Radiator problem

[Tomcat2006]

Hi,

Can I have some advice please.
My central heating system is only 3 years old, but because of the open plan layout of my house the downstairs wasn't warm enough and I changed two single skin rads to double (slightly larger rads too) and added an extra double rad in also.

For a week every thing was great, the house felt lovely and warm. The pipes are 15mm and when I drained the system I noticed the water was very clean and not sludgy or black.
However now, all the rads are cold at the bottom and hot at the top. That's affecting every rad in the house, although two bedrooms are turned off as there not used. I'm aware this is unlikely to be trapped air (I already bleed them) and usually points towards sludge. I'm finding this unlikely too as the system is quite new and the drained water quite clean.
Would I be right in looking to balance the rads, or could it be the pumps not up to pushing around the extra water?

Any advice would be greatly appreciated!

 

[HERTS P&D]

Try turning the pump speed up and balancing the whole system.

Andy

 

[Tomcat2006]

Do I need to remove the small silver screw on the front of the pump to do this?
Thanks Andy

 

[HERTS P&D]

There should be a switch on the pump, normally the size of a penny. Don't remove the silver screw, it's a bleed screw to remove air.

The switch will be on the pump.

Andy

 

[Tomcat2006]

Thanks very much Andy!