I’ve recently replaced a radiator downstairs and serviced the valves . The system has had sentinel 800 and been drained several times and purged of air. It’s 10mm microbire. Downstairs rads are on drops and other three downstairs rads work fine. The rad refuses to get properly hot. If you close the valve one end and open the drain valve there is a good flow of water through the rad which starts to get hot but only along the top of the rad and the same closing that valve opening the other end produces a good flow of water but the rad does not retain heat and does not produce heat when both valves are open . It’s as if the circulation isn’t right ie the hot coming from one end is circulated and the hot draining from the other us coming from upstair as the system starts to drain Either way I can’t see how there can be a blockage as the water flow even by gravity is good. The pump is at max speed and the boiler is new professionally fitted. I’m stumped! Any advice much appreciated! Thank you
Hi try turning all the radiators off in the house leaving the troubled one open on both sides and run the heating up
By doing this it will push any air in the pipes that have been caused from draining and filling up then balance the system at desired heat in each room
if this does not help then you have a blockage on either flow side or return and the only way to remove would be either a power flush or cut out pipe work and replace
Is this a fully pumped system or a gravity fed system
Hello I have read the above and sometimes a powerflush can cure this if a blockage is suspect by powerflushing each individual radiator you will improve the water flow in each radiator as you mentioned it only gets hot around the top edge. Another factor could be a sticking thermostatic radiator valve. So what I would do is close all the radiators and leave the defective radiator open and run the system as it might just require balancing properly if the radiator heats up. In addition although the pump may be running the rpm of the pump might not be upto speed I hope this helps
If a radiator is getting Hot at top and cold at bottom means that the fins are blocked up at the bottom and thus either need to replace radiator or remove radiator and have it cleaned and refitted
Simply turn of the other radiators downstairs and leave open the one not getting hot it will get hot very soon, then leave on for around 30 mins with the others off, then bleed the radiator agai, then turn the others back on one at a time 5 mins in between that should solve the problem.
close all rads apart from the one not working. when it gets hot open the rest if it goes cold then you need to close the others back down so they all get hot.