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Knowing it was going to be covered with insulation, was any containment considered? Oval, conduit will both greatly improve heat dissipation and should have been factored in with the cable calc design. Who designed the install?
 
Didn't give you a reference method whilst on the phone, did they? What's your answer from the BS7671 for the method? Table 4A2 has all the stipulations for deciding and the U value of your insulation.
 
Sounds and looks like 103 to me too. Vastly reduces the ccc. Were the sizes correctly selected for the install in your mind?
 
Job done, happy with the install. Anything special about it to show off photos?
 
Not as yet. The first one completed was a garage/workshop.

The 2nd was a family member. I will be taking pictures of that one when Im up there next.
 
Knowing it was going to be covered with insulation, was any containment considered? Oval, conduit will both greatly improve heat dissipation and should have been factored in with the cable calc design. Who designed the install?
Polite question honestly, are your comments regarding installing the cables in oval conduit and then enclosing them in insulation, the same as you would use for cables in an insulated roof space, or an insulated wall in a normal domestic traditionally built house? because in my humble opinion installing cables in insulation, is a problem but enclosing them in conduit, would this not compound the problem. I have no experience of timber framed houses by the way, maybe I'm missing something?
 
Any movement of air in a problematic space, to increase the dissipation of heat from a cable that is carrying a current in a timber framed house, in my opinion, will improve the longevity and the performance of the cable. 50x50 trunking down a 2.5 metre wall would only help that heat release, again, in my opinion - I'm still learning!
 
Any movement of air in a problematic space, to increase the dissipation of heat from a cable that is carrying a current in a timber framed house, in my opinion, will improve the longevity and the performance of the cable. 50x50 trunking down a 2.5 metre wall would only help that heat release, again, in my opinion - I'm still learning!
For an example a 2.5mm twin and earth cable in a wall in insulation will take 13.5 amps were as twin and earth in conduit in insulation it will take 20 amps so yes you are correct :)
 
Also I think that if you are involved with the planning stage of the install then this is something that could be implemented and the cost of the containment would be taken up by the savings in CSA of the cable. I may have to remove my rose tinted specs but it seems good practice and safe practice.
 
Oval, conduit will both greatly improve heat dissipation and should have been factored in with the cable calc design.

Any movement of air in a problematic space, to increase the dissipation of heat from a cable that is carrying a current in a timber framed house, in my opinion, will improve the longevity and the performance of the cable. 50x50 trunking down a 2.5 metre wall would only help that heat release, again, in my opinion - I'm still learning!

Sure, if you have to run a cable vertically through insulation, then putting it in 50x50 trunking may well allow it to run cooler, but only if the top, and preferably the bottom, are open to the air. Stuffing a piece of T&E in a bit of oval tube isn't likely to make much difference given the limited space available for convection, and may make it worse.
 
For an example a 2.5mm twin and earth cable in a wall in insulation will take 13.5 amps were as twin and earth in conduit in insulation it will take 20 amps so yes you are correct :)

I think the difference here is whether the cable or conduit is touching the (relatively thermally conductive) inner wall or not. Table 4D5 shows that the same cable in insulation but touching the inner wall is rated at 21A.

See also 4A2 for diagrams showing the various possible configurations.
 
I would say the best design is use method 102 , touching the inner wall surface, that way it looks like the standard cable sizing will still be within tolerance for you standard circuits in a house, but if the op has used method 103 he may have to rate ring circuits to 20amps if he has used 2.5mm twin and earth
 
Polite question honestly, are your comments regarding installing the cables in oval conduit and then enclosing them in insulation, the same as you would use for cables in an insulated roof space, or an insulated wall in a normal domestic traditionally built house? because in my humble opinion installing cables in insulation, is a problem but enclosing them in conduit, would this not compound the problem. I have no experience of timber framed houses by the way, maybe I'm missing something?
I agree Pete I was a bit lost on that, if you enclose a cable in any type of conduit the ccc is further reduced. It ain't going to act as a heat sink is it.
 
I agree Pete I was a bit lost on that, if you enclose a cable in any type of conduit the ccc is further reduced. It ain't going to act as a heat sink is it.
Well I was a bit skeptical to be honest, Westward 10
 
Well I was a bit skeptical to be honest, Westward 10
I think people worry too much the chance of lighting circuits and ring finals overloading to such a degree in a domestic property because of thermal insulation must be pretty small. I would probably consider shower circuits and the like more of a problem.
 

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