using where, whether the units
are CSA in mm^2, or diameter in micro furlongs does not make much
difference.

I can't believe that if you walked into an electrical wholesalers and
said "give me a reel of 2.5mm twin and earth" they would have any
difficulty understanding what you meant.

(in fact I can't ever remember asking for cable and going through the
verbal gymnastics required to include "squared" in the request)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Tue, 4 Sep 2007 00:55:11 UTC, John Rumm
wrote:

John wrote:

PLEASE tell us all that you no longer do any electrical work (even making an
allowance for Part P sillyness!). THIS is one of the very first things you
are taught in 'electrical college' after "DO NOT put the screwdriver in
there!!!"

In the grand scheme of things, it makes little difference. As long as
you know what size cable you should be using where, whether the units
are CSA in mm^2, or diameter in micro furlongs does not make much
difference.

For the record, in case MH finds it useful...!

Diameter of 2.5T+E is about 8.85 ufurlongs...

--
The information contained in this post is copyright the
poster, and specifically may not be published in, or used by
http://www.diybanter.com

Colin Wilson wrote:

You, sir, are a god :-p

A totally OTT remark, Sir, but at least you didn't use a capital G :~)


Anyway, I've previously posted a table of current ratings too. Here are
the two tables combined into one, together with some new ratings from
the draft 17th edition:

CSA (CPC) Ratings in amperes Strands Overall
square mm A B C D+ E+ No./dia. mm approx.
---------- ---- -- -- -- ---- ------- ----------
1 (1) 11.5 12 16 13 10.5 1/1.13 4.5 x 8.2
1.5 (1) 14.5 15 20 16 13 1/1.38 4.7 x 8.2
2.5 (1.5) 20 21 27 21 17 1/1.78* 5.3 x 9.9
4 (1.5) 26 27 37 27 22 7/0.85 6.1 x 11.4
6 (2.5) 32 35 47 34 27 7/1.04 6.8 x 13.1
10 (4) 44 47 64 45 36 7/1.35 8.4 x 16.8
16 (6) 57 63 85 57 46 7/1.71 9.6 x 19.5

* 7/0.67 also available (but rare)

Key to current rating columns:

A - in conduit in insulated wall (ref. method 6)
B - directly in insulated wall (ref. method 15)
C - clipped direct (ref. method 1)

Ratings (BS 7671 Table 4D5A) apply for ambient temperature of 30 deg.C
and conductor temperature of 70 deg.C

+ New ratings from draft 17th edition:

D - above plasterboard ceiling covered by thermal insulation,
insulation thickness 100 mm
E - as D but with insulation thickness 100 mm

(Technically these are not yet in force and should be regarded as
provisional.)

All the usual derating factors apply (see appendix 4 of BS 7671 or
appendix 6 of the OSG).

--
Andy

On 2007-09-04 00:21:52 +0100, "The Medway Handyman"
said:

Am I right in assuming that when T + E cable is referred to as 2.5mm that is
the diameter of the bare conductor?

Is there a chart anywhere that gives the outside dimensions including all
the insulation?

It's the cross sectional area in square millimetres (not dia in millimetres).

HI All

On Tue, 04 Sep 2007 09:28:59 +0100, Andy Wade
wrote:

Colin Wilson wrote:

You, sir, are a god :-p

A totally OTT remark, Sir, but at least you didn't use a capital G :~)


Anyway, I've previously posted a table of current ratings too. Here are
the two tables combined into one, together with some new ratings from
the draft 17th edition:

CSA (CPC) Ratings in amperes Strands Overall
square mm A B C D+ E+ No./dia. mm approx.
---------- ---- -- -- -- ---- ------- ----------
1 (1) 11.5 12 16 13 10.5 1/1.13 4.5 x 8.2
1.5 (1) 14.5 15 20 16 13 1/1.38 4.7 x 8.2
2.5 (1.5) 20 21 27 21 17 1/1.78* 5.3 x 9.9
4 (1.5) 26 27 37 27 22 7/0.85 6.1 x 11.4
6 (2.5) 32 35 47 34 27 7/1.04 6.8 x 13.1
10 (4) 44 47 64 45 36 7/1.35 8.4 x 16.8
16 (6) 57 63 85 57 46 7/1.71 9.6 x 19.5

* 7/0.67 also available (but rare)

Key to current rating columns:

A - in conduit in insulated wall (ref. method 6)
B - directly in insulated wall (ref. method 15)
C - clipped direct (ref. method 1)


snip

Not directly on topic - but a bit of advice, please...

