DIY Doctor UK DIY Forums

My question concerns the control of hot water in my indirect domestic water cylinder.The boiler is condensate 2 pipe boiler heating radiators and hot water.Control of domestic hot water is currently by thermostat control of boiler.This is fine in summer when hot water only is selected on boiler programmer and boiler stat is set low.Problem is in winter when hot water and heating selected and boiler stat turned up to keep house warm domestic water gets too hot.I realise I need to install stat on cylinder and probably another electric zone valve in line to cylinder coil.There is currently electric zone valve in radiator line which obviously isolates radiators when hot water only selected.I realise cylinder stat needs to operate valve to isolate water heating line when at temp required and if heating selected as well no problem aswater still being pumped to radiators.The problem I see is if only hot water selected will the pump pump water out of expansion pipe above header tank?there is a bridge pipe connecting flow and return from the boiler set above the cylinder in the airing cupboard.The circuit through the cylinder has a manuel wheel valve in which is partly shut which I assume is to create resistance to stop short circuiting the radiators? Many thanks.

Well, try to search in the internet I think you can find there some basic idea to know about the cylinder thermostat like you are saying here. The cylinder thermostat is the first level of safety and is usually set to operate at around 60 - 65 degrees C. The Immersion thermostat has an external probe for greater accuracy, with tank securing sheath. An energy cut out device is the second level of safety and is usually set at 85 - 90 degrees C to turn off the boiler or other source of heat.