Cold radiator.

[Uncle Buck]

I have one radiator that will not get as hot as the others. The one nearby is also not very hot and in fact both were cold until I spent time playing with the valves on all the other rads.

It seems I have to shut the lockshield valves right down to only a quarter turn on all the other rads, to force heat into these two. This was still not working well until I shut the TRV's down a bit as well on all the other rads and then the colder ones came up, but the bottom of the the coldest one is still cool.

The boiler is only a couple of years old and is a Worcester Bosch 18RI. The system has been flushed many times and all rads have been removed and flushed individually.

I am wondering if it is because these rads are the furthest from the boiler and maybe another pump in the system might help. By the way, the pump is on it's fastest speed and all rads have been bled.

 

[crashndie]

hi mate how how big is your house? 9 times out of 10 the pump is normaly fine for a standard house, do the 2 rads get hot when the other rads are turned off and dos the pump sound likes its strugling to push the water round ?

 

[crashndie]

hi mate how how big is your house? 9 times out of 10 the pump is normaly fine for a standard house, do the 2 rads get hot when the other rads are turned off and dos the pump sound likes its strugling to push the water round ?

 

[Uncle Buck]

hi mate how how big is your house? 9 times out of 10 the pump is normaly fine for a standard house, do the 2 rads get hot when the other rads are turned off and dos the pump sound likes its strugling to push the water round ?

Sorry for late response Crashndie. My place is a four bedroom detached - not that big. I've found that by winding all other rads lockshields down (some only just open) and closing the TRV's down a bit as well, the coldest ones come up. The pump does not sound as if it's labouring, it was replaced when the boiler was fitted.

Just to add - the boiler does not seem to modulate now, it turns off/on, so I've dropped the pump speed to see if it modulates better.