Indirect tanks & combination systems

When water heating is connected to space heating

An indirect water-heating arrangement uses a separate heat source, commonly a boiler, to heat water stored in a tank through a heat exchanger. A combination system serves both space heating and domestic hot-water needs. The exact layout matters more than the label.

Before replacing a tank, establish whether it is part of a wider heating system. A decision that looks like a simple water-heater swap may also affect controls, system scheduling and the supply of heat elsewhere in the property.

Ask about simultaneous needs

Have the designer explain what happens when the home needs space heating and hot water at the same time. Ask about the capacity calculation, priority controls, recovery and how the system is commissioned.

Compare the proposed system as a whole. NRCan notes that an efficiency figure for only the water-heating component does not describe all of a combination system’s performance. Keep proposals clear about which equipment and distribution work are included.

For shared and larger buildings

For a shared plant, document who owns the equipment, the shutdown plan and how affected occupants will be informed. An individual suite’s fixtures do not provide enough information to size a whole building.

Request drawings, equipment schedules, service access, a maintenance handover and clear responsibility for controls and commissioning. If the current system is poorly documented, make the survey part of the project before equipment is ordered.

Common questions

Sources & further reading

• NRCan combination systems

Check the selected manufacturer’s current instructions. Program eligibility and installation requirements can change.

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