STIEBEL ELTRON DHX 15 Select User manual

OPERATION AND INSTALLATION
FUNCIONAMIENTO E INSTALACIÓN
Electronically Controlled Electric Tankless Water Heaters
Calentadores de Agua Electrónicos sin Tanque
»DHX15Select
Certified to ANSI/UL Std. 499
Conforms to CAN/CSA Std. C22.2 No. 64
Certificación ANSI/UL Std. 499
Conforme a CAN/CSA Std. C22.2 No.64
Tested and certified by WQA to NSF/ANSI372
for lead free compliance.
Probado y certificado por WQA NSF/ANSI 372 para
el cumplimiento de las regulaciones sin plomo.

2| DHX 15 Select www.stiebel-eltron-usa.com
CONTENTS
QUICK START GUIDE
SPECIAL INFORMATION
OPERATION
1. General information ___________________________________________ 5
1.1 Safety instructions__________________________________________________ 5
1.2 Other symbols in this documentation __________________________ 5
1.3 Units of measurement _____________________________________________ 5
2. Safety____________________________________________________________ 5
2.1 Intended use_________________________________________________________ 5
2.2 General safety instructions _______________________________________ 5
2.3 Test symbols _________________________________________________________ 6
2.4 Licenses / certificates ______________________________________________ 6
3. Register your product _________________________________________ 6
4. Water heater description______________________________________ 7
5. Settings and displays __________________________________________ 7
5.1 DHX Select user interface_________________________________________ 7
5.2 Using the display menus __________________________________________ 8
5.3 DHX Select display__________________________________________________ 8
5.4 Recommended settings ___________________________________________ 9
6. Cleaning, care and maintenance _____________________________ 9
7. Troubleshooting _______________________________________________10
INSTALLATION
8. Safety___________________________________________________________10
8.1 General safety instructions ______________________________________10
8.2 Instructions, standards and regulations ______________________10
9. Water heater description_____________________________________10
9.1 Standard delivery__________________________________________________10
10. Preparation ____________________________________________________11
10.1 Installation site_____________________________________________________11
10.2 Minimum clearances______________________________________________11
11. Installation_____________________________________________________11
11.1 Standard wall-mounted installation___________________________11
11.2 Water connections_________________________________________________12
11.3 Electrical connection______________________________________________13
11.4 Electrical connection with short power cable _______________13
11.5 Wiring block ________________________________________________________14
12. Commissioning ________________________________________________14
12.1 Internal anti-scalding protection via jumper slot ___________14
12.2 Initial start-up______________________________________________________14
12.3 Operation with preheated water _______________________________15
12.4 Recommissioning__________________________________________________15
13. Water heater shutdown ______________________________________15
14. Service information ___________________________________________15
15. Maintenance ___________________________________________________16
15.1 Draining the water heater _______________________________________16
15.2 Cleaning the filter screen ________________________________________16
16. Troubleshooting _______________________________________________ 17
17. Specification ___________________________________________________18
17.1 Dimensions and connections____________________________________18
17.2 Wiring diagram ____________________________________________________18
17.3 Hot water output___________________________________________________18
17.4 Application areas/conversion table ____________________________19
17.5 Fault conditions ____________________________________________________19
17.6 Data table ___________________________________________________________19
18. Spare parts ____________________________________________________20
19. Warranty _______________________________________________________21

QUICK START GUIDE
ENGLISH
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QUICK START GUIDE
Before turning on power to the water heater, you MUST flush all air out of the
system, then engage the AE3 safety switch. The unit will NOT operate until
the AE3 safety switch has been engaged.
1 Mount the unit to the wall (see section 11.1, “Standard wall-mounted installation”, pg. 11).
2 Hook up water connections (see section 11.2, “Water connections”, pg. 12).
3 Hook up electrical connections, but keep circuit breaker off. (See section 11.3, “Electrical connec-
tion”, pg. 13)
PLQ
12
D0000053277
4 Open and close all connected draw-off valves at least 5 times, for at least 3 minutes total,
until all air has been purged from the pipework and the water heater.
5 Ensure there are no water leaks from any plumbing connections.
D0000094561-b
6 Engage the AE3 safety switch by firmly pressing the white reset button until it clicks and fully
locks in place (the water heater is delivered with the safety switch disengaged).
7 Turn on power to the water heater at the circuit breaker in the breaker panel.

SPECIAL INFORMATION
4| DHX 15 Select www.stiebel-eltron-usa.com
SPECIAL INFORMATION
- Read this entire manual. Failure to follow all the
guides, instructions and rules could cause personal
injury or property damage. Improper installation, ad-
justment, alteration, service and use of this unit can
result in serious injury.
- This unit must be installed by a licensed electrician
and plumber. The installation must comply with all
national, state and local plumbing and electric codes.
Proper installation is the responsibility of the install-
er. Failure to comply with the installation and operat-
ing instructions or improper use voids the warranty.
- Save these instructions for future reference. The
installer should leave these instructions with the
consumer.
- If you have any questions regarding the installation,
use or operation of this water heater, or if you need
any additional installation manuals, please call our
technical service line at 800.582.8423 (USA and Can-
ada only). If you are calling from outside the USA or
Canada, please call USA 413.247.3380 and we will
refer you to a qualified Stiebel Eltron service repre-
sentative in your area.
- The water heater is suitable for supplying a shower in
many climates (shower operation). If the water heater
is also or exclusively used for shower operation, the
qualified contractor must adjust the temperature set-
ting range to 122°F (50°C) or less using the internal
anti-scalding protection on the water heater. When
using preheated water, it must be ensured that the
inlet temperature does not exceed 131°F (55 °C).
- Ensure the water heater can be separated from the
power supply by a circuit breaker that disconnects all
poles with at least 1/8˝ (3mm) contact separation.
- The specified voltage must match the power supply.
See the type plate on the right-hand side of the water
heater for full information.
- CAUTION: DO NOT INSTALL IN A BATH ENCLOSURE OR
SHOWER STALL.
DO NOT CONNECT TO A SALT-REGENERATED WATER
SOFTENER OR A SALT-WATER WATER SUPPLY.
FOR USE ON AN INDIVIDUAL BRANCH CIRCUIT ONLY.
CAUTION: CONNECT ONLY TO A CIRCUIT PROTECTED
BY A CLASS A GROUND FAULT INTERRUPTER
USE BONDING CONDUCTOR IN ACCORDANCE WITH
THE CANADIAN ELECTRICAL CODE, PART I
- The water heater must be properly grounded. See
section 17.2, “Wiring diagram,” pg. 18.
- The water heater must be permanently connected to
fixed wiring. For use on an individual branch circuit
only. See section 17.2, “Wiring diagram,” pg. 18.
- Secure the water heater as described in chapter 11,
“Installation”, pg. 11.
- Observe the minimum permissible water supply
pressure of 26.1 psi (1.8 bar). See section 17.6, “Data
table,” pg. 19.
- Observe the maximum permissible water supply
pressure of 145 psi (10 bar). See section 17.6, “Data
table,” pg. 19.
- Drain the water heater as described in section 15.1,
“Draining the water heater”, pg. 16.

