IS 15558 Certification Made Easy with Agile Regulatory IS 15558 is a crucial Indian Standard that governs cross-linked polyethylene (XLPE) insulated thermoplastic sheathed cables used for working voltages up to and including 1100 volts. Read more: https://www.agileregulatory.com/blogs/bis-isi-for-domestic-water-heater-instantaneous-for-use-with-lpg-is-15558-2005