Which are the most reliable open vent boilers with SEDBUK rating A?
I've been advised against getting a combination boiler, as there is space (and an F&E tank) for an open vent boiler. However I've heard that some open vent boilers in practice make assumptions that hold in a pressurised system but that are not likely to hold in a fairly old radiator open vent setup such as mine. Perhaps these boilers are really just reworked versions of combination boilers. Some of those that aren't have SEDBUK rating B only, which is presumably on its way out.
I've been advised against getting a combination boiler, as there is space (and an F&E tank) for an open vent boiler. However I've heard that some open vent boilers in practice make assumptions that hold in a pressurised system but that are not likely to hold in a fairly old radiator open vent setup such as mine. Perhaps these boilers are really just reworked versions of combination boilers. Some of those that aren't have SEDBUK rating B only, which is presumably on its way out.