STIEBEL ELTRON Heat pumps, WPW 22 M, WPW 7, WPW 10, WPW 13 Technical Manual

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Hot wat e r rene w a b les a i r c ondit ion i n g room He at i n g

»ISSUE 2009

TEchnIcal GUIdE

hEaT pUmpS

Design/engineeRing anD installation

Issue March 2009

Reprinting or duplication, even partially, only with our express permission.

STIEBEL ELTRON, D-37601 Holzminden

Legal note:

In spite of the care taken in the production of this brochure, no guarantee can be given regarding the accuracy of its contents.
Information concerning equipment levels and specification are subject to modification. The equipment features described in this
brochure are not stated as agreed properties of our products. Due to our policy of ongoing improvement, some features may have
subsequently been changed or even removed. Our advisors will be happy to consult with you regarding the currently applicable
equipment features. Pictorial illustrations in this brochure only represent application examples. The illustrations also contain
installation components, accessories and special equipment, which is not part of the standard delivery.

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Heat pumps protect our energy reserves 6
How does a heat pump work? 7
Energy sources for heat pumps 8
Heat pump operating modes 10
The right heat pump for every application 11
This is could be your solution 12
Energy Savings Order EnEV [Germany] 13
Cost calculation to VDI 2067 21
Terminology and descriptions 23
Summary of formulae 24
System design 25
Regulations and guidelines/directives 26
Heating load calculation 28
Flow temperatures of heating surfaces 29
Sizing of heat pumps 30
Power supply and tariffs 32
Integration into the heating system 33
Heat pumps with buffer cylinder 34
Heat pumps without buffer cylinder 35
DHW heating with heat pumps 36
Freshwater station 38
Modernisation of older buildings 39
Cooling with the heat pump system 40
Cooling load calculation 41
Heat sinks for cooling operation 43
Cooling capacity 44
Distribution system for cooling operation 45
Cooling capacity, underfloor heating system 46
Cooling capacity, fan convectors 47
Cooling capacity, cassettes 48
Passive cooling with the WPC cool heat pump 49
Passive cooling with the WPF...E heat pump 50
Passive cooling with the WPF heat pump 51
Active cooling with the WPC heat pump 52
Active cooling with the WPF heat pump 53
Active cooling with the WPL heat pump 54
Air | water heat pump; external installation 55
Condensate connection 58
Air | water heat pump - internal installation 59
Air routing 60
Condensate connection 61
Checklist 62
Air | water heat pumps 63
Air | water heat pump WPL 5 N 64
Connection WPL 5 N 66
Connection WPL 5 N 67
Air | water heat pump WPL 10 68
Output details WPL 10 70
External installation WPL 10 71
Internal installation WPL 10 72
Heating system connection WPL 10. 76
Power supply WPL 10. 77
Air | water heat pumps WPL 13/18/23 E/cool 78
Output details WPL 13/18/23 E/cool. 80
External installation WPL 13/18/23 E/cool 82
Internal installation WPL 13/18/23 E/cool 83
Air routing of WPL 13/18/23 E for internal installations 87
Heating system connection WPL 13/18/23 E/cool 88
Power supply WPL 13/18/23 E/cool 89
Air | water heat pump WPL 33 90

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Output details WPL 33 92
External installation WPL 33 93
Internal installation WPL 33 94
Heating system connection WPL 33. 95
Power supply WPL 33. 96
Air | water heat pump WPL 14 HT 98
Output details WPL 14 HT 100
Internal installation WPL 14 HT 102
Heating system connection WPL 14 HT 104
Power supply WPL 14 HT 105
Air | water heat pump WPL 20/26 AZ 106
Installation WPL 20/26 AZ 108
Connection WPL 20/26 AZ 109
Notes 110
Geothermal collector 111
Sizing tables, geothermal collectors 115
Geothermal probe 117
Sizing tables, geothermal probes 121
Heat transfer medium 122
Checklist 123
Brine | water heat pumps 125
Brine | water heat pumps WPC 5/7/10/13 (cool) 126
Output details WPC 5/7/10/13 128
Installation WPC 5/7/10/13 130
Heating system connection WPC 5/7/10/13 131
Brine | water heat pump WPF 5/7/10/13/16 E/cool 132
Output details WPF 5/7/10/13/16 E/cool 134
Installation WPF 5/7/10/13/16 E/cool 136
Heating system connection WPF 5/7/10/13/16 E/cool 137
Brine | water heat pumps WPF 5/7/10/13/16 138
Output details WPF 5/7/10/13/16 140
Installation WPF 5/7/10/13/16 142
Heating system connection WPF 5/7/10/13/16 143
Brine | water heat pumps WPF 10/13/16 M 144
Output details WPF 10/13/16 M 146
Installation WPF 10/13/16 M 148
Heating system connection WPF 10/13/16 M 149
Power supply WPF 10/13/16 M (SET) 151
Brine | water heat pumps WPF 20/27/40/52/66 152
Output details WPF 20/27/40/52/66 154
Internal installation WPF 20/27/40/52/66 156
External installation WPF 20/27/40/52/66 157
Heating system connection WPF 20/27/40/52/66 158
Power supply WPF 20/27/40/52/66 160
Well installation 161
Assessing the water quality 164
Well installation with brine | water heat pumps 165
Checklist 166
Water | water heat pumps 167
Water | water heat pumps WPW 7/10/13/18 168
Output details WPW 7/10/13/18 170
Installation WPW 7/10/13/18 172
Heating system connection WPW 7/10/13/18 173
Water | water heat pumps WPW 13/18/22 M 174
Output details WPW 13/18/22 M 176
Installation WPW 10/13/16 M 178
Heating system connection WPW 10/13/16 M 179
Power supply WPW 13/18/22 M (SET) 181
Accessories for heating heat pumps 183
Heat pump manager 184

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Mixer, swimming pool module 186
Remote control unit and sensors 188
Communication 189
Heat meter 191
Underfloor heating control system 192
Low loss header 193
Buffer cylinder SBP 100 Komfort 194
Compact installation for SBP 100 Komfort 195
Buffer cylinder SBP 200 E, SBP 200 E cool 196
Buffer cylinder SBP 400 E, SBP 400 E cool 197
Buffer cylinder SBP 700 E, SBP 700 E SOL 198
Compact installations for SBP 200/400/700 199
Buffer cylinder SBP 1000 E, SBP 1000 E SOL, SBP 1000 E cool 200
Buffer cylinder SBP 1500 E, SBP 1500 E SOL, SBP 1500 E cool 201
Thermal insulation for SBP 1000/1500 E cool 202
Circulation pumps 203
Pump assemblies 206
Pressure hoses 207
Threaded immersion heater BGC 209
Brine kit 210
Brine circuit pumps 212
Brine manifold, heat transfer medium 213
Expansion vessel, antifreeze tester, brine pressure switch 214
Convector heater module LWM 250 215
Cooling module 217
Air hoses and connections 218
Duct silencer, silencer, condensate pump 219
DHW cylinder SBB 301/302 WP 220
DHW cylinder SBB 401/501 WP SOL 221
DHW cylinder SBB 751/1001 222
DHW cylinder SBB 751/1001 SOL 223
DHW cylinder SBS 800/1000/1500 224
DHW cylinder SBS 800/1000/1500 SOL 225
Thermal insulation; DHW cylinder 226
Freshwater station 227
Plate-type heat exchanger 228
Convector replacement 229
Standard circuits 230
DHW heat pumps 247
Hot water out of "thin air" 248
WWK 300 249
Special accessories WWK 300..SOL 252
Installation WWK 300..SOL 253
Installation WWK 300..SOL 254
WWP 300 255
Installation WWP 300 258
Installation WWP 300 259

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HEat pUmpS protEct oUr EnErgy rESErvES

Advanced heat pumps save energy
and reduce emissions

Heat is a fundamental human
need. Many people today not only
consider economy when they think
of heating, but also consider the
environmental impact. That both can
be combined effectively is shown by
the development of the heat pump.
This utilises the energy held in the
air, water and under ground. This it
converts into useful heating energy.
The positive aspect of this type of
"harvesting" available heat is that you
can draw deep without damaging the
environment.
The heat pump is regulated subject
to the outside temperature. This
control unit safeguards the selected
set temperature. As a result, the heat
pump achieves an excellent quotient
of "harvested" heat to expended
primary energy. To put it into figures:
Each kWh electrical energy spent
generates up to 5 kWh available
energy, subject to the respective heat
source, i.e. from the air, from the
groundwater and the ground of your
own property. The compact design
requires little space and ensures
an easy installation. The lowest
installation effort secures the air
|water heat pump the top prize for
easy installation. With internal and
external versions, it can yield heat
for domestic heating from outside
air down to a temperature of –20°C.
Future purchasing decisions will
increasingly favour products with
sound environmental credentials. Heat
pumps from STIEBEL ELTRON already
enable the basic premise of heating
an apartment or entire houses with
environmentally responsible and cost­effective methods to be achieved.

