STIEBEL ELTRON PER 18/21/24 Instruction Manual

OPERATION AND INSTALLATION
OBSLUHA A INSTALACE
OBSŁUGA I INSTALACJA
ОБСЛУЖВАНЕ И ИНСТАЛИРАНЕ
ЭКСПЛУАТАЦИЯ И УСТАНОВКА
Fully electronically controlled instantaneous water heater with mini FFB wireless pushbutton | Plně
elektronicky regulovaný průtokový ohřívač s tlačítkem bezdrátového ovládání Mini-FFB| Całkowicie
elektronicznie regulowany przepływowy ogrzewacz wody z pilotem zdalnego sterowania Mini-FFB |
Изцяло електронно регулиран проточен бойлер с безжичен превключвател Mini-FFB | Проточный
водонагреватель с автоматическим электронным управлением и пультом дистанционного
управления Mini-FFB
» PER 18/21/24
1ECO 2
Made in Germany

2| PER 18/21/24 www.stiebel-eltron.com
CONTENTS | SPECIAL INFORMATION
SPECIAL INFORMATION
OPERATION
1. General information������������������������������������������3
1.1 Safety instructions ����������������������������������������������� 3
1.2 Other symbols in this documentation������������������������ 3
1.3 Units of measurement ������������������������������������������ 3
2. Safety ����������������������������������������������������������3
2.1 Intended use������������������������������������������������������ 3
2.2 General safety instructions������������������������������������� 4
2.3 Test symbols ������������������������������������������������������ 4
3. Appliance description ����������������������������������������4
4. Settings��������������������������������������������������������5
4.1 Settings and displays on the appliance���������������������� 5
4.2 Settings in the INFO menu ������������������������������������� 6
4.3 Settings on the wireless remote control��������������������� 8
4.4 Further functions��������������������������������������������8
4.5 Recommended settings����������������������������������������� 8
5. Cleaning, care and maintenance ����������������������������8
6. Troubleshooting ����������������������������������������������9
INSTALLATION
7. Safety �������������������������������������������������������� 10
7.1 General safety instructions������������������������������������ 10
7.2 Instructions, standards and regulations �������������������� 10
8. Appliance description �������������������������������������� 10
8.1 Standard delivery ����������������������������������������������� 10
9. Preparations ������������������������������������������������ 10
9.1 Installation site �������������������������������������������������� 10
9.2 Water installation ����������������������������������������������� 11
10. Installation �������������������������������������������������� 11
10.1 Standard installation ������������������������������������������� 11
10.2 Installation options ��������������������������������������������� 14
10.3 Completing the installation ����������������������������������� 16
10.4 Installation of wireless remote control���������������������� 16
11. Commissioning ��������������������������������������������� 16
11.1 Initial start-up ��������������������������������������������������� 16
11.2 Recommissioning ����������������������������������������������� 16
12. Shutdown ��������������������������������������������������� 16
13. Troubleshooting �������������������������������������������� 17
13.1 Customer service mode���������������������������������������� 17
14. Maintenance ������������������������������������������������ 18
15. Specification ������������������������������������������������ 18
15.1 Dimensions and connections ��������������������������������� 18
15.2 Wiring diagrams ������������������������������������������������ 19
15.3 Factory settings�������������������������������������������������� 19
15.4 DHW output ������������������������������������������������������ 19
15.5 Application areas/ conversion table ������������������������ 19
15.6 Pressure drop���������������������������������������������������� 19
15.7 Fault conditions ������������������������������������������������� 20
15.8 Details on energy consumption ������������������������������ 20
15.9 Data tables ������������������������������������������������������� 20
GUARANTEE
ENVIRONMENT AND RECYCLING
SPECIAL
INFORMATION
- The appliance may be used by children aged 8
and up and persons with reduced physical, sen-
sory or mental capabilities or a lack of experience
and know-how, provided that they are supervised
or they have been instructed on how to use the
appliance safely and have understood the result-
ing risks. Children must never play with the ap-
pliance. Children must never clean the appliance
or perform user maintenance unless they are
supervised.
- Risk of scalding: The tap can reach temperatures
in excess of 60°C.
- Ensure the appliance can be separated from the
power supply by an isolator that disconnects all
poles with at least 3mm contact separation.
- Secure the appliance as described in chapter "In-
stallation/ Installation".
- Observe the maximum permissible pressure (see
chapter "Specification/ Data table").
- Drain the appliance as described in chap-
ter "Installation/ Maintenance/ Draining the
appliance".

OPERATION
General information
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ENGLISH
OPERATION
1. General information
The chapters "Special Information" and "Operation" are intended
for both the user and qualified contractors.
The chapter "Installation" is intended for qualified contractors.
Note Read these instructions carefully before using the appli-
ance and retain them for future reference.
Pass on the instructions to any new user where appro-
priate.
1.1 Safety instructions
1.1.1 Structure of safety instructions
!KEYWORD Type of risk
Here, possible consequences are listed that may result
from failure to observe the safety instructions.
 Steps to prevent the risk are listed.
1.1.2 Symbols, type of risk
Symbol Type of risk
Injury
Electrocution
Burns
(burns, scalding)
1.1.3 Keywords
KEYWORD Meaning
DANGER Failure to observe this information will result in serious in-
jury or death.
WARNING Failure to observe this information may result in serious
injury or death.
CAUTION Failure to observe this information may result in non-serious
or minor injury.
1.2 Other symbols in this documentation
Note General information is identified by the adjacent symbol.
 Read these texts carefully.
Symbol Meaning
Material losses
(appliance damage, consequential losses and environmental
pollution)
Appliance disposal
 This symbol indicates that you have to do something. The ac-
tion you need to take is described step by step.
1.3 Units of measurement
Note All measurements are given in mm unless stated other-
wise.
2. Safety
2.1 Intended use
This appliance is intended for domestic use. It can be used safely
by untrained persons. The appliance can also be used in a non-do-
mestic environment, e.g.in a small business, as long as it is used
in the same way.
This pressurised appliance is suitable for heating domestic hot
water or for reheating preheated water. The appliance can supply
one or more draw-off points.
Any other use beyond that described shall be deemed inappropri-
ate. Observation of these instructions and of instructions for any
accessories used is also part of the correct use of this appliance.
!
!

