STIEBEL ELTRON DHX 3.5-1 Trend Instruction Manual

OPERATION AND INSTALLATION
FUNCIONAMIENTO E INSTALACIÓN
Electronically Controlled Electric Tankless Water Heaters
Calentadores de Agua Electrónicos sin Tanque
» DHX 3.5-1 Trend
» DHX 6-2 Trend
» DHX 8-2 Trend
»DHX10-2Trend
»DHX12-2Trend
»DHX15-2Trend
»DHX12-2Plus
»DHX15-2Plus
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.
i

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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 Trend user interface _________________________________________ 7
5.2 DHX Plus user interface ___________________________________________ 8
5.3 Using the display menus __________________________________________ 8
5.4 DHX Trend display __________________________________________________ 8
5.5 DHX Plus display ____________________________________________________ 9
5.6 Recommended settings __________________________________________12
6. Cleaning, care and maintenance ____________________________12
7. Troubleshooting _______________________________________________13
INSTALLATION
8. Safety___________________________________________________________13
8.1 General safety instructions ______________________________________13
8.2 Instructions, standards and regulations ______________________13
9. Water heater description_____________________________________13
9.1 Standard delivery__________________________________________________13
10. Preparation ____________________________________________________14
10.1 Installation site_____________________________________________________14
10.2 Minimum clearances______________________________________________14
11. Installation_____________________________________________________14
11.1 Standard wall-mounted installation___________________________14
11.2 Water connections_________________________________________________15
11.3 Aerator installation at connected faucet ______________________16
11.4 Electrical connection______________________________________________16
11.5 Electrical connection with short power cable _______________17
11.6 Wiring block ________________________________________________________17
12. Commissioning ________________________________________________ 17
12.1 Internal anti-scalding protection via jumper slot ___________17
12.2 Initial start-up______________________________________________________17
12.3 Operation with preheated water _______________________________18
12.4 Recommissioning__________________________________________________18
13. Water heater shutdown ______________________________________18
14. Service information ___________________________________________ 19
15. Maintenance ___________________________________________________ 19
15.1 Draining the water heater _______________________________________19
15.2 Cleaning the filter screen ________________________________________19
16. Troubleshooting _______________________________________________20
17. Specification ___________________________________________________21
17.1 Dimensions and connections____________________________________21
17.2 Wiring diagrams ___________________________________________________21
17.3 Hot water output___________________________________________________22
17.4 Application areas/conversion table ____________________________22
17.5 Fault conditions ____________________________________________________22
17.6 Data table ___________________________________________________________23
18. Spare parts ____________________________________________________24
19. Warranty _______________________________________________________25

QUICK START GUIDE
ENGLISH
www.stiebel-eltron-usa.com DHX Trend & DHX Plus | 3
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. 14).
2 Hook up water connections (see section 11.2, “Water connections”, pg. 15).
3 Hook up electrical connections, but keep circuit breaker off. (See section 11.4, “Electrical connec-
tion”, pg. 16)
PLQ
12
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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 Trend & DHX Plus 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 diagrams,” pg. 21.
- The water heater must be permanently connected to
fixed wiring. For use on an individual branch circuit
only. See section 17.2, “Wiring diagrams,” pg. 21.
- Secure the water heater as described in chapter 11,
“Installation”, pg. 14.
- Observe the minimum permissible water supply
pressure of 26.1 psi (1.8 bar). See section 17.6, “Data
table,” pg. 23.
- Observe the maximum permissible water supply
pressure of 145 psi (10 bar). See section 17.6, “Data
table,” pg. 23.
- Drain the water heater as described in section 15.1,
“Draining the water heater”, pg. 19.

OPERATION
General information
ENGLISH
www.stiebel-eltron-usa.com DHX Trend & DHX Plus|5
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:
- All DHX models - qualified contractor adjustable: “Internal
anti-scalding protection”
- DHX Plus only - user adjustable: Temperature limit
(childproofing)
!
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 15-2 Plus (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
www.stiebel-eltron-usa.com DHX Trend & DHX Plus | 7
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 regulates
the correct heating output using only the minimum amount of power
necessary, subject to the temperature selected and the current in-
coming cold water temperature.
DHX Trend and DHX Plus are electronically controlled tankless water
heaters, and maintain a consistent outlet temperature. This is irre-
spective of the inlet water temperature, up to the maximum output
of the water heater.
DHX Plus models feature Advance Flow Control™, a technology pat-
ented by Stiebel Eltron in Germany (patent no. DE 3805441 C2). When
the maximum output of a DHX Plus model is met, rather than deviate
from the setpoint temperature and deliver cooler water, DHX Plus
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 position, 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 (DHX
Plus models only) and will flash. The water is not heated further.
DHX models are equipped with functions to permanently limit the
temperature (childproofing).
DHX Plus 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 Plus models allow the user to save different preset tempera-
tures and apply them quickly.
DHX Plus models also offer a more in-depth 2-line display with
enhanced functions. The DHX Trend has a single-line display and a
more basic user feature set.
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 Trend user interface
2
3
1
1 Display
2 Operating LED (flashes when output limit is reached)
3 Control knob
5.1.1 DHX Trend display overview
12
1 Digit display
2 Temperature unit indicator