Future-proof solutions from
STIEBEL ELTRON

Over the last 30 years, STIEBEL ELTRON
has invested a lot of time and energy
in the development of its heat pumps.
This has created a reliable, standard
technology that delivers every
conceivable convenience. Our range
of heat pumps satisfies the most
divers requirements in the heating
technology sector - conveniently and
economically. Our heat pumps are
part of the extensive range of systems
by STIEBEL ELTRON, the predominant
aim of which is to translate our high
quality standards into future-proof,
alternative technologies. As one of
the most important manufacturers of
products in the heating, ventilation,
air conditioning and domestic hot
water equipment sector, we feel a
great sense of responsibility for our
environment. For that reason will we
continue to adhere to our commitment
to this sector.

Exclusive technology -
hot water included.

Hot water and cosy ambience are
our business. You can safeguard
your domestic hot water supply with
DHW cylinders from STIEBEL ELTRON.
Or have you ever considered
separating your hot water heating
from your existing heating system?
For larger DHW demand you
could, for example in commercial
operations, use STIEBEL ELTRON
heat pumps exclusively for heating
your domestic hot water, irrespective
of whether you want to provide a
centralised or decentralised supply.
At STIEBEL ELTRON, a complete range
of energy-efficient electric appliances
awaits you.

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Heat pump principle

The most important contribution to
the heat pump function is made by
the refrigerant (in the following also
referred to as "process medium"). This
evaporates at the lowest temperatures.
If you route outside air or water to a
heat exchanger (evaporator), in which
the process medium circulates, then
that refrigerant extracts the required
evaporation heat from the heat source
and changes from a liquid into a
gaseous state. During this process,
the heat source cools down by a few
degrees. A compressor draws the
process medium in and compresses
it. The increase in pressure also raises
the temperature; in other words,
the process medium is "pumped"
to a higher temperature level. That
requires electrical energy. As the
compressor is of the suction gas­cooled design, the energy (motor
heat) is not lost, but reaches the
downstream condenser together with
the compressed process medium.
Here, the process medium transfers
its absorbed energy to the circulating
system of the hot water heating
system by being returned into the
liquid state again. An expansion valve
reduces the still prevalent pressure
and the circular process starts again.

Heat pump coefficient of performance

The coefficient of performance

ε

HP

is equal to the quotient of heating
output Q

HP

and electrical power

consumption P

HP

in accordance with

the following equation

It provides a factor, by which yield
exceeds expenditure. The coefficient
of performance is subject to the
temperature of the heat source
and that of the heat consumer. The
higher the heat source temperature
and the lower the heat consumer
temperature, the higher the coefficient
of performance. It relates, as current
value, always to a specific operating
condition.

How doES a HEat pUmp work?

ε

HP

=

Q

HP

P

HP

Main layout of a heat pump refrigeration circuit

Compressor

Inlet line

Gaseous process medium
low pressure

Pressure line

Gaseous process medium

high pressure

Liquid line

Liquid process medium

high pressure

Injection line

Liquid process medium
low pressure

Expansion valve

Flow

Return

Evaporator

Heating
energy

Environmental
energy

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Heat source air

Air heated by the sun is universally
available. Even at temperatures as low
as –20 °C, heat pumps yield sufficient
heat from the outside air. However, air
as heat source has the disadvantage
that it is coldest when the highest
heat demand arises. Although it is
still possible to extract heat from air
as cold as –20 °C, the heat pump
coefficient of performance is, however,
regressive in line with the outside
temperature. It is for that reason,
that in most cases a combination
with a second heat source is required
that boosts the heating system,
particularly during the colder season.
One particular benefit is the ease of
installation of air|water heat pumps,
as no extensive ground work or well
drilling is required.

Heat source water

Groundwater is a good store of solar
energy. Even on the coldest days in
winter, temperatures of +7 °C to +12
°C are achieved - and this is where
its advantage lies. The near constant
temperature level of this heat source
enables the heat pump to achieve a
favourable coefficient of performance
all the year round. Regrettably,
groundwater of adequate quality is
not universally available. Where it is
available, its utilisation is certainly
worthwhile. The use of groundwater
requires the approval of your local
water board [check local regulations].
Utilising this heat source requires the
drilling of a delivery and return well.
Your local water board will advise you
about the possibility of utilising these
waterways.

EnErgy SoUrcES for HEat pUmpS

Main layout of an air source heat pump system

Main layout a groundwater heat pump system

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EnErgy SoUrcES for HEat pUmpS

Heat source ground with geothermal
collector

At a depth of 1.2 to 1.5 m, the ground
remains warm enough, even on
colder days, to enable an economical
heat pump operation. However, this
requires the availability of a property
large enough to accommodate a
pipe system for collecting the heat
from the ground. In dry, sandy soil,
the collector can extract between 10
and 15 W/m² and up to 40 W/m² in
ground that carries groundwater.
An environmentally-friendly brine
mixture that cannot freeze and which
transports the yielded energy to
the heat pump evaporator courses
through the pipes. As a rule of thumb,
you would need approximately
two to three times as much ground
area as area to be heated. If your
property is large enough, you have an
inexhaustible reserve of energy and
ideal conditions for a STIEBEL ELTRON
brine |water heat pump.

Heat source ground with geothermal
probe

Geothermal probes that are set up
to 100 metres deep into the ground
by specialist drilling contractors,
require less space. Geothermal probes
comprise a probe foot and endless,
vertical probe pipes made from
plastic. As with geothermal collectors,
a brine mixture that extracts heat from
the ground circulates through the
plastic pipework. The extraction rate is
subject to the ground characteristics,
and generally lies between 30 and
100 W per metre geothermal probe.
Subject to heat pump and ground
conditions, several geothermal probes
can be linked up in a single system.
These systems must be notified to and
possibly approved by your local water
board.

Main layout geothermal probe heat source system

Main layout geothermal collector heat pump system

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Operating modes

For the different types of heat pump
operation, the heating technology
world uses the following terminology:

Mono-mode

The heat pump is the sole provider
of heating in the building. This
operating mode is suitable for all
low temperature heating systems up
to +60 °C flow temperature.

Mono-energetic

The heating system uses no second
form of energy. The air | water heat
pump operates down to an outside air
temperature of –20 °C. Upon demand,
an electric booster heater is started at
very low outside air temperatures.

HEat pUmp opEratIng modES

Dual-mode - alternative

Down to a fixed outside temperature
(e.g. 0 °C), the heat pump delivers
the entire heating energy. When the
temperature falls below that value,
the heat pump switches itself OFF
and the second heat source takes over
the heating operation. This operating
mode is suitable for all heating
systems up to 90 °C.

Dual-mode - parallel

Down to a certain outside
temperature, the heat pump alone
delivers the required heating energy.
A second heat source starts at low
temperatures. However, contrary
to the dual-mode alternative
operation, the heat pump proportion
of the annual output is higher.
This operating mode is suitable
for underfloor heating systems
and radiators up to +60°C flow
temperature.

Dual-mode - partially parallel

Down to a certain outside
temperature, the heat pump alone
delivers the required heating energy.
The second heat source starts, if the
temperature falls below that value. The
heat pump is stopped if the heat pump
flow temperature is inadequate. The
second heat source supplies the entire
heating output. This operating mode is
suitable for all heating systems above
60 °C flow temperature.

Illustration of the possible operating modes of a heat pump system

mono-mode dual-mode -

alternative

dual-mode partially
parallel

dual-mode - parallel,
mono-energetic

Heat distribution system tv < 60 °C Heat distribution system tv > 60 °C

HP = Heat pump
QN = Heating load
TU = Changeover point

BV = Dual-mode point
ZH = Booster heater
TE = Booster heater start

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tHE rIgHt HEat pUmp for EvEry applIcatIon

 For the use of a water | water heat

pump, groundwater of sufficient
volume and quality must be
available at an economical depth.
You have ideal conditions for a
mono-mode operation, if this heat
source is available to you.

 The utilisation of a brine | water

heat pump requires the availability
of property without buildings that
can be used for a geothermal
collector. The property should
be at least two to three times
the area to be heated. These
systems can be operated in mono­mode in conjunction with a low
temperature heating system.

We help before you start

Take an overview first; our table will
assist you in that. A good analysis,
from the building and heating
technology point of view is crucial.
In new build, generally all kinds of
heat sources can be utilised, i.e. air,
groundwater or ground. You judge
which is the optimum one for you
using the following criteria.