We have a new heat-pump installation for hot water and central heating
purposes - basically a giant fridge that sucks heat out of a
ground-loop and pushes it into the circulating water.....

....anyway....

The pump is installed in my 'studio' (=big timber shed !) -
and the electrical connection is via a sub-consumer unit in the
studio. The power consumption of the pump is (allegedly!- can't find a
rating plate on it) 15A - and it's fed from the CU with a spur of
2.5mm cable, clipped to the surface of the OSB that forms the inside
wall of the studio..

All works fine - but the cable is warm to the touch - not hot - just
warm - maybe 50C - will measure it later if anybody's interested.

Should I be worried that the cable's warm ?
Is it worth doubling-up the cable (2 x 2.5mm cables) - or is a
warm cable acceptable ??

Thanks
Adrian
West Cork, Ireland

Adrian wrote:

All works fine - but the cable is warm to the touch - not hot - just
warm - maybe 50C - will measure it later if anybody's interested.

Should I be worried that the cable's warm ?

"Warm" is OK, but I wouldn't expect a clipped direct 2.5 cable running
at 15 A to be particularly warm. 56% of the rated current implies about
31% of the permitted temperature rise of 40 deg. i.e. only around 12-13
deg. rise.

If you are worried, hire or borrow a clamp meter (preferably true RMS
reading) and measure the actual current.

Is it worth doubling-up the cable (2 x 2.5mm cables) - or is a
warm cable acceptable ??

Simpler to up it to a 4 or 6 mm^2 cable if necessary.

--
Andy

Adrian wrote:

Not directly on topic - but a bit of advice, please...

We have a new heat-pump installation for hot water and central heating
purposes - basically a giant fridge that sucks heat out of a
ground-loop and pushes it into the circulating water.....

...anyway....

The pump is installed in my 'studio' (=big timber shed !) -
and the electrical connection is via a sub-consumer unit in the
studio. The power consumption of the pump is (allegedly!- can't find a
rating plate on it) 15A - and it's fed from the CU with a spur of
2.5mm cable, clipped to the surface of the OSB that forms the inside
wall of the studio..

How do you "know" its 15A?

Not wishing to be pedantic (but one needs to be in this case, for
reasons I will cover), 15A is a current loading and not a power
consumption.

All works fine - but the cable is warm to the touch - not hot - just
warm - maybe 50C - will measure it later if anybody's interested.

It would be interesting to know what the actual temperature is.

Should I be worried that the cable's warm ?

Depends on how warm, and probably not for the reasons you expect! [1]

Is it worth doubling-up the cable (2 x 2.5mm cables) - or is a
warm cable acceptable ??

There is a popular misconception that something must be wrong when a
cable gets warm. The reality is that the way we deduce the cables
current carrying capacity, is based on how much current it will carry at
a maximum conductor temperature.

With PVC clad cables the maximum operating conductor temperature is 70
deg C. Cables running at up to this temperature should still enjoy a
reasonable and safe productive life. For a 2.5mm^2 cable clipped direct
to a surface as you describe, the current that would cause a rise to
this temperature is 27A. (it is this notion of a temperature "budget"
that means when you install cables in ways that prevent them losing heat
as quickly, you need to "derate" the current carrying capacity to take
account of the faster rate of temperature rise that will result).

[1] Unless the cable is dangerously hot then there is no direct problem
with the cable being warm, however it may suggest that your equipment is
drawing far more current than you previously thought.

Given that we are talking about a heat pump which probably has a
compressor driven by an induction motor, you may also have to consider
the implications of a poor power factor here. i.e. the cable may have to
carry a higher current than the power consumption alone would suggest -
but that will not necessarily correspond to a higher energy consumption.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Bob Eager wrote:

For the record, in case MH finds it useful...!

Diameter of 2.5T+E is about 8.85 ufurlongs...

8.87 according to google:

http://www.google.com/search?num=50&...gs&btnG=Search

(mind you that's the conductor diameter not the overall cable one)



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Tue, 4 Sep 2007 12:06:01 UTC, John Rumm
wrote:

Bob Eager wrote:

For the record, in case MH finds it useful...!

Diameter of 2.5T+E is about 8.85 ufurlongs...

8.87 according to google:

http://www.google.com/search?num=50&...gs&btnG=Search

(mind you that's the conductor diameter not the overall cable one)

That's why I said 'about'...! I only spent a few microfortnights
estimating it...

