Feed and vent position

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Hi I'm currently changing a pumped CH/gravity HW to fully pumped, the pump is going to be on what was the gravity flow from the left top tapping with two 2-port valves to do HW and CH. Only moving it to the other side due to space for valves.

The vent pipe is connected on what was the ch flow just before the top right tapping. The returns from CH and HW I was going to leave connected to the bottom left and right tapping's.

The feed from the expansion tank connects into a T at the cylinder return.

I know that both feed and vent ideally need to be before the pump, but would this work by leaving them connected as they are?

Thanks if anyone has any thoughts.
 
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It might work - depending on which boiler you have. But if you intend changing the boiler soon, it would be better to re-pipe now so both feed and vent pipes are on the flow side. The reason for this is that older boilers have a very small pressure loss across the heat exchanger, normally made of cast iron, while modern boiler have a very high pressure loss (made of aluminium or stainless steel). Ideally there should be no pressure difference where the feed and vent pipes connect, but up to 150mm apart, on the same side of the boiler, is OK.

Make and exact model no of existing boiler?
 

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