 Using an air | water heat pump is

always possible, as the heat source
air is available anywhere. It is
suitable for dual-mode and mono­energetic operation.

 Larger systems can be realised by

connecting several heat pumps
together. The electric and hydraulic
connection of brine | water or
water | water heat pumps is easily
achieved with the appropriate
accessories.

Central heating

Specific heat demand 50
W/m² living space, low
temperature heating
system, max. flow
temperature +60 °C
(desirable is +35 °C)

Heat source

Groundwater
exploration via a well

system

Operating mode

mono-mode

Heat pump size subject to
m

2

heated living space

up to 120 m2WPW 7

up to 180 m²

WPW 10

up to 220 m²

WPW 13

up to 300 m²

WPW 18

up to 420 m²

WPW 22 M

up to 440 m²

WPW 26 SET

up to 520 m²

WPW 31 SET

up to 600 m²

WPW 36 SET

up to 720 m²

WPW 40 SET

up to 840 m²

WPW 44 SET

Operating mode

mono-mode

Heat pump size subject to
m

2

heated living space

up to 100 m2WPF/C 5

up to 140 m²

WPF/C 7

up to 180 m²

WPF/C 10

up to 240 m²

WPF/C 13

up to 300 m²

WPF 16

up to 360 m²

WPF 20 SET

up to 420 m²

WPF 23 SET

up to 480 m²

WPF 26 SET

up to 540 m²

WPF 29 SET

up to 600 m²

WPF 32 SET

up to 380 m²

WPF 20

up to 500 m²

WPF 27

up to 800 m²

WPF 40

up t 950 m²

WPF 52

up to 1100 m²

WPF 66

Operating mode

mono-energetic dual­mode point -5 °C outside
temperature

Heat pump size subject to
m

2

heated living space

up to 160 m2WPF/C 5
up to 200 m²

WPF/C 7

up to 280 m²

WPF/C 10

up to 340 m²

WPF/C 13

up to 420 m²

WPF 16

up to 520 m²

WPF 20 SET

up to 640 m²

WPF 23 SET

up to 700 m²

WPF 26 SET

up to 760 m²

WPF 29 SET

up to 840 m²

WPF 32 SET

up to 600 m²

WPF 20

up to 760 m²

WPF 27

up to 1200 m²

WPF 40

up to 1560 m²

WPF 52

up to 1880 m²

WPF 66

Operating mode

mono-energetic dual­mode point -5 °C outside
temperature

Heat pump size subject to
m

2

heated living space

up to 80 m² WPL 5 N
up to 120 m2WPL 10

up to 180 m²

WPL 13

up to 220 m²

WPL 18

up to 300 m²

WPL 23

up to 360 m²

WPL 33

Operating mode

mono-mode

Heat pump size subject to
m

2

heated living space

up to 200 m2WPL 14 HT

Heat source

Ground
geothermal collectors -

geothermal probe

Heat source

Air
universally available

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tHIS coUld bE yoUr SolUtIon

General information

Naturally, all compact heat pumps
from STIEBEL ELTRON can be installed
in all new and existing heating
systems. In many cases, a mono­mode operation is feasible, so that
no additional, conventional heating
system and associated additional
investment is required, even on
those few exceptionally cold days
of the year. When deciding on the
potential Part of this is of a heat
pump, the heat distribution system
too, and in particular the required
flow temperature, must be given due
consideration. Generally speaking,
low temperature and conventional
heating systems (radiators) can
be supplied by heat pumps. When
developing new systems, allow for
low temperature heating systems with
max. flow temperatures of +55°C.
Existing systems with conventional
heat distribution too can generally be
combined with heat pumps without
requiring major changes. Generally,
such heating systems are designed for
maximum flow temperature of 90 °C.
However, most are oversized making
substantially lower flow temperatures
sufficient on account of subsequently
installed thermal insulation of the
building.

Heat pumps not only provide
heating but also produce hot water
economically.
All STIEBEL ELTRON heating heat
pumps also generate domestic hot
water, e.g. with special accessories,
such as the compact installation
and DHW cylinders. The heat pump
manager provides the automatic
changeover between central heating
and DHW heating operation.

Matching solutions for every
application

For many years, STIEBEL ELTRON
has been producing heat pumps
for all applications. Part of this is
an extensive installation accessory
range, e.g. buffer cylinders, pressure
hoses and control equipment. These
enable an easy and consequently
cost-effective installation. In the
following, two examples of heat pump
installations are shown. Naturally,
alternative installation options are
also feasible.

Design example 1
Water|water heat pump
Operating mode: mono-mode

Mono-mode operation is only feasible
in conjunction with a low temperature
heating system (maximum flow
temperature +60 °C). At a specific
heat demand of 50 Watt/m², suitable
heat pumps offer themselves from the
heating system sizes listed in the table
on page 11.

Important information:

 A water analysis is part of the first

design phase.

 Two results from that analysis are

relevant to the engineering of the
system: free chlorine and chloride.

Iron and manganese content.

 Construct the heat pump system in

accordance with the regulations of
your local water board.

 The system can be installed

subject to the availability of
groundwater of adequate quantity
and quality.

Design example 2
Air|water heat pump without
additional boiler

The mono-energetic air | water heat
pump WPL from STIEBEL ELTRON. As
the description suggest, the heating
system requires no second form of
energy. This heat pump operates with
outside air temperatures down to –20
°C where the outside air provides the
heat source. Between –5 °C and –20
°C, the heating water is additionally
heated by a small electric booster
heater integrated into the heat pump.
STIEBEL ELTRON offers the air | water
heat pump WPL in different versions,
from 10 to 30 kW heating output. This
produces adequate heating for small
to large houses with a living space of
up to approx. 500 m².

Installation information:

 The unrestricted air flow through

the inlet and discharge apertures
must be assured at all times.

 A thermal "short circuit" between

the inlet and discharge apertures
must be prevented. The direction
of the air flow should be in line
with the main wind direction,
where possible. An installation
in a corner is advisable when
selecting an internal installation.
Design the air ducts as directly and
as short as possible.

 Maintain as small a clearance as

possible between heat pump and
house to keep pipe runs short.
Select the installation location so
that no noise pollution is caused,
even though these appliances are
extremely quiet.

 The heat pump by necessity

creates condensate that must be
drained off in a suitable manner.
For internal installations via a
drain, possibly with a condensate
pump.

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EnErgy SavIngS ordEr EnEv [gErmany]

Energy Savings Order

The EU Energy Performance of
Buildings Directive obliged Member
States to translate measures regarding
energy and CO

2

reductions by
2006 into their national laws. The
EnEV 2002/2004 already laid down
requirements for new buildings and
introduced the energy performance
certificate. Adhering to the required
limits meets the energy-technical
requirements for new residential
properties to obtain planning
permission [in Germany]. The
EnEV 2007 introduces the energy
performance certificate for existing
residential buildings as well as for
non-residential buildings. The energy
performance certificate details the
energy-technical quality of a building
and retains its validity for ten years.

EnEV for residential properties
Calculation of the primary energy
demand Q

P

Energy requirements made of
residential buildings and the system
technology employed are considered in
unison. This global approach enables
an overall statement appertaining
the building envelope and the
system technology to be established
and is based on the primary energy
which allows losses during energy
generation and transmission to be
taken into consideration. To calculate
the annual primary energy demand Q

P

and the system expenditure of energy
value e

P

, the annual heat demand

Q

h

of the building and the available

surface area A

N

must be known. The
system expenditure of energy value
e

P

, which has no dimension and
which relates to the primary energy
for heating, ventilation and DHW,
enables the assessment of the entire
system technology. Furthermore,
this parameter forms the basis for
calculating the annual primary energy
demand Q

P

of a building, and describes
the system efficiency. The lower the
system expenditure of energy value,
the greater the scope for the building
envelope, i.e. the physical building
characteristics. This highlights the
importance of the cooperation between
all engineers and all those involved in
the process.

