Forgive me if this seems a stupid question, but would i be correct to assume that 2.5mm T+E in a ring config and buried in plaster will carry 37 amps assuming there are no other derating factors?
Its more usual to assume 27 Amps if ambient temperature of the wall is 30 deg, and maximum allowed temperature of the cable in its insulation jacket is 70 deg. The fact its a ring means that the total load can be more than this.
The true rating is a very variable thing, as it depends on the duration of the high current, the ambient temperature, and how hot you would like the cable to get, and how easy it is for the heat to get out. For this reason you will see many different mounting method dependant ratings for the same cross-section of cable.
On Kevin Boones cable calculator for a typical domestic ring circuit, it keeps telling me that I cant have a 32amp MCB protecting a 2.5mm ring main because the cable rating is only coming in at 27amps. Even 16th edition suggest's that this is a perfectly acceptable configuration? Can someone please shed a little more light on this subject for me? Also where does the 1.49 something factor come from on KB's web site for a ring main? I cant find any reference to this in the OSG and indeed the big book.
yeah but ring main cables don't have to be rated to the full breaker rating
iirc it used to say they had to be rated for 2/3 breaker rating now i think it says they have to be rated for 20A in practice there is little difference.
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local