OPERATION
Appliance description
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2.2 General safety instructions
CAUTION Burns During operation, the tap can reach temperatures in ex-
cess of 60 °C.
There is a risk of scalding at outlet temperatures in excess
of 43°C.
CAUTION Burns If operating with preheated water, e.g. from a solar ther-
mal system, the DHW temperature may vary from the se-
lected set temperature.
!WARNING Injury
The appliance may be used by children aged8 and up and
persons with reduced physical, sensory or mental capa-
bilities or a lack of experience and know-how, provided
that they are supervised or they have been instructed on
how to use the appliance safely and have understood the
resulting risks. Children must never play with the appli-
ance. Children must never clean the appliance or perform
user maintenance unless they are supervised.
Where children or persons with limited physical, sensory or men-
tal abilities are allowed to use this appliance, we recommend a
permanent temperature limit. A qualified contractor can set the
limit for you.
!Material losses
The user should protect the appliance and its tap against
frost.
Note The wireless remote control is supplied with power by a
lithium button cell battery.
Remove spent batteries. Leaking batteries result in dam-
age which is excluded from any warranty.
Never use rechargeable NiCd batteries.
2.3 Test symbols
See type plate on the appliance.
3. Appliance description
The appliance heats water as it flows through the appliance. The
DHW outlet temperature can be variably adjusted at the temper-
ature selector. From a certain flow rate, the control unit regulates
the correct heating output, subject to the temperature selected and
the current cold water temperature.
The flow rate is automatically reduced by the flow regulator valve
when inlet temperatures are low and the required outlet tempera-
ture is high. This ensures that the required temperature is reliably
achieved. If operating the appliance with preheated water, "Error"
will appear in the display at temperatures of 45°C and above.
Two different temperatures can be saved and called up quickly. The
ECO function limits the flow rate to the ECO flow rate and sets a
pre-defined ECO temperature. The appliance also has childproofing
functions, a Wellness program, automatic water volume control,
dynamic anti-scalding protection and a permanent temperature
limiting feature. The background lighting on the appliance's display
can also be used as an orientation light.
Heating system
The bare wire heating system has a pressure-tested plastic casing.
The heating system is suitable for hard and soft water areas and is
largely insusceptible to scale build-up. This heating system ensures
rapid and efficient DHW availability.
Note The appliance is equipped with an air detector that largely
prevents damage to the heating system. If, during op-
eration, air is drawn into the appliance, the appliance
shuts down for one minute, thereby protecting the heating
system.

OPERATION
Settings
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ENGLISH
4. Settings
4.1 Settings and displays on the appliance
26�02�02�0929
Temperature display
Bar graph showing output
Second display
e.g. time
Memory keys 1 and 2
Info and ECO button
ECO display
Temperature selector
Display field for additional information:
Service, error
Backlighting
Display field:
Wellness, automatic water volume control,
childproofing, ECO, second display, clock
Display field
Wellness Second line
Automatic water volume
control
Time
ECO mode Orientation light
Childproofing
Display field for additional information
 Please contact your qualified contractor if the following sym-
bols are displayed:
Error
Service
4.1.1 Setting the temperature
The desired temperature can be variably adjusted by turning the
rotary selector. The set temperature is displayed.
Operation Display
Select a temperature between
30 and 60°C via stepless
setting
e.g. 43°C
OFF = heating switched
off
4.1.2 Memory keys
Using the memory keys, you can quickly call up two preferred
temperatures. These temperatures can be selected by you.
Allocating memory keys
Select the temperature be-
tween 30 and 60°C that you
wish to save
e.g. 38°C.
Press button1 or button2 for
3seconds
e.g. 38°C and 43°C
Display flashes once brief-
ly, temperature is stored
Calling up memory keys
Press button1 or button2 e.g. 38°C and 43°C
4.1.3 Selecting/deselecting ECO
The ECO function is activated and deactivated with the ECO button.
If you have activated the ECO function, a green LED below the
button lights up. The ECO symbol is also displayed.
The ECO function limits the flow rate to the ECO flow rate and sets
a pre-defined ECO temperature. Both values can be adjusted via
the INFO menu.
Note The ECO function is deactivated each time you adjust the
temperature on the appliance (with the temperature se-
lector or via the memory keys). You must then re-activate
the ECO function if required.
If you have selected the temperature via the wireless remote con-
trol, the ECO function is re-activated automatically after water has
been drawn off.
Press the ECO button:
Selecting ECO
Green LED illumi-
nates.
Press the ECO button:
Deselecting ECO Off
LED is not lit.

