Radiators go cold after 20 minutes

[SavageW]

Check your 2port or 3port valve is still open when the boiler shuts off an they start to cool,this should tell you wether the thermostat is still calling for a demand,could be worth checking with multimeter your getting 240 on the orange in your wiring centre.
*just re read you said the boiler LED is continuously orange which would indicate the call for heating has gone,what room thermostat do you have?

 

[Chris54321]

Check your 2port or 3port valve is still open when the boiler shuts off an they start to cool,this should tell you wether the thermostat is still calling for a demand,could be worth checking with multimeter your getting 240 on the orange in your wiring centre.
*just re read you said the boiler LED is continuously orange which would indicate the call for heating has gone,what room thermostat do you have?

Yes the led is continuously orange once it stops firing. Green whilst it is firing. I have a Honeywell room thermostat, a very old one mind. It is in the living room. I do have a very small 1 bedroom house which only has 3 radiators.

 

[Chris54321]

Yes the led is continuously orange once it stops firing. Green whilst it is firing. I have a Honeywell room thermostat, a very old one mind. It is in the living room. I do have a very small 1 bedroom house which only has 3 radiators.

Sorry is the 2 port valve on the boiler or airing cupboard?

 

[SavageW]

Would normally be in your airing cupboard, small box looking thing with brass body underneath it after the pump. May have A & B written on it (little lever should be on B if programmer and room stat still calling for heat) or if it’s an metal looking box check the lever is loose which would mean it’s open. I don’t think it would be this as the boiler led goes continuous orange which means you now have no demand for heating.

 

[Chris54321]

Would normally be in your airing cupboard, small box looking thing with brass body underneath it after the pump. May have A & B written on it (little lever should be on B if programmer and room stat still calling for heat) or if it’s an metal looking box check the lever is loose which would mean it’s open. I don’t think it would be this as the boiler led goes continuous orange which means you now have no demand for heating.

Think I know the one, it is a metal box which is on auto.