Heating or hot water system, or its associated control: APHC, BESCA, Blue Flame Certification, Gas Safe Register, Certsure, HETAS, NAPIT, OFTEC, Stroma
System wresogi neu ddŵr poeth, neu ei reolaeth cysylltiedig: APHC, BESCA, Tystysgrif Blue Flame, Cofrestr Nwy Diogl, Certsure, HETAS, NAPIT, OFTEC, Stroma.