Size of Feed/Expansion pipe

[Mike2007]

I thought the "expansion" section of the Feed/expansion pipe on a conventional vented system was 15mm (1/2inch if you like) swept up into the tank. The remainder done in 22mm for the DHW flow.
What about the expansion pipe on the primary flow and return pipes?

Feel free to correct me if I am wrong?

 

[ManxPlumber]

Feed is usually 15mm if it's mains, 22mm if it's gravity
Expansion is usually 22mm from the cylinder to the tank
Primary's are 22mm unless it's solid fuel heating in which case it's 28mm min.

 

[tamz]

Feed usually 15mm or 22mm if combined F&E
Expansion 22mm right over tank.