The Stainless Steel Indirect (SSI) range from Adveco is designed to serve as an indirect calorifier in domestic hot water (DHW) installations. The unit has no integral burner, instead, it contains a single, high-output internal heat exchange coil situated at low level which heats water circulated over it.

Commercial installations where heat is already being generated, such as light industry, leisure sites, and hospitals are perfect locations for the use the SSI as a method of indirect heating.

Without a directly connected gas supply, and therefore no need for a flue, an SSI indirect calorifier is simpler to install as part of a wider heating and hot water system where the heat is provided by a separate appliance – typically a gas boiler, heat pump or solar collector. The fluid in the coil – which is immersed in the water within the SSI – is filled by heated liquid (water or solar fluid) and the heat then exchanged from the coil into the vessel, hence indirectly heated. The insulated storage tank retains energy longer, permitting hot water production year-round in greater quantities and at a reasonable cost.

Commercial systems should harness the efficiency of the modern boiler for both the heating circuit and the DHW system. This counters requirements for a dedicated boiler to heat the calorifier. During the winter, when the indirect water heater is used for the heating, only a small fraction of the heat is used for DHW. In the summer when the space heating is not needed, all of the heat is used for hot water preparation, so this does mean the boiler needs to be operating year round. There are system advantages to this approach as continuous use of the boiler for DHW helps prevent costly deterioration which can occur if a boiler is idle for long periods. The SSI coil is also easy to remove for cleaning and maintenance purposes.

Available in a range of tank sizes, SSI can also be upgraded at any time with a range of coil options making the design highly modular. There is even the option to add an electric immersion heater, turning the SSI into a direct heating appliance, perfect for cost-effectively building redundancy into a system that could otherwise be reliant on a continuous gas supply.