I just did a system upgrade. The old system was being run on a 60,000 Btu Boiler with 22mm heating primaries. The system had been extended twice and it just wasn't working. The heat requirement was nearly 30Kw so I stuck a 30Kw logic+ heat only in and upgraded the heating pipework to 28mm until it split. Due to the extensive pipe runs I used a combine feed and vent but as I was already using plenty of 28mm I used 28 for the feed and vent. I also stuck a 25 gallon cistern in to use as the F&E to cope with the quantity of water in the system. I had visions of some fairly severe pumping over as TRV's shut down across the house.
