Bosch TRONIC 5000C Pro Technical Document

en Installation Manual and Operating Instructions 2
es Instrucciones de instalación y funcionamiento 28
fr Instructions d'installation et d'utilisation 54
PRO tankless electric water heaters
TRONIC 5000C Pro
6720646951-00.1V
Models: WH17 / WH27
6 720 646 951 (2011/09) US
IMPORTANT: This booklet should be given to the customer after installation and demonstration.
For Service & Installation contact:
BOSCH Thermotechnology Corp.
50 Wentworth Avenue, Londonderry
NH 03053
Phone: [phone]
www.bosch-climate.us

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Table of contents
1 Explanation of symbols and safety information . 3
1.1 Explanation of symbols . . . . . . . . . . . . . . . . 3
1.2 Safety precautions . . . . . . . . . . . . . . . . . . . 3
2 General information . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1.1 Approval number . . . . . . . . . . . . . . . . . . . . 5
2.2 Technical identification code . . . . . . . . . . . 5
2.3 Model name and number identification . . . 5
2.4 Package contents . . . . . . . . . . . . . . . . . . . . 5
2.5 Components Diagram . . . . . . . . . . . . . . . . . 6
2.6 Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.7 Wiring diagram . . . . . . . . . . . . . . . . . . . . . . 8
2.8 Function . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.9 Technical specifications . . . . . . . . . . . . . . 10
3 Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1 Important information . . . . . . . . . . . . . . . 12
4.2 Selection of place of installation . . . . . . . 12
4.2.1 Freeze prevention . . . . . . . . . . . . . . . . . . . 12
4.2.2 Recommended minimum clearances
for servicing . . . . . . . . . . . . . . . . . . . . . . . 13
4.3 Mounting the water heater . . . . . . . . . . . . 13
4.4 Water connections . . . . . . . . . . . . . . . . . . 14
4.4.1 Water quality . . . . . . . . . . . . . . . . . . . . . . . 14
4.5 Electrical connections . . . . . . . . . . . . . . . 14
4.6 Starting up . . . . . . . . . . . . . . . . . . . . . . . . 18
4.6.1 Checking for leaks and purging air . . . . . . 18
4.6.2 Adjusting the temperature dial . . . . . . . . . 18
4.6.3 Adjusting the flow . . . . . . . . . . . . . . . . . . . 18
5 Operation instructions . . . . . . . . . . . . . . . . . . . . 19
5.1 Before using the water heater . . . . . . . . . 19
6 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . 22
8 Spare Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Explanation of symbols and safety information | 3US
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1 Explanation of symbols and safety information
1.1 Explanation of symbols
Warnings
Signal words at the beginning of a warning are used to
indicate the type and seriousness of the ensuing risk if
measures for minimizing damage are not taken.
•NOTE indicates possible minor to medium personal
injury.
•CAUTION indicates possible minor to medium
personal injury.
•WARNING indicates possible severe personal injury.
•DANGER indicates that severe personal injury may
occur.
Important information
Additional symbols
1.2 Safety precautions
When using this electrical equipment, basic safety
precautions should always be followed, including the
following:
BREAD AND FOLLOW ALL INSTRUCTIONS.
BThis appliance must be grounded.
BDisconnect this product from the electrical supply
before cleaning, servicing or removing the cover.
BTo reduce the risk of injury, close supervision is
necessary when the product is used near children or
elderly persons.
BWarning: Mount the unit onto a flat section of wall,
well away from any potential splashes of water or
spray and away from areas where direct moist or wet
contact could occur.
BWarning: Indoor installation only, where it will NOT be
exposed to freezing.
BWarning: Do not install a check valve or any other type
of back flow preventer within ten feet of the cold
water inlet.
BThe electrical installation must conform to current
National Electrical Codes.
BWarning: Do not switch the heater on if you suspect
that it may be frozen. Wait until you are sure that it
has completely thawed out.
BThe Tronic 5000C Pro is designed to heat potable cold
water for domestic purposes. The heater is not
designed to accept inlet water temperatures above
86° F. Contact Bosch Thermotechnology Corp. before
specifying or installing the appliance in any other
application.
Warnings are indicated in the text by a
warning triangle and a gray background.
In case of danger due to electric shock, the
exclamation point on the warning triangle is
replaced with a lightning symbol.
Important information that presents no risk
to people or property is indicated with this
symbol. It is separated by horizontal lines
above and below the text.
Symbol Meaning
Ba step in an action sequence
→a reference to a related part in the
document or to other related documents
•a list entry
–a list entry (second level)
Tab. 1