OPERATION
Settings
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4.2 Settings in the INFO menu
Use the ECO button to access the INFO menu, where you can set
comfort functions to individual preferences and/or call up values:
ECO temperature/flow rate adjustment, childproofing, Wellness
program, automatic water volume control. The ECO button can
also be used to set the brightness of the display and the orienta-
tion light.
You can access the setting options by pressing the ECO button for
longer than three seconds.
Then press the ECO button again repeatedly to access each function.
When you have reached the required function, you can change
the settings for that function by turning the temperature selector.
Operation Display
Accessing the menu
Press the ECO button for
3seconds
38°C
All settings in the INFO menu are saved immediately.
Exiting the menu
Press the ECO button for
3seconds.
Selected settings
If no button is pressed for approx.40seconds, the INFO menu is
exited.
4.2.1 ECO function
Setting the ECO temperature
Press the ECO button for
3seconds
38°C
Set the temperature,
range: 30-60°C
e.g. 40°C
Setting the ECO flow rate
Press the ECO button for
3seconds
38°C
Briefly press the ECO button 8.0 l/min
Set the flow rate
4-15l/min
e.g.
6.0 l/min.
4.2.2 Setting the brightness of blue and red backlighting
The display on the appliance is equipped with background lighting.
When you set a temperature up to 42.5°C, the background lighting
lights up blue; at temperatures of 43.0°C and above, the display
switches to red.
The display background lights up when you press a button, turn
the temperature selector or if water flows through the appliance
at a flow rate greater than the starting flow rate.
If no water is drawn off or the appliance is not operated for 30sec-
onds, the background lighting switches off or is only dimly lit (if
the orientation light is activated).
If water is drawn off for longer than 15minutes, the brightness
is reduced.
The brightness of both the red and blue light can be individually
adjusted in 5 stages.
Press the ECO button for
3seconds
38°C
Press the ECO button briefly
several times
blue
red
Select the brightness for the
red and blue lighting
100%
20%
4.2.3 Activating/deactivating the orientation light
The backlighting helps you find your way in dark rooms. For this
purpose, you can set the lighting so it is constantly on. It will then
remain alight at the lowest intensity (output approx.0.2watts).
Press the ECO button for
3seconds
38°C
Press the ECO button briefly
several times
OFF
Select "OFF"/"ON" OFF:
ON:
deactivated
activated
4.2.4 Activating/deactivating/adjusting the childproofing
function
You can set the appliance to a maximum temperature.
Press the ECO button for
3seconds
38°C
Press the ECO button briefly
several times
OFF
Select "OFF"/"ON". OFF:
ON:
deactivated
activated
Briefly press the ECO button 43°C
Setting the temperature e.g. 36°C

OPERATION
Settings
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ENGLISH
4.2.5 Activating/deactivating the Wellness comfort function
You can permanently program a Wellness comfort function which,
after water has been drawn for three minutes, reduces the temper-
ature by 10°C and then increases it again after 10 seconds. After
a further 10seconds, the temperature is lowered again by 10°C
and then raised again after 10seconds. This temperature change
continues for the entire period that water is being drawn.
Press the ECO button for
3seconds
38°C
Press the ECO button briefly
several times
OFF
Select "OFF"/"ON" OFF:
ON:
deactivated
activated
4.2.6 Activating/deactivating/adjusting the automatic water
volume control
You can set the automatic water volume control function so that the
flow rate is reduced to approx.4l/min once a specified volume has
been drawn off. This enables you to influence the amount of water
drawn as well as the duration of a shower. The selected automatic
water volume control only applies to the next draw-off.
Press the ECO button for
3seconds.
38°C
Press the ECO button briefly
several times.
OFF
Select "OFF"/"ON" OFF:
ON:
deactivated
activated
When set to "ON", briefly press
the ECO button
80 l
Adjust the water volume
5-200 l
e.g. 150 l
4.2.7 Selecting the second line in the display
You can select what additional information is displayed in the sec-
ond line:
l/min Flow rate
kWh Energy consumption (you can set the values of these con-
sumption indicators to zero)
m³ Water volume (you can set the values of these consumption
indicators to zero)
Clock Time (if the power supply has been interrupted you will
need to reset the clock)
Press the ECO button for
3seconds
38°C
Press the ECO button briefly
several times
Select the display value for the
second line
Selected display
Setting the "energy consumption and water volume" consumption
indicator to zero.
In the INFO menu, press but-
ton1 and button2 simultane-
ously when the corresponding
consumption value appears in
the display
0
4.2.8 Setting the time
Press the ECO button for
3seconds
38°C
Press the ECO button briefly
several times
Set the time E.g. 12:15
Please note:
Reset the time after
a power supply in-
terruption.
4.2.9 Wireless remote control – checking, registering,
deregistering
The appliance can be controlled remotely by means
of a wireless remote control. The transmitter is water-
proof and can also be used whilst showering or bath-
ing. Up to four wireless remote controls can be combined.
The wireless remote control enables you to control the temperature
of the appliance remotely from another location (e.g. from the
kitchen sink).
The wireless remote control has four buttons for selecting the tem-
perature (38°C and 55°C are fixed settings; plus and minus button
for changing the temperature in 0.5°C stages). When a signal is
being sent to the appliance, the red LED on the wireless remote
control lights up.
If you press any button on the remote control while the appliance
is in ECO mode, the ECO function is cancelled for the next draw-off.
ECO mode is resumed two minutes after the draw-off.
If the appliance is in standard mode, a constant temperature can
be selected via the wireless remote control.
Wireless remote control check on the appliance
Press the ECO button for
3seconds 38°C
Press the ECO button briefly
several times
rc 1-4
Number of registered
wireless remote controls
(rc: remote control)
Registering a wireless remote control at the appliance
Press the ECO button for
3seconds 38°C
Press the ECO button briefly
several times
rc 1
Press button1: Self-learning
phase is activated.
Press any button on the wire-
less remote control.
Bar graph is shown.
Green LED flashes.
rc 2
Bar graph display goes
out.
Wireless remote control is
recognised
Deregistering a wireless remote control from the appliance
Press the ECO button for
3seconds 38°C
Press the ECO button briefly
several times
rc 2
In "rc" mode, press button2 rc 0: All wireless remote
controls are deregistered

