Unvented cylinder size

[Notagainpike]

You are assuming the feed and vent are connected either side of the boiler? I'd have the feed and vent both on the suction side of the pump on a low head system, no pumping over and only consideration is enough head to prevent cavitation.

Bit beond me at present tbh...

 

[Sparkgap]

Like this. Both cold feed and vent on the flow pipe off the boiler.

 

[Notagainpike]

Like this. Both cold feed and vent on the flow pipe off the boiler.

I have no F+E tank

 

[Basher]

I have no F+E tank

You mentioned one in post #56
"Raise f+e tank in loft."

 

[Notagainpike]

You mentioned one in post #56
"Raise f+e tank in loft."

Removed now