Adding a rad to a system

Hi All,

My question is in regards to a bungalow with gravity fed hot water system and sealed pressurised heating system.
The heating system currently has 7 rads running off microbore fed from 22mm manifold.
Some years ago an extension was built above garage but no heating was installed.
Is it possible to add a radiator fed off the existing manifold without causing any issues, would there be a limit to the size rad to use and could use 15mm or should i stick to microbore?

Cheers

 

Thanks leaky Pete, I'd prefer to use 15mm, not a fan of microbore