OPERATION
Cleaning, care and maintenance
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4.2.10 Resetting to factory defaults
Press button1 and button2
simultaneously for 2seconds
Display flashes to confirm.
Anti-scalding protection and registered wireless remote controls
are not reset (for factory defaults, see chapter "Specification").
4.3 Settings on the wireless remote control
OFF
3s
D0000041708
Press 38°
Press 55°
Press +
Press -
38°C
55°C
Press 1x: Set value raised by 0.5°C.
Press 1x: Set value lowered by 0.5°C.
You can switch the appliance heater to OFF using the wireless
remote control. To do this, press the minus button for at least3sec-
onds. Press any key to switch it back on.
4.4 Further functions
4.4.1 Dynamic anti-scalding protection
The appliance is equipped with dynamic anti-scalding protection.
The user who is first to select a temperature on the appliance or
via the wireless remote control sets the temperature for the next
draw-off. No other user can increase the temperature above 43°C
in the following two minutes or during a draw-off or for two min-
utes following the end of a draw-off.
4.4.2 Anti-scalding protection
The qualified contractor can permanently limit the temperature
(see chapter "Troubleshooting/ Customer service mode"). This
prevents water from flowing out of the appliance at temperatures
which could cause injury.
4.5 Recommended settings
Saving energy
The following recommended settings will result in the lowest en-
ergy consumption:
-38°C for basins, showers, bath
-55°C for kitchen sinks
Thermostatic valve
If the appliance is being operated with a thermostatic valve, we
recommend setting the temperature on the appliance to maximum
(temperature selector set to 60°C). You can then select the required
temperature at the thermostatic valve.
Following an interruption to the water supply
!Material losses
Following an interruption of the water supply the appli-
ance must be recommissioned by carrying out the follow-
ing steps, in order to prevent the destruction of the bare
wire heating system.
 Disconnect the appliance from the power supply by
removing the fuses/tripping the MCBs.
 Open the tap for one minute until the appliance and
its upstream cold water inlet line are free of air.
 Switch the mains power back ON again.
5. Cleaning, care and maintenance
 Never use abrasive or corrosive cleaning agents. A damp cloth
is sufficient for cleaning the appliance.
 Check the taps regularly. Limescale deposits at the tap out-
lets can be removed using commercially available descaling
agents.

OPERATION
Troubleshooting
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ENGLISH
6. Troubleshooting
Problem Cause Remedy
The appliance will not
start despite the DHW
valve being fully open.
There is no power. Check the fuses/MCBs in
your fuse box/distribution
panel.
The aerator in the tap or
the shower head is scaled
up or contaminated.
Clean and/or descale the
aerator or shower head.
Required temperature
>45°C is not achieved.
The water supply has
been interrupted.
Vent the appliance and
the cold water inlet line
(see chapter "Settings").
The cold water inlet tem-
perature is >45°C.
Reduce the cold water
inlet temperature.
The flow rate is too low. ECO mode is activated and
the flow rate value in ECO
mode is set too low.
Set a higher ECO flow
rate.
It is not possible to set a
temperature higher than
43°C.
Dynamic anti-scalding
protection is enabled.
Is cancelled automatically
two minutes after draw-
ing has ceased.
If you cannot remedy the fault, notify your qualified contractor.
To facilitate and speed up your enquiry, please provide the serial
number from the type plate (000000-0000-00000):
Nr.: 000000-0000-00000
D0000041614
Flat batteries in the wireless remote control
Problem Cause Remedy
LED on the wireless
remote control flashes
during and after trans-
mission.
Battery in the wireless
remote control is flat.
Replace batteries.
 Open the housing of the wireless remote control. To do this,
unscrew the two screws on the back and prise off the casing.
 Remove the old battery and insert a new one, type CR 2032.
Note Ensure correct polarity of the new battery: Positive (+)
must be at the top. Observe the information in chapter
"Environment and recycling".
 Close the casing. When doing so, pay attention to the recess
on the edge of the lid. The recess determines the correct posi-
tioning of the lid and ensures the casing is tightly sealed.

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INSTALLATION
Safety
INSTALLATION
7. Safety
Only a qualified contractor should carry out installation, commis-
sioning, maintenance and repair of the appliance.
7.1 General safety instructions
We guarantee trouble-free function and operational reliability only
if original accessories and spare parts intended for the appliance
are used.
!Material losses
Observe the maximum inlet temperature. Higher tem-
peratures may damage the appliance. You can limit the
maximum inlet temperature by installing a central ther-
mostatic valve.
7.2 Instructions, standards and regulations
Note Observe all applicable national and regional regulations
and instructions.
- The IP 25 (hoseproof) rating can only be ensured with a cor-
rectly fitted cable grommet.
- The specific electrical resistance of the water must not fall
below that stated on the type plate. In a linked water net-
work, observe the lowest electrical water resistance (see
chapter "Specification/ Application areas/ Conversion table").
Your water supply utility will advise you of the specific electri-
cal resistance or conductivity of the water.
8. Appliance description
8.1 Standard delivery
The following are delivered with the appliance:
- Wall mounting bracket
- Threaded stud for wall mounting bracket
- Installation template
- 2 twin connectors (cold water with shut-off valve)
- Flat gaskets
- Cable grommet (power cable from above/ below)
- Screws/ rawl plugs for securing the back panel to allow for
water connection on finished walls
- FFB mini wireless remote control
For appliance replacement
- 2 tap extensions
Wireless remote control
OFF
3s
D0000041699
1 2 3
1 Transmitter incl. battery
2 Wall mounting bracket
3 Adhesive pad
9. Preparations
9.1 Installation site
!Material losses
Install the appliance in a room free from the risk of frost.
 Always install the appliance vertically and near the draw-off
point.
The appliance is suitable for undersink and oversink installation.
Undersink installation
26�02�02�1345
1
2
1 Cold water inlet
2 DHW outlet
Oversink installation
12
26�02�02�1344
1 Cold water inlet
2 DHW outlet
Note  Mount the appliance on the wall. The wall must have
a sufficient load-bearing capacity.

