Solar Thermal Repair Leicestershire

​If your solar hot water system is not circulating, the heat collected by the roof panels cannot transfer into the hot water cylinder. This usually results in the solar collector becoming very hot while the cylinder temperature remains low. The most common causes are a failed circulation pump, air trapped in the pipework, low system pressure, a faulty temperature sensor, or a controller issue preventing the pump from activating. In some cases degraded glycol or debris in the system can also restrict flow. Diagnosing the fault requires checking the pump operation, sensor readings, controller settings and system pressure to restore proper circulation and heat transfer.

Many solar hot water systems installed between 2000 and 2015 are now experiencing component failures. We replace circulation pumps, solar controllers, sensors and expansion vessels and recommission systems to restore reliable hot water production.

Controller and Sensor Faults

Solar thermal systems rely on a differential temperature controller to operate the circulation pump. The controller compares the temperature of the solar collector with the temperature of the hot water cylinder and activates the pump when sufficient heat is available. If a temperature sensor fails or the controller develops a fault, the system may stop circulating altogether or run at the wrong times. Common symptoms include the pump not starting even when the collector is hot, incorrect temperature readings on the display, or intermittent system operation. Diagnosing these issues involves checking sensor resistance values, wiring connections and controller settings to ensure the system responds correctly to collector and cylinder temperatures.

Solar thermal systems can overheat during periods of strong sunlight when hot water demand is low, causing the system to reach very high temperatures. Repeated overheating can degrade the heat transfer fluid (glycol), reducing its ability to carry heat and protect the system from corrosion and freezing. When glycol breaks down it can become dark, acidic, or form deposits that restrict circulation and damage pumps or valves. Symptoms may include poor solar performance, unusual smells from the expansion vessel, discoloured fluid, or frequent pressure fluctuations. A service inspection can test the condition of the glycol and determine whether the system requires flushing, glycol replacement, or adjustments to prevent excessive stagnation temperatures.