Open Vent pipe layout question

[ap0115]

Open-vent 4-port boiler was recently changed for a new 2-port model.
The diagram shows the connections to the FE tank.
The junctions are numbered to make it easy to refer to.
Can anyone comment on the layout?

 

[Johntheo5]

It looks more like a combined vent and feed than the traditional VCP system, where, on the boiler flow, you have, from the boiler 3, the vent 2, then the feed 1, then the pump 4. I have a combined vent and cold feed with the pump on the return to the (oil) boiler which has worked to perfection for decades with a few rads over 40 years old.

 

[ap0115]

Interesting. I'm thinking that the usual "combined" arrangement is when the original 15mm feed is scrapped and the 22m vent is repurposed to be a single 22mm feed from the tank down. In the above, the F & V drop two floors together, are then combined and finally T'd into the flow 22mm later ... as opposed to the F being the last T to the flow before the pump.