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BAdditional Canadian safety instructions:
–As per the Canadian Electrical Code, C22.1-02
Section 26-744, an auxiliary terminal block must be
fitted to the unit before connecting to the electrical
supply (Kit Part N° “AE Canada Kit”).
(See Page 17).
–A green terminal (or a wire connector marked “G,”
“GR,” “GROUND” or “GROUNDING”) is provided
within the control. To reduce the risk of electrical
shock, connect this terminal or connector to the
grounding terminal of the electrical service of
supply panel with a continuous copper wire in
accordance with the Canadian Electrical Code,
Part I.
–This product shall be protected by a Class A ground
fault circuit interrupter.
BKeep this manual in a safe place once the unit has
been installed as it may be needed for future
reference.

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2 General information
2.1 Disclaimer
2.1.1 Approval number
Commonwealth of Massachusetts
In the Commonwealth of Massachusetts a licensed
plumber or electrician must perform the installation.
(Approval number: P1-09-25).
2.2 Technical identification code
EI Electronic Instantaneous
17 Maximum output (kW)
E/M Electronic / mechanical temperature control
WWall hung
IIndoor
HHorizontal installation
BWater connections
2.3 Model name and number
identification
2.4 Package contents
•Tankless electric water heater.
•4 screws and gasket.
EI 17 E/M W I H B
EI 27 E/M W I H B
Tab. 2
Model Name Model Number
WH17 EI 17 E/M W I H B
WH27 EI 27 E/M W I H B
Tab. 3

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2.5 Components Diagram
Fig. 1
AHeating module
BHeating element assembly
CHeating module PCB
DHot water outlet
ECold water inlet
FTemperature adjustment knob
GFlow transducer
HTerminal block (CANADA ONLY)
I6 way terminal block
JTemperature sensor
KControl PCB
LDouble pole thermal cut-out
MInlet water filter
NFlow regulator
6720646951-14.1V
G
E
L
J
H
I
N
MF K
A
D
C
B

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2.6 Dimensions
Fig. 2
1Outlet ¾ " NPT (hot water)
2Inlet ¾ " NPT (cold water)
3Temperature knob
4LED
Dimensions
(inches) WH17 / WH27
A (Width) 15 ¼ "
B (Height) 12 ½ "
C (Depth) 4 ½ "
D12
5
/
8
"
E12
5
/
8
"
F2 ½ "
G3 ½ "
H6
1
/
8
"
I5 ¾ "
J1 ¾ "
Water connections ¾ "
Tab. 4 Dimensions

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2.7 Wiring diagram
Fig. 3 Internal wiring schematic for single phase WH27 unit.
DANGER: Risk of electric shock!
BAlways switch off the electricity supply to
the unit before any intervention in the
heater.
6720646951-02.1V

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Fig. 4 Internal wiring schematic for single phase WH17 unit.
2.8 Function
How the water heater works:
•The Tronic 5000C Pro heats water continuously as it
flows through the heater modules.
•The electronic control PCB monitors the flow rate and
the incoming water temperature and then switches
on the required number of heater elements to reach
the temperature set by the temperature adjustment
dial.
•As the flow rate or the incoming water temperature
changes, the electronic control adjusts the number of
heater elements used so that the outlet temperature
is maintained.
•The outlet water temperature can change slightly as
the flow rate changes due to the steps in power as
different heater elements are switched on and off.
•The outlet water temperature can also vary if the
maximum flow rate is exceeded (see Fig. 11) or if the
supply voltage changes.
•Each heater module is protected by an electro-
mechanical thermal cut-out. This cut-out will only trip
in exceptional circumstances.
Contact Technical Support 800-798-8161 for further
instruction.
•The WH17 unit is supplied from two independent
voltage supplies and the WH27 unit from three
independent voltage supplies. (In Canada the unit has
just one voltage supply).
•Depending on the region of the country, the
temperature of the water supply can vary between
40 °F in winter to 70 °F in summer, with an average of
55 °F. The output temperature and maximum flow of
the heater is dependent on inlet water temperature.
6720646951-03.1V

