gravity fed radiator used to work but doesn't anymore

[barney11]

Have a gravity fed radiator in my bathroom. For over 25 years it has worked when boiler on 'central heating & hot water' and when on 'hot water only', but now will only work properly when boiler on 'hot water only' which it is in the summer. It started to get hot on the top one third only when central heating on. Plumber/boiler man said I should have system flushed. Had system flushed, and since radiator v. old also had it replaced. Plumber had to weld on smaller pipework. However same problem, will not work fully when heating on. Bathroom is v. cold! Plumber has disappeared and will not answer phone calls. Is there anything I can do?

 

[justlead1]

Hi. Difficult to comment with out seeing the situation. But the reduction in pipe size would have an effect on the circulation along with elbows and rad valves. As the pressure that supports circulation on gravity systems is measured in Milli meters rather than metres, and can soon be used up with the frictional resistance the smaller pipe and fittings create.

 

[johnmcginty]

Bleed it , check both valves are ok? is there a trv ? remove the top and pull up the pin if there is. Are the pipes getting hot at all? , turn up the pump, manually move the 2 port valve to fully open , is the rad definateley hooked up to primaries and not onto the hot water pipes for the bathroom? why did he have to solder on smaller pipework? Check ball cock in f&e tank not stuck. Just some things to try before phoning a plumber.

 

[barney11]

Hi. Difficult to comment with out seeing the situation. But the reduction in pipe size would have an effect on the circulation along with elbows and rad valves. As the pressure that supports circulation on gravity systems is measured in Milli meters rather than metres, and can soon be used up with the frictional resistance the smaller pipe and fittings create.

Thanks for your reply. My oil fired boiler was there when I moved in 30 years ago, and all pipework is above the floor, and all other pipework is a smaller diameter. Bathroom radiator has no TRVs, and the old radiator had the same problem (hot at top, cold at bottom) with larger pipework. A plumber came to see the old radiator and said it should be raised up at one end as it is gravity fed - was he pulling my leg or is this correct?

 

[barney11]

Bleed it , check both valves are ok? is there a trv ? remove the top and pull up the pin if there is. Are the pipes getting hot at all? , turn up the pump, manually move the 2 port valve to fully open , is the rad definateley hooked up to primaries and not onto the hot water pipes for the bathroom? why did he have to solder on smaller pipework? Check ball cock in f&e tank not stuck. Just some things to try before phoning a plumber.

Thanks for reply, have bled it and plumber/heating engineer did as well. Does not have a trv. Ingoing pipe is hot, outgoing pipe is cold. How do I turn up the pump? I have a very old oil fired boiler. Rad is gravity fed, but used to work when system put onto hot water and central heating. Pipework too big to fit new radiator. Bathroom radiator only one with such big pipework. Other radiators get very hot.

 

[johnmcginty]

Turn off all rads but this one (if two pipe system), also if flow pipe hot but rad is cold, make sure lockshield is fully open (for now) and turn heating on again, try swapping this valve if it still does not come on. DId'nt read question properly as per gravity, so no pump then.

 

[justlead1]

Hi Barney. There are factors like the vertical height between boiler and rad and horizontal distance between the two. If the rad is on first floor and boiler the ground floor, circulation would be better than in a bungalow. As for raising one end of the rad that's a new one on me. Is all else fails, it is likley that a plumber/heating engineer could hook the rad up on the heating circuit.

 

[Avatar]

Maybe its time to bite the bullet and put a nice new combi system on - a 25 year old gravity fed system is asking for trouble - one problem can lead to another, and could leave your wallet hemmoraging money!

Best economy is to get the job done right (remember that one guys!)

 

[ab54666]

Did you find a solution to this? I have exact same problem. Radiator warms nicer when only on HW but not when HW & CH. I believe I should have an anti gravity valve but can't find it!