Only 4 out of 8 radiators working

[madge82]

Hi, new here and just wondered if anybody had any suggestions or ideas as to why only 4 of my 8 radiators are heating up.
The system features a hot water tank in the airing cupboard and the relevant tanks in the attic. The house I believe is only 20 years old and has what looks like 8mm/10mm plastic piping for the central heating to the rads.
only my 2 lounge downstairs toilet and upstairs front bedroom are heating up. The others are all stone cold and not even the pipes to them get warm or anything?
I’ve tested the pins on the TRV valves and they are all free.
Any ideas would be greatly appreciated

 

[JohnD]

Turn off ALL the hot ones.

What happens?

 

[madge82]

I tried this and turned the heating up to max but nothing happened

 

[JohnD]

you mean the hot ones stayed hot?

or all 8 went cold?

Did the tapwater get surprisingly hot?

 

[madge82]

No All the radiators were cold. I’d seen somewhere to turn off the working ones and open up the others fully and crank the heat up. Didn’t try the tap water. Just seems weird that the pipes to the not working rads don’t even get warm like there’s a blockage somewhere

 

[Hugh Jaleak]

Turn off the HW, just leave the CH on at the programmer. Repeat test by turning off all hot rads. Does boiler continue to fire? Picture of HW cylinder would help, particularly of any Motorised Valves you may have.

 

[Deleted member 267285]

Check the lockshield valves (opposite end to trv), might be closed.

 

[madge82]

Checked they were open yup

 

[madge82]

Here’s some pics

 

[Deleted member 267285]

Did these ever work? Is it a new fault? Have you checked they have water in them?

 

[madge82]

Yeah the boiler continued to fire when the hot water was turned off.

 

[madge82]

Yeah they all used to work

 

[Deleted member 267285]

Seems like a possible pump or 3 port valve issue.

 

[Bodd]

I tried this and turned the heating up to max but nothing happened

Run......

 

[Hugh Jaleak]

Yeah the boiler continued to fire when the hot water was turned off.

Right, that means the heated water from the boiler is going somewhere around the system. If the Rads known to be working were off, then it has to be going somewhere, my guess at them moment would be, the 3 way valve is letting by and some flow is going through the cylinder. Repeat the test, then check the pipe going upwards from the 3 way valve, does it get ridiculously hot when the boiler kicks in? (Also, does the Hot Water at the taps seem exceptionally hot? Would also point towards this issue.)