2 Radiators not heating up

[lotus3692]

Having a problem on my mothers radiators at the moment.

She is running Worcester 24CDI RSF combi boiler.

Problem is started to lose heat in only two radiators, one on ground floor one on first, upstairs one is directly above the downstairs radiator. Heat can be felt on flow in pipe, only a little heat can be felt at the top of radiator & nothing on the return pipe, stone cold. all the other radiators are red hot maybe even too hot.

Don't know it this helps but the pressure on boiler keeps dropping down to almost zero when it is normally set at 1.5 bar. The system pipes are all plastic.

Both radiators have been replaced as has a plastic manifold she tells me.

Would appreciate any help as she is losing faith in the plumber she is using.

Thanks

Chris

 

[seco services]

when the pressure drops does it need refilling ?

 

[lotus3692]

She told me that once the pressure has dropped it has been put back up to 1.5, but the fault is still there.

The last plumber seemed to think that there is a blockage somewhere & wants to rip the floor up to investigate, this will cause a lot of mess though as there is a wooden floor in the upstairs room.

 

[seco services]

if your boilers losing pressure and has to keep being refilled.
it must be loosing it somewhere.

as for the two rads if they are both fed off the same flow/return.
try shutting the others to push the heat the two cold ones.
then re-open the others.

if the systems balanced you may want to count the turns you shut each valve.

 

[lotus3692]

Thanks for the reply will try that.

Does it sound unlikely to you that there will be a blockage ?

Thanks again.

 

[seco services]

more air than a blockage.

is the downstairs pipework fed from the rad upstairs pipework ?
is it the furthest from the boiler ?

 

[lotus3692]

Yes the downstairs rad is fed from the rad upstairs pipework & think your right the downstairs rad is probably the furthest away from the boiler.

 

[lotus3692]

Have tried shutting off the other rads apart from the two that don't heat up, turned heating up to max, left for a while, still the two rads not fully heating up, only one of them gets a little warm.