This problem turned out to be 'simply' a stuck pin/needle on the Drayton thermostat valve on the hot water cylinder.The Potterton Netaheat Mk2 boiler may well be 25 years old but the problem was not there. A light tapping freed the pin/needle part of the valve- it popped up and the water began...
Yes I have done a search but so far cannot find answer.
Potteron Netaheat MK11 10 - 16. Probably very ancient.When central heating valve is turned to its usual 90 degrees 'on' position on the cylinder the hot water circulates to rads normally - hot water immersion heater turned off.
When hot...
