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Central Heating

Hot water using Greenstar Heatslave oil fired 25/32 condensing combination boiler

Rob Wood 28/09/2026 - 8.11 AM

Hi, we've moved into a house that has a Greenstar Heatslave oil fired 25/32 condensing combination boiler and has a Hive heating and hot water controller. I've read that oil boilers don't instantly heat hot water the same way gas combi boilers do and some pre-heating is required if I've understood this correctly. Question is, if the heating is set to come on anyway, do I need to also set the hot water to come on to get hot water or will the required pre-heat happen when the heating comes on? Presumably in summer when the heating is not set to come on, I would need to set the hot water to come on? Any advice gratefully received. Thank you.

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1 Answer

Peter Swiecicki

Rating: 4.5 out of 5

Belfast

The Greenstar Heatslave is an oil-fired combi boiler and provides hot water without a separate hot water cylinder. The boiler has a hot water store/pre-heat function to improve response time. Your central heating and hot water controls are separate, so you should set the hot water according to when you normally need it rather than relying on the heating being on. In summer, the hot water can operate independently while the central heating remains off.

Answered28 September 2026