9
Planning Notes
Heat Pumps, General Information
Planning and installation must be
carried out in compliance with the
relevant rules and regulations (SWKI,
SIA, AWP, VDI 4640, etc.).
Prior Clarifications / Approvals
It is recommended to clarify the
following items early on in the planning
phase:
With electric company:
- Connection permit
- Starting current
- High/low/special rates
- Blocked times
Heat sources:
Water extraction from public waters
and the positioning/repositioning of a
geothermal probe or tube collector
must be approved by the respectively
responsible local office or authority.
This is usually the Office of Energy
and Water Management or Environ-
mental Protection Agency (indicate
coordinate of house location).
Heat Pump Dimensioning
Compared with other heat generators,
the heat pump has a smaller applica-
tion scope. The heat output and the
required power and with that the utili-
zation ratio of the heat pump vary
depending on heat source and heat
utilization temperatures.
A basic principles applicable here
states that the smaller the difference
between heat utilization and heat
source temperature the more efficient
(better performance number) the
system can be operated. This is why
the planner/installer of the heat pump
must take boundary conditions into
account.
The system must be configured and
dimensioned in such a way that usage
limits are not exceeded.
Water Heating
In addition to heating rooms, a heat
pump can also be used to heat water.
This makes sense since the energy
savings are considerable compared
with electrical water heaters.
Depending on the refrigerant used,
different max. hot water temperatures
are reached (50°C - 60°C). These are
the result from the operating limits of the
refrigerant as well as the structure of
the cooling circuit of the heat pump.
Water is heated indirectly with the
following typical solutions:
- Coil storage tank
- Combination storage tank (heat
storage with integrated boiler) or
Spira storage
- Storage with external plate
exchanger (Magro system)
When selecting coil or external plate
storage tanks, it is especially important
to make sure the heat exchanger
surface is sufficient. This requires taking
water volume, temperature differences,
as well as heat pump capacity into
consideration. A combination with solar
collectors is quite possible. using a
suitable water heat, e.g. a combination
storage tank, it is possible to heat water
entirely with solar collectors, especially
during the summer.
Buffer Storage
Always make sure the entire output of
the heat pump is always accepted
regardless of the type of storage installa-
tion.
Integrating a technical storage or
heat storage tank is generally recom-
mended.
It ensures optimal operating
conditions such as the following:
• Output excesses of the heat pump
are absorbed
• Bridging EC off periods
• Enables several heating circuit
Connections
Buffer storage tank should be omitted
only in the following cases:
• If the heating water volume is
greater than 25 liters per kW
heating output or with a good
storage capability of the heat
emission system (floor heater
configured < 40 °C)
• No thermostatic valves
t = V * c * ∆t
Qh * 60
V = Tank volume in liters
Qh = Heat demand in watt
t = Bridging time in minutes
c = 4187 W/s
∆t = Temp. difference, heating circuit
Circulating Pumps
The evaporator and condenser flow
volume specified by the heat pump
(HP) must be adhered to consistently
to configure and dimension the
circulating pumps. Speed-controlled
circulating pumps may not used for
the thermal emission of the HP.
The heat source pumps (brine/
groundwater) must be suitable for use
with cold water. The viscosity of the
heat carrier medium must be consid
ered when configuring the system.
Overflow Valve
In case of heating systems with
variable or hot water flows that can be
shut off (e.g. thermostatic valves) and
serially installed storage tank, an over-
flow valve must be integrated
upstream of the circulating pump.
This ensures the min. flow of heated
water and prevents frequent switching,
which may lead to malfunctions.
The overflow valve must be set and
dimensioned properly.
The size of the buffer storage depends
on the max. heat output and the max.
permissible activation frequency of the
heat pump.
A general reference value is approx.
30 lto 50 liters per kW heat output.
For an increased buffering also more.
For the coverage time (without
considering the internal storage
capacity of the heating system) of the
heat demand using a buffer storage,
e.g. in case of an EC off period or
outage, can be calculated as follows:
