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Figure 31 Installer’s Digital Input Connections (AS02 units)
A link wire should be placed between the terminals for the ‘Master On/Off’ and also between
terminals for the ‘Mode Heat/Cool’ function. This will ensure the unit is on and set in heating
mode. Volt-free connections can then be made to the ‘DHW On/Off’ and ‘Heat/Cool On/Off’
from a remote source such as a timeclock, programmer or room stat. Connecting the terminals
for ‘DHW On/Off’ will set the unit into DHW mode. Connecting the terminals for ‘Heat/Cool
On/Off’ will set the unit into heating mode (provided the link wire is connected between the
‘Mode Heat/Cool’ terminals.
NOTE: Connections are volt-free, no voltage should be connected into any of them.
Connecting any kind of voltage to the terminals will damage the control board inside the
unit.
3.10.3 Digital Outputs
The digital outputs section allows the connection of ancillaries which are turned on or off via the
units controller. The total rated current of all the outputs together must be less than 3.0Amps.
Items such as immersion heaters and high powered pumps can still be controlled by the outputs
but they should be connected via a relay with an external power supply. The following outputs
can be controlled by connecting into the appropriate connection blocks.
RO 09 Immersion – This output (230Vac) is for controlling an immersion heater in the DHW
storage cylinder. The immersion may be called to switch on to provide thermal disinfection of
the DHW cylinder. This may be the case if a DHW storage temperature of 60°C cannot be
achieved by the heat pump alone. As the immersion heater will have a high electrical load, it
must be wired via a relay with an external power supply. The outputs from RO 09 should be
wired to the coil of the relay which then will switch the external power supply to the immersion
heater. Cable cross sectional areas should be calculated according to the current at full load
together with the on-site conditions and the cable length between the relay, the immersion
heater and the consumer unit. The control settings of the immersion should be set during
commissioning.
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