I'm currently renovating an old cottage, as I'm having to put up some
stud work I'm thinking of installing some insulation (100mm) before I
plasterboard it.

This will mean that I'll end up with about15 meters of the ring main
cable (2.5mm T&E on a 32 amp fuse) sandwiched between the outside wall
(which is 2' solid stone) and the insulation (not in the insulation
itself). Do I need to worry about de-rating the cable in this
situation?

The electrics are in good condition and were tested about two years
ago.

Thanks for any advice.

Tony

On Jan 22, 8:25 pm, Tony wrote:
I'm currently renovating an old cottage, as I'm having to put up some
stud work I'm thinking of installing some insulation (100mm) before I
plasterboard it.

This will mean that I'll end up with about15 meters of the ring main
cable (2.5mm T&E on a 32 amp fuse) sandwiched between the outside wall
(which is 2' solid stone) and the insulation (not in the insulation
itself). Do I need to worry about de-rating the cable in this
situation?

I would hope the 2ft stone wall would keep any cable heating under
control - so I think not.

PS have you considered using insulated plasterboard dot n dabbed
straight onto the stone (i.e. no battening & associated ****ing
about)? did it here onto solid brick - no probs so far (5+ years)

Jim K

On Jan 22, 8:30*pm, Jim K wrote:
On Jan 22, 8:25 pm, Tony wrote:

I'm currently renovating an old cottage, as I'm having to put up some
stud work I'm thinking of installing some insulation (100mm) before I
plasterboard it.

This will mean that I'll end up with about15 meters of the ring main
cable (2.5mm T&E on a 32 amp fuse) sandwiched between the outside wall
(which is 2' solid stone) and the insulation (not in the insulation
itself). Do I need to worry about de-rating the cable in this
situation?

I would hope the 2ft stone wall would keep any cable heating under
control - so I think not.

PS have you considered using insulated plasterboard dot n dabbed
straight onto the stone (i.e. no battening & associated ****ing
about)? did it here onto solid brick - no probs so far (5+ years)

Jim K

Hi Jim,

I did look at dot n dabbing but the walls are too uneven for that (or
"rustic" in estate agent parlance) so I'm stuck with battening out and
****ing around unfortunately. Worth looking into insulated
plasterboard though - thanks for the tip.

Tony

John Rumm wrote:
On 22/01/2011 20:25, Tony wrote:
I'm currently renovating an old cottage, as I'm having to put up some
stud work I'm thinking of installing some insulation (100mm) before I
plasterboard it.

This will mean that I'll end up with about15 meters of the ring main
cable (2.5mm T&E on a 32 amp fuse) sandwiched between the outside
wall (which is 2' solid stone) and the insulation (not in the
insulation itself). Do I need to worry about de-rating the cable in
this situation?

This sounds like reference method 102. See:

http://wiki.diyfaq.org.uk/index.php?...es#Cable_Sizes

and

http://wiki.diyfaq.org.uk/index.php?...lation_Methods


So no, the current carrying capacity still meeds the requirements for
a normal ring circuit.

(in reality a stone wall will perform better than a plasterboard - so
you have more latitude than the raw numbers suggest)

There is an important point on installation method 102 that the cable should
be on the internal side of the insulation.

This is because the cable will have to pass through the installation to
reach an accessory on the internal wall.

However with reference to table 52.2 in
http://wiki.diyfaq.org.uk/index.php?...ca lculate_Iz
I believe that the 100mm of insulation should not be a problem as the cable
derating factor is 0.78.


--
Adam

On Jan 22, 9:18*pm, "ARWadsworth"
wrote:
John Rumm wrote:
On 22/01/2011 20:25, Tony wrote:
I'm currently renovating an old cottage, as I'm having to put up some
stud work I'm thinking of installing some insulation (100mm) before I
plasterboard it.

This will mean that I'll end up with about15 meters of the ring main
cable (2.5mm T&E on a 32 amp fuse) sandwiched between the outside
wall (which is 2' solid stone) and the insulation (not in the
insulation itself). Do I need to worry about de-rating the cable in
this situation?

