Dowstairs radiators keep going cold

[dlicenceskydive]

Here is a problem for an experienced central heating expert that no visiting plumber has been able to solve.

We have an Ideal Mexico System boiler (12 years old) serving 11 radiators (9 new recently installed) and the hot water tank of course.

The problem I am experiencing is that with the central heating switched on, periodically some of the radiators (all the downstairs ones ) stop working and start going cold.The upstairs ones continue to remain hot. After a period of time (can be some hours) the downstairs radiators come back on again of their own accord. This problem has been going on for about two years now. Visiting plumbers have changed out 9 of the rads but still the symptoms persist.

Another thing I have noticed is that the header tank water is normally tepid and frequently the water there is so hot you can't put your hand in it. Nothing comes out the overflow. The plumbers who have visited can't give any explanation for this.

The recommendation from the plumbers in the last few days has been the replacement of the boiler with a combination boiler. I'm reluctant to go down that route if the problem will still exist afterwards.

Anybody come across these problems before??
and have a solution?

 

[kimbo]

Are the downstairs rads fed from above.

 

[stevetheplumber]

pump failure on old systems often allows upstairs rads to heat on gravity
but you say they get hot intially
when ever i get a system acting eraticly first suspect is blocked cold feed turn of main and drain down see if header tank empties properly
if your system has the cold feed u bend where it joins the system it will be solid

 

[dlicenceskydive]

Are the downstairs rads fed from above.

No the boiler is floor mounted in the downstairs kitchen.

 

[kimbo]

If you turn off all the top ones will the bottom ones get hot then.

 

[dlicenceskydive]

It varies. Sometimes all the radiators come on OK and then the downstairs one go cold. Sometimes the downstairs ones don't come on initially but become hot of their own accord later. There is no pattern to it.

As far as the blocked cold feen is concerned, do you mean the cold water mains feed into the header tank? I know that the plumbers who filled up the system last had to "blow through" the cold water feed as there was no supply.

Many thanks for your help.

 

[dlicenceskydive]

I've not tried that. I will let you know.

Thanks

 

[markproperjob]

what was meant by downstairs rads being fed from above, do you have pairs of pipes dropping down from ceilings to each downstairs radiator, or do the pipes dive under the ground floor?
what was said about pump problem, if you have an old circulation pump, then this can cause havoc if it starts to stick, or become restricted in performance as it heats up with water temp.
that would explain top rads staying hot with conduction and downstairs going cold due to poor circulation, plus a symptom of poor circulation (and pump power switch set on too high a number!) is boiling hot expansion tank.