[kevindobson]

Is it possible to feed heated water (from a solar system) at mains pressure into the DHW loop of an oil fired combi boiler?
I have a closed circiut solar system that relies on mains pressure (ie not pumped). This system as a 250litre store tank and in summer provides a very good supply of hot water to the house. However in winter there are more days than not when the solar panels do not give anything more than lukewarm water. On these days the DHW is heated by a 26kw/h oil fired combi boiler which again gives a more than adequate supply of hot water. The 2 systems are in isolation of each other and require manual switching from one to the other, (soon to be automated).
However I wonder if, in winter (definitely not summer), it would be possible to feed the combi boiler DHW loop directly from the solar storage tank instead of from the cold mains. Thus reducing the need to raise the temperature as much.
Would the reduced temperature raising difference give reduced fuel consumption or just hotter water at the outlet?