Section 5: Domestic Hot Water Page 21
5.3 Legionella
It is possible to use the heat pump to raise the HW cylinder to around 50 to
55°C.
For protection against Legionella the temperature can be periodically raised
to 60°C using the Grant Automatic DHW Boost Kit 2, available from Grant
IRL (product code: HPDHWBK2).
This boost kit also allows the cylinder immersion element to be used to raise
the temperature to 60°C for one hour either daily or weekly to sterilise the
cylinder against Legionella.
5.3.1 Legionella Sanitisation Regime
Care must be given to vulnerable people who may be exposed to potentially
life-threatening legionella. This group of people include the elderly, pregnant
women, young children and those with breathing difficulties.
Care must also be given to households who do not use a lot of water on a
daily basis. While this chart is not exhaustive, it is important that you discuss
any potential issues with the occupants before deciding on the appropriate
regime. It is important that this decision is based on the welfare of the
occupants and not on energy saving measures.
Table 5-2: Legionella group sanitisation regime
Uses less than 50
litres of hot water
per day
Uses more than 50
litres of hot water
per day
Vulnerable Group
Store at 50°C and raise
hot water cylinder to
60°C for 1 hour every
day
Store at 50°C and raise
hot water cylinder to
60°C for 1 hour every
3 days
Non-Vulnerable Group
Store at 50°C and raise
hot water cylinder to
60°C for 1 hour every
week
Store at 50°C and raise
hot water cylinder to
60°C for 1 hour every 2
weeks
5.4 Automatic DHW Boost Kit
This system uses both the existing cylinder immersion via the Grant DHW
boost kit. This is switched via a contactor operated by a small timeswitch,
both enclosed in a separate unit to be mounted next to the cylinder. Thus the
immersion element can be programmed to operate for the required period on
either a daily or weekly basis.
5.4.1 Installation
The Automatic DHW Boost Kit 2 comes pre-wired within its enclosure, ready
for installation. The connections to the Immersion heater switch and immersion
heater must be made after it is installed on site.
When installed, this kit interrupts the electrical supply between the existing
immersion heater switch and immersion heater. Refer to Figure 5-4 for
electrical connection details.The use of any other type of cylinder thermostat,
or any modification to an existing thermostat, will invalidate the product
guarantee and may result in a potentially dangerous installation.
IMPORTANT
Do not alter the pre-wired connections within the enclosure
and only make the external connections as shown in the wiring
diagrams. See Figure 5-4.
For this system to operate, the existing
immersion switch must be left set permanently
to ON.
To totally prevent operation of the immersion
element, the existing immersion switch must be
set to OFF.
NOTE
WARNING
Where a 3-phase supply is present, ensure that
BOTH the immersion switch and heating system
controls are taken from the same phase. If in
doubt, contact a qualified electrician.
To Next Page
Loading...
