DIY Doctor UK DIY Forums

Hi I'm new to this forum and I am having a problem with my central heating, it's an old system about 20 years and started banging and clicking also downstairs rads took a long time to heat up. Last week it stopped working altogether so drained it and removed pump there was a lot of scale etc so replaced pump and refilled adding Fernox descaler system started up and banging more or less disappeared but rads still took a long time to heat. This morning heating did not come on so still did as I intended drained and flushed through with water I even removed pump to check it was not blocked but heating doesn't come on. I have hot water but no heating, pump is running and pipes are hot both sides. the boiler is a Baxi and the system runs 2x2 port motorised valves for heating and hot water. I am wondering if valves could be problem and if so which one?
Thanks in advance

drummer46,
Hopefully the MVs have a manual opening lever on them - turn on the hot water, the one where the lever has no resistance is the hot water MV. Turn on the heating and try the lever on the other valve - if this does not feel the same as the hot water MV (no resistance) then this is probably the cause of no heating. You may be able to lock the lever over which will give you heating temporarily.
end

Thanks for the reply Stoneyboy just thought I'd let you know how I've sorted it out, might help someone else. Drained system and fitted 2 new valves the CH valve was almost completely blocked I think the Fernox must have loosened dirt and the valve being partly blocked caught it all. Hot water valve looked clean but with both being 20 years old thought I'd replace both anyway while system drained, so if anyone has same problem as described above might be worth a look.
Thanks