Sorry, as I am not an expert, I may have not explained the situation correctly. I will try again.
There is a unit (ACL Lifestyle Model no LP522) which controls the hot water and the central heating. This unit can also be used as a timer, but we do not use this facility. When we want either or both functions we cick the appropriate button(s).
This unit is connected to the immersion heater (green cyclinder tank) and the gas central heating. There is also the main water tank in the loft. As far as I am aware we do not have a storage heater.
In this case, when the hot water only button is switched on, the radiators in the house are also activated which is not too bad in winter, but now the warmer weather is here, it is not so good.
Is it simply an electrical fault with the ACL unit or something more serious?
Thanking you in advance.