True Tony, on most as you say they are not fitted as standard but are an available and necessary add on for units that are converted to sealed or combined feed/open vent systems.
Its just Reading through, the boiler was ok after the pump was fitted for DHW and short cycling on central heating which indicates poor circulation through the rad circuit (most likely air locked)
then the op operated the pump isovalves but wasn't sure which way was open or closed,
It's reasonable to presume that he may have closed them, fired the boiler which then overheated and tripped out the "if present" O/H stat as reading through it looks like hes fully pumped on an s-plan.
Its worth checking. IMO
Thanks to all those who posted on this topic - I am very grateful for the advice.
Time to blow any Christmas cash (downside of being in London!) and get an 'expert' in methinks.
I've switched the controls off and I am using the immersion for hot water 'pro tem'.
Two questions though please:
(1) Would an airlock in the rad pipework eventually trigger this O/H stat if I was trying to run the heating? Reason I ask is that I spent a few hours trying to get the rads warmed on that evening and it was the next day the boiler had issues (fyi - the plumber appeared to have the valves open and the cylinder filled with hot water on day 1 so I am assuming this O/H stat wasn't triggered by the valves being closed)
(2) Is it worth me clearing the airlock in the rad pipework anyway? (I was thinking that, at least then, the rads would heat up when the engineer gets the boiler going)
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