Radiators cold but boiler circulating hot water

[SlabConfusion]

Hi,

I have a standard two storey house (less than ten years old) with dual zone (upstairs/downstairs) heating and a Baxi combi boiler.

I've come to put the boiler on and most of the radiators are not working - the motorised valves move and the boiler fires so I know there is hot water in the system but only one radiator actually is hot - one is slightly warm and the rest are stone cold. The pump sounds as if it is sending water around and radiator output from the boiler seems like there is hot water coming out, the boiler seems to suggest that it is regulating the temperature.

There are TRV's on each and I've tried hitting the pin with a hammer and nothing, still think that eight TRV's sticking is a little bit unusual. The front bedroom has a radiator without a TRV on it and that is cold (if anything I would think that would be the hot one).

Am a bit lost for ideas - does anyone have any suggestions - I was thinking possibly a blockage/restriction in a pipe? Try and drain the system and see how much water is in it?

Thanks

 

[terryplumb]

Does the boiler fire up for hot water at your taps ok ?
What model Baxi boiler do you have ?

 

[JohnD]

Turn off the hot one.

What happens to the others?

 

[CBW]

Feel the pipes after the motorised valves, are they hot?

 

[SlabConfusion]

Does the boiler fire up for hot water at your taps ok ?
What model Baxi boiler do you have ?

Yep the HW side of it works fine - its a Baxi Neta Tec 33 Ga

Turn off the hot one.

What happens to the others?

No change I am afraid after turning that one off

Feel the pipes after the motorised valves, are they hot?

There is only about 4" of pipe (so not sure if this is just transfer of heat or not) before they go into the ceiling but the temp is the same on the outside of the pipe before and after the valve. I've measured it at 50°C on the pipe surface, looks to be 22mm pipe.

Thank you everyone for the replies - if it means anything the pipes to the radiators (plastic stuff, looks about 12mm) are cold also before the TRV - last year I did put Flomasta Inhibitor/Cleaner (sold in a pack at Screwfix) in the system as the boiler was making a noise and the radiators worked just fine after then but the system has pretty much been off since not long after.

 

[JohnD]

last year I did put Flomasta Inhibitor/Cleaner (sold in a pack at Screwfix) in the system as the boiler was making a noise and the radiators worked just fine after then but the system has pretty much been off since not long after.

Did you flush out the loosened sediment after using the cleaner?

 

[SlabConfusion]

Did you flush out the loosened sediment after using the cleaner?

Yep I did - there was a fair bit that came out of it but I wouldn't say it resembled crude oil or anything

 

[martygturner]

Lack of pressure, fill the system, Airlock, bleed the rads, sludge build up , add some cleaner, run, drain refill.

 

[SlabConfusion]

Lack of pressure, fill the system, Airlock, bleed the rads, sludge build up , add some cleaner, run, drain refill.

I think you were right with a lack of pressure - turns out the last person to look at a leak on it (I almost forgot about it) isolated the radiator circuit and never turned it back on

Don't know how one radiator was getting warm unless the valve was not closed completely or just passing the heat through the pipes!!

 

[JohnD]