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ENGLISH
INSTALLATION
Installation
9.2 Water installation
- No safety valve is required.
- Safety valves are not permissible in the DHW pipe.
 Flush the water line thoroughly.
Taps/valves
Use appropriate pressure taps. Open vented taps are not permitted.
Note Never use the shut-off valve in the cold water inlet to
reduce the flow rate. It is intended for shutting off the
appliance.
Permissible water line materials
- Cold water supply line:
Galvanised steel pipe, stainless steel pipe, copper pipe or
plastic pipe
- DHW outlet line:
Pipes made from stainless steel, copper or plastic
!Material losses
If plastic pipework systems are used, take into account the
maximum inlet temperature and the maximum pressure
(see chapter "Specification/ Data table").
Flexible water connection lines
 If the appliance is installed with flexible water connection
lines, ensure that the pipe bends with bayonet fittings do not
become twisted inside the appliance.
 Secure the back panel at the bottom with two additional
screws.
10. Installation
10.1 Standard installation
- Electrical connection from above; installation on unfinished
walls
- Water connection on unfinished walls
- Medium connected load is preset
For further installation options, see chapter "Alternative installation
methods":
- Electrical connection from below on unfinished walls
- Electrical connection on finished walls
- Connecting a load shedding relay
- Water installation on finished walls
- Water connection on unfinished walls for appliance
replacement
- Operation with preheated water
-Installation of wireless remote control
Opening the appliance
D0000041615
 Open the appliance by releasing the snap lock.
NT
T-
so
X1
26�02�02�0762
 Remove the back panel by pressing the two locking hooks and
pulling the base part of the back panel forwards.

12 | PER 18/21/24 www.stiebel-eltron.com
INSTALLATION
Installation
Preparing the power cable
160
≥ 30
26�02�02�0887
Fitting the wall mounting bracket
26�02�02�0972
 Mark out the holes for drilling using the installation template.
If the appliance is to be installed with water connections on
finished walls, also mark out the fixing holes in the lower part
of the template.
 Drill the holes and secure the wall mounting bracket with
2screws and 2rawl plugs (screws and rawl plugs are not part
of the standard delivery).
 Fit the threaded stud provided.
 Fit the wall mounting bracket.
Fitting the cable grommet
26�02�02�0950
 Fit the cable grommet. For connecting cables >6mm², en-
large the hole in the cable grommet.
Making the water connection
!Material losses
Carry out all water connection and installation work in
accordance with regulations.
26�02�02�0948
 Seal and insert the twin connectors.
!Material losses
Never use the shut-off valve in the cold water inlet to
reduce the flow rate.
Preparing the back panel
!Material losses
If you break open the wrong knock-out in the back panel
by mistake, you must use a new back panel.
18
kW
24
21
26�02�02�0884
 Break out the cable grommet knock-out in the back panel.
Deburr any sharp edges with a file if necessary.

www.stiebel-eltron.com PER 18/21/24 | 13
ENGLISH
INSTALLATION
Installation
Installing the appliance
18
kW
24
21
26�02�02�0885
 Push the back panel over the threaded stud and the cable
grommet. Pull the cable grommet by the locking hooks into
the back panel using pliers, until both locking hooks audibly
click into place.
 Remove the protective transport plugs from the water
connections.
 Press the back panel firmly into place and lock the fixing tog-
gle by turning it clockwise through 90°.
D0000041925
 Screw the water connection pipes with flat gaskets onto the
twin connectors.
!Material losses
The strainer must be fitted for the appliance to function.
 When replacing an appliance, check whether the
strainer is installed (see chapter "Maintenance").
Making the electrical connection
WARNING Electrocution Carry out all electrical connection and installation work
in accordance with relevant regulations.
WARNING Electrocution The connection to the power supply must be in the form of
a permanent connection in conjunction with the remova-
ble cable grommet. Ensure the appliance can be separated
from the power supply by an isolator that disconnects all
poles with at least 3mm contact separation.
WARNING Electrocution Ensure that the appliance is earthed.
!Material losses
Observe the type plate. The specified voltage must match
the mains voltage.
 Connect the power cable to the mains terminal (see chapter
"Specification/ Wiring diagrams").

14 | PER 18/21/24 www.stiebel-eltron.com
INSTALLATION
Installation
Re-plugging the coding card
In its delivered condition, the appliance is set to 21kW. When
changing to a different connected load, carry out the following
steps:
18
kW
24
21
18
kW
24
21
D0000037821
 Re-plug the coding card according to the selected connected
load (for selectable connected load and fuse protection of the
appliance, see "Specification/ Data table").
 Tick the selected connected load on the type plate. Use a ball-
point pen to do this.
Fitting the base part of the back panel
3
L3’
4
L2’
1
L1’
2
LLL
NT C
T- sol l
X11
26�02�02�1348
 Position the lower back panel on the main back panel and
click it into place.
 Align the mounted appliance by loosening the fixing toggle,
aligning the power supply and back panel, and then re-tight-
ening the fixing toggle. If the back panel is not flush with the
wall, the appliance can be secured at the bottom with two
additional screws.
10.2 Installation options
10.2.1 Electrical connection from below on unfinished walls
18
kW
24
21
26�02�02�0890
 Fit the cable grommet.
!Material losses
If you break open the wrong knock-out in the back panel
by mistake, you must use a new back panel.
 Break out the cable grommet knock-out in the back panel.
Deburr any sharp edges with a file if necessary.
 Reposition the mains terminal in the appliance from the top
to the bottom.
 Push the back panel over the threaded stud and the cable
grommet. Pull the cable grommet by the locking hooks into
the back panel using pliers, until both locking hooks audibly
click into place.
 Press the back panel firmly into place and lock the fixing tog-
gle by turning it clockwise through 90°.