--
The information contained in this post is copyright the
poster, and specifically may not be published in, or used by
http://www.diybanter.com

Andy Wade wrote:

If you are worried, hire or borrow a clamp meter (preferably true RMS
reading) and measure the actual current.

Indeed, but not forgetting to get access to the live or neutral in the
cable and clamp round that individually, rather than the whole cable.

(one of my great disappointments using a clamp meter for the first time
many years ago; that you can't just clamp round a complete cable and get
a reading!)

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Bob Eager wrote:
On Tue, 4 Sep 2007 12:06:01 UTC, John Rumm
wrote:

Bob Eager wrote:

For the record, in case MH finds it useful...!

Diameter of 2.5T+E is about 8.85 ufurlongs...
8.87 according to google:

http://www.google.com/search?num=50&...gs&btnG=Search

(mind you that's the conductor diameter not the overall cable one)

That's why I said 'about'...! I only spent a few microfortnights
estimating it...

That's what I like about the google calculator, you can slap in all
sorts of daft (and not so daft) calculations with weird and wonderful
units, and let it sort out the mess of conversions required...

it can knock 10s of nano millenia of you calculation times ;-)

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

HI Andy

Thanks for the reply

On Tue, 04 Sep 2007 12:28:38 +0100, Andy Wade
wrote:

Adrian wrote:

All works fine - but the cable is warm to the touch - not hot - just
warm - maybe 50C - will measure it later if anybody's interested.

Should I be worried that the cable's warm ?

"Warm" is OK, but I wouldn't expect a clipped direct 2.5 cable running
at 15 A to be particularly warm. 56% of the rated current implies about
31% of the permitted temperature rise of 40 deg. i.e. only around 12-13
deg. rise.

I'll get a thermometer on it.....


If you are worried, hire or borrow a clamp meter (preferably true RMS
reading) and measure the actual current.


Yes - got one of those 'somewhere'...
Still sorting out boxes after the big move 12 months ago -
never did find that nice fluorescent bench lamp !

Is it worth doubling-up the cable (2 x 2.5mm cables) - or is a
warm cable acceptable ??

Simpler to up it to a 4 or 6 mm^2 cable if necessary.

Well - possibly - but it's only a run of 6ft or so - and I happen to
have some spare 2.5mm 'by me'.... g

The wiring from the FCU down to the heat pump has been done in the
same T&E - guess I could double up on that as well.....

Probably unnecessary - but given that it's a timber workshop
containing all of my market stock plus vast amounts of stained glass &
etc - I'd rather be safe than barbecued g

Regards
Adrian

Hi John

On Tue, 04 Sep 2007 13:18:36 +0100, John Rumm
wrote:

Andy Wade wrote:

If you are worried, hire or borrow a clamp meter (preferably true RMS
reading) and measure the actual current.

Indeed, but not forgetting to get access to the live or neutral in the
cable and clamp round that individually, rather than the whole cable.

(one of my great disappointments using a clamp meter for the first time
many years ago; that you can't just clamp round a complete cable and get
a reading!)

I know _exactly_ what you mean -
"Huh - this thing doesn't work !"
reads manual
"Oh - I see g"

Regards
Adrian

Hi John

On Tue, 04 Sep 2007 12:58:59 +0100, John Rumm
wrote:

Adrian wrote:

Not directly on topic - but a bit of advice, please...

We have a new heat-pump installation for hot water and central heating
purposes - basically a giant fridge that sucks heat out of a
ground-loop and pushes it into the circulating water.....

...anyway....

The pump is installed in my 'studio' (=big timber shed !) -
and the electrical connection is via a sub-consumer unit in the
studio. The power consumption of the pump is (allegedly!- can't find a
rating plate on it) 15A - and it's fed from the CU with a spur of
2.5mm cable, clipped to the surface of the OSB that forms the inside
wall of the studio..

How do you "know" its 15A?

Not wishing to be pedantic (but one needs to be in this case, for
reasons I will cover), 15A is a current loading and not a power
consumption.

All works fine - but the cable is warm to the touch - not hot - just
warm - maybe 50C - will measure it later if anybody's interested.

It would be interesting to know what the actual temperature is.

Should I be worried that the cable's warm ?

Depends on how warm, and probably not for the reasons you expect! [1]

Is it worth doubling-up the cable (2 x 2.5mm cables) - or is a
warm cable acceptable ??

There is a popular misconception that something must be wrong when a
cable gets warm. The reality is that the way we deduce the cables
current carrying capacity, is based on how much current it will carry at
a maximum conductor temperature.

