Radiators towards front of house no longer heating up

[Suhail]

A new boiler fitted about a year ago and all the radiators were working but those in the front were never as warm as those in the back.

Normal boiler and is a compression system with expansion vessel.

I have had a basement put in with underfloor heating which works fine.
The radiators in the back of the house are working fine.

However the radiators in the front of the house, on the ground floor, First floor and attic are no longer getting warm. As mentioned they did seem to be working a few weeks ago but were warm and not hot.

I have bled the radiators and they are all full of water.

A friend has mentioned that the hot water pipe going up the front of the house from the basement to the ground, first floor and attic is only a 15mm pipe. He mentioned it should be changed to a 22mm pipe.

Any advice to resolve this issue would be greatly appreciated.

 

[denso13]

If you turn off all the working radiators do the others heat up?

 

[Suhail]

If you turn off all the working radiators do the others heat up?

Thanks for your quick reply.

That seems to have partly worked

Some radiators have warmed up on the first floor and one has got hot.

Radiators in the attic - one is hot and one warm.

On the ground floor the radiators have not warmed up at all.