Boiler or Pump problem?

[MartinTucks]

Have a problem with heating, only the radiator closest to pump is getting hot but hot water for taps is constantly hot even when the boiler is set to central heating only.
The boiler comes on for about a minute, then stops this repeats constantly.
Have checked the 3 way valve this is working ok. Have bled rads and not getting air out.
Have an Economist combi bolier if this helps.

Just to addto this, someone suggested turning off valve to rad that is getting hot, and see what happens, did that and no change at all, no other rads are getting hot.

 

[oilman]

How old is the system?

 

[MartinTucks]

About 10 years, we've been in house 8, was about 2 years old then..also we had a new pump put in 3 years ago.

 

[MartinTucks]

Also, just tried bleeding the pump to see if any air and nothing at all came out apart from a few drips of water.

 

[ollski]

How did you diagnose the 3 port valve as working properly?

 

[MartinTucks]

Turned the heating only on first on the boiler controls, then water only then both on together and the valve moved into the different positions

 

[oilman]

Well it's obviously no circulation, so it's either a blockage or an airlock.

 

[MartinTucks]

Thanks..have bled all the rads and got no air out, so will go the blockage root and put some refresher in the system.

 

[ollski]

I know you have bled the rads but have you bled the pipework vent/s aswell?

 

[oilman]

ollski's point is a good one, there can be vens in surprising places.

I'm afraid if you have a blockage, chemicals won't help. The chemicals can't get there because of the blockage. It will need a bit of detective work and then some mechanical intervention.