General
This function enables an external additional heater, e.g.
an oil boiler, gas boiler or district heating exchanger to
aid with heating.
The heat pump controls a shunt valve (QN11) and a cir-
culation pump (GP10) via AXC 40. If the heat pump
cannot manage to maintain the correct supply temper-
ature, the additional heat starts. When the boiler tem-
perature has increased to about 55 °C, the heat pump
sends a signal to the shunt to open from the additional
heat. The shunt is governed so the true supply temperat-
ure corresponds with the control system’s theoretical
calculated set point value. When the heating require-
ment drops sufficiently, so that the additional heat is no
longer required, the shunt closes completely. Factory-set
minimum run time for the boiler is 12 hours (can be ad-
justed in menu 5.3.2).
Prioritised additional heat refers to heating from an ex-
ternal, non-controlled heat source which, if available, is
prioritised to be used before the heat pump. An example
of prioritised additional heat would be a wood fired
boiler or back boiler.
Compatible products
■F1145
■F1155
■F1245
■F1255
■VVM 225
■VVM 310
■VVM 320
■VVM 325
■VVM 500
Pipe connections
The external circulation pump (GP10) is positioned ac-
cording to the outline diagram.
Shunt valve
The shunt valve (QN11) must be placed on the supply
line to the climate system after the heat pump according
to the outline diagram.
■Connect the supply line from the heat
pump to the external heat source via
the T-pipe to port B on the shunt
valve (closes on reduce signal).
■Connect the supply line to the climate
system from the shunt valve to the common port AB
(always open)
■Connect the supply line from the external additional
heat to the shunt valve to port A (opens on increase
signal).
Temperature sensor
■Install the boiler sensor (BT52) in a suitable location in
the external additional heat.
■External supply temperature sensor (BT25, connected
in the heat pump/indoor module) must be installed
on the supply line to the radiators, after the shunt valve
(QN11).
Install the temperature sensors using cable ties, together
with the heat conducting paste and aluminium tape.
Then insulate with the enclosed insulation tape.
NOTE
Sensor and communication cables must not be
placed near power cables.
7Chapter 4 | Shunt controlled additional heatAXC 40
4 Shunt controlled additional heat