OPERATION
General information
ENGLISH
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OPERATION
1. General information
The chapters "Special information" and "Operation" are intended for
both users and qualified contractors.
The chapter "Installation" is intended for qualified contractors.
Note
Read these instructions carefully before using the water
heater and retain them for future reference.
Pass on the instructions to a new user if required.
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.
f 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.
f Read these texts carefully.
Symbol Meaning
Material losses
(water heater damage, material losses, and installation site
damage)
f 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 inches (millimeters) unless
otherwise stated.
2. Safety
2.1 Intended use
This water heater is suitable for heating domestic hot water or for
reheating preheated water. The water heater can supply one or
more draw-off points.
Water will not be reheated if the maximum inlet temperature for
reheating is exceeded.
The water heater is intended for domestic use. It can be used safely
by untrained persons. The water heater can also be used in non-do-
mestic environments, e.g. in small businesses, as long as it is used
in the same way.
Any other use beyond that described shall be deemed inappropriate.
Observation of these instructions and of the instructions for any
accessories used is also part of the correct use of this water heater.
2.2 General safety instructions
DANGER: Burns
Water temperatures over 125 °F (52°C) can cause severe
burns instantly or death from scalding. A hot water scald-
ing potential exists if the thermostat on the water heater
is set too high. Households with small children, disabled
or elderly persons may require that the thermostat be set
at 113°F (45 °C) or lower to prevent possible injury from
hot water.
CAUTION: Burns
If operating with preheated water, e.g.from a solar ther-
mal system, the DHW temperature may vary from the
selected set temperature.
!
!

OPERATION
Register your product
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CAUTION: Burns
During operation, the tap can reach temperatures up to
149°F (65°C).
There is a risk of scalding at outlet temperatures in excess
of 110°F (43 °C).
!
DANGER: Injury
Please read and follow these instructions. Failure to follow
these instructions could result in serious personal injury
or death.
!
CAUTION: DO NOT INSTALL IN A BATH ENCLOSURE
OR SHOWER STALL. DO NOT CONNECT TO A
SALT-REGENERATED WATER SOFTENER OR A WATER
SUPPLY OF SALT WATER.
FOR USE ON AN INDIVIDUAL BRANCH CIRCUIT ONLY.
CAUTION: CONNECT ONLY TO A CIRCUIT PROTECTED BY A
CLASS A GROUND FAULT INTERRUPTER
USE BONDING CONDUCTOR IN ACCORDANCE WITH THE CA-
NADIAN ELECTRICAL CODE, PART I
DANGER: Electrocution
Before proceeding with any installation, adjustment,
alteration, or service of this appliance, all circuit break-
ers and disconnect switches servicing the appliance
must be turned off. Failure to do so could result in seri-
ous personal injury or death.
DANGER: Electrocution
Never remove the water heater’s cover unless the elec-
tricity servicing the water heater is turned off. Failure to
do so could result in personal injury or death.
WARNING Electrocution
The connection to the power supply is only permissible as
a permanent connection in conjunction with a ¾˝Romex
clamp. Ensure the water heater can be separated from
the power supply by an isolator that disconnects all poles
with at least 1/8˝(3mm) contact separation.
!
WARNING: Injury
Where children or persons with limited physical, sensory
or mental capabilities are to be allowed to control this
water heater, ensure that this will only happen under su-
pervision or after appropriate instructions by a person re-
sponsible for their safety. Children should be supervised to
ensure that they never play with the water heater.
!
DAMAGE TO THE WATER HEATER AND THE ENVIRON-
MENT:
The water heater must be installed by a licensed electrician
and plumber. The installation must comply with all nation-
al, state and local plumbing and electric codes.
Service of the water heater must be performed by qualified
service technicians.
!
DAMAGE TO THE WATER HEATER AND THE ENVIRON-
MENT:
Supply this appliance only from a grounded system. A
green terminal (or a wire connector marked “G”, “GR”,
“GROUND”, OR “GROUNDING”) is provided for wiring the
appliance. To reduce the risk of electric shock, connect
this terminal or connector to the grounding terminal of the
electric service or supply panel with a continuous copper
wire in accordance with the electrical installation code.
Where children or persons with limited physical, sensory or mental
abilities are allowed to use this water heater, we recommend a
permanent temperature limit. The following limitation options are
available:
- DHX Select - user adjustable: Temperature limit (childproofing)
- Qualified contractor adjustable: “Internal anti-scalding
protection”
!
Material losses
The user should protect the water heater against frost.
2.3 Test symbols
See type plate on the water heater.
2.4 Licenses / certificates
- UL (USA) Std. 499
- CSA (Canada) Std. C22.2 No. 64
3. Register your product
You must register this product within 90 days of pur-
chase on our web site in order to activate the standard
warranty. Go to our web site at
www.stiebel-eltron-usa.com and click on “Register
Your Product.”
Before beginning the registration process, we suggest that you
gather the necessary information which will be as follows:
Type, Example: DHX 15 Select (from the label that is on the unit)
Number listed after “Nr.”
Place of Purchase
Purchase Date
First & Last Name
Email address
Physical Address
Phone Number
Installation Date
If you have any questions concerning the registration pro-
cess or warranty, please contact Stiebel Eltron USA directly at
800.582.8423.

