Regular boiler

1 What is in the set-up

Worcester Bosch describes three parts: the boiler, a cold water tank that feeds the hot water store, and a hot water tank that holds heated water in bulk¹. Baxi adds that open vented systems usually have two loft tanks, a larger one feeding the cylinder and a smaller one keeping the heating system topped up and leaving room for expansion⁴.

Because the stored water and the cold tank do the work, Worcester Bosch says these systems can operate well even with low mains pressure, and that an existing older system can often be replaced using its pipework and radiators¹. That is a maker's own description of its product, so an installer's survey of the actual house matters more.

2 Not every regular boiler is open vented

A regular boiler can still have a gauge to watch. The Baxi 600 Heat guide says a heat-only boiler may be on either an open-vented or a sealed system, and tells anyone unsure to ask their installer². Worcester's 8000+ regular boiler manual makes the same split: open vented systems have pressure kept automatically by the header tank, while sealed ones are pre-pressurised and must be kept topped up⁵.

On the Greenstar Heatslave oil range, Worcester treats the gauge as unused on open vent systems, with a word to the installer if it ever shows over 1 bar⁶. That is one model family's wording, and may not carry across.

3 Upkeep

A loft tank and cylinder add parts a combi does not have. Inspection and servicing fall to a qualified engineer; see boiler service. For the store itself, see hot water cylinder.