Draining down central heating

Hi In response to your first question, yes without adequate system pressure, the boiler would not function and there would also be a risk of the boiler itself "kettling". in terms of safety, it is always good to have an active radiator circuit with adequate pressure as some boilers use this circuit as a bypass in case of overheating. The second question, it is ok to cap off and isolate redundant radiators but to keep at least one radator active on the radaitor circuit for the same reasons above. Finally, overtime metal dissolves within the central heating pipework and forms a black sludge. This sludge is detrimental to the performance and efficiency of your boiler and may also reduce the boiler's functional lifetime. The central heating pipework is helped with the addition of inhibitor as it slows down and prevents the formation of the black sludge.

Hi, Not disputing my colleagues response, which is also correct, there may also be an automatic by-pass connected between the flow and return. If so you could note where it is set now, for when you bring the system back in use, turn it to lowest by-pass setting. This will act the same as creating a loop and is in place so if both zone valves close and your radiator TRV's are closed, there is still a small circuit to prevent the pump from "Dead Heading". Ensure your heating programmer is turned off and you can use your hot water as usual. Inhibitor - For a short spell OK without inhibitor as you aren't circulating the water but do install it when you refill and return to heating use. There "should" be a magnetic filter in place which will help keep your system clean. It increases the warranty period on new boiler installations!. If not I would recommend installing one on the return line close to the boiler. It is also an easy way to install inhibitor when refilling. Best Regards John