Continuous flow systems
These advanced gas water heating systems provide a virtually endless supply of hot water as required. 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, not from storage, so an abundant supply of hot water is assured.
Continuous flow systems can be used in houses, multi-unit developments and low rise apartments and are ideal for:
- families where there is a large, intermittent demand for hot water
- households which have a fluctuating demand because of frequent visitors
- people who take frequent trips away from home, as these systems eliminate the need to store water.
Boosted solar heating
Continuous flow units can also be used to boost solar hot water systems. When demand for hot water out-strips the stored solar heated water in a tank, a continuous flow unit can reheat water as required. Units can be easily installed into existing solar hot water heating systems.
Size and placement
Units are compact; with dimensions often around 600mm (height) by 350mm (width) by 170mm (depth). Both internal and external models are available.
Exterior models are most commonly used and are mounted on the exterior wall of a building. They can also be recessed into a wall cavity using a recess box.
Flued internal models take up little space inside a building, freeing up valuable space.
Manifolding
When hot water demand exceeds the capacity of either a single storage unit or a continuous flow system, manifolding may be used to join two or more units together. This ensures abundant availability of hot water.
External unit installation and location
External continuous flow hot water heaters are mounted on the exterior wall of a building. There are clearances required from windows, doors and ventilation grills to prevent products of combustion entering a dwelling. As a water heater is considered a source of ignition, clearances are also required from gas and electrical meters.
These units must be installed in an accessible location that has an electrical power source available. Sufficient clearances are required for access for servicing and the appliance should not be installed more than 3.5m from ground level, unless permanent access can be arranged.
External unit
Continuous flow water heaters most commonly have fan assisted flues, which are located on the top face of the appliance. The appliance must therefore be located in accordance with NZS5261:2003, Table 16. For more details refer to the Ventilation and flueing section.
Some external water heaters can be fitted into a discreet recess box which is installed into an external wall of a dwelling.
External unit in recess box
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
Internal unit installation and location
Internal continuous flow water heaters must be installed in an accessible location. Sufficient clearances are required for access for servicing. The appliance should not be installed more than 3.5m from ground level, unless permanent access can be arranged. These units must not be installed in a bedroom, living room or bathroom.
An electrical power source must be provided, which is clear of any water and gas connections. Most of the units have a 1.5m power cord.
These appliances weigh about 16kg and the wall or structure to which it is mounted must be capable of supporting the weight of the appliance and associated pipework.
Internal continuous flow water heaters most commonly have fan assisted flues and the flue terminal must exit the building in accordance with NZS5261:2003, Table 16. For more details refer to Ventilation and flueing.