no heat downstairs on rads

[bjl]

hi My partner seems to be having lots of trouble with her heating system the gas boiler is in loft, heats the upstairs rads, but the downstairs rads are very slow or intermittent at all to heat up. She had a plumber come out before xmas and all he did was close the lockshield valves upstairs to force more water to downstairs which has worked for a while but now the downstairs rads seem to take ages to get hot . any ideas or things i could try ? thanks

 

[missplumb]

pump??

 

[SimonG]

faulty bypass?

 

[Dotty]

What boiler is it? Make and model.

External pump?

 

[bjl]

its a Potterton combi 80, whats best way to test pump ???

 

[bjl]

its a Potterton combi 80, whats best way to test pump ???

the radiators do seem to heat up after about 2 hours downstairs but not as hot as upstairs ????