Any help with this problem will be very much appreciated. We have put a new towel rail into an ensuite. The central heating system is open vented, with a single pump and a three way valve. The feed for the towel rail is teed from the main CH flow pipe and is the first tee after the 3 way valve. The return is teed into the main CH/HW return and is the last tee before the return enters the boiler. We seem to have two problems: one, the CH takes ages to warm up when the HW is also on - is this normal? Two, when I turn the towel rail on, some of the radiators don't work at all, whereas they all work when the towel rail is off? The towel rail is fitted with ordinary valves, ie there is no TRV on it.
Thanks for the replies. No I haven't balanced the system, so I will do that.
I suppose I have created a bypass, but I have closed the valves on the towel rail right down and the system seems to be working normally again, apart from the last radiator in the system never gets properly hot, so hopefully balancing the system will fix that. Thanks once again.