Manifolded continuous flow units
Continuous flow gas water heating systems transform cold water to hot on demand. Energy is used only to heat the amount of water required, to the temperature selected, as and when it is needed. Hot water is provided directly from the source so an abundant supply of hot water is assured.
When hot water demand exceeds the capacity of a single unit, manifolding may be used to join two or more units together. This ensures an abundant availability of hot water which is ideal for:
- larger homes
- homes where multi jet showers are installed
- sports clubs
- hospitals
- hotels
- apartments.
Manifolded continuous flow systems provide significant cost efficiencies because no hot water needs to be stored and no back up system is required. A back up system is not necessary individual units are joined together and maintenance can be carried out on one unit while the others manage the workload.
Selection and design
Individual units are compact; with dimensions often around 600mm (height) by 350mm (width) by 170mm (depth), and both internal and external models are available. They come in a variety of capacities to suit different applications – from 16 to 32 litres per minute – and vary between suppliers.
The volume of hot water required will dictate how many units will be manifolded. For example, six 32 litre units can be manifolded together and can supply a total of 192 litres of hot water per minute at a 25deg rise, enough for 120+ apartments.
Electronic control systems can automatically turn each unit on as demand requires. Systems are also available which will rotate the work load between the units to prevent wear and tear.
Units can also be factory pre-set to specified temperatures which is ideal for kitchens and sanitary areas where an instant and reliable supply of water at high temperatures is required.
Installation/location
Exterior models are most commonly used and can be:
- mounted on the exterior wall of a building
- mounted on the roof of a building
- recessed into a wall cavity in the case of new buildings.
Internal models take up little space inside a building, freeing up valuable space. Minimum clearances are required from windows, doors and ventilation grills to prevent products of combustion entering the building. As a water heater is considered a source of ignition, clearances are also required from gas and electrical meters. Following is an installation clearances guide for an individual continuous flow unit. Similar clearances apply for manifolded continuous flow units
External continuous flow hot water heater installation clearances (ref: NZS 2.6.13.3)
Note
Clearances from front of the water heater flue terminal (not illustrated) = 1500mm
* For appliances over 150MJ/hr the minimum clearance is 1500mm and for appliances under 150MJ/hr the minimum clearance is 1000mm