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Oil-fired range cooker provides four-zone underfloor and radiator heating, plus mains pressure hot water
A Sandyford oil-fired range cooker provides mains pressure domestic hot water and four zones of energy-efficient underfloor and radiator heating for a stone cottage in Cornwall. The system is designed to maximise energy efficiency and minimise firing of the Sandyford's boiler to prolong its life.
The entire installation was designed, supplied and installed by the bespoke heating specialist, Stove Shop, whose own “Casaverde” water interface cylinder provides heat storage until it is needed.
The two underfloor heating and two radiator heating zones are each regulated by a Honeywell wireless programmable thermostat. Being wireless, they required no cabling and can rest on a surface or slot into a wall bracket . The Honeywell wireless receivers (one per zone) operate Honeywell valves on the underfloor heating manifolds or radiator circuits, as appropriate. Each CM60RF is capable of six time/temperature changes daily, to match temperatures with needs at that time of day: this provides comfort while avoiding burning fuel unnecessarily.
 Hot water from the Sandyford enters the top of the “Casaverde” water insulated cylinder, designed by Stove Shop, and returns from the bottom. Domestic hot water at mains pressure is heated by passing through a coil in the top of the cylinder. The draw-off temperature is 75 degrees C, but is blended to provide 45 degrees C at the taps. “We're delighted that the hot water is always comfortably hot but cannot scald, having experienced dangerously hot water while staying in someone else's home”, commented the client.
Whereas the radiator heating circuits are fed by the boiler, water for underfloor heating is drawn from storage in the bottom third of the cylinder. Stove Shop assisted the efficiency of the system with accurate temperature regulation of the cylinder using Honeywell immersion thermostats and the relatively low draw-off temperature for underfloor heating – about 60 degrees C, blended down to deliver 50 degrees C to the manifolds. This ensures there are no large cycles of depletion and recovery within the cylinder, says Stove Shop. The lower temperature is also safer than is customary in conventional underfloor systems, where the boiler links with the manifolds directly.
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