Determination Of The Heating Surface Temperature; Operating Mode And Determination Of The Bivalence Point - Panasonic Aquarea WH-ADC0309J3E5 Planning And Installation Manual

Planning
CAUTION
Danger of illnesses due to growth of Legionella in water
Legionella can grow in domestic hot water tanks, and can cause infectious diseases in humans.
► Respect European and national requirements for avoiding Legionella multiplication
!
IMPORTANT
The domestic hot water demand has the highest influence on the degree of coverage of solar
systems for domestic hot water production. A proven ratio between tank volume and the surface
area of the solar collectors is between 50 to 80 litres per square metre of collector area.
Hot water circulation increases the heat demand for the domestic hot water production and can be
up to 100 % of the heat load for domestic hot water production if the connection distance is very
long. Hot water circulation pumps should therefore always be operated in a time- and temperature-
dependent manner.

5.1.3 Determination of the heating surface temperature

The temperature of the heating surfaces at design outside temperature should not be taken any
higher than 55 °C. Surface-embedded heating systems with a supply temperature of 35 °C and
radiators with a supply temperature of 45 °C are recommended. When replacing heat sources with
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burners in existing buildings for an Aquarea heat pump, reduce the supply temperature as much as
possible by using additional heat insulation and refurbishing measures. Conventional heat sources
with burners are operated with supply temperatures up to 75 °C. By adapting proper refurbishing
measures, the old radiators can often continue to be used at a lower temperature and thermal
output. For this purpose, check on the basis of conversion factors, whether the heating capacity of
the radiators suffices even at a lower supply temperature.
If it is not possible to reduce the supply temperature, the Aquarea HT series with supply
temperatures up to 65 °C can be used.

5.1.4 Operating mode and determination of the bivalence point

First, the desired operating mode of the heat pump must be defined (→
20). In order not to over-dimension the heat pump and to save on costs, a bivalent mode is
p.
preferred. In this case, another heat source is hooked up below a defined outside temperature and
the associated heating capacity of the heat pump. The additional heat source can be integrated
externally (e.g. a boiler or fireplace) or internally through the electric backup heater of the heat
pump. If the additional heat source uses electric power for heat production, the operating mode is
called mono-energetic.
The bivalent mode only supports the air-to-water heat pump while the outside temperatures are
very low. As this is the case only for a few days a year, the heat generated by the electric backup
heater only amounts to a few percent of the totally generated amount of heat.
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(example in Germany: DVGW Worksheet W551). For domestic hot water tanks with more
than 400 litres volume as well as in buildings with more than two residential units, there
may be higher requirements than for one and two family houses.
Aquarea air-to-water heat pumps - Planning and installation manual - 02/2022
4.3.2 Operating mode,