This sounds like reference method 102. See:

http://wiki.diyfaq.org.uk/index.php?...es#Cable_Sizes

and

http://wiki.diyfaq.org.uk/index.php?...lation_Methods

So no, the current carrying capacity still meeds the requirements for
a normal ring circuit.

(in reality a stone wall will perform better than a plasterboard - so
you have more latitude than the raw numbers suggest)

There is an important point on installation method 102 that the cable should
be on the internal side of the insulation.

This is because the cable will have to pass through the installation to
reach an accessory on the internal wall.

However with reference to table 52.2 inhttp://wiki.diyfaq.org.uk/index.php?title=Calculating_A_Cable_Size#Ho...
I believe that the 100mm of insulation should not be a problem as the cable
derating factor is 0.78.

--
Adam

Thanks to both of you - looks like I'm OK.

Tony

On Jan 22, 8:50 pm, Tony wrote:
On Jan 22, 8:30 pm, Jim K wrote:



On Jan 22, 8:25 pm, Tony wrote:

I'm currently renovating an old cottage, as I'm having to put up some
stud work I'm thinking of installing some insulation (100mm) before I
plasterboard it.

This will mean that I'll end up with about15 meters of the ring main
cable (2.5mm T&E on a 32 amp fuse) sandwiched between the outside wall
(which is 2' solid stone) and the insulation (not in the insulation
itself). Do I need to worry about de-rating the cable in this
situation?

I would hope the 2ft stone wall would keep any cable heating under
control - so I think not.

PS have you considered using insulated plasterboard dot n dabbed
straight onto the stone (i.e. no battening & associated ****ing
about)? did it here onto solid brick - no probs so far (5+ years)

Jim K

Hi Jim,

I did look at dot n dabbing but the walls are too uneven for that (or
"rustic" in estate agent parlance) so I'm stuck with battening out and
****ing around unfortunately. Worth looking into insulated
plasterboard though - thanks for the tip.

Tony

shame - how uneven we talking abt?

Jim K

On 2011-01-22 20:50:18 +0000, Tony said:

On Jan 22, 8:30*pm, Jim K wrote:
On Jan 22, 8:25 pm, Tony wrote:

I'm currently renovating an old cottage, as I'm having to put up some
stud work I'm thinking of installing some insulation (100mm) before I
plasterboard it.

This will mean that I'll end up with about15 meters of the ring main
cable (2.5mm T&E on a 32 amp fuse) sandwiched between the outside wall
(which is 2' solid stone) and the insulation (not in the insulation
itself). Do I need to worry about de-rating the cable in this
situation?

I would hope the 2ft stone wall would keep any cable heating under
control - so I think not.

PS have you considered using insulated plasterboard dot n dabbed
straight onto the stone (i.e. no battening & associated ****ing
about)? did it here onto solid brick - no probs so far (5+ years)

Jim K

Hi Jim,

I did look at dot n dabbing but the walls are too uneven for that (or
"rustic" in estate agent parlance) so I'm stuck with battening out and
****ing around unfortunately. Worth looking into insulated
plasterboard though - thanks for the tip.

I'm using Kingspan K18 for this:
http://www.insulation.kingspan.com/uk/pdf/k18.pdf. You'd use K17 is
dot and dabbing (but like you, I've got seriously rustic walls).

On Jan 23, 9:22 am, Piers Finlayson wrote:
On 2011-01-22 20:50:18 +0000, Tony said:



On Jan 22, 8:30 pm, Jim K wrote:
On Jan 22, 8:25 pm, Tony wrote:

I'm currently renovating an old cottage, as I'm having to put up some
stud work I'm thinking of installing some insulation (100mm) before I
plasterboard it.

This will mean that I'll end up with about15 meters of the ring main
cable (2.5mm T&E on a 32 amp fuse) sandwiched between the outside wall
(which is 2' solid stone) and the insulation (not in the insulation
itself). Do I need to worry about de-rating the cable in this
situation?