OPERATION
Settings and displays
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5.2 DHX Plus user interface
D0000073619
2
3
1
8
5
6
7
4
1 Control knob
2 Operating LED (flashes when output limit is reached)
3 Temperature memory keys
4 Backlit display
5 Main display | info display | parameter display
6 Segment display [10–100%]
7 Second row of screen
8 “i” button to retrieve information and select menus
5.2.1 DHX Plus display overview
1
2
3
4
678
9
10
1112
13
14
5
1 Primary digit display
2 Power capacity status
3 Display-lock indicator
4 Error code symbol
5 Secondary digit display
6 Tmax indicator
7 Savings statistics indicator
8 x1000 secondary display value
9 Gallons secondary display unit
10 kWh secondary display unit
11 Liters & liters per minute secondary display unit
12 Gallons per minute secondary display unit
13 Temperature unit for secondary display
14 Temperature unit for primary display
5.3 Using the display menus
The DHX Trend and DHX Plus feature 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.
5.3.1 DHX Trend user input
User input
Control knob (turn knob to change settings)
5.3.2 DHX Plus user input
User input
Information button (pressing or holding this
button performs different functions)
Preset 1 button (pressing or holding this but-
ton performs different functions)
Preset 2 button (pressing or holding this but-
ton performs different functions)
Control knob (turn knob to change settings)
5.4 DHX Trend display
The DHX Trend display features a temperature readout capable of
showing the currently selected temperature in either Fahrenheit
or Celsius.
For the name of each display element on the DHX Trend, consult
section 5.1.1, “DHX Trend display overview”, pg. 7.

OPERATION
Settings and displays
ENGLISH
www.stiebel-eltron-usa.com DHX Trend & DHX Plus | 9
5.4.1 Base display
The base display shows the current temperature setpoint in your
preferred temperature unit.
Changing the setpoint temperature
Temperature settings
Range Increment Range Increment
68–140°F 1°F 20–60°C. 1 °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.
5.4.2 Temperature units parameter setting
The DHX Trend is capable of displaying temperature in either Fahr-
enheit or Celsius.
f To change between Fahrenheit (default) and Celsius, first rotate
the control knob to the left until the display reads “Off.”
f Once “Off” is showing on the display, turn the control knob 5
full 360° rotations to the left. This will open the temperature
parameter menu:
Turn full 360°
5 times to the left
Turn full 360°
5
t
i
mes to the le
f
t
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.
5.4.3 Returning to the base display
The display will revert to the base display after a 30-second period
with no user input.
5.5 DHX Plus display
The DHX Plus features a primary and secondary display area al-
lowing for multiple parameters or information to be displayed. The
DHX Plus is capable of displaying the current flow rate of the water
passing through the water heater, as well as calculating the accu-
mulated cost savings of having a tankless water heater compared
to a tank-type water heater.
For the name of each display element on the DHX Plus, consult
section 5.2.1, “DHX Plus display overview”, pg. 8.
5.5.1 Base display
The DHX Plus base display shows the current setpoint temperature
in your preferred temperature unit in the top half of the display.
The bar below the temperature shows the current fraction of total
capacity that the water heater is running at. 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 operating at 30% of full capacity.
The bottom half of the display shows the current flow rate through
the unit in either gallons per minute (gpm) or liters per minute (l/
min).
All other menus will revert back to the base display either after a
15-second period of time without user input, or after a 5-second
hold of the Information 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.
5.5.2 Information menu
The information menu structure displays additional information for
the user. The information menu is accessed by pressing the Infor-
mation button while at the base display.
Accumulated cost savings display
If the Information button is pressed while the display is showing
the base display, the display will advance to the accumulated cost
savings display.
The accumulated cost savings display will display the current set-
point temperature in the top half of the display, and the bottom half
of the display will alternate between “Cur” and the accumulated
savings of the water heater.

OPERATION
Settings and displays
10 | DHX Trend & DHX Plus www.stiebel-eltron-usa.com
The accumulated cost savings updates daily, and shows the esti-
mated savings for the user compared to an installation where a
50-gallon tank-type water heater was used.
Note
The energy saving values are calculated starting from the
last reset.
This savings estimate is based on the users electricity cost. For the
most accurate estimate, the electricity cost per kWh should be set in
the electricity cost parameter setting menu. For information on how
to do this, see section “Electricity cost parameter setting”, pg. 10.
Pressing the Information button will advance back to the base dis-
play. The display will also revert back to the base display if no user
input is detected for 10 seconds.
5.5.3 Parameters menu
The parameter menu allows multiple settings on the DHX Plus to
be altered. The parameter menu can be accessed by holding the
Information button for 5 seconds.
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
real possibility.
At the Tmax setting menu, the temperature value 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
decreased by turning it counter-clockwise. The Tmax value can be
deactivated 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 function
is active and limiting the maximum allowable temperature.
Pressing the Information button once while at this menu will move
the display onto the temperature units parameter setting.
Temperature units parameter setting
The DHX Plus is capable of displaying temperature in either degrees
Fahrenheit or degrees Celsius.
The current unit will be shown and the secondary display value will
be flashing to indicate that the value can be changed. Rotate the
control knob to change the value between degrees Fahrenheit and
degrees Celsius.
Pressing the Information button once while at this menu will move
the display onto the volume units parameter setting.
Volume units parameter setting
The DHX Plus is capable of displaying volume or volume flow in
either gallons per minute (gpm) or liters per minute (l/min).
The current volume unit will be displayed and the value will be
flashing to indicate that it can be changed. Rotate the control knob to
change the value between gallons per minute and liters per minute.
Pressing the Information button once while at this menu will advance
the display to the electricity cost parameter setting.
Electricity cost parameter setting
The DHX Plus has a built-in feature where it calculates the energy
savings of the unit when compared to the average energy use of a
tank-type water heater. In order for this feature to be accurate, the
cost per kWh of electricity must be programmed into the software.