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2.9 Technical specifications
Technical characteristics Units WH17 WH27
Voltage supply V 2 X 240VAC (Canada 240VAC) 3 X 240VAC (Canada 240VAC)
Amperage A 2 X 40A (Canada 80A) 3 X 40A (Canada 120A)
Maximum output kW 17.25kW 26.85kW
Temperature control range 95 °F to 131 °F 95 °F to 131 °F
Minimum water pressure psi 15psi 15psi
Maximum water pressure psi 150psi 150psi
Minimum flow rate gal/min 0.6 US gal / min 0.8 US gal / min
Maximum flow rate (refer to Fig. 11) (refer to Fig. 11)
Weight (without water) lbs 20 lbs 22 lbs
The unit will work at lower supply voltages but the following changes will apply:
Maximum output 15kW at 220V 22.5kW at 220V
13kW at 208V 20kW at 208V
Maximum flow rate
(refer to Fig. 11)
84% of maximum at 220V 84% of maximum at 220V
75% of maximum at 208V 75% of maximum at 208V
Tab. 5

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3 Regulations
Any local by-laws and regulations pertaining to
installation and use of electric water heating appliances
must be observed. Please refer to the laws that should
be attended in your country.
•The electrical installation must conform to current
National Electrical Codes.
•As per the Canadian Electrical Code, C22.1-02
Section 26-744, an auxiliary terminal block must be
fitted to the unit before connecting to the electrical
supply (Kit Part N° “AE Canada Kit”).
•A green terminal (or wire connection marked “G”,
“GR”, “GROUND” or “GROUNDING”) is provided
within the control box. Aditional Canadian safety
instructions, to reduce the risk of electrical shock,
connect this terminal or connector to the grounding
terminal of the electrical service of supply panel with
a continuous copper wire in accordance with the
Canadian Electrical Code, Part I.
•In Canada this product shall be protected by a Class
A ground fault circuit interrupter.
•In the Commonwealth of Massachusetts a licensed
plumber or electrician must perform the installation.
(Approval number: P1-09-25).
•In the Commonwealth of Massachusetts a pressure
relief valve shall be installed on the cold water side by
a licensed plumber. (MGL 142 Section 19, Approval
number P1-09-25).
•The unit must be wired by a qualified electrician, in
accordance with the current version of the National
Electrical Code US) or Canadian Electric Code
(Canada).
•When the heater is not within sight of the electrical
circuit breakers, a circuit breaker lockout or
additional local means of disconnection for all non-
grounded conductors must be provided that is within
sight of the appliance. (Ref NEC 422.31.).
•The power cable size and the installation must be in
accordance with the Canadian Electrical Code, C22.1-
02.
WARNING:
California Proposition 65 lists chemical
substances known to the state to cause
cancer, birth defects, death, serious illness
or other reproductive harm. This product
may contain such substances, be their
origin from fuel combustion (gas, oil) or
components of the product itself.

