Cold downstairs radiators and hot upstairs radiators after draining central heating

[CJCymru]

Today, I've drained our central heating to put X400 in to the system via F&E tank in the loft. Now, I've refilled all radiators. Turned the heating back on, and only the upstairs radiators are getting hot. There is 1 or 2 downstairs radiators getting slightly warm.

Our system seems to be a pumped gravity fed system. I've turned off the working radiators, to see if this will force hot water through to the downstairs ones with no luck. The pump next to the boiler is a Grundfos Alpha 2, and seems to be working okay. And it seems to be on its fastest setting.

Could really do with some help here.

Thank you

 

[CJCymru]

Update: I turned up the water temp dial on our boiler to max so the boiler is working at max power. I turned all radiators off upstairs bar 1 to keep the boiler healthy. Now I've had 2 come on downstairs. I will now turn off the one upstairs, and keep 1 on downstairs instead while I try to get the rest downstairs working.

So hopefully I'll get them all working soon

 

[terryplumb]

Trapped air probably,did you vent the pump and cylinder coil ?