If your pump is now limited to 65% then its only a 3M pump, if it ran at full speed (6.8M) then you should get ~ 5.1LPM, still pretty hopeless, did you just hose through the rads individually or/and did you hose through the system with the manifolds and rads connected up?. Unlikely the problem but you might remove the TRV actuators from 3 or 4 rads and ensure the valve pins are fully out.
Have you a sealed system?., if so, and if you have a boiler pressure gauge note how much it rises (or falls) when you start the boiler/circ pump, if the pump is producing a 3M head then the boiler PG should rise by 0.3bar.
Even with a dT of 30C and assuming you have 18kw of installed rads then the boiler should still output ~ 12.7kw (67%). though 30C dT might be controlling the max boiler output.
Have you a sealed system?., if so, and if you have a boiler pressure gauge note how much it rises (or falls) when you start the boiler/circ pump, if the pump is producing a 3M head then the boiler PG should rise by 0.3bar.
Even with a dT of 30C and assuming you have 18kw of installed rads then the boiler should still output ~ 12.7kw (67%). though 30C dT might be controlling the max boiler output.
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