OPERATION
Water heater description
ENGLISH
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4. Water heater description
The water heater switches on automatically as soon as a hot water
valve at a tap or other draw-off point is opened. DHX heats water as
it flows through the unit. When the tap is closed, the water heater
switches off automatically.
From the activation flow rate, the electronic control unit controls the
correct heating output using only the minimum amount of power
necessary, subject to the temperature selected, the current incoming
cold water temperature, and the flow rate.
DHX Select models are electronically controlled tankless water heat-
ers, and maintain a consistent outlet temperature. This is irrespec-
tive of the inlet water temperature, up to the maximum output of
the water heater.
DHX Select models feature Advance Flow Control™, a technology
patented by Stiebel Eltron in Germany (patent no. DE 3805441 C2).
When the maximum output of a DHX Select model is met, rather
than deviate from the setpoint temperature and deliver cooler water,
DHX Select models use an electronically-controlled motorized valve
to slightly reduce the flow of water only as much as is necessary
to maintain the user-selected temperature. When the demand can
again be fully met, the motorized valve returns to the fully open posi-
tion, allowing the full flow rate. This ensures uninterrupted comfort,
and hot water delivered at the desired temperature at all times.
If the water heater is operated with preheated water, and the inlet
temperature exceeds the selected set temperature, the inlet tem-
perature will be displayed on the second row of the screen and will
flash. The water is not heated further.
DHX Select models are equipped with functions to permanently limit
the temperature (childproofing).
DHX Select models feature a backlit display that switches on auto-
matically as soon as water flows through the unit, or if a change is
made at the user interface. The backlight switches off automatically
if no changes are made for 30seconds, or 5seconds after hot water
stops being drawn.
DHX Select models allow the user to save different preset tempera-
tures and apply them quickly.
Domestic Hot Water (DHW) temperature
The DHW outlet temperature can be variably adjusted from 68–140°F
(20–60°C). The selected temperature is displayed.
Heating system
The Direct Coil™heating system is comprised of a pressure-tested,
glass-reinforced polyamide heating chamber with a nichrome wire
direct heating coil. It is suitable for hard and soft water areas and
is largely insusceptible to scale build-up. The Direct Coil™heating
system ensures rapid and efficient DHW production.
Note
The water heater is equipped with an air detector that
largely prevents damage to the heating system. If, during
operation, air is drawn into the water heater, the water
heater shuts down the heating output for one minute to
protect the heating system.
5. Settings and displays
5.1 DHX Select user interface
3
2
4
7
5
6
1
1 Backlit display
2 Temperature memory keys
3 Operating LED (flashes when output limit is reached)
4 Control knob
5 Main display | info display | parameter display
6 Segment display [10–100%]
7“T
max” button
5.1.1 DHX Select display overview
1
2
3
4
5
1Digitdisplay
2 Power capacity status
3T
max indicator
4 Temperature unit indicator
5 Display-lock indicator

OPERATION
Settings and displays
8| DHX 15 Select www.stiebel-eltron-usa.com
5.2 Using the display menus
The DHX Select features an interactive display that allow for user
customization to increase the level of comfort for the user.
The menu structure is designed in an intuitive, linear way to make
it as navigable as possible.
5.2.1 DHX Select user input
User input
Tmax button (pressing or holding this button
performs different functions)
Preset 1 button (pressing or holding this button
performs different functions)
Preset 2 button (pressing or holding this button
performs different functions)
Control knob (turn knob to change settings)
5.3 DHX Select display
The DHX Select display features a temperature and power capacity
display. The display is backlit and will illuminate whenever user
input is detected. The backlight will time out and deactivate if no
user input has been detected for 30 seconds.
For the name of each display element on the DHX Select, consult
section 5.1.1, “DHX Select display overview”, pg. 7.
5.3.1 Base display
The base display shows the current temperature setpoint in your
preferred temperature unit. The bar below the temperature shows
the current operating capacity. As the hot water demand fluctuates,
the power capacity status will change to show between 0 and 10
segments. The display below shows that the water heater is oper-
ating at 40% of full capacity.
All other menu displays will revert back to the base display either
after a 15-second period of time without user input, or after a 5-sec-
ond hold of the Tmax button.
Changing the setpoint temperature
Temperature settings
Range Increment Range Increment
68–140°F 1°F 20–60°C. 0.5°C
The setpoint temperature can be set between 68 °F (20°C) and 140°F
(60 °C).
The setpoint can be increased by turning the control knob clockwise,
and decreased by turning it counter-clockwise. The water heater
can be deactivated while still powered by turning the control knob
counter-clockwise, past the 68 °F (20 °C) setting.
5.3.2 Parameters menu
While at the base display, holding the Tmax button for 5 seconds will
advance the display to the first parameter menu.
Tmax parameter setting
The first parameter menu sets the value for Tmax. The value of Tmax
acts as a high temperature limiter. If the Tmax value is set, the set-
point of the water heater cannot be set above the Tmax value. This
feature is useful in scenarios where scalding from hot water is a
concern.
At the Tmax setting menu, the display will flash, indicating that the
value can be changed by rotating the control knob. The Tmax value
can be increased by turning the control knob clockwise, and de-
creased by turning it counter-clockwise. The Tmax value can be de-
activated by turning the control knob counter-clockwise, past the
68 °F (20 °C) setting. The display will read “Off” if Tmax is inactive.
If the Tmax symbol is visible at the base display, then the Tmax func-
tion is active and is limiting the maximum allowable temperature
to the preset level.
Pressing the Tmax button once while at this display will move the
display onto the temperature units parameter setting.