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4 Installation
4.1 Important information
Please follow these instructions. Failure to follow
instructions may result in:
•Damage or injury.
•Improper installation/operation.
•Loss of warranty.
4.2 Selection of place of installation
•If being used in a public place, locate the heater out
of easy reach to discourage vandalism.
•Mount the unit onto a flat section of wall, well away
from any potential splashes of water or spray and
away from areas where direct moist or wet contact
could occur.
•Install the heater in a place that provides easy access
for any service or maintenace.
4.2.1 Freeze prevention
Introduction
Please note that the installation manual states that the
water heater must not be installed in a location where it
may be exposed to freezing temperatures. If the heater
must be left in a space that is likely to experience
freezing temperatures, all water must be drained from
the heater. See Section 6.
Freeze damage is not covered under the warranty.
DANGER: Risk of electric shock!
BFor safety reasons, disconnect the power
supply to the heater before any service or
testing is performed.
WARNING:
BThis heater must be electrically grounded
in accordance with the most recent
edition of the National Electrical Code.
NFPA 70. In Canada, all electrical wiring
to the heater must be in accordance with
local codes and the Canadian Electrical
Code, CSA C22.1 Part 1.
DANGER:
BThe installation must only be performed
by a qualified person in accordance with
these instructions.
BBosch Thermotechnology Corp. is not
responsible for improperly installed
appliances.
WARNING:
BThe heater must only be mounted in a
vertical position with the water fittings
located at the bottom of the heater.
Under no circumstances should the
heater be mounted differently.
WARNING:
BThe appliance should be located in an
area where leakage of the heater or
connections will not result in damage to
the area adjacent to the appliance or to
lower floors of the structure.
WARNING: Risk of freezing!
BDo not install the water heater in an area
where there is a chance of freezing.
Damage to the water heater as a result of
freezing will not be covered under
warranty.
WARNING:
BELECTRICITY IS EXTREMELY
DANGEROUS. TAKE EXTRA
PRECAUTIONS AND ENSURE ALL
CIRCUIT BREAKERS ARE OFF BEFORE
PERFORMING ANY WORK TO THE
HEATER.
WARNING:
BIndoor installation only, where it will NOT
be exposed to freezing.
Use of chemical agents such as anti-freeze
are not allowed as they may cause damage
to the water heater’s internal components.

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4.2.2 Recommended minimum clearances for
servicing
Should it be necessary to service the Tronic 5000C Pro,
observe the following clearances. These are not required
clearances, but would facilitate any service work.
Fig. 5 Recommended minimum clearances
4.3 Mounting the water heater
BUndo the retaining screws on the front cover and take
the cover off the heater. Hold the back plate in
position against the wall and mark the four mounting
holes.
BDrill the holes and secure the heater using the four
wood screws supplied.
Fig. 6 Vertical mounting position
WH17 WH27
Top (A) 12" 12"
Sides 0" 0"
Bottom (B) 6" 6"
Front (C) 12" 12"
Tab. 6 Recommended minimum clearances
WARNING:
BThe heater must only be installed in the
orientation shown in Fig. 6 i.e., mounted
in a vertical position with the water
fittings located at the bottom of the
heater. Under no circumstances should
the heater be mounted differently.

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4.4 Water connections
BThe heater must be connected directly to the main
cold water supply and not to pre-heated water. (The
inlet water temperature must not be greater than
86 °F).
BThe heater must be installed with shutoff valves on
both the inlet and outlet connections.
BIt is recommended that you use ¾ inch or ½ inch
copper or high-pressure flex connections.
BDo not use plastic piping within 3 feet on either side
of heater.
BUse Teflon tape for sealing pipe threads. Do NOT use
pipe dope.
BRemember to keep the hot water pipe runs as short
as possible.
After the heater has been plumbed, and before you
wire it, flush it with water to remove any debris or
loose particles. Heater must be full of water and air
purged before power is turned on. Failure to do so
may result in damage to the product that is not
covered by warranty.
BAfter flushing and filling the heater with water, (with
power off) disconnect the inlet connection and
inspect the filter screen for any debris that may have
been flushed through the system.
BCheck the pressure of the main water supply. To
operate correctly, the heater needs the running
pressures mentioned in Tab. 5.
4.4.1 Water quality
Water quality can have an impact on appliance longevity
and may not be covered under the manufacturer's
warranty.
BFor water analysis data call your local water
department, or if on a well, have well water analyzed
periodically.
If water quality exceeds one or more of the values
specified below, Bosch recommends consulting a
local water treatment professional for water
softening/conditioning options.
4.5 Electrical connections
WARNING:
BDo not install a non-return check valve
within 10 feet of the inlet.
WARNING:
BDo not apply heat or solder to
connections or pipe if they are already
connected to the unit.
NOTICE: Disclaimer
BIn the Commonwealth of Massachusetts
a pressure relief valve shall be installed
on the cold water side by a licensed
plumber. (MGL 142 Section 19, Approval
number P1-09-25).
The inlet and outlet connections are clearly
marked on the heater. They each have a
¾ inch NPT connector.
Description Max. Levels
pH pH 6.5 - 8.5
TDS (total Dissolved Solids) mg/l or ppm 500
Total hardness mg/l or ppm 100
Aluminum mg/l or ppm 2.0
Chlorides mg/l or ppm 250
Copper mg/l or ppm 1.0
Iron mg/l or ppm 0.3
Manganese mg/l or ppm 0.05
Zinc mg/l or ppm 5.0
Table 7
WARNING:
BThe unit must be wired by a qualified
electrician, in accordance with the
current version of the National Electrical
Code US) or Canadian Electric Code
(Canada).
When the heater is not within sight of the
electrical circuit breakers, a circuit breaker
lockout or additional local means of
disconnection for all non-grounded
conductors must be provided that is within
sight of the appliance. (Ref NEC 422.31.).