www.stiebel-eltron.com PER 18/21/24 | 15
ENGLISH
INSTALLATION
Installation
10.2.2 Electrical connection on finished walls
Note This type of connection changes the protection rating of
the appliance.
 Change the type plate. Cross out "IP 25" and mark the
box "IP 24". Use a ballpoint pen to do this.
!Material losses
If you break open the wrong knock-out in the back panel
by mistake, you must use a new back panel.
 Cleanly cut or break out the required cable entries in the back
panel (for positions, see chapter "Specification/ Dimensions
and connections"). Deburr any sharp edges with a file if
necessary.
 Route the power cable through the cable grommet and con-
nect it to the mains terminal.
10.2.3 Connecting a load shedding relay
When operating additional electric appliances, such as electric
storage heaters, install a load shedding relay in the distribution
board. The relay responds when the instantaneous water heater
starts.
!Material losses
Connect the phase that switches the load shedding relay
to the indicated terminal of the mains terminal in the
appliance (see chapter "Specification/ Wiring diagrams").
10.2.4 Water installation on finished walls
Note This type of connection changes the protection rating of
the appliance.
 Change the type plate. Cross out "IP 25" and mark the
box "IP 24". Use a ballpoint pen to do this.
26�02�02�0765
 Fit water plugs with gaskets to seal the in-wall connection.
 Fit a suitable pressure tap.
26�02�02�1006
 Click the lower section of the back panel into place in the
upper section of the back panel.
 Secure the connection pipes to the appliance.
 Secure the back panel at the bottom with two additional
screws.
!Material losses
If you break open the wrong knock-out in the back panel
by mistake, you must use a new back panel.
 Cleanly break out the knock-outs in the appliance cover. De-
burr any sharp edges with a file if necessary.
 Slide the lower back panel under the connection pipes of the
tap and click the lower back panel into place.
 Secure the connection pipes to the appliance.
10.2.5 Water installation on unfinished walls for appliance
replacement
If the existing twin connectors of the old appliance only protrude
from the wall by approx.16mm, you cannot use the twin connec-
tors provided.
Note With this connection, the cold water supply can only be
shut off within the domestic installation.
16
D0000041634
 Seal and fit the screw-in tap extensions provided.
 Connect the appliance.
10.2.6 Operation with preheated water
You can limit the maximum inlet temperature by installing a central
thermostatic valve.

16 | PER 18/21/24 www.stiebel-eltron.com
INSTALLATION
Commissioning
10.3 Completing the installation
 Open the shut-off valve in the twin connector or the cold
water inlet line.
10.4 Installation of wireless remote control
You can attach the transmitter to the wall using the wall mounting
bracket.
 Secure the wall mounting bracket to the wall using the adhe-
sive pad provided or a suitable countersunk screw (∅3mm
or less).
11. Commissioning
WARNING Electrocution Commissioning must only be carried out by a qualified
contractor in accordance with safety regulations.
11.1 Initial start-up
D0000041617
 Open and close all connected draw-off valves several times,
until all air has been purged from the pipework and the
appliance.
 Carry out a tightness check.
 Activate the safety pressure limiter by firmly pressing the reset
button (the appliance is delivered with the safety pressure
limiter deactivated).
 Plug the temperature selector cable plug into the PCB.
 Fit the appliance cover, ensuring it clicks into place. Check that
the appliance cover is seated correctly.
 Switch the mains power ON.
 Check the function of the appliance.
FFB mini wireless remote control
The wireless remote control is registered with the appliance at the
factory. If there is no data communication during commissioning,
carry out the self-learning process as follows:
 Use the ECO button to switch to the comfort function "Wireless
remote control (rc)"
 Press memory button1 on the appliance (the self-learning
phase is activated, bar graph is shown on display).
 Then press a button on the wireless remote control.
Anti-scalding protection
In customer service mode, you can limit the temperature to be-
tween 31 and 60°C.
Appliance handover
 Explain the appliance function to users and familiarise them
with its operation.
 Make the user aware of potential dangers, especially the risk
of scalding.
 Hand over these instructions.
11.2 Recommissioning
Vent the appliance and the cold water inlet line (see chapter "Set-
tings").
See chapter "Commissioning".
12. Shutdown
 Isolate all poles of the appliance from the power supply.
 Drain the appliance (see chapter "Maintenance").