OPERATION
Cleaning, care and maintenance
ENGLISH
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Temperature units parameter setting
The DHX Select is capable of displaying temperature in either Fahr-
enheit or Celsius.
The current unit will be shown and the display will be flashing to
indicate that the value can be changed. Rotate the control knob to
change the value between Fahrenheit and Celsius.
Pressing the Tmax button once while at this display will move the
display onto the display-lock parameter setting.
Display-lock parameter setting
The display can be locked to prevent changes to the temperature set-
point. This menu will flash, indicating that the value can be changed
by rotating the control knob. While the display shows “Off”, the lock
is not active. The lock is active when it reads “On”.
If the display-lock parameter is set to “On” and the user either holds
the Tmax button for 5 seconds or lets the display time out for 15
seconds, the display-lock will become active.
If the display-lock is active, a lock symbol will appear on the base
display, and no parameters can be changed. In order to disable the
lock, hold the Tmax button for 12 seconds. The lock will disappear
from the display and all parameters can be changed again.
Pressing the Tmax button once while at the display-lock parameter
setting menu will move the display back onto Tmax parameter setting
menu.
5.3.3 Returning to the base display
While navigating the display and on any menu other than the base
display, holding the Tmax button for 5 seconds will return the display
to the base display. Additionally, the display will revert to the base
display after a 15-second period with no user input.
5.4 Recommended settings
Your electric tankless water heater offers maximum precision and
convenience for DHW production. Should you nonetheless operate
the water heater with a thermostatic valve, we recommend that you:
f Adjust the set temperature on the water heater to over 122 °F
(50°C). Then set the required set temperature on the thermo-
static valve.
Saving energy
The following recommended settings will result in the lowest energy
consumption:
- 100 °F (38 °C) for hand washbasins, showers, bath
- 131°F (55°C) for kitchen sinks
Internal anti-scalding protection (qualified contractors)
If required, the qualified contractor can set a permanent tempera-
ture limit, for example in nurseries, hospitals,etc., see section 12.1,
“Internal anti-scalding protection via jumper slot”, pg. 14.
Recommended setting for operation with a thermostatic valve
and water preheated by solar energy
f Set the temperature at the water heater to the maximum
temperature.
Following an interruption to the water supply
!
Material losses
To ensure that the Direct Coil™heating system is not dam-
aged following an interruption to the water supply, the
water heater must be restarted by taking the following
steps:
f Check the supply pressure. The reading on the gauge
should read more than 26.1psi, but not more than
145psi.
f Disconnect the water heater from the power supply by
turning off the connected circuit breaker.
f Open and close all connected draw-off valves at least 5
times, for at least 3 minutes total, until all air has been
purged from the pipework and the water heater.
f Switch the power back at the circuit breaker back ON.
6. Cleaning, care and maintenance
f Never use abrasive or corrosive cleaning agents. A damp cloth
is sufficient for cleaning the water heater.
f Check the taps regularly. Limescale deposits at the tap outlets
can be removed using commercially available descaling agents.

INSTALLATION
Troubleshooting
10 | DHX 15 Select www.stiebel-eltron-usa.com
7. Troubleshooting
Problem Cause Solution
The water heater will not
start despite the DHW
valve being fully open
There is no power Check to ensure circuit
breaker in breaker panel
hasn’t tripped. Reset if
necessary
The white AE3 safety
switch has not been en-
gaged during initial start-
up. Activate if necessary
(see section 12.2.1, “Initial
AE3 safety switch activa-
tion”, pg. 14). If the AE3
switch has tripped after
initial installation, contact
a qualified contractor to
fix the cause
The aerator in the tap or
the shower head is scaled
up or dirty
Clean and/or descale the
aerator or shower head
The water supply has
been interrupted
Vent the water heater and
the cold water inlet line
When hot water is being
drawn off, cold water
flows for a short period
The air detector detects
air in the water. It switch-
es off the heating output
briefly
The water heater restarts
automatically after 1min-
ute
Boiling noises are heard
during operation
The water heater has not
been vented
Vent the water heater (see
section 12.2, “Initial start-
up”, pg. 14)
The supply pressure is
too low
Ensure that the minimum
supply pressure of 26.1
psi is met, and that max
pressure doesn’t exceed
145 psi (see section 17.6,
“Data table”, pg. 19)
The required temperature
cannot be set
Internal anti-scalding pro-
tection is active
The internal anti-scalding
protection can only be
adjusted by qualified con-
tractors
If you cannot solve the problem, contact your qualified contractor.
To facilitate and speed up your inquiry, please provide the serial
number from the type plate (000000-0000-000000). For live technical
assistance, please contact us at 800.582.8423. Alternatively, you may
email us at [e-mail]
Nr.: 000000-0000-00000
D0000094552-b
INSTALLATION
8. Safety
Only a qualified contractor should carry out installation, commis-
sioning, maintenance and repair of the water heater.
8.1 General safety instructions
We guarantee trouble-free function and operational reliability only
if original accessories and spare parts intended for the water heater
are used.
!
Material losses
Observe the maximum inlet temperature. Higher tempera-
tures may damage the water heater. You can limit the max-
imum inlet temperature by installing a central thermostatic
valve.
WARNING Electrocution
This water heater contains capacitors which are discharged
when disconnected from the power supply. The capacitor
discharge voltage may briefly exceed60VDC.
8.2 Instructions, standards and regulations
Note
Observe all applicable national and regional regulations
and instructions.
- The electrical resistivity of the water must not fall below that
stated on the type plate. In a linked water network, factor in
the lowest electrical resistivity of the water. Your water supply
utility will advise you of the electrical resistivity or conductivity
of the water in your area.
9. Water heater description
9.1 Standard delivery
The following are delivered with the water heater:
- Filter screen, factory installed in cold water inlet
- Jumper for anti-scalding protection, attached
- Jumper, spare, attached
- 2 x mounting screws
- 2 x wall anchors