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US wiring
•The minimum recommended wire size is 8 AWG. (The
terminal block will accept cables up to 6 AWG size).
•The cable entry is via the 1¼ inch cable entry hole on
the bottom right hand edge of the back plate.
•Strip back the insulation on the power wires about
½ inch. Connect the live wires to the terminals
marked “L1” and “L2.” There are two pairs of live
wires in the WH17 and three pairs of live wires in the
WH27. (See Fig. 7 and Fig. 8, page 16).
•Any insulation on the ground wires should be stripped
back about ¾ inch. The ground leads must be
connected to the pillar terminal marked “GR”. (See
Fig. 7 and Fig. 8, page 16).
•Make sure the terminal block screws are tightened
securely. Loose connections can cause wires to heat
up.
•Make sure that the ground wires are wrapped around
its terminal stud and into the saddle washer. The nut
should be tightened securely.
•Attach the front cover and tighten the retaining
screws.
As per the Canadian Electrical Code, C22.1-
02 Section 26-744, an auxiliary terminal
block must be fitted to the heater before
connecting to the electrical supply. This is
available as a kit from Bosch
Thermotechnology Corp. Part Number “AE
Canada Kit”. (Contact 800-798-8161).

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The WH17 requires two independent 240V AC circuits protected by two separate and independent double pole
breakers (as shown) rated at 40A each.
Fig. 7 WH17 terminal block connection (U.S.A. only)
The WH27 requires three independent 240V AC circuits protected by three separate and independent double pole
breakers (as shown) rated at 40A each.
Fig. 8 WH27 terminal block connection (U.S.A. only)

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Canada Wiring - auxiliary terminal block and
connections
Fitting the auxiliary terminal block (see diagram below).
Fig. 9 For Canada only (Not for U.S.A.)
Fig. 10 For Canada only (Not for U.S.A.)
BConnect the red wires from the left hand terminal of
the new block to the L1 terminals in the unit. (There
are two red wires required in the WH17 and three in
the WH27).
BConnect the blue wires from the right hand terminal
of the new block to the L2 terminals in the unit.
(There are two blue wires required in the WH17 and
three in the WH27).
BPush and click the auxiliary terminal block onto the
louvered rail in the backplate.
Connecting the supply cable - Canada only - not for the
USA.
•The power cable size and the installation must be in
accordance with the Canadian Electrical Code, C22.1-
02.
•The incoming hole diameter on auxiliary terminal
block can accept up to 1/0 AWG size cables.
•The cable entry is via the 1 ¼ inch cable entry hole on
the bottom right hand edge of the backplate.
•Strip back the insulation on the power wires about
½ inch. Connect the ungrounded conductors to the
terminals “L1” and “L2” on the auxiliary terminal
block.
•Any insulation on the ground wire should be stripped
back about ¾ inch. The ground lead must be
connected to the pillar terminal marked “GR.”
•Make sure the terminal block screws are tightened
securely. Loose connections can cause wires to heat
up.
•Make sure that the ground wire is wrapped around its
terminal stud and into the saddle washer. The nut
should be tightened securely.
•Attach the front cover and tighten the retaining
screws.
The WH17 requires an 80A 240V AC
single phase supply protected by an 80A
double pole circuit breaker.
The WH27 requires a 120A 240V AC
single phase supply protected by a 120A
double pole circuit breaker.