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ENGLISH
INSTALLATION
Troubleshooting
13. Troubleshooting
WARNING Electrocution To test the appliance, it must be supplied with power.
Fault Cause Remedy
The flow rate is too
low.
Strainer and/or aera-
tor are dirty
Clean the strainer and/or aerator.
The motorised valve
is faulty.
Check the motorised valve. Replace
it if required.
Permanent error dis-
play on the program-
ming unit
The sensor/PCB is
faulty.
Further analyse the fault in cus-
tomer service mode (see chapter
"Customer service mode").
Communication be-
tween the program-
ming unit and the
control unit is faulty.
Check the programming unit and
the connecting cable.
The background
lighting in the pro-
gramming unit is
completely off.
No mains power Check the fuses/MCBs in your fuse
box/distribution panel.
Loose connecting
cable to the program-
ming unit
Reconnect the cable.
Safety pressure limit-
er has triggered.
Remove the cause.
Open a downstream draw-off valve
for 1minute. This depressurises
and cools down the heating sys-
tem, protecting it against over-
heating.
Activate the safety pressure limiter
at flow pressure by pressing the
reset button.
Faulty PCB. Check the PCB and replace if re-
quired.
Heater does not
switch on / no hot
water.
Heater is faulty. Check the heater and replace it if
required.
Flow meter faulty or
not plugged in.
Check the connection.
Check the flow meter in the cus-
tomer service mode.
The high limit safety
cut-out has respond-
ed or suffered a lead
break.
Remove the cause.
Activate the high limit safety cut-
out, replace the high limit safety
cut-out if required.
Error display only ap-
pears when water is
being drawn off.
One phase has
dropped out.
Check the fuses/MCBs in your fuse
box/distribution panel.
Inlet temperature
>45°C.
See chapter "Water installation";
limit inlet temperature if neces-
sary.
Intermittent cold
water.
Wellness function
enabled.
Disable the Wellness function.
Brief drop in flow rate The appliance restarts automati-
cally when an adequate flow rate
has been detected.
Air detector responds
(cold water for ap-
prox.1min).
The appliance restarts automati-
cally after a delay.
13.1 Customer service mode
Activate/deactivate customer service mode with the SERVICE button
on the back of the user interface (connection to "T-set" must be
present). Use the ECO button to move to the next menu item (see
chapter "Settings/ Settings in the INFO menu").
Scroll through the respective submenu by turning the temperature
selector.
1
26�02�02�0920
13.1.1 Fault menu
This menu is only shown if there is a fault.
Code Meaning
E1, ELEC The electronic assembly is faulty.
Replace the electronic assembly.
E 3, ntc Check the electrical connection to the outlet sensor. Replace it if
required.
E 4, mot Check the electrical connection to the motorised valve. Replace
it if required.
13.1.2 Control menu
Code Meaning
C 1, 36.5°C Display of the current inlet temperature. If the cold water sensor
is faulty, a temperature of 1.0°C is displayed.
C 2, 47.5°C Display of the current outlet temperature. If the cold water sen-
sor is faulty, a temperature of 65.0°C is displayed.
C 3, 6.8 l/min Display of the current flow rate.
C 4, 21.5kW Display of the current power consumption.
13.1.3 Data menu
Code Meaning
d 1, 8042 Service code for customer support
d 2, 2341 Number of days, on which the appliance is connected to the
power supply.
d 3, 172h Heating time in hours.
d 4, 24kW Maximum output in kW: This output may deviate from the rated
output, e.g. if the mains voltage is not 400V.

18 | PER 18/21/24 www.stiebel-eltron.com
INSTALLATION
Maintenance
13.1.4 Anti-scalding protection menu
Code Meaning
OFF Anti-scalding protection switched off.
ON Anti-scalding protection switched on.
31-60°C Maximum selectable value on appliance when ON
Factory defaults (see chapter "Specification").
After exiting customer service mode, you cannot change the set
maximum temperature via the user interface.
CAUTION Burns If operating with preheated water, the set temperature
limit and anti-scalding protection may be ineffective.
In such cases, limit the temperature with an upstream
central thermostatic valve.
14. Maintenance
WARNING Electrocution Before any work on the appliance, ensure omnipolar dis-
connection from the power supply.
Draining the appliance
The appliance can be drained for maintenance work.
WARNING Burns Hot water may escape when draining the appliance.
 Close the shut-off valve in the twin connector or the cold
water inlet line.
 Open all draw-off valves.
 Undo the water connections on the appliance.
 Store the dismantled appliance in a room free from the risk
of frost, as water residues remaining inside the appliance can
freeze and cause damage.
Cleaning the strainer
26�02�02�0949
If contaminated, clean the strainer in the threaded cold water fit-
ting. Close the shut-off valve in the cold water inlet line before
removing, cleaning and refitting the strainer.
15. Specification
15.1 Dimensions and connections
395
100
485
325
45
5
93
226
190
50
112
190
35
c01
c06
b02
D0000017757
b02 Entry electrical cables I
c01 Cold water inlet Male thread G 1/2 A
c06 DHW outlet Male thread G 1/2 A
Alternative connection options
325
50
50
35
40
b03
b02
b04
b04
b04
D0000019778
b02 Entry electrical cables I
b03 Entry electrical cables II
b04 Entry electrical cables III

