POTT SIRIUS THREE 2X 250kW CASCADE KIT

Commercial boilers heat larger buildings such as offices, schools, shops and blocks of flats. This category covers wall-hung and floor-standing condensing gas boilers from around 30kW to over 400kW, plus cascade frames and headers, plate heat exchanger kits, low loss headers, connection kits, zone controls and casing parts.

Single boilers and cascades

Large heat loads are often met by several boilers working together in a cascade, mounted on a shared frame with common flow and return headers. Sequence control brings boilers on and off as demand changes. In England, Approved Document L Volume 2 expects boiler systems over 100kW to have optimum start and stop control and either high and low firing or multiple boilers with sequence control, and gas boilers over 500kW to have fully modulating burners. Check that the boilers, frame, header and controls are made to work together.

Hydraulic separation

When new condensing boilers are connected to an existing heating system, hydraulic separation is important. A plate heat exchanger keeps the boiler circuit completely separate from the building's pipework and protects the new boilers from dirt carried in older systems. A low loss header is the other common way to separate the boiler and system circuits. Choose kits matched to the boiler model and total output.

Regulations and safety

Work on gas pipework, appliances and their gas parts must only be carried out by a Gas Safe registered engineer. The back of each engineer's ID card lists the categories of work they are qualified for, so check it includes the non-domestic work you need. New and replacement boilers in non-domestic buildings in England should meet the efficiency and controls guidance in Approved Document L Volume 2.

For replacement parts, see boiler spares, or browse circulation pumps.