INSTALLATION
Preparation
ENGLISH
www.stiebel-eltron-usa.com DHX 15 Select | 11
10. Preparation
10.1 Installation site
!Material losses
Install the water heater in a room that is free from the risk
of frost.
fInstall DHX in a frost free area. If frost may occur, remove the
unit before freezing temperatures set in.
fAlways install the water heater vertically with plumbing fittings
pointing downward. Install the water heater near the draw-off
point to minimize pipe runs and thermal losses.
fTaps: Do not use open vented or non-pressurized taps.
The water heater is suitable for under-sink and over-sink installa-
tion.
Typical under-sink installation
D0000089950-a
6
5
13
2
7
4
1 Electrical junction box
2 ½˝ water supply line for faucet installation
3 Shut-off valve
4 Cold water supply
5 Sink
6 Cold valve (right)
7 Hot valve (left)
Note
fInstall the water heater flush to the wall. The wall
must have sufficient load bearing capacity.
10.2 Minimum clearances
Ý
Ý
Ý
Ý
D0000079442
fMaintain the minimum clearances to ensure trouble-free oper-
ation of the water heater and facilitate maintenance work.
11. Installation
Factory default settings All DHX Models
Internal temperature limit 140 °F (60 °C)
11.1 Standard wall-mounted installation
11.1.1 Preparing the power cable
4Ǭ–5ǩÝ (125–130 mm)
D0000094559-b
fPrepare the power cable.
11.1.2 Mounting instructions
fInstall DHX as close as possible to the hot water draw-off point,
for example, directly underneath the sink.
fInstall DHX in a frost free area. If frost may occur, remove unit
before freezing temperatures set in.
fObserve minimum clearances on all sides to ensure unob-
structed servicing if necessary.
fRemove plastic cover by loosening the screw on the bottom.
Lift cover off from the bottom.
D0000094555-b
fMark the 2drill holes, referencing their position using the
water heater rear panel as a guide.
fSet water heater rear panel aside and drill the 2 marked holes.

INSTALLATION
Installation
12 | DHX 15 Select www.stiebel-eltron-usa.com
f Install wall anchors in the wall, then insert and tighten each
mounting screw partially. Screws and plastic wall anchors for
mounting on drywall or wood are provided.
f Hang the unit on the 2 mounting screws, ensuring the rear of
the unit is flush against the wall.
f Once the unit is in position, mount the unit securely to the wall
by fully tightening the 2 mounting screws.
D0000089951-a
11.2 Water connections
!
CAUTION: DO NOT INSTALL IN A BATH ENCLOSURE OR
SHOWER STALL OR CONNECT TO A SALT-REGENERATED
WATER SOFTENER OR A WATER SUPPLY OF SALT
WATER
FOR USE ON AN INDIVIDUAL BRANCH CIRCUIT ONLY
CAUTION: CONNECT ONLY TO A CIRCUIT PROTECTED BY A
CLASS A GROUND FAULT CIRCUIT INTERRUPTER
USE COPPER CONDUCTORS ONLY
USE BONDING CONDUCTOR IN ACCORDANCE WITH THE
CANADIAN ELECTRICAL CODE, PART I
!
Material losses
Carry out all water connection and installation work in
accordance with regulations.
!
Material losses
Excessive heat from soldering on copper pipes near the
DHX may cause damage to the unit or the plastic filter
screen located in the cold water inlet.
NOTICE
The cold water connection to the unit MUST be discon-
nected periodically in order to clean the filter screen.
It is required to use water connections that are easily
detachable such as braided steel flex connectors.
NOTICE
Hard water or water with a high mineral count may dam-
age the unit. Damage to the unit caused by scale or a high
mineral count is not covered under the warranty.
NOTICE
Tankless water heaters such as the DHX Select are not
required to be equipped with a temperature and pressure
relief valve (T&P). If the local inspector will not pass the
installation without a T&P, it should be installed on the
hot water outlet side of the unit.
11.2.1 Permissible water connection materials
f The DHX’s hot water outlet (left) is designed for connection to
copper tubing, PEX tubing or a braided stainless steel hose
with a ½˝ NPT female tapered thread.
f The plumbing on the cold water inlet side (right) needs to be
such that it can easily be removed to allow access to the inlet
filter screen. The easiest way to achieve this is to use a braided
steel flex connector with a ½˝ female NPT connection.
!
Material losses
If plastic pipework systems are used, take into account the
maximum inlet temperature and the maximum permissible
pressure.
11.2.2 Flow rate
f Ensure that the minimum activation flow rate for switching on
the water heater is met: 0.264 gal (1.0 l/min).
f If the required minimum activation flow rate is not met when
the draw-off valve is fully opened, increase the water line pres-
sure. Minimum supply pressure is 26.1 psi (1.8 bar).
11.2.3 Water connection instructions
!
Material losses
If soldering near the unit is necessary, please direct the
flame away from the housing of the unit in order to avoid
damage. Note that excessive heat from soldering (not rec-
ommended) near the cold water inlet fitting may damage
the plastic filter screen located inside it.
All plumbing work must comply with national and applicable state
and local plumbing codes.
Cold water connection (inlet) is on the right side of the unit, hot
water connection (outlet) is on the left side of unit.
f A pressure reducing valve must be installed if the cold water
supply pressure exceeds 150 psi (10 bar).
f Make certain that the cold water supply line has been flushed
to remove any scale and dirt.
f Install shut-off valve in cold water line as shown in the illus-
tration on page 14. This allows the unit to be easily isolated for
maintenance purposes.

