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BERYLLIUM thanks for reply, you can actually run C/H off solar you just have to use a thermal store to do it. this is what I have been investigating. I will actually end up with a tank of hot water (85 degrees) that is powered by wood burner, conventional boiler and Solar, the boiler is there just to top up any loss thru high demand. contact me for details as I have had the system designed now. I wasnt sure about how efficient the solar would be but am clear now.