It is a central-heating appliance that works with a separate hot-water cylinder. Many major heating components are built into the boiler, but the full system still needs design.
Cylinder-Based Heating for Higher Hot-Water Demand
A system boiler heats the radiators and a separate hot-water cylinder, making stored water available for baths, showers and taps. MacBlair stocks models for replacement and new installations within the central-heating boiler range.
Because hot water is stored, several outlets can often be supplied more effectively than with an on-demand arrangement. Actual performance depends on the cylinder, controls, pipework, pressure and recovery rate. The chosen hot-water cylinder must be sized for household demand.
The installer should calculate building heat loss and check the existing radiators rather than copying the old appliance output. Expansion components may be built into the boiler, but the complete sealed system still needs correct pressure, safety controls and commissioning.
Compare this layout with combination heating appliances where cylinder space is limited. A Gas Safe registered engineer must assess gas supply, flue position and condensate drainage, while specified system cleaner and inhibitor protect the heating circuit.
System Boiler FAQ's
A system boiler stores hot water in a cylinder. A combi heats mains water on demand and does not need a separate cylinder.
They can be, because a correctly sized cylinder stores hot water for simultaneous demand. Performance also depends on pressure, pipework and cylinder recovery.
Capacity depends on occupancy, baths, showers and usage pattern. An installer should calculate both storage volume and recovery rate rather than using bedrooms alone.
A Gas Safe registered engineer qualified for boilers must install and commission it. Work on an unvented cylinder also requires the relevant competence.