u/Mysterious-Bag-44

We are changing all radiators. The feeds were microbores but now they are replaced with standard 15mm pipes, but before the feed it's still 8mm microbores. Are we fooling ourselves?

All we want is to have a working, efficient heating system. And for me that means the boiler can run on the condensing mode. Is this fine?

This is a 1960s house and it's microbores all the way from the boiler. Would it cost a lot to change all the pipes? We are doing a renovation now and floor boards are already up. Should we change the pipes? Need you advices 🙏

Edit: thanks for the replies! Now we know it's fine like this and we probably just need to flush the system and put money on insulation. Cheers!