With PVC clad cables the maximum operating conductor temperature is 70
deg C. Cables running at up to this temperature should still enjoy a
reasonable and safe productive life. For a 2.5mm^2 cable clipped direct
to a surface as you describe, the current that would cause a rise to
this temperature is 27A. (it is this notion of a temperature "budget"
that means when you install cables in ways that prevent them losing heat
as quickly, you need to "derate" the current carrying capacity to take
account of the faster rate of temperature rise that will result).

[1] Unless the cable is dangerously hot then there is no direct problem
with the cable being warm, however it may suggest that your equipment is
drawing far more current than you previously thought.

Given that we are talking about a heat pump which probably has a
compressor driven by an induction motor, you may also have to consider
the implications of a poor power factor here. i.e. the cable may have to
carry a higher current than the power consumption alone would suggest -
but that will not necessarily correspond to a higher energy consumption.

OK - will look out the clamp meter and a digi thermometer and see if I
can't catch the thing when it's running (control is by means of a
_really clever_ micro with an instruction manual in a mix of Engish
and German... so it's not as simple as just throwing a switch g

Still - gives me time to look for that clamp meter !

Thanks
Adrian

"Lurch" wrote

Be aware that insulation thickness can vary wildly.
--
Wise words!
I recently replaced a damaged old cooker cable with new 6 sqmm. and had to
mic up the new stuff to check it.
The existing cable had far thicker insulation both on the individual
conductors and the grey sheathing.

Phil

"The Medway Handyman" wrote in message
...
John wrote:
"The Medway Handyman" wrote in
message ...
Am I right in assuming that when T + E cable is referred to as 2.5mm
that is the diameter of the bare conductor?

Is there a chart anywhere that gives the outside dimensions
including all the insulation?

PLEASE tell us all that you no longer do any electrical work (even
making an allowance for Part P sillyness!). THIS is one of the very
first things you are taught in 'electrical college' after "DO NOT put
the screwdriver in there!!!"

The reason I want to spot the difference quickly & easily is so I don't
get into problem situations. I've been asked to remove an old electric
cooker and install a new one. The new one is 9kw. Before I get involved
I want to check that the cable is big enough. If not I will turn the job
down.

I would expect a hard wired 9kw oven to be cabled in 10mm T&E which is
(normally) multistranded (7 x 1.35mm)

Its called "if you are not sure check it out". Basic common sense.

It can also be quoted as "if you're not sure, don't do it" especially with
electricity and gas, basic survival sense.

And don't talk to me about 'qualified electricians'.

Who mentioned qualified electricians, I said 'electrical college' this can
also include engineering, TV & Radio engineers, etc.

I've seen more bodge ups & sloppy work from them than anything else.

but not as many as I have seen by so called 'competent' DIYers and handymen!

Cheers

John

HI All

On Tue, 04 Sep 2007 13:42:31 +0100, Adrian
wrote:

Hi John

On Tue, 04 Sep 2007 12:58:59 +0100, John Rumm
wrote:

Adrian wrote:

Not directly on topic - but a bit of advice, please...

We have a new heat-pump installation for hot water and central heating
purposes - basically a giant fridge that sucks heat out of a
ground-loop and pushes it into the circulating water.....

...anyway....

The pump is installed in my 'studio' (=big timber shed !) -
and the electrical connection is via a sub-consumer unit in the
studio. The power consumption of the pump is (allegedly!- can't find a
rating plate on it) 15A - and it's fed from the CU with a spur of
2.5mm cable, clipped to the surface of the OSB that forms the inside
wall of the studio..

How do you "know" its 15A?

Not wishing to be pedantic (but one needs to be in this case, for
reasons I will cover), 15A is a current loading and not a power
consumption.

All works fine - but the cable is warm to the touch - not hot - just
warm - maybe 50C - will measure it later if anybody's interested.

It would be interesting to know what the actual temperature is.

Should I be worried that the cable's warm ?

Depends on how warm, and probably not for the reasons you expect! [1]

Is it worth doubling-up the cable (2 x 2.5mm cables) - or is a
warm cable acceptable ??

There is a popular misconception that something must be wrong when a
cable gets warm. The reality is that the way we deduce the cables
current carrying capacity, is based on how much current it will carry at
a maximum conductor temperature.

With PVC clad cables the maximum operating conductor temperature is 70
deg C. Cables running at up to this temperature should still enjoy a
reasonable and safe productive life. For a 2.5mm^2 cable clipped direct
to a surface as you describe, the current that would cause a rise to
this temperature is 27A. (it is this notion of a temperature "budget"
that means when you install cables in ways that prevent them losing heat
as quickly, you need to "derate" the current carrying capacity to take
account of the faster rate of temperature rise that will result).