Calculation of the primary energy demand

Effects of standards

Optional compensations between the building and the system

Total energy demand

Energy efficient version

Energy inefficient version

Ratio external surface area / volume (1/m)

Q

p,max

= permissible annual energy demand (kWh/

(m² p.a.)) relative to the area of available space

Energy savings

calculation

System engineering

calculations

Calculating the structural

physical parameters

Max. annual energy demand

Annual heat demand

System expenditure of energy value

Primary energy

demand

Heating energy

demand

DHW

demand

System expenditure

of energy value

* (QtW fixed value 12.5 kWh/m² p.a. acc. to EnEV)

QP = ( Qh + QtW* ) x e

P

( )

= + x

Building

System

14 WWW.STIEBEL-ELTRON.COM

EnErgy SavIngS ordEr EnEv [gErmany]

Outline DIN V 18599
Part 1 General statement procedure, terminology,

zoning and assessing fuel types
Part 2 Demand for useable energy for heating and cooling building zones
Part 3 Demand of useable energy for air treatment with energy
Part 4 Useable energy and net energy demand for lighting
Part 5 Net energy demand of heating systems
Part 6 Net energy demand of domestic ventilation systems

and air heating systems for residential buildings
Part 7 Net energy demand for air handling and air conditioning systems

for non-residential buildings
Part 8 Useable energy and net energy demand for DHW heating systems
Part 9 Net and primary energy demand of CHP systems
Part 10 Utilisation framework conditions, climate data
Supplement 1

Examples

System description - reference system technology
Central Low temperature boilers
heating Pressure-jet boilers

Natural gas

Installation outside the thermal envelope

System temperature 55/45 °C

Hydraulically balanced

Twin-pipe heating system

Distribution lines - unheated area

Riser and connection lines, internal

Dp constant

Pump sized in accordance with demand
WWB Common heat generation with the heating system
(central) Indirectly heated cylinder

Installation outside the thermal envelope

with DHW circulation

Dp constant

Pump sized in accordance with demand

Compensation options

The better the equipment performs,
the lower the requirement for thermal
insulation of the building envelope.
The EnEV opens up interesting
compensation options. The optimum
use of primary energy is ensured
by systems such as heat pumps or
domestic ventilation systems with heat
recovery.

System technology

It is generally recommended to
calculate the heat source expenditure
of energy value in accordance
with the detailed procedure in DIN
4701-10 applying manufacturer's
details. Subject to heat source,
performance factors are applied at
different operating conditions that
can sometimes vary significantly from
standard values. This also applies to
the expenditure as a result of losses
and auxiliary energy, for example
caused by components such as
cylinders and auxiliary drives. STIEBEL
ELTRON offers you a calculation
service or the calculation basics and
software free of charge on CD ROM.

EnEV for non-residential buildings

As part of the EnEV 2007 update,
applicable from the 1st October
2007, the EU Energy Performance of
Buildings Directive" for the statement
of non-residential buildings was
adopted in the form of the extensive
standard DIN V 18599 that determines
the calculations principles.

DIN V 18599 - Energy assessment of
buildings

Contrary to the calculation for
residential buildings to DIN 4108
part 6 and DIN 4701 part 10, the
DIN V 18599 provides a statement
not only for the energy demand for
heating, DHW heating and domestic
ventilation, but also for cooling and
lighting. It comprises 10 parts that
are linked through cross-references.
The essential difference when
considering non-residential buildings
is the assessment of the respective
utilisation profile. The primary energy
demands are no longer simply
dependent on the area and volume
covered by the building envelope,
but additionally relate to different
room temperatures, lighting, air
changes, times of utilisation, density

of occupation and the internal heating
loads. A further update of the EnEV
2007 (scheduled for 1 January 2009)
envisages replacement of the currently
applicable method of calculation for
residential buildings through that
specified in the DIN V 18599.

The reference building procedure

To determine the permissible annual
primary energy demand of a non­residential building, a reference
building is determined that in
geometry, net floor area, orientation
and utilisation profile matches the
building to be assessed perfectly.
The energy quality of the building
envelope of the reference building
is specified in the EnEV via default
transmission heat transfer coefficient
HT ‘. System technology is also
specified for the reference building

covering heating, DHW heating, air
conditioning, air handling technology
and lighting. For this reference
building, in the first instance the
permissible annual primary energy
demand is determined. Then the
actual value is determined applying
the actual building characteristics
and system technology. To meet the
requirements of the EnEV the existing
annual primary energy demand must
be below the maximum permissible
value of the reference building. Heat
pumps are particularly suitable heat
sources for heating and DHW heating,
as they deliver a more favourable
primary energy statement than the
reference system technology. This
enables the EnEV requirements
to be met quite easily, given a
corresponding quality of the building
envelope.

15WWW.STIEBEL-ELTRON.COM

The DIN V 18599 provides a
segregation of the overall building
into various zones, since diverse
areas within the building are used for
various purposes and these require
different conditioning. A zone includes
those rooms within a building that
demand similar parameters on
account of their use (temperature,
ventilation, illumination, internal
loads, daylight provision, technical
equipment) with similar framework
conditions. Every zone has one of
33 programmed utilisation profiles
applied to it (e.g. office, hotel room,
kitchen, toilet, transit areas). The
energy demand for heating and
cooling must be defined separately
for each conditioned zone. Up to
a proportion of 3% of the overall
available floor area, living space may
be appropriately assigned to different
zones than those to which they should
be designated, as long as the internal
loads are not substantially different.
To simplify the calculation process it is
permissible to determine the annual
primary energy demand in accordance
with a single zone model for the
following types of building: Schools,
kindergartens, office buildings, hotels
(without internal swimming pool),
pubs and commercial premises.
However, different framework
conditions must still be applied.
Main areas of use and passages must
account for at least one third of the
total area; the building must only be
equipped with a central system used
to provide DHW and central heating
and must not be cooled. Illumination
must largely correspond to the
reference lighting technology.
The calculations according to DIN V
18599 are extensive and can, because
of the interactions that occur can
only be resolved by iterative means,
only be done with computer-aided
support. STIEBEL ELTRON offers
software solutions for this calculation.
This enables complex calculations
to be carried out, and even includes
manufacturer's data. In this
connection, our specialist department
offers support in all areas concerning
the Energy Savings Order 2007.

EnErgy SavIngS ordEr EnEv [gErmany]

Primary energy demand for non-residential buildings

Primary energy

demand = heating + cooling + steam + DHW + light + auxiliary energy

QP = Q

P.h

+ Q

P.c +

Q

P.m

+ Q

P.w +

Q

P.l +

Q

P.aux

16 WWW.STIEBEL-ELTRON.COM

ExpEndItUrE of EnErgy valUES of HEat pUmpS

EnEV – calculation to DIN V 4701-10

The EnEV provides three possible
certification processes:

 Diagram process
 Tabular process
 Detailed process

For the detailed certification process,
verification can be provided using
standard values or manufacturer's
details. Generally, the certification
process with standard values is
sufficient for heat pumps, since their
high efficiency level allows results to
fall below the required expenditure of
energy value.

Where better expenditure of energy
values are demanded by more
stringent subsidy stipulations, e.g.
KFW 40 or KFW 60, these may possibly
be achieved with verification based on
the manufacturer's details.

IT programs or the calculation process
of the EnEV should be applied where
manufacturer's details are to be used.
For calculating the ep figure, STIEBEL
ELTRON offers the software "Energy
efficiency in residential buildings".
Where the certification utilises the
tabular process, draw the expenditure
of energy value eg from the
DIN V 4701-10 according to "Table
C3-4c expenditure of energy value eg
and drive auxiliary energy qg, HE for
heat pumps with electric drive".

Electrically operated heating heat pumps

The heat generation expenditure of energy value is calculated using the annual
performance factor in accordance with the following equation:

e

H,g

= 1 : β

HP

e

H,g

= Expenditure of energy value for the heat pump

β

HP

= Seasonal performance factor of the heat pump, calculated subject to

type of heat pump

Brine|water heat pumps

The seasonal performance factor of brine | water heat pumps is calculated in
accordance with the following equation:

β

HP

= εN x Fϑ x F

∆ϑ

βHP = Annual performance factor of heat pump

ε

N

= Coefficient of performance to EN 14511 at B0/W35

F

ϑ

= Correction factor to table 5.3.7

F

∆ϑ

= Correction factor to table 5.3.8

Water|water heat pumps

The annual performance factor of water|water heat pumps is calculated in
accordance with the following equation:

β

HP

= εN x Fϑ x F

∆ϑ

βHP = Annual performance factor of heat pump

ε

N

= Coefficient of performance to EN 14511 at W10/W35

F

ϑ

= Correction factor to table 5.3.7

F

∆ϑ

= Correction factor to table 5.3.8

Air|water heat pumps

The annual performance factor of air|water heat pumps is calculated in
accordance with the following equation:

βHP = (ε

N

(A-7/W35)

x Fϑ + ε

N

(A2/W35)

x F

ϑ2

+ ε

N

(A10/W35)

x F

ϑ10

) x F

∆ϑ

βHP = Annual performance factor of heat pump

ε

N

= Coefficient of performance to EN 14511 at A-7/W35

ε

N

= Coefficient of performance to EN 14511 at A2/W35

ε

N

= Coefficient of performance to EN 14511 at A10/W35

F

ϑ-7

= Correction factor to table 5.3.10

F

ϑ2

= Correction factor to table 5.3.10

F

ϑ10

= Correction factor to table 5.3.10

F

∆ϑ

= Correction factor to table 5.3.8

17WWW.STIEBEL-ELTRON.COM

ExpEndItUrE of EnErgy valUES of HEat pUmpS

Table 5.3.8 - Correction factors FDϑ for deviating temperature differentials at the condenser

