I have 8.5 sqm DIY solar hot water panels on the roof feeding a 300 liter cylinder, in summer there is a large excess of heat to get rid of. This is to get max heating in the winter months.
The controller opens a bypass valve when it detects the water in the bottom of the cylinder exceeds 80 Celsius, this diverts the returning hot water from the panels through a zig zag run of copper tubing clamped between 2 sheets of mini corrugate aluminum sheet mounted sideways under the floor, painted mat black, this acts as a heat sink having a total surface area of 2 sqm and effectively cools down the water prior to entering the cylinder. The system is self regulating and works well especially when away on holiday with no hot water draw off.
There is a backup circuit, a 12 volt DC solenoid valve opens and dumps hot water down the drain should the water temp exceed 90 c, this draws cold water into the bottom of the cylinder which gets pumped to the panels thus lowering their temp. We have really good water, so potable water circulates though the system.
Cheers
Mike
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