Solar Overheating

Solar overheating can occur within solar water heating systems for a number of reasons but it's basically because the heated water being produced is far greater than the actual demand for heated water by users (supply is greater than demand).

This can be because:

• The solar heating system is oversized - capacity larger than what's needed
• The system has no way of dumping the excess heat
• Low pitched solar collectors
• Switching on the electric backup immersion heater for long periods

If your system is oversized or not, you can safely dump any excess heat to a radiator or heat exchanger within the house to provide space heating. Heat can also be dumped into a swimming pool if you have one.

Solar heating with a dran-back system is another way of preventing overheating. A drain-back is a system that drains water from the collectors when the pump is not operating, i.e, when the storage temperature has been achieved the thermostat will shut the pump down. When the pump is switched off, the water will drain down from the collectors into a receiver tank thereby preventing overheating.