Baxi Andrews Hiflo Evo Unvented System Kit, unvented cylinder kit, hot water system installation kit, unvented system accessories

Commercial water heaters provide hot water in larger volumes for sites such as hotels, gyms, salons and laundrettes. This category covers gas-fired storage heaters, wall-hung continuous flow heaters and their kits: flues, anodes, unvented kits, LPG conversion kits and controllers.

Types

• Storage heaters: a gas burner heats water directly in an enamel-lined steel tank, holding a store ready for busy periods.
• Continuous flow heaters: compact wall-hung units that heat water as it passes through. Several can be linked for more output; check whether a controller kit is needed.
• Condensing or non-condensing: condensing models are the high-efficiency option and need a condensate trap and drain.
• Fuel: natural gas and LPG versions are made, and some natural gas models can be converted with an LPG kit.

Sizing, flues and parts

Size the heater from the site's peak hot water demand. Storage volume covers the busiest period, and the recovery rate, in litres per hour at a stated temperature rise, shows how quickly it catches up. Many heaters come without a flue, so choose the matching conventional, balanced or fan flued kit. Anodes help protect the steel tank.

Safety and regulations

Work on gas pipework, appliances and their gas parts must only be carried out by a Gas Safe registered engineer. In England, an unvented hot water system comes under Part G of the Building Regulations (G3) and should be installed by a competent person. HSE guidance on legionella control says stored hot water should be kept at 60°C or more and reach outlets at 50°C or more within one minute (55°C in healthcare premises), so include the heater in the site's legionella risk assessment.

For domestic hot water storage, see cylinders and water heaters and unvented cylinders.