Operation
DϑB
(K)

Temperature differential at the test bed DϑM (K) DIN EN 255

3 4 5 6 7 8 9 10 11 12 13 14 15
3 1.000 0.990 0.980 0.969 0.959 0.949 0.939 0.928 0.918 0.908 0.898 0.887 0.877
4 1.010 1.000 0.990 0.980 0.969 0.959 0.949 0.939 0.928 0.918 0.908 0.898 0.887
5 1.020 1.010 1.000 0.990 0.980 0.969 0.959 0.949 0.939 0.928 0.918 0.908 0.898
6 1.031 1.020 1.010 1.000 0.990 0.980 0.969 0.959 0.949 0.939 0.928 0.918 0.908
7 1.041 1.031 1.020 1.010 1.000 0.990 0.980 0.969 0.959 0.949 0.939 0.928 0.918
8 1.051 1.041 1.031 1.020 1.010 1.000 0.990 0.980 0.969 0.959 0.949 0.939 0.928
9 1.061 1.051 1.041 1.031 1.020 1.010 1.000 0.990 0.980 0.969 0.959 0.949 0.939

10 1.072 1.061 1.051 1.041 1.031 1.020 1.100 1.000 0.990 0.980 0.969 0.959 0.949

Table 5.3.7 - Correction factor Fϑ for brine | water heat pumps

Minimum brine temperature at the
evaporator inlet (°C)

Heating circuit design temperature

35°C / 28°C 55 °C / 45 °C
2 1.113 0.917
1 1.100 0.904
0 1.087 0.890
–1 1.074 0.877
–2 1.062 0.864
–3 1.051 0.852

Table 5.3.9 - Correction factor Fϑ for water | water heat pumps

Minimum water temperature at the
evaporator inlet (°C)

Heating circuit design temperature

35°C / 28°C 55 °C / 45 °C
12 1.106 0.892
11 1.087 0.873
10 1.068 0.853
9 1.049 0.834
8 1.030 0.815

Table 5.3.10 - Correction factor Fϑ for air | water heat pumps

Outside air inlet (°C) Heating circuit design temperature

35°C / 28°C 55 °C / 45 °C
–7 0.103 0.080
+2 0.903 0.745
+10 0.061 0.053

Table C3-4c - Expenditure of energy value eg and auxiliary drive energy qgHE for electric heat pumps

Electric heat pump Heating circuit temperature Expenditure of energy value Auxiliary energy

e

g qgHE (kWh/m² p.a.)

Water/Water 55 °C / 45 °C 0.23

3.2 x A

N

-0.1

35°C / 28°C 0.19

Ground/Water 55 °C / 45 °C 0.27

1.9 x A

N

-0.1

35°C / 28°C 0.23

Air/Water 55 °C / 45 °C 0.37

0

35°C / 28°C 0.30

18 WWW.STIEBEL-ELTRON.COM

ExamplE 1: brInE | watEr HEat pUmp

Diagram system expenditure of energy value e

p

System description

Brine | water heat pump WPF with 100
litre buffer cylinder and 300 litre DHW
cylinder

DHW heating

Centralised provision; no DHW
circulation; distribution outside the
thermal envelope; indirectly heated
cylinder; installation outside the
thermal envelope; heating heat pump
brine|water powered by electricity.

Ventilation

No mechanical ventilation.

Central heating

Integral heating surface (e.g.
underfloor heating system); individual
room regulation with two-point
controller, switching differential
Xp=2 K; heating system design 35/28
°C; centralised system; horizontal
distribution outside the thermal
envelope, lines running internally;
regulated pump; buffer cylinder
installed; installation outside the
thermal envelope; heating heat pump
brine | water powered by electricity.

Example:

Annual heat demand
60 kWh/m² p.a.
Heated living space 200 m²

Result:

System expenditure of energy value =

1.04

System layout

Diagram system expenditure of energy value e

p

Annual
heating
demand

Heated available area in A

N

in m²

kWh/m² p.a. 100 200 300 400 500
40 1.42 1.17 1.08 1.04 1.01
50 1.31 1.09 1.02 0.98 0.96
60 1.22 1.04 0.98 0.95 0.92
70 1.16 1.00 0.94 0.93 0.90
80 1.11 0.96 0.91 0.89 0.87
90 1.07 0.94 0.89 0.87 0.86

Underfloor heating
system

Ground

Heated available area in AN in m²

System expenditure of energy value e

p

19WWW.STIEBEL-ELTRON.COM

ExamplE 2: aIr | watEr HEat pUmp

Diagram system expenditure of energy value e

p

System description

Air | water heat pump WPL with 200
litre buffer cylinder and 300 litre DHW
cylinder

DHW heating

Centralised provision; no DHW
circulation; distribution outside the
thermal envelope; indirectly heated
cylinder; installation outside the
thermal envelope; heating heat pump
brine | water powered by electricity;
peak load: Electric heater rod.

Ventilation

No mechanical ventilation.

Central heating

Integral heating surface (e.g.
underfloor heating system);
individual room regulation with
two-point controller, switching
differential Xp=2 K; heating system
design 35/28°C; centralised system;
horizontal distribution outside the
thermal envelope, lines running
internally; regulated pump; buffer
cylinder installed; installation outside
the thermal envelope; heating
heat pump air | water powered by
electricity. Electric heater rod.

Example:

Annual heat demand
60 kWh/m² p.a.
Heated living space 200 m²

Result:

System expenditure of energy value =

1.31

System layout

Diagram system expenditure of energy value e

p

Annual
heating
demand

Heated available area in A

N

in m²

kWh/m² p.a. 100 200 300 400 500
40 1.72 1.44 1.35 1.30 1.27
50 1.60 1.37 1.29 1.25 0.23
60 1.52 1.31 1.25 1.23 1.20
70 1.46 1.28 1.22 1.20 1.17
80 1.41 1.25 1.20 1.18 1.16
90 1.37 1.23 1.18 1.16 1.14

Underfloor heating
system

Air

Heated available area in AN in m²

System expenditure of energy value e

p

20 WWW.STIEBEL-ELTRON.COM

ExamplE 3: aIr | watEr HEat pUmp wItH Solar

Diagram system expenditure of energy value e

p

System description

Air | water heat pump WPL with 200
litre buffer cylinder and 300 litre DHW
cylinder

DHW heating

Centralised provision; no DHW
circulation; distribution outside the
thermal envelope; indirectly heated
dual-mode cylinder; installation
outside the thermal envelope; heating
heat pump air|water powered by
electricity; peak load: Electric heater
rod; with solar DHW heating.

Ventilation

No mechanical ventilation.

Central heating

Integral heating surface (e.g.
underfloor heating system);
individual room regulation with
two-point controller, switching
differential Xp=2 K; heating system
design 35/28°C; centralised system;
horizontal distribution outside the
thermal envelope, lines running
internally; regulated pump; buffer
cylinder installed; installation outside
the thermal envelope; heating
heat pump air | water powered by
electricity. Electric heater rod.

Example:

Annual heat demand
60 kWh/m² p.a.
Heated living space 200 m²

Result:

System expenditure of energy value =

1.00

System layout

Diagram system expenditure of energy value e

p

Annual
heating energy
demand

Heated available area in AN in m²

kWh/m² p.a. 100 200 300 400 500
40 1.17 1.04 1.00 0.97 0.95
50 1.13 1.02 0.98 0.96 0.94
60 1.10 1.00 0.97 0.95 0.94
70 1.08 0.99 0.97 0.95 0.94
80 1.06 0.98 0.96 0.94 0.93
90 1.05 0.98 0.96 0.94 0.93

Underfloor heating
system

Air

SOLAR

Heated available area in AN in m²

System expenditure of energy value e

p

21WWW.STIEBEL-ELTRON.COM

coSt calcUlatIon to vdI 2067

Cost calculation

Calculation in accordance with VDI
2067
To establish the total costs, carry out
the following calculations.

Hours run at full utilisation
VDI 2067 sheet 1 to 6

The hours at full utilisation are
required for calculating the annual
heat demand. The calculation is based
on the number of heating days during
the heating season, the average
building temperature, the average
outside temperature and the lowest
outside temperature.

Energy costs
VDI 2067 sheet 1 to 6

The energy costs result from the
energy consumption, the energy price
and the standing charges.

Operating costs
VDI 2067 sheet 1, table A2

Costs for maintenance, cleaning and
chimney sweeping.

