Primary or System?

[Paul]

Hi. I have decided against buying a combi boiler. But what is the difference between a system boiler and a primary boiler? Thanks.

[Set Square]

A system boiler usually has additional components - typically pump, expansion vessel, filling loop, etc. - ready installed inside its casing. A non-system boiler doesn't - and these components have to be supplied and installed externally. [I assume 'primary' refers to an ordinary, non-system boiler - but am not too familiar with the term].

A system boiler requires less effort to install - but the integrated components are often proprietary, and more expensive to replace than the generic components used in a conventional setup.

[Paul]