The OSG talks about cable passing through thermal insulation and its effect on cable size.
On the latest project I am going I have to put acoustic insulation in the stud walls and floors.
Is acoustic insulation regarded as the same as thermal insulation in this case?
Cheers
Martin
Personally I'd say yes, because both types of insulation hold still air in a trap. Therefore, derate the cable by around 1.5 - 2 % per 10 mtr length within the insulation. If the length through the stud is only a couple of metres or so, then ignore the derating.
In article , BigWallop writes
Thanks for that.
As regards the length of cable going through the insulation, presumably I just need to look at the longest run through any insulation not the total in all parts of the cable.
Cheers
Martin
Yes. If the cable is passing through anything less than 3 mtrs of insulation, forget the rule. But only if it's one run of up to 3 mtrs of insulation. Any more insulation on the same run of cable, the whole run of cable needs to be derated.
An example. If the total cable run is 12 mtrs, of which 2 mtrs are buried in the insulation. Forget the derating. If the total run of cable is 15 mtrs, of which 10 mtrs are buried in the insulation. You have to derate the whole cable run.
If you have 50mm in insulation the cable is derated by about 10%. 500mm derates it by 50% Further length doesn't increas tis figure.
For accurate figures see the On Site Guide.
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