Capital costs
VDI 2067 sheet 1, table A8

Interest and repayments of system
costs.

Maintenance
VDI 2067 sheet 1, table A2

The maintenance costs are calculated
as a percentage of the system costs.

Annuity calculation

The VDI 2067 uses the annuity
method. Part 6 is responsible for
calculations in connection with
heat pumps. The annuity factor
determines the uniform payments in
connection with an investment that
are due annually. The annuity method
provides a dynamic investment
calculation that converts the payments
received and made into equal annual
contributions (annuities). Primarily,
the annuity method is used in the
investment and finance sector. In
addition, it is used in cost calculation
regarding long-term decisions, such
as the selection of processes or
whether to manufacture in-house or
use outside suppliers.

Amortisation calculation

An investment is viable if, with the
given interest rate, an average annual
surplus can be achieved that is greater
or equal to zero. Using the cash
value and the cash value factor the
amortisation can be calculated.

Cash value

The value of one or several capital
sums due in future within the

reference time. The cash value or
present value is the current value of
future receipts or payments resulting
from discounting. The cash value (K0)
is determined when regular equal
payments are made:
a = periodically due retroactive
payments (interest).

Cash value factor

The discounting total factor (cash
value factor, interest cash value
factor, discounting total factor,
capitalisation factor) is one of the
financial-mathematical factors. It
applies interest to the segments g of
a series of payments, taking the rate
of interest and compound interest
into consideration, and adds the cash
values together.

22 WWW.STIEBEL-ELTRON.COM

Building heating load 7.0 kW
Hours run at full utilisation 1744
Specific heat demand 50 W/m² (underfloor heating system 35/28 °C)
Number of occupants 4
Energy consumption DHW 2.00 kWh/person/day
Amortisation 0.0963 annuity table (depreciation 15 years with 5% interest)

Air | water heat

pump

Brine | water

heat pump

Water | water

heat pump

Oil heating with

solar

Gas condensing

with solar

Wood heating

(pellets)

1. System details

Energy price heating Ct/kWh 13.00 13.00 13.00 7.50 7.00 4.80
Domestic energy price Ct/kWh 18.00 18.00 18.00 18.00 18.00 18.00
Standing charge p.a. Euro 60.00 60.00 60.00 170.00
Efficiency distribution 0.98 0.98 0.98 0.98 0.98 0.98
Heat source efficiency 1.00 1.00 1.00 0.90 0.99 0.90
DHW efficiency 1.00 1.00 1.00 0.80 0.80 0.80
Annual performance factor 3.60 4.40 4.70
Heating coverage 0.98 1.00 1.00
DHW coverage 0.95 1.00 1.00
Coverage solar heating/DHW 5% 5%

2. Investment

Heat source complete Euro 10.000.00 9.000.00 7.200.00 3.000.00 4.000.00 10.000.00
Heating system with DHW Euro 4.800.00 4.800.00 4.800.00 4.800.00 4.800.00 4.800.00
Installation costs Euro 2.400.00 2.400.00 2.400.00 2.400.00 2.400.00 2.400.00
Electrical installation Euro 1.050.00 1.050.00 1.050.00 350.00 350.00 350.00
Solar thermal system Euro 4.600.00 4.600.00
Oil tank/storage room and gas connection

Euro 2.000.00 1.300.00
Chimney Euro 2.000.00 2.000.00 2.000.00
Heat source system Euro 7.000.00 5.000.00
Total Euro 18.250.00 24.250.00 20.450.00 19.150.00 19.450.00 21.550.00

3. Capital costs

Capital costs Euro 1.758.00 2.336.00 1.970.00 1.845.00 1.874.00 2.076.00
Maintenance Euro 183.00 243.00 205.00 192.00 195.00 216.00
Total Euro 1.941.00 2.579.00 2.175.00 2.037.00 2.069.00 2.292.00

4. Operational costs

Maintenance Euro 150.00 150.00 250.00
Chimney sweep Euro 70.00 70.00 70.00
Total Euro 220.00 220.00 320.00

5. Costs of consumption

Central heating
Annual energy demand kWh 12.208 12.208 12.208 12.208 12.208 12.208
Energy consumption, heating kWh 3.391 2.831 2.650 13.149 11.954 13.841
Energy consumption, booster heater

kWh 249
Annual auxiliary energy demand kWh 200 400 400 200 200 200
DHW
Annual energy demand kWh 2.920 2.920 2.920 2.920 2.920 2.920
Energy consumption DHW kWh 771 664 621 1.825 1.825 3.650
Energy consumption, booster heater

kWh 146
SOLAR
Energy yield kWh 2.070 2.070
Energy consumption solar kWh 160 160

Results

Total energy consumption kWh/p.a. 4.757 3.895 3.672 15.334 14.139 17.691
Emissions CO

2

in total kg/p.a. 3.235 2.648 2.497 4.928 3.690 245
System energy costs Euro/p.a. 688.00 586.00 558.00 1.187.80 1.199.80 875.00
Total system costs Euro/p.a. 2.629.00 3.165.00 2.733.00 3.444.80 3.488.80 3.487.00
Primary energy factor 2.7 2.7 2.7 1.1 1.1 0.2
Primary energy demand kWh/p.a. 12.843 10.516 9.914 16.868 15.553 3.538

ExamplE: coSt calcUlatIon to vdI 2067

23WWW.STIEBEL-ELTRON.COM

Defrosting

Removal of a frost or ice coating
from the evaporator of the air|water
heat pump by supplying heat.
STIEBEL ELTRON heat pumps are
defrosted on demand through the
refrigerant circuit.

Process medium

Special term for refrigerant in heat
pump systems.

Dual-mode temperature

Outside temperature, which dictates
when a second heat source is started.

Enthalpy

According to its definition, it is
the sum of internal energy and
displacement work. The specific
enthalpy (kJ/kg) is used for all
calculations.

Expansion appliance

Component of the heat pump between
the condenser and the evaporator for
reducing the condensation pressure to
the evaporation pressure that equates
to the evaporation temperature. In
addition the expansion valve regulates
the injection volume of the process
medium, subject to the evaporator
load.

Fill level

The mass of the process medium
inside the heat pump.

Heating output

The heating output is the available
heat produced by the heat pump.

lg p, h-diagram

Graphic representation of the thermo­dynamic properties of process media
(enthalpy h, pressure p).

Annual performance factor

Quotient of heat and compressor drive
work over a definite period.

Annual expenditure of energy

The annual expenditure of energy
is the flip-side of the annual
performance factor.

Cooling capacity

Heat flow extracted by the heat pump
evaporator.

Refrigerant

Material with a low boiling point,
which is evaporated by heat
absorption and re-liquefied through
heat transfer in a circular process.

Circular process

Constantly repeating changes in
condition of a process medium by
adding and extracting energy in a
sealed system.

Coefficient of performance (COP)

Factor comprising the heating output
and the compressor drive rating.
The COP can only be quoted as an
actual value at a defined operating
condition. The heating load is always
greater than the compressor drive
rating; hence the COP is always > 1.
Equation symbol: ε

Rated consumption (compressor)

The maximum power consumption
of the heat pump during constant
operation under defined conditions.
It is decisive only for the power
connection to the supply network and
is given on the manufacturer's type
plate.

Standard efficiency

Quotient derived from the used and
related expended work or heat.

Evaporator

Heat exchanger of a heat pump, in
which the thermal flow is extracted
through condensation of the heat
source process medium.

Compressor

Machine for the mechanical
transportation and compression of
vapours and gases. Differentiation
according to the type of construction.

Condenser

Heat exchanger of a heat pump where
the thermal flow is transferred to a
heat transfer medium by condensing a
process medium.

Heat pump

Machine that absorbs a thermal flow
at a low temperature (cold side) and
transfers it through energy supplied
at a higher temperature (hot side).
When using the "cold side" we refer
to refrigerators, when using the "hot
side" we refer to heat pumps.

Heat pump system

Total system, comprising a heat source
and a heat pump system.

Compact heat pump system

Fully-wired appliance, where the
complete refrigerant circuit, incl.
safety and control equipment, has
been manufactured and tested.

Heat source

Medium, from which the heat pump
extracts energy.

Heat utilisation system

Equipment for heat transfer to the
heating system.

Heat source system (WQA)

Equipment for the extraction of
energy from a heat source and the
transportation of the heat transfer
medium between the heat source
and the "cold side" of the heat pump,
including all auxiliary equipment.

Heat transfer medium

Liquid or gaseous medium (e.g. water
or air), with which heat is transported.

Auxiliary energy

Energy required for the operation of
auxiliary equipment.

