Commissioning
49
MAXXfl o EVO 150/302
5.4 FROST PROTECTION & LEGIONELLA
5.4.1 FROST PROTECTION
The Heater is fi tted with automatic Frost Protection. Provided there is mains power, gas connected and the
heater is not in a lockout condition, if the temperature registered by the DHW tank temperature sensor falls
below 5°C the heat engine will ignite to bring DHW tank temperature up to 6°C before turning off again.
5.4.2 ANTI-LEGIONELLA GENERAL
Legionella bacteria is commonly found in water. The bacteria multiply where temperatures are between
20 - 45°C and nutrients are available. The bacteria are dormant below 20°C and do not survive above 60°C.
Legionnaires’ disease is a potentially fatal type of pneumonia, contracted by inhaling airborne water droplets
containing viable Legionella bacteria. Anyone can develop Legionnaires’ disease, but the elderly, smokers,
alcoholics and those with cancer, diabetes or chronic respiratory or kidney disease are at more risk.
The Health and Safety Executive in the UK Advises conducting a complete risk assessment of the hot and cold
water systems and ensure adequate measures are in place to control the risks. Recognised measures include
but not limited to the following:
•
Cold water should be stored and distributed below 20ºC
•
Hot water cylinders should store water at 60
o
C or higher.
•
Hot water should be distributed at 50
o
C or higher (any thermostatic mixer valves need to be fi tted as close
as possible to outlets)
•
Use a DHW return pump to circulate water around the system for at least 10 minutes every hour, even
when hot water is not required
•
Regular temperature checks of hot water tanks (at least every month)
•
Regular temperature checks of cold water tanks (if used, at least every 6 months)
•
Regular temperature checks of outlets closest and furthest from the hot water tank
•
To avoid stagnation, introduce fresh water by ensuring that all outlets are used at least once per week. This
draw off must be equal to at least the total quantity of water in the complete system (this includes all stored
water in any appliance)
•
Clean and de-scale shower heads every 3 months
•
Inspect the DHW tank for signs of debris during the annual service. Clean as necessary.
•
Design water systems to minimise Legionella growth, by:
•
Keeping pipe work as short as possible
•
Avoid dead legs/dead ends in pipe work
•
Keep water turning over regularly. Fit an anti-legionella valve on the expansion vessel to maintain
circulation around the vessel
•
Insulating circulation pipes and any cold water tanks
Other methods to control legionella include copper and silver ionisation and biocide treatments. Consult a water
treatment expert for advice on these measures.
This heater has been designed to minimise the formation of Legionella bacteria. The pumped tank charging
process ensures that the water at the bottom of the tank reaches the same temperature as in the rest of the
tank and all of the water is circulated, with no stagnation possible. A hatch in the main tank can be used for
inspection and cleaning. Only metals listed in 4MSI are used in this heater, and the heater has a WRAS UK
approval pending.
5.4.3 ANTI-LEGIONELLA SETTINGS
When activated via the heater controls, the anti-legionella function will be satisfi ed when the DHW tank tem-
perature sensor (B3) has detected that the anti-legionella setpoint has been reached for the length of time set
(1646 Legionella function duration). However, when the return sensor (B39) has been installed the tempera-
ture requirement to satisfy the anti-legionella function moves from the DHW tank sensor (B3) to the return sen-
sor (B39) mounted on the return pipe before its return to the DHW tank (see illustration on next page).
