Solar Hot Water - How It Works
Most solar hot water systems consist of:
- A solar panel (or collector) on the roof where water is heated by solar energy
- A pump to circulate the solar heated water down to a thermal store (the hot water cylinder)
- A dual coil hot water cylinder which contains a highly efficient heat exchanger to transfer the heat from the solar pipes to the water in the cylinder.
- Sensors and a controller
We have taken a great deal of care to select a tried and tested. straight forward system using a trouble free technology at the right price. The suppliers have been through a rigorous, competitive tender exercise supervised by the Procurement section of Nottingham City Council. The systems have been evaluated by independent experts.
The result is a flat - plate drainback system.
The Drainback System
The drainback solar hot water system has been selected for its safety features. The above diagrams are both of the drainback system.
Frost Protection
The sensor in the solar panel tells the controller when the temperature falls to freezing. The controller turns off the pump and all the water from the solar panel and the pipes runs back down to the drainback vessel. There is no water in the solar panel to freeze!
Overheat Protection
Amazingly, it is possible for the solar panel to heat the water to boiling point. But the drainback system uses a sensor in the hot water cylinder to turn the pump off. Again the water runs back down to the drainback vessel. So there is no water in the solar panel to boil!
These features ensure a worry free system. What is the worst thing that can happen? A power cut on a hot day; the trip on the fuse box on a hot day (when you are on holiday) – with the drainback system there is no risk of valves blowing with super heated steam, since the pump will stop and all the water will drainback.