Water running from temperature relief valve
It is normal for a small quantity of water to escape during the heating cycle. 
Steady flow of water from temperature relief valve
Mains pressure may sometimes rise above designed water pressure of tank. The system should have a pressure limiting valve fitted. If one is fitted it may not have a high enough pressure rating. Advise customer to contact installer to have correct valve fitted.
Small amount of water running continually from temperature relief valve
There may be foreign matter inside the relief valve. Try gently raising the easing lever on the relief valve for a few seconds then release it gently. This may dislodge any foreign matter and clear the fault. If water continues to run a service call is required.
Red light flashing on solar control unit
Check to see if the cold sensor located at the cold inlet at the bottom of the tank has not been dislodged or damaged. Note: there should be a small clamp holding it into position. If the sensor lead is damaged a service call will be required.
The water is not as hot as it was from my old hot water system
Due to Australian standards all new installations must have a tempering valve fitted to the system which must temper the water to 50°c (refer to Australian Standard (AS/NZS 3500.4)). 
Water is much too hot
The tempering valve may be malfunctioning or it might not have been fitted by installer (the valve is fitted after the outlet of the storage tank). If the tempering valve is fitted a service call is required. If the tempering valve has not been fitted the