Radiators working then not!

[alan blackburn]

Open vented central heating system. grundfos pump one motorised two way valve.

Drained system and refilled to fit new pump. Radiators upstairs working, downstairs working too. Slowly downstairs rads go cold. Turned off upstairs rads, still no heat to downstairs.Opened upstairs rad valves again.
Have tried draining and refilling without success, pulling water through by draining whist system on.

System shut off overnight. Now some upstairs rads not working either!

Any suggestions helpful guys?

 

[B.O.B DOLE]

Open vented central heating system. grundfos pump one motorised two way valve.

Drained system and refilled to fit new pump. Radiators upstairs working, downstairs working too. Slowly downstairs rads go cold. Turned off upstairs rads, still no heat to downstairs.Opened upstairs rad valves again.
Have tried draining and refilling without success, pulling water through by draining whist system on.

System shut off overnight. Now some upstairs rads not working either!

Any suggestions helpful guys?

sounds like the pump not wired up correctly

 

[cross thread]

try venting the pump,check valves open fully,is it pumping the right way? you would not be the first.