I would hope the 2ft stone wall would keep any cable heating under
control - so I think not.

PS have you considered using insulated plasterboard dot n dabbed
straight onto the stone (i.e. no battening & associated ****ing
about)? did it here onto solid brick - no probs so far (5+ years)

Jim K

Hi Jim,

I did look at dot n dabbing but the walls are too uneven for that (or
"rustic" in estate agent parlance) so I'm stuck with battening out and
****ing around unfortunately. Worth looking into insulated
plasterboard though - thanks for the tip.

I'm using Kingspan K18 for this: http://www.insulation.kingspan.com/uk/pdf/k18.pdf. You'd use K17 is
dot and dabbing (but like you, I've got seriously rustic walls).

is there a difference?

Jim K

On Jan 23, 9:27 am, Jim K wrote:
On Jan 23, 9:22 am, Piers Finlayson wrote:



On 2011-01-22 20:50:18 +0000, Tony said:

On Jan 22, 8:30 pm, Jim K wrote:
On Jan 22, 8:25 pm, Tony wrote:

I'm currently renovating an old cottage, as I'm having to put up some
stud work I'm thinking of installing some insulation (100mm) before I
plasterboard it.

This will mean that I'll end up with about15 meters of the ring main
cable (2.5mm T&E on a 32 amp fuse) sandwiched between the outside wall
(which is 2' solid stone) and the insulation (not in the insulation
itself). Do I need to worry about de-rating the cable in this
situation?

I would hope the 2ft stone wall would keep any cable heating under
control - so I think not.

PS have you considered using insulated plasterboard dot n dabbed
straight onto the stone (i.e. no battening & associated ****ing
about)? did it here onto solid brick - no probs so far (5+ years)

Jim K

Hi Jim,

I did look at dot n dabbing but the walls are too uneven for that (or
"rustic" in estate agent parlance) so I'm stuck with battening out and
****ing around unfortunately. Worth looking into insulated
plasterboard though - thanks for the tip.

I'm using Kingspan K18 for this: http://www.insulation.kingspan.com/uk/pdf/k18.pdf. You'd use K17 is
dot and dabbing (but like you, I've got seriously rustic walls).

is there a difference?

Jim K

ah foil-backed or "tissue"-backed

Jim K

On Jan 23, 9:22*am, Piers Finlayson wrote:
On 2011-01-22 20:50:18 +0000, Tony said:









On Jan 22, 8:30*pm, Jim K wrote:
On Jan 22, 8:25 pm, Tony wrote:

I'm currently renovating an old cottage, as I'm having to put up some
stud work I'm thinking of installing some insulation (100mm) before I
plasterboard it.

This will mean that I'll end up with about15 meters of the ring main
cable (2.5mm T&E on a 32 amp fuse) sandwiched between the outside wall
(which is 2' solid stone) and the insulation (not in the insulation
itself). Do I need to worry about de-rating the cable in this
situation?

I would hope the 2ft stone wall would keep any cable heating under
control - so I think not.

PS have you considered using insulated plasterboard dot n dabbed
straight onto the stone (i.e. no battening & associated ****ing
about)? did it here onto solid brick - no probs so far (5+ years)

Jim K

Hi Jim,

I did look at dot n dabbing but the walls are too uneven for that (or
"rustic" in estate agent parlance) so I'm stuck with battening out and
****ing around unfortunately. Worth looking into insulated
plasterboard though - thanks for the tip.

I'm using Kingspan K18 for this: *http://www.insulation.kingspan.com/uk/pdf/k18.pdf. *You'd use K17 is
dot and dabbing (but like you, I've got seriously rustic walls).

Thanks for the link - I'll check up with the builders merchants on
Monday and see what they have in stock up here.

One question I have is that looking at prices it'd look cheaper to
fill the battens and plasterboard on top - does K18 offer any other
advantages over this approach? (I can see it being quicker to install
for one.)

Tony