www.stiebel-eltron.com PER 18/21/24 | 19
ENGLISH
INSTALLATION
Specication
15.2 Wiring diagrams
3/PE ~ 380-415 V
85�02�02�0005
1 Heater
2 High limit safety cut-out
3 Safety pressure limiter
Priority control with LR 1-A
85�02�02�0003�
2
1
1 Control cable to the contactor of the 2nd appliance (e.g. elec-
tric storage heater).
2 Control contact opens when switching the instantaneous
water heater on.
15.3 Factory settings
Wellness OFF
Automatic water volume
control
OFF/ 80 l
ECO 38°C / 8 l/min
Childproofing OFF/ 43.0°C
Second line of the display l/min
Orientation light OFF
Backlighting blue/ red 100%
15.4 DHW output
The DHW output is subject to the mains voltage, the appliance's
connected load and the cold water inlet temperature. The rated
voltage and rated output can be found on the type plate (see chap-
ter "Troubleshooting").
Connected load in kW 38°C DHW output in l/min.
Rated voltage Cold water inlet temperature
380 V 400 V 415 V 5°C 10°C 15°C 20°C
16.2 7.0 8.3 10.1 12.9
16.3 7.1 8.3 10.1 12.9
18.0 7.8 9.2 11.2 14.3
19.0 8.2 9.7 11.8 15.1
19.4 8.4 9.9 12.0 15.4
21.0 9.1 10.7 13.0 16.7
21.7 9.4 11.1 13.5 17.2
22.6 9.8 11.5 14.0 17.9
23.5 10.2 12.0 14.6 18.7
24.0 10.4 12.2 14.9 19.0
24.4 10.6 12.4 15.2 19.4
25.8 11.2 13.2 16.0 20.5
Connected load in kW 50°C DHW output in l/min.
Rated voltage Cold water inlet temperature
380 V 400 V 415 V 5°C 10°C 15°C 20°C
16.2 5.1 5.8 6.6 7.7
16.3 5.2 5.8 6.7 7.8
18.0 5.7 6.4 7.3 8.6
19.0 6.0 6.8 7.8 9.0
19.4 6.2 6.9 7.9 9.2
21.0 6.7 7.5 8.6 10.0
21.7 6.9 7.8 8.9 10.3
22.6 7.2 8.1 9.2 10.8
23.5 7.5 8.4 9.6 11.2
24.0 7.6 8.6 9.8 11.4
24.4 7.7 8.7 10.0 11.6
25.8 8.2 9.2 10.5 12.3
15.5 Application areas/ conversion table
Specific electrical resistance and specific electrical conductivity (see
chapter "Data table").
Standard specifica-
tion at 15°C 20°C 25 °C
Resist-
ance
ρ≥
Conductivity
σ≤
Resist-
ance
ρ≥
Conductivity
σ≤
Resist-
ance
ρ≥
Conductivity σ ≤
≥ Ωcm mS/m μS/cm ≥ Ωcm mS/m μS/cm ≥ Ωcm mS/m μS/cm
900 111 1111 800 125 1250 735 136 1361
1000 100 1000 890 112 1124 815 123 1227
1100 91 909 970 103 1031 895 112 1117
1200 83 833 1070 93 935 985 102 1015
1300 77 769 1175 85 851 1072 93 933
15.6 Pressure drop
Taps/valves
Tap pressure drop at a flow rate of 10 l/min
Mono lever mixer tap, approx. MPa 0.04 - 0.08
Thermostatic valve, approx. MPa 0.03 - 0.05
Hand shower, approx. MPa 0.03 - 0.15

20 | PER 18/21/24 www.stiebel-eltron.com
INSTALLATION |GUARANTEE |ENVIRONMENT AND RECYCLING
Specication
Sizing the pipework
When calculating the size of the pipework, an appliance pressure
drop of 0.1MPa is recommended.
15.7 Fault conditions
In the event of a fault, loads up to a maximum of 95 °C at a pressure
of 1.2MPa can occur temporarily in the installation.
15.8 Details on energy consumption
The product data complies with EU regulations relating to the Di-
rective on the ecological design of energy related products (ErP).
PER 18/21/24
233990
Manufacturer STIEBEL ELTRON
Load profile S
Energy efficiency class A
Annual power consumption kWh 479
Energy conversion efficiency % 39
Default temperature setting °C 60
Sound power level dB(A) 15
Special information on measur-
ing efficiency
Data at Pmax.
15.9 Data tables
PER 18/21/24
233990
Electrical data
Rated voltage V 380 400 415
Rated output kW 16.2/19/21.7 18/21/24 19.4/22.6/25.8
Rated current A 27.6/29.5/33.3 29/31/35 30.1/32.2/36.3
MCB/fuse rating A 32/32/35 32/32/35 32/32/40
Phases 3/PE
Frequency Hz 50/60 50/60 50/-
Max. mains impedance at 50Hz Ω 0.284 0.270 0.260
Specific resistance ρ15 ≥ (at
ϑcold ≤ 25°C)
Ω cm 900 900 1000
Specific conductivity σ15 ≤ (at
ϑcold ≤25°C)
μS/cm 1111 1111 1000
Specific resistance ρ15 ≥ (at
ϑcold ≤45°C)
Ω cm 1200 1200 1300
Specific conductivity σ15 ≤ (at
ϑcold ≤45°C)
μS/cm 830 830 770
Connections
Water connection G 1/2 A
Application limits
Max. permissible pressure MPa 1
Max. inlet temperature for re-
heating
°C 45
Values
Max. permissible inlet tempe-
rature
°C 60
On l/min >2.5
Flow rate for pressure drop l/min 5.2/6.0/6.9
Pressure drop at flow rate MPa 0.08/0.1/0.13
DHW delivery l/min 9.4/11.0/12.6
Δϑon delivery K 26
Hydraulic data
Nominal capacity l 0.4
Versions
Connected load adjustable X
Temperature setting range °C 30-60
Insulating block Plastic
PER 18/21/24
Heating system heat generator Bare wire
Cover and back panel Plastic
IP rating IP25
Dimensions
Height mm 485
Width mm 226
Depth mm 93
Weights
Weight kg 3.8
Mini FFB
Dimensions (H/W/D) excluding
wall mounting bracket
mm 50/50/17
Radio frequency MHz 868.3
Range inside a building incl. one
separating ceiling
m approx. 25
Temperature setting range °C 30-60
IP rating to EN60529 Shower
Bath
IP X5
IP X7
Battery type CR 2032
Guarantee
The guarantee conditions of our German companies do not
apply to appliances acquired outside of Germany. In countries
where our subsidiaries sell our products a guarantee can only
be issued by those subsidiaries. Such guarantee is only grant
-
ed if the subsidiary has issued its own terms of guarantee. No
other guarantee will be granted.
We shall not provide any guarantee for appliances acquired in
countries where we have no subsidiary to sell our products.
This will not aect warranties issued by any importers.
Environment and recycling
We would ask you to help protect the environment.
After use,
dispose of the various materials in accordance with national
regulations.
GUARANTEE
ENVIRONMENT AND RECYCLING