For the sake of completeness in this saga, the following is an extract from a recent e-mail from WB.
"The only time you would normally have to wait for a large temperature drop before the boiler fires back up is if the primary sensor on the heat exchanger gets excessively hot.
For example, you have set the boiler flow temp to 70C. If there was any circulation issue with the pipework to the cylinder or through the cylinder coil and the primary sensor gets hotter and hotter due to poor circulation and goes to say 90C the boiler shuts down and it wouldn’t then re-fire until the flow temperature goes down into the late 30’s or 40 degree temperature range.
If the boiler was working as it should once the temperature drops a couple of degrees below what your asking for it would re-fire."
From this and looking at my plots of the flow temperature it is almost certain that the boiler is going over temperature and shutting off. (Installation and maintenance manual suggests set point + 5C which is about what I am seeing.) Typically 15+ minutes and significant temperature drop before re-ignition.
Options -
1. Have new cylinder - disruptive and costly. May consider next year.
2. Gate valve on return line to throttle flow through the coil - easy to do without draining system. (
@Johntheo5 You advised against this in an earlier post. Do you think that it is a viable option?)
3. Do nothing for the time being - I do have sufficient hot water as I have said before. Probably the preferred otion at this time of year.
