few rads not heating up

[koey2036]

hi i've just installed a new heating system in a 3 storey house. its a indirect sealed system im not getting any heat to the rads at the end of the runs. could an air lock be causing these rads not to work? rads at the core of the run are hot. the flow pipe is piping hot between the boiler and cylinder but the return line is not that hot near the boiler? why is the system not circulating properly? don't think there is a problem with the pump. any ideas would be greatly appreciated

 

[Billy Bob Bob]

try turning the working ones off,if that fails drain trough returns until hot

 

[fixter1]

try turning all rads off apart from the ones that are cold to try and push the heat to them

 

[koey2036]

done that and they start to warm up but as soon as you turn the other rads back on they cool down again.

 

[Puddle]

have you got pipe sizes right ?

What size pump is fitted ?

 

[koey2036]

pipe sizes are correct 22mm and branches to 15mm to feed maximum 2 rads. pump is built in to boiler vaillant eco tech plus 630

 

[turnpin]

suggest the system needs to be balanced as cold rads get hot when hot rads shut downregards turnpin

 

[fuzzy]

yeh sounds like a balancing prob if the pipe sizes are right