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4.6 Starting up
4.6.1 Checking for leaks and purging air
BVerify all circuit breakers supplying power to the
water heater are turned off.
BOpen all hot water taps supplied by the water heater
and inspect all water connections for leaks.
BWith all hot water taps still open, inspect each tap to
ensure all air in the lines has been purged out.
BWith the air purged and taps still flowing, turn on all
circuit breakers supplying the water heater.
BClose all hot water taps and proceed to the next
section.
4.6.2 Adjusting the temperature dial
BThe temperature adjustment is made using the dial on
the bottom edge of the unit. The adjustment is
between approximately 95 °F and 131 °F. Turning the
dial clockwise increases the temperature setting as
indicated by the marking on the unit.
4.6.3 Adjusting the flow
BOpen fully both inlet and outlet shut-off valves at the
heater, then:
BTurn on fully the highest flowing hot water faucet
(e.g., bathtub) served by the water heater.
BAdjust the outlet shut-off valve until the water flow
rate from the hot faucet corresponds to the value
given in Fig. 11 below.
Fig. 11
For example:
•For the WH17 unit, using the outlet ball valve, ensure
the flow rate does not exceed 2.3 gallons/minute.
•For the WH27 unit, using the outlet ball valve, ensure
the flow rate does not exceed 3.5 gallons/minute.
These figures are based on an inlet water temperature of
55 °F and a supply voltage of 240 volts. If the inlet water
temperature is lower than 55 °F, or if the supply voltage
is less than 240 volts, then the outlet temperature will be
lower than what is shown in Fig. 11. If a higher outlet
water temperature is desired, then reduce the flow rate
and/or supply the unit with 240 volts.
95 100 105 110 130115 120 125 135
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Outlet temperature (ºF)
Max Flow Rate (US gal/min)
Outlet temperature vs Maximum flow rate setting
(based on incoming water temperature of 55ºF)
17kW Heater
27kW Heater
6720646951-09.1V
131
Before leaving the site, the installer should
demonstrate the unit to the user and give
them this guide.

Operation instructions | 19US
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5 Operation instructions
5.1 Before using the water heater
BCheck that the power is switched on at the circuit
breaker panel.
BTurn on the hot water faucet FULLY.
•If the unit has been used recently, run the water
through for a few seconds to let the temperature cool
down. You may initially get a short burst of very hot
water that was in the plumbing lines from previous
use.
•If a second outlet connected to the unit is also turned
on, the hot water will be shared between the two.
WARNING:
BDo not use the unit if you think it may be
frozen, as this could result in serious
damage to the unit. Wait until you are
sure that it has completely thawed out
before you switch it on.
The hot water temperature can be changed
by adjusting the temperature dial on the
bottom surface of the unit. (The dial adjusts
the temperature typically between 95°F and
131°F. The factory sets the temperature dial
at the lowest position).

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6 Maintenance
Draining the heater
Due to the shape of the heat exchangers and connecting
pipe, it is extremely difficult to get all of the water out of
the heater. Follow the procedure below to best minimize
the chance of freezing:
BDisconnect electric supply.
BDisconnect cold and hot water pipes from fittings on
bottom of heater. Allow water to drain out (have a
catch basin ready).
BAfter allowing all water to drain out, the heater should
be blown out with low pressure compressed air to
remove as much water as possible from water heater
modules. Bursts of air work better than continuous
flow.
Remember, these suggestions are only made to help
minimize the potential for freeze damage and are not to
be construed as the guaranteed method for dealing with
freeze possibilities.
Check inlet water filter screen once a year
BCheck that the power is switched off at the circuit
breaker panel.
BShut off the installer supplied cold water isolation
valve to the heater. If one is not installed, install
before proceeding.
BOpen nearest hot water tap to relieve pressure in the
plumbing lines.
BPosition a bucket under the cold water inlet
connection of the heater to catch any water that may
drain.
BDisconnect the cold water plumbing connection from
the inlet (bottom right of heater) to access filter
screen.
BRemove filter, clean with water and inspect for
damage. If the filter is at all damaged, it should be
replaced.
BReplace the filter into the inlet housing
BDO NOT leave the filter out.
BDO NOT remove the flow regulator (located behind
the filter).
BDO NOT clear the filter by back flushing.
BNEVER use an air line to blow out the heater (the flow
transducer will be permanently damaged).
BBefore switching power back on, open all hot water
taps and inspect each tap to ensure all air in the lines
has been purged out. With the air purged and taps still
flowing, turn on all circuit breakers supplying the
water heater.
BClose all hot water taps and proceed for normal
operation.