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Aquarea air / water heat pump – design handbook 07 / 2014
Heat pump system
Heat utilisation
Heating
2.3 Heat utilisation
2.3.1 Heating
4. Bivalent parallel operating mode
Besides the heat pump, a second heat generator is used using a further
energy source. Both heat generators are operated simultaneously
(e.g. heat pump + condensing boiler for outside temperatures < 0 °C).
In contrast to heat generators such as boilers that produce water supply
temperatures of over 80 °C, the maximum water supply temperature of
the Aquarea heat pump is limited at 55 °C or 65 °C for Aquarea HT. This
must be accounted for during the designing of heat emitter circuits.
Underfloor heating is ideal with a heat pump as the floor is a large emit-
ter area and therefore you can use a low temperature to heat the room.
Fan convectors have the advantage of good heat dissipation to the indoor
air and are easily controllable, with the advantage of using a lower tem-
perature than standard radiators to heat the room. At the same time they
can be used for either heating or cooling operation.
When radiators are used, they should be planned likewise with a low
design temperature of e.g. 45 °C in order to ensure a high efficiency of
the heat pump system. An additional electric heater of 3 to 9 kW caters
for sustained heating comfort even under very low outside temperatures,
due to the mono-energetic mode. A bivalent operation in combination
with an external heater is a possible alternative.
The Aquarea heat pump is provided with an outside temperature
dependent control of the supply water temperature and can activate
a heating circuit in connection with a room thermostat. The control
of further heating circuits can occur via an additional heating circuit
controller or an overriding system controller on site.
Note
When the heat pump is operated in connection with an additional
electric heater in mono-energetic mode, the additional electric heater
should cover a maximum of 15 % of the heat requirement.
If your system must comply with the UK Microgeneration Certification
Scheme’s MIS 3005 document, an additional electric heater should be
only designed to operate for space heating for the coldest 1 % of the year.
Note
To comply with UK subsidy requirments for sub-45 kW appliances,
the document “Heat Emitter Guide” should also be consulted:
www.microgenerationcertification.org
