Boiler was installed 3 winters ago. First winter very poor, rads took hours to heat and boiler was off when thermostat calling for heat. Then I discovered some controls and set pump overrun at 15 min and things got much better for 2nd winter. This winter I've still got rads cold when should be hot so reduced anti cycling to 10 min.

I could continue to experiment but what are the best settings for Pump overrun, anticycling and part load for a small two bed house. The house probably needs only 8 to 10 KW to heat it but the boiler is 30 kw. I keep it at 30kw

I bought the 30 kw for the hot water supply.

David Stockton, November 2010

Enter service menu, enter password in parameter 97 = 35
set parameter 93 = 3. CH is now set for an output of 5 to
12Kw. When CH starts flame will ramp-up to 12Kw instead of 18 as in default setting. Boiler modulates properly as well.

Ted, December 2010

If your system worked OK before this boiler was installed then it might be that your boiler is overrated for this installation and the boiler is causing the output temp. to be too high compared to the return temp. These boilers typically look to hold the flow and return temp. range to less than 20 degrees or so. Whilst I know they are supposed to self modulate it would be wise to set the kw output down to a level nearer to what you need. My 38kw boiler is now set at 28kw and now works well (38Hxi). If this improved matters then you probably ought to try and balance your radiators as well as they should all be at similar temperatures. Do some google searching on this as it's not hard to get your system set to a reasonable level yourself.

Smal, December 2010

The chap who installed it was a GlowWorm Valliant trained engineer.

David Stockton, November 2010

re-set the boiler to factory settings and stop messing about with it. if the heating isn't working properly mucking around with pump overrun and other parameters isn't going to help. get a qualified engineer out to solve your problem. also the boiler will automatically modulate to suit the heating load so no need to adjust the heat output, and that's direct from a glowworm / vaillant technical trainer.

Ian, November 2010