Downstairs colder then upstairs

[saabuldin]

Originaly the central heating system was piped 15mm going from the boiler across the 2 bedroom terrace house. Of the 15mm they took 10mm to all the rads upstairs and downstairs.

I repiped all the upstairs rads to 15mm. But left the downstairs kitchen, backroom, frontroom and hallway which are still 10mm coming of the main 15mm. Because these were buried in the wall i didnt want to rip the plaster off to repipe.

The other thing is the downstairs front room rad is tapped of the hallway so the hallway is 10mm of the 15mm and front room is 10mm of the hallway so it stays cold when i have the hallway on full and vice versa.

The problem im having is upstairs gets alot warmer then downstairs, is there anything i can do to make it equally warm. if i have to balance, how do i do that?
How do i solve the hallway and front room issue. Front room is always cold?

Thanks in advance.

I have heatline c24 boiler

 

[JCplumb]

Have a search on here/google/youtube on how to balance your central heating system.
If balancing doesn't work you'll need dedicated feeds for your hallway/front room and another balancing.