changed central heating programmer - now some rads dont work

[phnxlewis]

I replaced an old landis and gyr programmer with a siemens rwb29 - no problem. Now one bedroom radiator is cold, altho pipe to it is hot, and one downstairs rad is tepid.
I wasn't sure which position to put the dipswitch on the back regarding gravity/pumped. I've now tried both positions, but it doesn't make a difference. Any ideas, please folks?

 

[Hugh Jaleak]

Dip switch positions are dependant on type of system you have. Gravity HW/pumped CH or fully pumped?

 

[phnxlewis]

Yes - I know that, but I don't know which my system is (is there an easy way for an absolute novice to tell?). I've tried both positions and it hasn't altered the problem with the rads.

 

[Hugh Jaleak]

Fully pumped should have 2 pipes from the boiler with motorised valves controlling flow to heating and hot water cylinder. Gravity should have 4 pipes. (2x28mm to cylinder, 2x22mm to heating which is pumped.)

 

[Hugh Jaleak]

TBH changing the programmer shouldnt affect the rads. If most are working ok, then its a circulation issue. Switch system off and bleed rad. If air comes out, might be issue solved. If not then a balance may be needed to force the water to the 'lazy' rads. See FAQ's for balancing info.