Converting to a sealed/pressurised central heating system-Expansion vessel size

[John D v2.0]

Ah ok so that's your issue, the expansion pipe doesn't connect into the loop at the same point as the feed.
Looks like someone has tried to make the expansion pipe go higher to try to help the problem, but failed.

Increasing the peak of the expansion pipe relative to the tank would help pumping over, raising the tank relative to the heating circuit join point would help suction. Seems you still have both issues though.

For background, your heating system has a pressure gradient all the way round the system when the pump is running. The further apart in the system they are, the more likely to get suction or pumping over.

Solution is to move them closer together and preferably on the suction side of the pump to avoid negative head. Or convert to sealed system

 

[firebladerrw]

Ah ok so that's your issue, the expansion pipe doesn't connect into the loop at the same point as the feed.
Looks like someone has tried to make the expansion pipe go higher to try to help the problem, but failed.

For background, your heating system has a pressure gradient all the way round the system when the pump is running. The further apart in the system they are, the more likely to get suction or pumping over.

Solution is to move them closer together and preferably on the suction side of the pump to avoid negative head. Or convert to sealed system

Thanks, and yes that looks like the problem. Without ripping walls and ceilings apart to move the F&E pipes, I think a sealed system looks like the best and possibly the simplest answer?

 

[John D v2.0]

Thanks, and yes that looks like the problem. Without ripping walls and ceilings apart to move the F&E pipes, I think a sealed system looks like the best and possibly the simplest answer?

Yes I'd do that, at least with a sealed system you can just pump it up to be greater than the head of the pump. Just the caveats about dealing with the discharge pipe.
PS some of the experienced members will no doubt be along with more practical rather than my theoretical advice.

 

[firebladerrw]

Yes I'd do that, at least with a sealed system you can just pump it up to be greater than the head of the pump. Just the caveats about dealing with the discharge pipe.
PS some of the experienced members will no doubt be along with more practical rather than my theoretical advice.

Thank you - well if there's anyone in West of Scotland wants a small job, let me know! Parts and fittings supplied