Off-periods

In Germany, heat pumps can be
stopped, subject to your tariff, by the
power supply utility for 3 x 2 hours
daily.

tErmInology and dEScrIptIonS

24 WWW.STIEBEL-ELTRON.COM

SUmmary of formUlaE

Heat amount

Q = m

x c x (t

2

– t1)

Q = Heat amount Wh
m = Water volume kg
c = Specific heat Wh/kgK
1 163 Wh/kgK
t

1

= Cold water temperature °C

t

2

= DHW temperature °C

Heating output

Q = A

x k x ∆ϑ

Q = Heating output W
A = Surface m²
k = Heat transition coefficient
W/m²K
∆ϑ = Temperature differential K

k value

1 + d + 1
αi λ α

a

1

k =

k = k value W/m²K
α

i

= Heat transfer
coefficient, internal W/m²K
α

a

= Heat transfer coefficient,
external W/m²K
λ = Thermal conductivity W/mK

Connected load

P =

m

x c x (t

2

- t1)

T x η

P = Connected load W
m = Water volume kg
c = Specific heat Wh/kgK
t

1

= Cold water temperature °C

t

2

= DHW temperature °C
D = Heat-up times h
η = Efficiency

Heat-up time T

D =

m x c x (t2 - t1)
P

x η

D = Heat-up time h
m = Water volume kg
c = Specific heat Wh/kgK
t

1

= Cold water temperature °C
t

2

= DHW temperature °C
P = Connected load W
η = Efficiency

Pressure drop calculation

∆p = L

x R + Z

∆p = Pressure differential Pa
R = Tubes frictional resistance
L = Pipe length (m)
Z = Pressure drop from the
individual resistances Pa

Individual resistances

Z = Σz x x v

2

ς

2

z = Resistance coefficient
ς = Density
v = Flow velocity (m/s)

Z can be taken from the total z and the
velocity in the pipework in the tables.

Duct work curve

∆p

1

∆p

2

V

1

V

2

)

2

=

∆p1 = Pressure differential Pa
∆p

2

= Pressure differential Pa

V

1

= Air flow rate m³/h

V

2

= Air flow rate m³/h

Mixed water temperature

(m1 x t1) + (m2 x t2)

t

m

=

(m

1

+ m2)

tm = Mixed water temperature °C
t

1

= Cold water temperature °C

t

2

= DHW temperature °C

m

1

= Cold water volume kg

m

2

= DHW volume kg

Mixed water volume

m2 x (t2 - t1)

m

m

=

t

m

- t

1

mm = Mixed water volume kg
m

1

= Cold water volume kg

m

2

= DHW volume kg

t

m

= Mixed water temperature °C

t

1

= Cold water temperature °C

t

2

= DHW temperature °C

DHW volume

mm x (tm - t1)

m

2

=

t

2

- t

1

mm = Mixed water volume kg
m

1

= Cold water volume kg

m

2

= DHW volume kg

t

m

= Mixed water temperature °C

t

1

= Cold water temperature °C

t

2

= DHW temperature °C

Approximate heating load according
to oil consumption

Q

N

= Ba x h x Hu / b

VH

QN = Heating load (kW)
B

a

= Annual oil consumption (l)
Average consumption over the
last five years, minus 75 litres
of oil per person for DHW
heating.
h = Seasonal efficiency [to DIN]
(h = 0.7)
H

u

= Calorific value of fuel oil
(10 kWh/l)
b

VH

= Hours run at full utilisation

(average value 1800 h/p.a.)

Q

N

= Ba / 250

(

25WWW.STIEBEL-ELTRON.COM

SyStEm dESIgn

Design information

To size heat pump systems accurately,
the following points regarding the
building to be heated or cooled must
be known:

 Calculation of heating load to

DIN EN 12831

 Calculation of the cooling load to

VDI 2078

 Determination of the heating

surface temperature

New build: Determine the

maximum flow temperature

Older building: Determine the

maximum flow temperature

 Determine or select the most

favourable heat source

 Determine the operating mode of

the heat pump according to the
heating system

 Size the heat pump according to

heat demand and operating mode

 Power connection conditions and

requirements for the heat pump
control unit

 Connection of the heat pump to

the heating system

 DHW heating with the heating heat

pump

 General regulations and

guidelines/directives

Existing system Heat pump Buffer cylinder DHW heating

26 WWW.STIEBEL-ELTRON.COM

rEgUlatIonS and gUIdElInES/dIrEctIvES

The positioning, installation,
adjustment and commissioning of
heat pump systems must only be
carried out by qualified personnel,
giving due consideration to the
operating and installation instructions.
Only a qualified person authorised by
the relevant electricity supply utility
may carry out the heat pump power
connection, giving due consideration
to the relevant wiring regulations and
the conditions applied by the power
supply utility. The installer should also
make the relevant application to the
power supply utility.

Observe the following acts, standards,
regulations and orders during the
installation and operation of heat
pump heating systems in Germany:
Outside Germany, observe all
regulations and guidelines/directives
that may apply to your specific
country.

General conditions:

Building Regulations and others

Observe all relevant local and national
standards since heat pumps represent
"structural systems" in accordance
with the state building regulations
[Germany]. Therefore check with the
local Building Regulations authority
regarding applicable regulations prior
to the installation of a heat pump. The
building owner may need to notify
the relevant authority of the system
installation after the heat pump
installation has been completed. This
notification should be accompanied
by a manufacturer's declaration
that the intended installation will
comply with the requirements
of the building regulations
[Germany]. The requirement for
a permit in accordance with the
"Wasserhaushaltsgesetz" remains
unaffected by this exemption.

Special laws governing the utilisation
of various heat sources

The utilisation of heat latent in the
environment may, be subject to legal
regulations that are designed to
ensure that other private and public
concerns are not impeded, and
that these measures will not exert
dangerous environmental influences.

Groundwater as heat source

The extraction of groundwater
as heat source for a heat pump
and the reintroduction of the
cooled groundwater is regulated
by paragraph 3 sect. 1 no. 6 and
paragraph 3 sect. 1 no. 5 of the
"Wasserhaushaltsgesetzes (WHG)"
[Germany] and is subject to a permit.

The ground is the source of thermal
energy

The extraction of heat by
pipework buried under ground
that are filled with a means for
transporting heat, generally requires
notification to the water board or
a permit. If the ground collector
is in contact with groundwater,
a duty to obtain a permit may be
determined in accordance with
the "Wasserhaushaltsgesetz".
However, this case has not been
finally regulated. It is, nevertheless,
recommended that discussions are
held prior to commencement with the
relevant water authority (see chapter
"Heat source system").

Heat source

The utilisation of the outside air
as heat source with regard to the
entitlement to cool the outside air is
not subject to statutory regulations.
However, observe the technical
instructions regarding protection
against noise emissions [TA-Lärm in
Germany, or local regulations] from
evaporators. The expelled chilled
air may result in a nuisance for
neighbours (LBO sect.18).

Federal Immission Protection Act
(BImSchG) and TA-Lärm [Germany].

Heat pumps are "Systems" in the
sense of the Federal Immissions
Protection Act. The BlmSchG
differentiates between systems
subject to permit (paras. 44, 22) and
systems requiring no permit. Systems
requiring permits are listed finally
in the fourth BImSchV. Heat pumps
of any kind are not listed here. For
that reason, heat pumps are subject
to para. 22 to 25 BlmSchG, i.e. they
must be installed and operated in
such a way that avoidable nuisance is
limited to a minimum. Regarding the
noise emitted by heat pump systems,
observe the technical instructions
appertaining to the protection
against noise as per TA-Lärm [or
local regulations]. For living areas,
the sound pressure levels in the
table LS-Lärm that are subject to the
surrounding development have been
set as emission values.

TA-Lärm (VDI 2058).

The following sound pressure levels at
the neighbours' windows must not be
exceeded:
In commercial residential areas
day 60 dB(A)
night 45 dB(A)
In general residential areas
day 55 dB(A)
night 40 dB(A)
In exclusively residential areas
day 50 dB(A)
night 35 dB(A)

27WWW.STIEBEL-ELTRON.COM

rEgUlatIonS and gUIdElInES/dIrEctIvES

DIN standards

– DIN EN 12831 Heating systems in

buildings – procedure to calculate
the standard heating load.

– DIN 4108 Thermal insulation and

energy saving in buildings.

– DIN 4109 Sound insulation in

buildings.

– DIN 8901 Refrigerating systems

and heat pumps – protection of
the ground, groundwater and
surface water – technical safety,
environmental requirements and
test.

– DIN 4701-10 Energy assessment of

heating and air handling system:
Heating, DHW heating, ventilation.

VDI guidelines

– VDI 2067 Efficiency of technical

building systems.

