Mitsubishi Electric PAC-IF051B-E Installation Manual page 38

. Main controller operation
Explanation of DHW operation
• When the DHW tank temperature drops from "DHW max. temp" by more than the
"DHW max. temperature drop" (set by installer), DHW mode operates and the
flow from the primary heating/cooling circuit is diverted to heat the water in the
DHW tank.
• When the temperature of the stored water reaches the 'DHW max. temp.' set by
the installer or if the 'DHW max. operation time' set by the installer is exceeded
DHW mode ceases to operate.
• Whilst DHW mode is in operation primary hot water is not directed to the space
heating/cooling circuit.
• Directly after DHW max. operation time 'DHW mode restriction' will routinely op-
erate. The duration of this feature is set by the installer and during its operation
DHW mode can not (normally) be reactivated, allowing time for the system to
deliver primary hot water to the space heating/cooling if required. However, if at
this time there is no current demand for space heating/cooling, the system will
automatically resume DHW mode. This will continue until it receives a demand
for space heating/cooling.
• After the 'DHW mode restriction' operation the DHW mode can operate again and
DHW tank heating will continue according to system demand.
<Eco mode>
DHW mode can run in either 'Normal' or 'Eco' mode. Normal mode will heat the
water in the DHW tank more quickly using the full power of the heat pump. Eco
mode takes a little longer to heat the water in the DHW tank but the energy used is
reduced. This is because heat pump operation is restricted using signals from the
FTC4 based on measured DHW tank temperature.
Note: The actual energy saved in Eco mode will vary according to outdoor
ambient temperature.
Return to the DHW/legionella prevention menu.
Legionella Prevention Mode settings (LP mode)
1. Use button F3 to choose legionella mode active YES/NO.
2. Use button F4 to edit the legionella function.
3. Use F1 and F2 keys to scroll through the menu selecting each subtitle in turn by
pressing CONFIRM. See the table below for description of each setting.
4. Enter the desired number using the function keys and press CONFIRM.
During Legionella Prevention Mode the temperature of the stored water is in-
creased above 60°C to inhibit legionella bacterium growth. It is strongly recom-
mended that this is done at regular intervals. Please check local regulations for the
recommended frequency of heat ups.
Note: When failures occur on the hydrobox, the LP mode may not function
normally.
Menu subtitle Function
Hot water temp. Desired temp of stored hot water
Frequency Time between LP mode DHW tank heat ups
Start time Time when LP mode will begin
Max. operation time Maximum time allowed for LP mode DHW tank heat
Duration of max. temp. The time period after LP mode max. water temp has been reached
Explanation of Legionella Prevention Mode operation
• At the time entered by the installer 'Start time' flow of useful heat from the system
is diverted to heat the water in the DHW tank.
• When the temperature of the stored water exceeds the 'Hot Water temp.' set by
the installer (above 65°C) primary circuit water is no longer diverted to heat the
DHW tank.
• Whilst LP mode is in operation hot water is not directed to the space heating
/cooling circuit.
• Directly after LP mode operation 'Duration of max. temp' will operate. The dura-
tion of this feature is set by the installer and during its operation stored water
temperature will be monitored.
• If stored water temperature should drop to LP restart temp, LP mode will restart
and primary water flow from the heat source(s) will be directed to the DHW
tank to boost the temperature. Once the set time for Duration of Max. temp has
passed LP mode will not recur for the set interval (set by installer).
• It is the responsibility of the installer to ensure the settings for legionella preven-
tion are compliant with local and national guidelines.
Please note that LP mode uses the assistance of electric heaters (if present) to
supplement the energy input of the heat pump. Heating water for long periods
of time is not efficient and will increase running costs. The installer should give
careful consideration to the necessity of legionella prevention treatment whilst
not wasting energy by heating the stored water for excessive time periods. The
end user should understand the importance of this feature.
ALWAYS COMPLY WITH LOCAL AND NATIONAL GUIDANCE FOR YOUR
COUNTRY REGARDING LEGIONELLA PREVENTION.
3
DHW tank temp.
Stop
DHW max.
temp.
DHW max.
temp. drop
Start
DHW mode
DHW tank temp.
DHW max.
Stop
temp.
DHW max.
temp. drop
Start
DHW max. DHW mode
operation time restriction
Range
60–70
1–30
0:00–23:00
1–5
1–120
DHW tank temp.
Stop
Stop temp.
Legionella
hot water temp.
Restart temp.
Space
Start
heating/
LP mode
cooling
Duration of Max. temp.
(LP mode: Legionella Prevention mode)
Restart
Time
DHW mode
Stop
Restart
Time
DHW mode
Unit Default value
°C 65
day 15
- 03:00
hour 3
min 30
Stop
Restart
Mode
LP mode
finish
Time