INSTALLATION
Installation
ENGLISH
www.stiebel-eltron-usa.com DHX 15 Select | 13
D0000094555-b
f Connected braided steel flex connectors (recommended for hot
outlet, required for cold inlet, not supplied) to the twin ½˝ NPT
male connectors.
f Open the shut-off valve in the cold water inlet line.
When all plumbing work is completed, check for leaks and take
corrective action before proceeding.
11.3 Electrical connection
WARNING: Electrocution
Before beginning any work on the electric installation,
be sure that main breaker panel switches are “Off” to
avoid any danger of electric shock. All mounting and
plumbing must be completed before proceeding with
electrical hook-up.
The unit must be properly grounded in accordance with
state and local codes, or in absence of such codes, in
accordance with national electric code or the Canadian
electric code. Failure to electrically ground the product
could result in serious personal injury or death.
!
CAUTION: DO NOT INSTALL IN A BATH ENCLOSURE
OR SHOWER STALL. DO NOT CONNECT TO A
SALT-REGENERATED WATER SOFTENER OR A WATER
SUPPLY OF SALT WATER.
FOR USE ON AN INDIVIDUAL BRANCH CIRCUIT ONLY.
CAUTION: CONNECT ONLY TO A CIRCUIT PROTECTED BY A
CLASS A GROUND FAULT INTERRUPTER
USE BONDING CONDUCTOR IN ACCORDANCE WITH THE CA-
NADIAN ELECTRICAL CODE, PART I
WARNING Electrocution
The connection to the power supply is only permissible as
a permanent connection in conjunction with a ¾˝Romex
clamp. Ensure the water heater can be separated from
the power supply by an isolator that disconnects all poles
with at least 1/8˝(3mm) contact separation.
!Supply this appliance only from a grounded system. A
green terminal (or a wire connector marked “G”, “GR”,
“GROUND”, OR “GROUNDING”) is provided for wiring the
appliance. To reduce the risk of electric shock, connect
this terminal or connector to the grounding terminal of
the electric service or supply panel with a continuous
copper wire in accordance with the electrical installation
code.
!
Material losses
Observe the type plate. The specified rated voltage must
match the supply line voltage.
f All electrical work must comply with national and applicable
state and local electrical codes.
f The DHX should be connected to a properly grounded dedicat-
ed branch circuit of proper voltage rating. In installations with
several DHX units, each unit requires an independent circuit.
Please refer to the technical data table for the correct wire and
circuit breaker size.
f A 3/4˝ Romex clamp (required, not supplied) should be in-
stalled in the opening located between the hot and cold water
connections. The wire should be fed through the Romex clamp.
The “live” wires must be connected to the slots on the terminal
block marked L and L. The ground wire must be connected
to the slot marked with the ground symbol. See section 17.2,
“Wiring diagram,” pg. 18.
4Ǭ–5ǩÝ (125–130 mm)
D0000089948-a
11.4 Electrical connection with short power cable
If the power cable is not quite long enough, you can install the wiring
block closer to the aperture in the water heater.
f Reposition the wiring block from the top to the bottom. To do
so, unclip the wiring block by pushing it firmly to the left and
pulling it forwards.

INSTALLATION
Commissioning
14 | DHX 15 Select www.stiebel-eltron-usa.com
D0000095302-b
fClip the wiring block in at the bottom by pushing it inwards and
to the left until it clicks into place.
11.5 Wiring block
Consult the chart below for the recommended torque amounts on
the wiring block screws.
Screw Size (mm) Min. Torque (N•cm) Min. Torque (lbf•in)
M6 200-250 17.7–22.1
Using the proper torque specifications to secure wire to the wiring
block helps to avoid personal loss or property damage.
12. Commissioning
12.1 Internal anti-scalding protection via jumper slot
For increased safety, the qualified contractor can set an internal an-
ti-scalding temperature limit via the “Tmax” jumper. The anti-scald-
ing protection feature limits the maximum output temperature of
the water heater. This feature overrides the temperature adjust-
ment display on the front cover (both the temperature selection
and temperature limit via software functions). A user can still make
temperature adjustments below the anti-scalding limit using the
display, however, any temperature selected that is higher than the
Tmax limit set will be ignored, and the output temperature will be
limited to the Tmax value.
38°C | 100°F
43°C | 109°F
50°C | 122°F
60°C | 140°F
D0000094558-b
Jumper position Description
38 °C | 100 °F Code-compliant hand washing applications
43°C | 109°F Applications where risk of scalding may be a
concern
50 °C | 122 °F DHW for kitchen sink, utility sink, etc.
60 °C | 140 °F Full 68–140°F (20–60 °C) temperature range
[factory default setting ]
No jumper Limit 38 °C | 100 °F
fInstall the jumper in the required position on the “Tmax” pin
strip.
CAUTION Burns
If the water supplied to the water heater is preheated, the
internal anti-scalding protection and the user-adjustable
temperature limit may be exceeded.
In such cases, limit the temperature with an upstream
central thermostatic valve.
12.2 Initial start-up
Note
During initial start-up, you MUST engage the AE3 safety
switch by depressing the white reset button before supply-
ing power to the water heater. The unit will NOT operate
until the safety switch has been engaged.
PLQ
12
D0000053277
fOpen and close all connected draw-off valves at least five times
total. Let water run for at least three minutes, until all air has
been purged from the pipework and the water heater.
fEnsure there are no water leaks from any plumbing
connections.
12.2.1 Initial AE3 safety switch activation
D0000094561-b
fEngage the AE3 safety switch by firmly pressing the white reset
button until it clicks and fully locks in place (the water heater is
delivered with the safety switch disengaged).

INSTALLATION
Water heater shutdown
ENGLISH
www.stiebel-eltron-usa.com DHX 15 Select | 15
D0000082937
fConnect the display unit connecting cable plug to the PCB.
Note
It is essential to plug the connecting cable from the display
unit into the PCB before switching on the power. Otherwise,
the display will not function.
D0000073642
fHook the water heater cover into the water heater back panel
at the top rear. Pivot the cover downwards. Check that the cover
is securely seated at both top and bottom.
fSecure the cover with the screw.
fRemove the protective film from the front panel.
D0000053281
fSwitch on the power supply.
fEnsure the display is functioning correctly.
12.2.2 Water heater handover
fExplain the water heater functions to users, and familiarize
them with how it works.
fMake the user aware of potential dangers, especially the risk of
scalding.
fHand over the instructions.
12.3 Operation with preheated water
The maximum inlet temperature may be limited by installing a
central thermostatic valve. Use the thermostatic valve for central
premixing, for example when operating an tankless water heater
with preheated water. For use in shower operation, the valve must
be set to a maximum of 131°F (55°C).
12.4 Recommissioning
!Material losses
To ensure that the Direct Coil™heating system is not dam-
aged following an interruption to the water supply, the
water heater must be restarted by taking the following
steps:
fCheck the supply pressure. The reading on the gauge
should read more than 26.1psi, but not more than
145psi.
fDisconnect the water heater from the power supply by
turning the connected circuit breaker.
fOpen and close all connected draw-off valves at least 5
times, for at least 3 minutes total, until all air has been
purged from the pipework and the water heater.
fSwitch the power back ON.
13. Water heater shutdown
fTurn the connected circuit breaker too the “Off” position.
fTo avoid electric shock, make sure that nobody can activate
the circuit breaker during the entire time service work is being
performed.
fDrain the water heater (See section 15.1, “Draining the water
heater,” pg. 16").
14. Service information
Connection overview/component overview
1
2
3
5
6
7
4
D0000095301-a
1 Motorized valve
2Flowsensor
3 High limit safety cut-out, automatic reset, klixon
4NTCsensor
5 Pin strips for connected load and anti-scalding protection
6 Display plug-in position
7 Diagnostic traffic lights