[1] Unless the cable is dangerously hot then there is no direct problem
with the cable being warm, however it may suggest that your equipment is
drawing far more current than you previously thought.

Given that we are talking about a heat pump which probably has a
compressor driven by an induction motor, you may also have to consider
the implications of a poor power factor here. i.e. the cable may have to
carry a higher current than the power consumption alone would suggest -
but that will not necessarily correspond to a higher energy consumption.

OK - will look out the clamp meter and a digi thermometer and see if I
can't catch the thing when it's running (control is by means of a
_really clever_ micro with an instruction manual in a mix of Engish
and German... so it's not as simple as just throwing a switch g

Still - gives me time to look for that clamp meter !


Darn - can't find the clamp meter...
....but could find the digital thermometer...

Ambient temperature in the Studi was running at about 30 C this
afternoon.

Tucking the temperature probe between the cable and the wall
gave a reading of 41 C after the heat pump had been running for 30
mins or so....

Is it fair to assume that 10 C above ambient is OK
for this cable ??

Many thanks
Adrian


Thanks
Adrian

Adrian wrote:

Ambient temperature in the Studi was running at about 30 C this
afternoon.

Tucking the temperature probe between the cable and the wall
gave a reading of 41 C after the heat pump had been running for 30
mins or so....

Is it fair to assume that 10 C above ambient is OK
for this cable ??

Yup, that sounds about right for a cable like that at about half
capacity; especially if you allow for some insulating properties of the
PVC sheath.


--
Cheers,

John.

/================================================== ===============\
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| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Hi John

On Tue, 04 Sep 2007 21:12:42 +0100, John Rumm
wrote:

Adrian wrote:

Ambient temperature in the Studi was running at about 30 C this
afternoon.

Tucking the temperature probe between the cable and the wall
gave a reading of 41 C after the heat pump had been running for 30
mins or so....

Is it fair to assume that 10 C above ambient is OK
for this cable ??

Yup, that sounds about right for a cable like that at about half
capacity; especially if you allow for some insulating properties of the
PVC sheath.

Ah - excellent - I'll have to find something else to worry about ! g

Thanks
Adrian

John wrote:
"The Medway Handyman" wrote

PLEASE tell us all that you no longer do any electrical work (even
making an allowance for Part P sillyness!). THIS is one of the very
first things you are taught in 'electrical college' after "DO NOT
put the screwdriver in there!!!"

The reason I want to spot the difference quickly & easily is so I
don't get into problem situations. I've been asked to remove an old
electric cooker and install a new one. The new one is 9kw. Before
I get involved I want to check that the cable is big enough. If not
I will turn the job down.

I would expect a hard wired 9kw oven to be cabled in 10mm T&E which is
(normally) multistranded (7 x 1.35mm)

Its called "if you are not sure check it out". Basic common sense.

It can also be quoted as "if you're not sure, don't do it" especially
with electricity and gas, basic survival sense.

Which is exactly what I'm doing. I'm not entirely sure so. I'm asking those
wiser than I am. If I'm not sure I won't do it. Once I am sure I will.

And don't talk to me about 'qualified electricians'.

Who mentioned qualified electricians, I said 'electrical college'
this can also include engineering, TV & Radio engineers, etc.

I assumed 'qualified electricians' went to 'electrical college'.

I've seen more bodge ups & sloppy work from them than anything else.

but not as many as I have seen by so called 'competent' DIYers and
handymen!

Debateable point :-)

Cheers yourself!


--
Dave
The Medway Handyman
www.medwayhandyman.co.uk
01634 717930
07850 597257

In article ,
The Medway Handyman wrote:
Am I right in assuming that when T + E cable is referred to as 2.5mm
that is the diameter of the bare conductor?

No - strictly it should be 2.5mm² as it's the cross sectional area of a
single conductor - but not the earth.

--
*Stable Relationships Are For Horses.

Dave Plowman London SW
To e-mail, change noise into sound.

The Medway Handyman wrote:

Am I right in assuming that when T + E cable is referred to as 2.5mm that is
the diameter of the bare conductor?

Is there a chart anywhere that gives the outside dimensions including all
the insulation?

Thw wiki is good for handy but hard to find data like this
http://www.wiki.diyfaq.org.uk/index.php?title=Cables


NT

wrote:
The Medway Handyman wrote:

Am I right in assuming that when T + E cable is referred to as 2.5mm that is
the diameter of the bare conductor?

