heating boiler

[strain]

If some of my radiators only heat towards the top and I have bled them until the water comes out does this mean that my boiler may not be stong enough to heat them - I added 3 radiators to my house after extending it although i have always found my home hard to heat.

[Hamish]

Two possabilities - sediment in the radiator (if they are old) or flow through the radiator is too slow, ie the pump is not set high enough ........ but I'm just a DIYer theres probably a professional on here with some other suggestions.

[Hamish]

How sharply does the temp vary up the radiator and how level is the point at wich the temp changes?

[Catso]

The radiators may need balancing, particularly since you've added some more. Do you have some rads that are properly hot?

[strain]

Thanks for your replies - yes some of the radiators are hot -

The top two thirds of a few of them is hot.
One of the radiaors in question would be at the furthest end of the house from the boiler. The radiators upstairs in the loft would not be as hot as the ones downstairs. I find the heat has to be on for a long time until the house is warm (apart form the summer months). The radiators dont seem to throuh aot of heat into the rooms despite feeling hot.

[Catso]

That some work and the the furthest don't does tend to indicate a balancing problem.

Balancing: the water prefers to take the shortest route from the boiler and back again IE through the nearest rads only. What you have to do is partially close the valves on the nearest rads to the boiler so as to force the water on the longer path, to the furthest rads. In simple terms, start with the nearest to the boiler and shut down the valve until you can feel a temperature difference between the water going in and that going out. Then move to the next and repeat - etc etc.

If you're going to say "the water coming out is already cold" then balancing isn't going to help, your problem is something else.

It also sounds like your boiler isn't up to the job. Does it have a thermostat to set the output temperature? Turn it up. As Hamish said, turn your pump up, if you can.

[strain]

Thank you Hamish and Catso - my husband has taken on all the advice I have been giving him and hopefully our problems will be solved - thanks again

[Hard@it]

Sounds like your pump is not working and you are getting a touch of heat through gravity.