INSTALLATION
Maintenance
16 | DHX 15 Select www.stiebel-eltron-usa.com
15. Maintenance
WARNING Electrocution
Before beginning any work on the water heater, be sure
that main breaker panel switches are “Off” to avoid any
danger of electric shock.
15.1 Draining the water heater
The water heater can be drained for maintenance work.
WARNING Burns
Hot water may escape when you drain the water heater.
f Close the shut-off valve in the cold water inlet line.
f Open all draw-off valves.
f Undo the water connections on the water heater.
f Store the dismantled water heater free from the risk of frost,
as water residues remaining inside the water heater can freeze
and cause damage.
15.2 Cleaning the filter screen
WARNING Burns
Hot water may escape when you drain the appliance.
!
Material losses
To ensure that the Direct Coil™heating system is not dam-
aged following an interruption to the water supply, the
water heater must be restarted by taking the following
steps:
f Check the supply pressure. The reading on the
gauge should read more than 26.1psi, but not more
than 145psi.
f Shut off power to the unit at the breaker panel by
making sure that connected circuit breakers are
“OFF” to avoid any danger of electric shock.
f Open and close all connected draw-off valves at
least 5 times, for at least 3 minutes total, until all air
has been purged from the pipework and the water
heater.
f Switch the power back ON at the breaker panel.
The DHX has a built in sediment filter screen that should be cleaned
periodically:
f Turn off power to the water heater at the circuit breaker.
f Turn off the water supply to the water heater at the shut-off
valve.
f Open a connected hot water tap to relieve built-up pressure
(this will minimize leakage when removing the connection from
the cold water inlet).
f Disconnect the braided steel flex connector from the cold water
inlet fitting (right).
f To remove the filter screen from the bottom of the cold water
inlet, carefully insert a flathead screwdriver just above the
plastic lip of the filter screen, and gently pull downward.
f Clean the filter screen, re-insert securely into the cold water
inlet fitting, and reconnect the braid steel flex connector to the
cold water inlet.
f Open the cold water supply shut-off valve.
f Vent the air from pipes and the water heater by opening and
closing all connected draw-off valves at least 5 times, for at
least 3 minutes total, until all air has been purged from the
pipework and the water heater.
f Turn on circuit breaker to bring electrical power to the unit.

INSTALLATION
Troubleshooting
ENGLISH
www.stiebel-eltron-usa.com DHX 15 Select | 17
16. Troubleshooting
WARNING Electrocution
Never remove or reinstall the water heater’s cover
unless the electricity servicing the unit is turned off.
Failure to do so could result in personal injury or death.
WARNING Electrocution
To test the water heater using the internal diagnostic
lights, it must be connected to the power supply.
When testing with the cover off, never touch any part
of the water heater. Doing so could result in serious
personal injury or death.
Note
When testing the water heater using the diagnostic lights,
water must be flowing through the unit.
Diagnostic lights
Red Lights up in the event of an error
Yellow Lights up in heating mode/flashes when capacity limit
reached
Green Flashing: Water heater connected to power supply
Diagnostic lights Problem Cause Solution
No LED is lit The water heater does not
heat up
There is no power Check to ensure the connected circuit breaker in the main
breaker panel hasn’t tripped. Reset if necessary
The PCB is faulty Replace the PCB
Green flashing, yellow
off, red off
No DHW The shower head/aerator is scaled up Descale or replace the shower head/aerators if necessary
The filter screen in the cold water inlet is dirty Clean the filter screen
The flow sensor is not plugged in Connect the cable to the PCB
The flow sensor is faulty Replace the flow sensor
The PCB is faulty Replace the PCB
Green flashing, yellow
on, red off
The display on the heater
is off
There is a loose cable between the PCB and the
display unit
Check the cable and plug the cable into the display and/
or PCB
The display cable is faulty Check the cable and replace if necessary
The display unit is faulty Replace the display, only available with a new heater
cover
The PCB is faulty Replace the PCB
Green flashing, yellow
on, red off
The outlet temperature does
not match the set value
The display unit was not plugged in before power
was switched on
Perform a reset by switching off the power to the water
heater
The outlet sensor is faulty Replace the outlet sensor
The tap is faulty Replace the tap
The heating system is faulty Replace the heating system
The PCB is faulty Replace the PCB
Green flashing, yellow
flashing, red off
The outlet temperature does
not match the set value
Motorized valve limit reached Reduce the set temperature
Motorized valve is faulty Replace the motorized valve
Green flashing, yellow
off, red on
No DHW Air detected Continue draw-off for >1 minute
Diagnostic lights Display readout Problem Cause Solution
Green flashing, yellow
off, red on
Wrench flashes (displays
E1 and wrench in menu
“Fault code display”)
No DHW AE3 safety switch not activated during
commissioning
Activate AE3 safety switch by pressing the reset button
firmly. See section 12.2.1, “Initial AE3 safety switch acti-
vation,” pg. 14
AE3 safety switch triggered by
self-resetting high limit safety cut-out
Klixon
Check high limit safety cut-out, Klixon (plug-in connec-
tion, connecting cable); activate AE3 safety switch
AE3 safety switch responds again after
high limit safety cut-out Klixon has been
checked; high limit safety cut-out faulty
Replace high limit safety cut-out Klixon activate AE3 safe-
ty switch and draw off water at the maximum set value
for >1 min
Safety switch responds again; PCB faulty Replace the PCB
Wrench flashes (displays
E2 and wrench in menu
“Fault code display”)
No DHW PCB faulty (lead break or short circuit in
inlet sensor)
Replace the PCB
Wrench flashes (displays
E3 and wrench in menu
“Fault code display”)
No DHW Short circuit in outlet sensor Check the outlet sensor, replace if necessary

