recommended pump?

[Neil T]

Been to see a customer and top floor rads are struggling to heat properly. I've balanced and bled the system and improved it slightly.
The house is 3 storey with 10 rads and run on a greenstar high flow 440 cdi boiler. There are 2 vertical rads on system with one of them on very top floor which is really struggling. I bled it for about 30 mins to get the cold and air out of it and managed to get it to warm slightly but there was no flow from the return valve, which leads me to think there isn't enough pressure to make it work properly. Middle floor rads are working OK but not brilliant and ground floor are working well.
There are 10 rads altogether and they want an extra one installing in a room on top floor also.
They want me to replace 6 of the rads as they are probably 20 to 30 years old and not very efficient. The rads are all run on 10mm pipe too.
Can anyone recommend a suitable ch pump to put on the system to help the top floor rads? They have given me option to replace the vertical rads but if I can save them money with just the pump then I'd prefer to do it that way.
Cheers

 

[ShaunCorbs]

Sounds like could do with some cleaner in the system

open vented or sealed

 

[Neil T]

Its a sealed system. I did mention to them that there could be a sludge build up due to age of rads but they want them replacing. I may recommend adding an inline cleaner to system such as a fernox f1 when i do the install. Regarding the top floor rads, a pump would help wouldnt it?

 

[ShaunCorbs]

Yes worth a try depends how old the existing pump is

 

[Neil T]

Boiler is sited in the basement and i havent seen a pump in that room

 

[ShaunCorbs]

Boiler is sited in the basement and i havent seen a pump in that room

Should be where the cylinder is it not by boiler

 

[Best]

I have cured a lot of similar systems by fitting a 6metre pump.
Microbore pipe really needs the stronger pump, as does 3 floor buildings.
I am careful to check for any easy bypass routes and balance them well down - like on a coil at a cylinder.

 

[heliotrope]

Have you tried increasing the system pressure?
Bump it up to close on 2 bar.