Floor standing Boiler with 1 flow pipe and 2 return pipes leading into it

[quattro64]

Hi, I hope someone can help.
I am starting a job tomorrow replacing some radiators in a house.
The system appears quite unusual - to me anyway. the boiler is a Stelrad (Ideal) Mexico slimline cf55 boiler and appears to have one flow pipe leading from the top of the boiler but two return pipes comming back in either side at the bottom. Added to this part of the house utilises a one pipe system and another part a conventional 2 pipe system for heating. Because of the layout and the fact that a lot of the pipes are buried it is very difficult to trace where they all go to. could someone tell me if this type of arrangement is correct and also why wouldnt the boiler just have 1 return?
many thanks

 

[kirkgas]

you will have a heating return and a hot water return, if they are piped together it is possible when on hot water only the nearest rads might heat up due to reverse circulation, the way it is done means you wont get rads heating when on hot water only