insulation over wires or not?

[joe-90]

It's 12 years since I passed the regs exam. +++ unhelpful part deleted +++

If the cables can handle the worst case scenario (hot pipes) then they can handle a more benign scenario (drafty shed).

It's the way all new houses are cabled. +++ unhelpful part deleted +++

 

[Softus]

It's 12 years since I passed the regs exam.

It shows.

If the cables can handle the worst case scenario (hot pipes) then they can handle a more benign scenario (drafty shed).

You're confused, and you probably were 12 years ago. Hot pipes don't impede heat loss from cable, whereas insulation does.

It's the way all new houses are cabled.

There's not necessarily anything wrong with insulation around cables, but the cable size has to be chosen with its environment in mind, rather than guessing that it will be OK because the shed is draughty.

The person best placed to do that calculation is the person who should have done it when the cables were installed.

 

[ricicle]

Possible scenario ;_
The shed burns down and someone gets hurt.When they find its an electrical faut and your up before the judge will you feel safer saying

A)I followed the BS7671 IEE wiring regulations which are compiled by a group of highly qualified, experienced engineers and did all I could to prevent danger so something else must have happened.

B)I did it my way because I didn't think that insulation on cables mattered in a shed even when the ambient temp in the middle of summer was 35°c

 

[joe-90]

Possible scenario ;_
The shed burns down and someone gets hurt.When they find its an electrical faut and your up before the judge will you feel safer saying

A)I followed the BS7671 IEE wiring regulations which are compiled by a group of highly qualified, experienced engineers and did all I could to prevent danger so something else must have happened.

B)I did it my way because I didn't think that insulation on cables mattered in a shed even when the ambient temp in the middle of summer was 35°c

An engineer is someone with a degree in engineering.

If it complied with the regs - then yes, I'd be quite happy to say so.

Oh and the ambient temperature of heating pipes is over 35 degrees.

Just as a matter of interest, what size cable would you have run for a socket in the shed? What choices do you have?

 

[joe-90]

Hot pipes don't impede heat loss from cable, whereas insulation does.

So cables run cold when draped all over central heating pipes? Go and lift a few boards on your landing and see how cool they are. +++ unhelpful part deleted +++

 

[RF Lighting]

+++ unhelpful part deleted +++

What is the ambient temperature of a floor void with pipes in it?

 

[joe-90]

+++ unhelpful part deleted +++

 

[RF Lighting]

Ok then, what is the maximum ambient temperature that could occour, so we can work out a worst case scenario.

 

[joe-90]

+++ unhelpful part deleted +++

 

[joe-90]

+++ unhelpful part deleted +++

 

[joe-90]

+++ unhelpful part deleted +++

 

[joe-90]

+++ unhelpful part deleted +++

 

[RF Lighting]

How do you measure the ambient teperature?

With a thermometer

And what about where the cables actually lay on the pipes?

I do not install cables touching pipes, and neither does any proper electrician

And what about the length of the void as a proportion of the cable?

If any of the piece cable is subjected to the ambient temperature then that entire piece of cable has to be derated.

 

[martlewis]

Wow, I go to work and when I come back it's like world war 3 in here LOL.

To answer a few questions;

The shed is more a workshop kitted out with various power tools. The spark put me a 2.5mm t&e ring in, and a 16amp supply for the table saw. Also a 1.5mm t&e lighting circuit running 3 8ft tubes and an 11w energy saving bulb.

The heater is an oil filled rad 2kw left on frost setting to help with damp. Has worked fine for a few years to stop stuff rusting but now I've moved I actually have a space big enough to work in and a bit of monay became spare to insulate which I was going to manage without.

The insulation is an after thought. To run the cabling will simply be a matter of removing cable clips and re-installing them (with the power off obviously).

 

[joe-90]

How do you measure the ambient teperature?

With a thermometer

And what about where the cables actually lay on the pipes?

I do not install cables touching pipes, and neither does any proper electrician

And what about the length of the void as a proportion of the cable?

If any of the piece cable is subjected to the ambient temperature then that entire piece of cable has to be derated.

If you are a real electrician you will have worked on hundreds of houses where real electricians have draped the cables into the same (cut too deep) notch the heating people have cut.

Are you saying that all these houses are wired by cowboys and need rewiring?

BTW what type of thermometer do you use and do you turn the heating on in mid-summer to take a reading? (or do you really live in the real world in your real working day)