Hot water, boiler seems fine but only luke warm radiators!

[KatieH]

Hello All,

I am having a bit of a problem with my heating. Its a valiant combi boiler and the hot water is coming out fine but the radiators are slightly warm and the top and colder as you go down. I've checked the link the the portable controller and that is fine, the boil seems fine and is going through all the steps it needs to do to heat the radiators etc.

Over the last few days the radiators are getting colder. They come on at the correct times and go off at the correct times but are just not getting hot enough!

Any suggestions as i've not got a clue and am stumped!

[plumbbob]

This may sound stupid, but are you sure the radiator water temperature is set to max and not accidentally set to min?

Is the radiator sign constantly showing in the display when the heat is on?

When the heating has been on for a while but the rads are still cold, what does the boiler display for water temperature?

Has the system been drained and re-filled in the last few weeks?

[KatieH]

Hi Plumbob,

The temp is set at the usual and i've not changed it. The system hasn't been drained since I moved in which was in March 2010.

The display shows that the heating is on and it flashes when it should whilst the hot water is being pumped around the system.

A new thing has happened since i last posted the rads closest to the boiler are hotter than the ones furthest away with them slowly feeling hardly warm at all as days go on.

Soon i'm expecting the heat to go altogether! But i can't think of what it could be if i've bleed them all that the system itself seems to be working fine.

HELP!!

[plumbbob]

You haven't really answered my questions directly, so I have very little new information to help with a diagnosis.

The temp is set at the usual and i've not changed it.

So we can't actually discount the possibility that the water temp is set too low? Turn it up to maximum.

The system hasn't been drained since I moved in which was in March 2010.

So we can discount any airlocks. On that basis, bleeding won't solve your problem.

The display shows that the heating is on and it flashes when it should whilst the hot water is being pumped around the system.

Forgive me, but how do you know that? The display shows a range of symbols each indicating different boiler activity. I asked if the radiator symbol was showing because that would indicate the room thermostat was working correctly. You have checked the room stat haven't you?

A new thing has happened since i last posted the rads closest to the boiler are hotter than the ones furthest away with them slowly feeling hardly warm at all as days go on.

Not so good.

Soon i'm expecting the heat to go altogether! But i can't think of what it could be if i've bleed them all that the system itself seems to be working fine.

There is a possibility of this so we must come to a conclusion sooner rather than later.

I need to know the boiler water temperature after the heating has been run for 10 to 15 mins. This is crucial to any diagnosis.