Is there a chart anywhere that gives the outside dimensions including all
the insulation?

Thw wiki is good for handy but hard to find data like this
http://www.wiki.diyfaq.org.uk/index.php?title=Cables

Yup, shamelessly pinched from Andy's post last time ;-)

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Andy Wade wrote:

Anyway, I've previously posted a table of current ratings too. Here are
the two tables combined into one, together with some new ratings from
the draft 17th edition:

CSA (CPC) Ratings in amperes Strands Overall
square mm A B C D+ E+ No./dia. mm approx.
---------- ---- -- -- -- ---- ------- ----------
1 (1) 11.5 12 16 13 10.5 1/1.13 4.5 x 8.2

Have they changed 1mm^2 method 1 to 16? (was 15.5 IIRC)

1.5 (1) 14.5 15 20 16 13 1/1.38 4.7 x 8.2
2.5 (1.5) 20 21 27 21 17 1/1.78* 5.3 x 9.9
4 (1.5) 26 27 37 27 22 7/0.85 6.1 x 11.4
6 (2.5) 32 35 47 34 27 7/1.04 6.8 x 13.1
10 (4) 44 47 64 45 36 7/1.35 8.4 x 16.8
16 (6) 57 63 85 57 46 7/1.71 9.6 x 19.5

* 7/0.67 also available (but rare)


OK, I have updated the table he

http://wiki.diyfaq.org.uk/index.php?title=Cables#T.26E

Can you have a quick check and make sure I have transposed it correctly?

Key to current rating columns:

A - in conduit in insulated wall (ref. method 6)
B - directly in insulated wall (ref. method 15)
C - clipped direct (ref. method 1)

Ratings (BS 7671 Table 4D5A) apply for ambient temperature of 30 deg.C
and conductor temperature of 70 deg.C

+ New ratings from draft 17th edition:

D - above plasterboard ceiling covered by thermal insulation,
insulation thickness 100 mm
E - as D but with insulation thickness 100 mm

I take it D & E don't have method numbers yet?

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 05/09/2007 02:32, John Rumm wrote:

wrote:
http://www.wiki.diyfaq.org.uk/index.php?title=Cables

Yup, shamelessly pinched from Andy's post last time ;-)

I have a query over that section of the wiki, it says that XLPE can be
used as the OUTER covering of SWA, I've only used SWA a couple of times,
but I thought the "waxy plastic" insulation of the individual cores was
the XLPE, no?

Andy Burns wrote:
On 05/09/2007 02:32, John Rumm wrote:

wrote:
http://www.wiki.diyfaq.org.uk/index.php?title=Cables

Yup, shamelessly pinched from Andy's post last time ;-)

I have a query over that section of the wiki, it says that XLPE can be
used as the OUTER covering of SWA, I've only used SWA a couple of times,
but I thought the "waxy plastic" insulation of the individual cores was
the XLPE, no?

The short answer is that the description should not be so exact in
specifying "outer" - since I think you will probably find the outer and
the individual wires insulation are all in XLPE.

The manufacturers tend to refer to "PVC extruded bedding" which is the
layer of insulation directly under the armour and over the individually
insulated wires. Some cables use ethylene propylene rubber for this -
which may give you the slightly waxy feel. I would expect either way
this would also need to be a cross linked (XL) material in a 90 deg C cable.

I have reworked the description a bit:

http://www.wiki.diyfaq.org.uk/index....tle=Cables#SWA

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

"Lurch" wrote in message
...
On Tue, 04 Sep 2007 00:23:11 GMT, "The Medway Handyman"
mused:

John wrote:
"The Medway Handyman" wrote in
message ...
Am I right in assuming that when T + E cable is referred to as 2.5mm
that is the diameter of the bare conductor?

Is there a chart anywhere that gives the outside dimensions
including all the insulation?

PLEASE tell us all that you no longer do any electrical work (even
making an allowance for Part P sillyness!). THIS is one of the very
first things you are taught in 'electrical college' after "DO NOT put
the screwdriver in there!!!"

The reason I want to spot the difference quickly & easily is so I don't
get
into problem situations. I've been asked to remove an old electric cooker
and install a new one. The new one is 9kw. Before I get involved I want
to
check that the cable is big enough. If not I will turn the job down.

Be aware that insulation thickness can vary wildly.
--
Regards,
Stuart.

You are not wrong about the differences. I used some 6.0 LSF T&E today. It
looked and felt like 4mm T&E.

Adam