INSTALLATION
ZĤ¼êÐ|ŒêĒĉ
18 | DHX 15 Select www.stiebel-eltron-usa.com
17. Specification
17.1 Dimensions and connections
c06 c01
c01
c06
b01
715/16Ý(202) 13 /8Ý(35)
45/16Ý(109)
19/16Ý(40)
37/8Ý(98)
143/16Ý(360)
Mounting holes, rear cover
125/8Ý(320)
½Ý(13)
315/16Ý(100)
D0000094547-b
DHX
b02 Entry electrical cables I Finished walls
c01 Cold water inlet Male thread ½˝ NPT
c06 DHW outlet Male thread ½˝ NPT
17.2 Wiring diagram
DHX 15 Select
L L 2/GND ~ 208 / 240V
L N 1/N/GND ~ 208 / 240V
N
L
L
L
D0000077991
1
3
4
2
1 Power PCB with integral safety switch
2 Direct Coil™heating system
3 Self-resetting high limit safety cut-out, Klixon
4 Wiring block
17.3 Hot water output
The domestic hot water (DHW) output is subject to the connected
power supply, and the cold water inlet temperature. The rated volt-
age and rated output can be found on the type plate.
Power output in kW 100°F DHW output in gpm
Rated voltage Cold water inlet temperature
Model ŝƃÄŨp ŝÔƃŨp 41°F 50°F 59°F 68 °F
DHX 15
Select 10.8 1.24 1.46 1.78 2.28
14.4 1.67 1.97 2.4 3.07
Power output in kW 122°F DHW output in gpm
Rated voltage Cold water inlet temperature
Model ŝƃÄŨp ŝÔƃŨp 41°F 50°F 59°F 68 °F
DHX 15
Select 10.8 0.9 1.02 1.16 1.35
14.4 1.21 1.37 1.56 1.82
Power output in kW 38 °C DHW output in l/min
Rated voltage Cold water inlet temperature
Model ŝƃÄŨp ŝÔƃŨp 5°C 10°C 15°C 20°C
DHX 15
Select 10.8 4.6 5.5 6.6 8.5
14.4 6.2 7.3 8.9 11.4
Power output in kW 50°C DHW output in l/min
Rated voltage Cold water inlet temperature
Model ŝƃÄŨp ŝÔƃŨp 5°C 10°C 15°C 20°C
DHX 15
Select 10.8 3.4 3.8 4.4 5.1
14.4 4.6 5.1 5.9 6.9

INSTALLATION
ZĤ¼êÐ|ŒêĒĉ
ENGLISH
www.stiebel-eltron-usa.com DHX 15 Select | 19
17.4 Application areas/conversion table
Here data is shown for electrical resistivity and electrical conduc-
tivity.
Standard specifica-
ŒêĒĉ|ŒĜÑŨ³ ŝƃŨ³ ŝÑŨ³
Min.
resistivity
ρ≥
Max.
conductivity ı≤
Min.
resistivity
ρ≥
Max.
conductivity ı≤
Min.
resistivity
ρ≥
Max.
conductivity ı≤
Ωcm mS/m μS/cm Ωcm mS/m μS/cm Ωcm mS/m μS/cm
1100 91 910 970 103 1031 895 112 1117
17.4.1 Sizing the pipework
When calculating the size of the pipework, an water heater pressure
drop of 14.5 psi (0.1MPa) is recommended.
17.5 Fault conditions
In the event of a fault, temperatures up to 176°F (80°C) at a pressure
of 145 psi (1.0 MPa) can occur briefly in the installation.
17.6 Data table
DHX 15 Select
Item no. 204812
Electrical data
Phase (50/60 Hz) 1/N/GND | 2/GND
Rated voltage 240 V208 V
Rated output 14.4 kW 10.8 kW
Amperage draw 60 A 52 A
Min. recommended circuit breaker size160 A 60 A
Min recommended wire size2(copper) 6/2 AWG 6/2 AWG
Min. resistivity ρ15 ≥ 1100 Ω cm
Max. conductivity ı15 ≤ 910 μS/cm
Connections
Water connections ½˝ NPT
Application limits
Maximum permissible pressure 145 psi (1 MPa)
Maximum inlet temperature for reheating 131°F (55°C)
Maximum inlet temperature 149°F (65 °C)
User selectable temperature range 68–140°F (20–60 °C)
Internal anti-scalding protection
temperature limiter values
100, 109, 122, 140°F (38, 43, 50, 60°C), factory default: 140 °F (60 °C)
Hydraulic data
Minimum water flow to activate unit 0.264 gal (1.0 l/min)
Nominal water volume 0.07 gal (0.277 l)
Other
Type of installation Over-sink/under-sink
Protection class 1
Insulating block Glass-reinforced polyamide
Heating system Direct Coil™
Cover and back panel Plastic
Color White
Dimensions
Height 141/8˝ (360 mm)
Width 8˝ (202 mm)
Depth 45/16˝ (109 mm)
Weights
Weight 5.5 lbs (2.5 kg)
1Overcurrent protection sized at 100% of load. Tankless water heaters are
considered a non-continuous load. Use only GFCI Class A circuit breakers.
2Copper conductors with a temperature rating of 75°C or greater must be
used. Conductors should be sized to maintain a voltage drop of less than 3%
under load.
These are our recommendations. Check local codes for compliance if necessary.

INSTALLATION
Spare parts
20 | DHX 15 Select www.stiebel-eltron-usa.com
18. Spare parts
No. Spare part DHX 15 Select
1Housing (front) 351644
2PCB connection cable 158010
3O-Ring 9.5x2 EPDM 269351
4 Control knob 323686
5LCD display 349444
8Housing (back) 348144
10 Heating system 344147
11 Flow sensor 339979
12 Self-resetting high limit safety cut-out, Klixon,
with outlet sensor
340528
13 Motorized valve 220502
14 Pipe elbow set 340542
15 Pipe elbow connection set
(includes clips and gaskets)
320540
20 PCB electronic board 348499
21 Jumper plug (red) 283455
22 Wiring block 326655
23 Electronics cover 344146
40 Water connection fittings (2) - ½˝NPT / G⅜˝ 326589
41 Locking sheet 326234
42 Filter screen 275981