Working on a heating system at the minute where all the rads arent heating , by shutting down certain rads too get others too heat, I came too the conclusion the pump was on its way out or undersized.
With the new pump fitted system is still the same, noticed that the boiler is only running for 90 seconds and off for 120s, so flow doesnt seem to be getting the chance too reach 82degrees

homer, November 2010