– VDI 2068 Measuring/monitoring

and control equipment in heating
systems with water as heat transfer
medium.

– VDI 2715 Noise reduction in hot

water heating systems.

– VDI 4640-2 Thermal utilisation of

the ground – ground source heat
pump systems.

– VDI 4650 (Draft) Heat pump

calculations. Abridged procedure for
calculating the annual expenditure
of energy values of heat pump
systems.

– VDI 2078 Cooling load calculation

for air conditioned rooms.

Regulations regarding the water side

– DIN EN 806 Technical rules for DHW

installations.

– DIN 4708-1 Central DHW heating

systems – part 1: Terminology and
calculation principles.

– DIN EN 378 Refrigeration systems

and heat pumps – technical safety
and environmental requirements.

– DIN EN 14511-1 to 4 Air handling

units, chillers and heat pumps with
electrically operated compressors
for central heating and cooling –
part 1: Terminology, part 2: Test
conditions, part 3: Test procedures,
part 4: Requirements.

– DIN EN 12828 Heating systems in

buildings - Designing hot water
heating systems.

– TRD 721 Safety equipment to

prevent excess pressure; safety
valves for steam boilers category II.

– DVGW Code of Practice W 101

Guideline for protected potable
water areas, part 1: Protected
groundwater areas.

– DVGW Code of practice W501

Potable water heating and routing
systems - technical measures for the
reduction of the growth of legionella
bacteria – engineering, installing,
operating and modernising potable
water installations.

Regulations regarding the power side

– VDE 0100 Regulations for the

installation of HV systems up to
1000 V.

– VDE 0105 Regulations for the

operation of three-phase systems.

– VDE 0700 Safety of electrical

equipment for domestic use and
similar purposes.

Accident prevention instructions
by the governing body of the trade
associations

– BGV D4 Accident prevention

instructions; refrigerating
equipment, heat pumps and cooling
facilities.

Additional standards and regulations
for dual-mode heat pump systems.

Observe the following acts, standards,
regulations and orders during
the installation of an additional
combustion system for solid, liquid or
gaseous fuels:

Combustion Order [or local/national
equivalent]

– Feu Vo part II, para. 4, sect. 2, sect.

4

– DIN EN 267 Oil combustion system

– technical rules - oil combustion
installation (TRÖ) - test.

Safety principles

– DIN 4787 Oil atomisation burners,

terminology, technical safety
requirements, testing, identification.

– DIN EN 12285-1 Factory-produced

steel tanks – part 1: Horizontal
single or twin-wall cylindrical tanks

for the subterranean storage of

combustible and non-combustible

liquids that represent a risk to

groundwater.
– DIN EN 12285-2 Factory-produced

steel tanks – part 2: Horizontal

single or twin-wall cylindrical tanks

for the above-ground storage of

combustible and non-combustible

liquids that represent a risk to

groundwater.
– DIN 6618-1 Vertical steel containers

(tanks), single wall, for above-

ground storage of combustible

and non-combustible liquids that

represent a risk to groundwater.
– DIN 6619-1 Vertical steel

containers (tanks), single wall, for

subterranean storage of combustible

and non-combustible liquids that

represent a risk to groundwater.
– DIN 6620-1; Cylinder banks (tanks)

made from steel for the above-

ground storage of combustible

liquids, safety category A III.
– DIN 6625-1 Locally manufactured

steel containers (tanks), for above-

ground storage of combustible

liquids safety category A III that

represent a risk to groundwater

and non-combustible liquids that

represent a risk to groundwater.
– DIN 18160-1; Flue systems.
– DIN 18381 VOB Payment and

contract order for construction

services – part C: General technical

contract conditions for construction

services (ATV) – gas, water and

drainage installation systems inside

buildings.

DVGW guidelines
(DVGW Codes of practice)

– TRF 1996 Technical rules for LPG.
– G 430 Guideline for the installation

and operation of low pressure gas

tanks.
– G 600 Technical rules for gas

installations.
– G 626 Technical rules for the

mechanical routing of flue gases for

open flue combustion equipment in

flue and central ventilation systems.
– G 666 Guidelines for the cooperation

between the gas supply utilities and

the contract installation companies.

28 WWW.STIEBEL-ELTRON.COM

HEatIng load calcUlatIon

Heating load

Firstly determine the required heating
load of the building. Observe the
calculation to DIN EN 12831 for
reliable quotations and design.

The heating load can also be
estimated for dual-mode heat pump
systems with an existing heat source.

1. Subject to the heated living space

See adjacent table for the heating
load per m² living space.

Q

N

= Living space x Watt/m²

2. Subject to oil consumption

The annual consumption can be
determined from the average oil
consumption over the last five years.

Q

N

= Ba x h x Hu / b

VH

QN = Heating load (kW)
B

a

= Annual oil consumption (l)
h = Seasonal efficiency [to DIN] (h
= 0.7)
H

u

= Calorific value of fuel oil
(10 kWh/l)
b

VH

= Hours run at full utilisation
(average value 1800 h/p.a.)

Brief formula

Q

N

= Ba / 250

3. Subject to gas consumption

The annual consumption can be
determined from the average gas
consumption over the last five years.

Q

N

= Ba x h / b

VH

QN = Heating load (kW)
B

a

= Annual gas consumption (kWh)
h = Seasonal efficiency [to DIN] (h
= 0.8)
b

VH

= Hours run at full utilisation

(average value 1800 h/p.a.)

Detached or two-family home

Thermal insulation of
the external wall

Window Floors W per m²

living space
no single glazed 1 160
no single glazed 2 140
no double glazed 1 to 2 100
yes double glazed 1 to 2 80
yes low-E glass 1 to 2 50

29WWW.STIEBEL-ELTRON.COM

flow tEmpEratUrES of HEatIng SUrfacES

Heating surface temperature

The flow temperature of the heating
system is decisive for the application
options and the operating mode of
the heat pump. Heating systems that
require a flow temperature in excess
of +60°C can only be operated in
dual-mode together with a second
heat source. The changeover point
of the heat pump is determined not
only by the heating output of the heat
pump, but also by the sizing of the
heating surfaces. Radiator heating
systems used to be sized around a
flow temperature of +90°C. Today,
retrofitting thermal insulation or
oversizing generally means, that a
flow temperature of only +70°C or
less is generally required. The heating
surfaces of new systems should be
sized around a flow temperature of no
more than +55°C to enable a mono­mode operation.

Example:

Up to what outside temperature
can a heating system with a flow
temperature of +75°C (heating
curveB) be operated with a heat
pump operating with a flow
temperature of up to +60°C? In this
example, the point of intersection
between heating curve B and the max.
heat pump flow temperature of +60°C
arrives at an outside temperature
of –4°C. The application limit of
this heat pump therefore lies at an
outside temperature of – 4°C because
of the heat distribution system. It is
often noted in practice that, through
external and internal energy recovery,
the heating limits can be extended to
meet lower temperatures. This means
that the heat pump covers a higher
percentage of the annual heating
load.

Rule of thumb:

The lower the flow temperature of the
heating system, the higher the output
of the heat pump.

According to the above diagram the following flow temperatures produce the
following changeover points to start the second heat source:

Curve A: Flow temperature 90°C changeover point – 0°C OT
Curve B: Flow temperature 75°C changeover point – 4°C OT
Curve C: The flow temperature is lower than +60 °C, enabling the heat pump
to operate in mono-mode.
Curve D: The flow temperature is lower than +60 °C, enabling the heat pump
to operate in mono-mode.

Flow temperatures for the corresponding outside temperatures

Heating flow temperature

External temp

Heat pump
flow temp.

30 WWW.STIEBEL-ELTRON.COM

SIzIng of HEat pUmpS

Sizing of heat pumps

Some electricity supply utilities can
shut down the power supply of heat
pumps for specific periods in return
for favourable tariffs. However, the
heat demand of the building must be
covered 24 hours per day. That means
that the building heating load must be
raised by a factor of 1.1.

Q

HP

= Q

Nbuil.

x 1.1

Air | water heat pumps

The heating output of air | water
heat pumps is subject to the
outside temperature. This has the
disadvantage that the heating output
of the heat pump also falls with
falling outside temperatures, whilst
the heating load actually increases.
This is why air | water heat pumps are
operated in mono-energetic mode.

Brine | water or water | water heat
pumps

As the heat source offers a near
constant temperature throughout the
year, the heating output of the heat
pump is constant. These heat pumps
are operated in mono-mode.

Sizing air|water heat pumps

Sizing brine|water heat pumps

Sizing water|water heat pumps

Air inlet temperature °C

Heating output (kW)

Heat source temperature °C

Heating output (kW)

Heat source temperature °C

Heating output (kW)