Correction, from OSG 17th...
p52 & 53 are of particular interest to you.
Installation Method for BS6004 70oC (6242YH).
C = Clipped Direct
Cable CSA 1.5mm = 20A, 10.0mm = 64A, 16.0mm = 85A
100 = Cable CONTACTS plasterboard ceiling or joists covered in thermal
insulation NOT exceeding 100mm.
Cable CSA 1.5 = 16A, 10.0mm = 45A, 16.0mm = 57A
101 = Cable CONTACTS plasterboard ceiling or joists covered in thermal
insulation EXCEEDING 100mm.
Cable CSA 1.5 = 13A, 10.0mm = 36A, 16.0mm = 46A
103 = Cable SURROUNDED by thermal insulation with cable NOT touching a
Cable CSA 1.5 = 8A, 10.0mm = 23.5A, 16.0mm = 42.5A.
Domestic lighting using 6A MCB/RCBO...
- 1.5mm 6242YH is sufficient under install method 103 (8 Amp)
- Assuming the cable is not grouped with other light/power circuit
- PVC is ok - a 10A lighting circuit would require 6242BH (XPLE)
Domestic 11.5kW shower using 50A MCB/RCBO...
- 16.0mm 6242YH is insufficient under install method 101 or 103
- 6242BH (XLPE) using 10.0mm cable would be necessary
So generally you try to prevent cable being covered with thermal
Particularly when you price out a reel of 10.0mm 6242BH :-)