Bosch WH27, WH17 Installation Manual

PRO tankless electric water heaters

6720646951-00.1V

TRONIC 5000C Pro

Models: WH17 / WH27

en Installation Manual and Operating Instructions 2 es Instrucciones de instalación y funcionamiento 28 fr Instructions d'installation et d'utilisation 54

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: 800-798-8161 www.bosch-climate.us

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2 | Table of contents US

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

Copyright6 720 646 951 (2011/09)

Explanation of symbols and safety information | 3US

1 Explanation of symbols and safety information

1.1 Explanation of symbols

Warnings

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.

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

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.

Additional symbols

Symbol Meaning

B a step in an action sequence

1.2 Safety precautions

When using this electrical equipment, basic safety precautions should always be followed, including the following:

B READ AND FOLLOW ALL INSTRUCTIONS. B This appliance must be grounded. B Disconnect this product from the electrical supply

before cleaning, servicing or removing the cover.

B To reduce the risk of injury, close supervision is

necessary when the product is used near children or elderly persons.

B Warning: 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.

B Warning: Indoor installation only, where it will NOT be

exposed to freezing.

B Warning: Do not install a check valve or any other type

of back flow preventer within ten feet of the cold water inlet.

B The electrical installation must conform to current

National Electrical Codes.

B Warning: 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.

B The 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.

→ 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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B Additional 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.

B Keep 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

General information | 5US

2.1.1

Commonwealth of Massachusetts

In the Commonwealth of Massachusetts a licensed plumber or electrician must perform the installation. (Approval number: P1-09-25).

Approval number

2.2 Technical identification code

EI 17 E/M W I H B

EI 27 E/M W I H B

Tab. 2

EI Electronic Instantaneous 17 Maximum output (kW) E/M Electronic / mechanical temperature control W Wall hung I Indoor H Horizontal installation B Water connections

2.3 Model name and number

identification

Model Name Model Number

WH17 EI 17 E/M W I H B

WH27 EI 27 E/M W I H B

Tab. 3

2.4 Package contents

• Tankless electric water heater.

• 4 screws and gasket.

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6720646951-14.1V

F K

2.5 Components Diagram

Fig. 1

A Heating module B Heating element assembly C Heating module PCB D Hot water outlet E Cold water inlet F Temperature adjustment knob G Flow transducer H Terminal block (CANADA ONLY) I 6 way terminal block J Temperature sensor K Control PCB L Double pole thermal cut-out M Inlet water filter N Flow regulator

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2.6 Dimensions

General information | 7US

Fig. 2

1 Outlet ¾" NPT (hot water) 2 Inlet ¾" NPT (cold water) 3 Temperature knob 4 LED

Dimensions

(inches) WH17 / WH27

A (Width) 15 ¼ "

B (Height) 12 ½ "

C (Depth) 4 ½ "

D 12 5/8"

E 12 5/8"

F 2 ½ "

G 3 ½ "

H 6

/8"

I 5 ¾ "

J 1 ¾ "

Water connections ¾ "

Tab. 4 Dimensions

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6720646951-02.1V

2.7 Wiring diagram

DANGER: Risk of electric shock!

B Always switch off the electricity supply to

the unit before any intervention in the heater.

Fig. 3 Internal wiring schematic for single phase WH27 unit.

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General information | 9US

6720646951-03.1V

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 electromechanical 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.

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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

Maximum flow rate

(refer to Fig. 11)

Tab. 5

13kW at 208V 20kW at 208V

84% of maximum at 220V 84% of maximum at 220V

75% of maximum at 208V 75% of maximum at 208V

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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 nongrounded 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.

Regulations | 11US

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

DANGER: Risk of electric shock!

B For safety reasons, disconnect the power

supply to the heater before any service or testing is performed.

WARNING:

B This 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.

4.1 Important information

DANGER:

B The installation must only be performed

by a qualified person in accordance with these instructions.

B Bosch Thermotechnology Corp. is not

responsible for improperly installed appliances.

WARNING:

B The 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:

B The 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.

4.2 Selection of place of installation

WARNING: Risk of freezing!

B Do 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.

• 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

WARNING:

B ELECTRICITY IS EXTREMELY

DANGEROUS. TAKE EXTRA PRECAUTIONS AND ENSURE ALL CIRCUIT BREAKERS ARE OFF BEFORE PERFORMING ANY WORK TO THE HEATER.

WARNING:

B Indoor installation only, where it will NOT

be exposed to freezing.

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.

Please follow these instructions. Failure to follow instructions may result in:

• Damage or injury.

• Improper installation/operation.

• Loss of warranty.

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.

Installation | 13US

4.3 Mounting the water heater

WARNING:

B The 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.

B Undo 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.

B Drill the holes and secure the heater using the four

wood screws supplied.

Fig. 5 Recommended minimum clearances

WH17 WH27

Top (A) 12" 12"

Sides 0" 0"

Bottom (B) 6" 6"

Front (C) 12" 12"

Tab. 6 Recommended minimum clearances

Fig. 6 Vertical mounting position

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4.4.1 Water quality

4.4 Water connections

WARNING:

B Do not install a non-return check valve

within 10 feet of the inlet.

WARNING:

B Do not apply heat or solder to

connections or pipe if they are already connected to the unit.

NOTICE: Disclaimer B 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).

B The 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).

B The heater must be installed with shutoff valves on

both the inlet and outlet connections.

B It is recommended that you use ¾ inch or ½ inch

copper or high-pressure flex connections.

B Do not use plastic piping within 3 feet on either side

of heater.

B Use Teflon tape for sealing pipe threads. Do NOT use

pipe dope.

B Remember 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.

B After 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.

The inlet and outlet connections are clearly marked on the heater. They each have a ¾ inch NPT connector.

Water quality can have an impact on appliance longevity and may not be covered under the manufacturer's warranty.

B For 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.

Description Max. Levels

pH pH 6.5 - 8.5

TDS

(total Dissolved Solids)

Total hardness mg/l or ppm

mg/l or ppm 500

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

4.5 Electrical connections

WARNING:

B 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.).

B Check the pressure of the main water supply. To

operate correctly, the heater needs the running pressures mentioned in Tab. 5.

Copyright6 720 646 951 (2011/09)

As per the Canadian Electrical Code, C22.102 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).

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.

Installation | 15US

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16 | Installation US

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)

Copyright6 720 646 951 (2011/09)

Installation | 17US

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.)

Connecting the supply cable - Canada only - not for the USA.

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.

• 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.

Fig. 10 For Canada only (Not for U.S.A.)

B Connect 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).

B Connect 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).

B Push and click the auxiliary terminal block onto the

louvered rail in the backplate.

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18 | Installation US

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

4.6.2 Adjusting the temperature dial

4.6 Starting up

4.6.1 Checking for leaks and purging air

B Verify all circuit breakers supplying power to the

water heater are turned off.

B The 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.

B Open all hot water taps supplied by the water heater

and inspect all water connections for leaks.

B With all hot water taps still open, inspect each tap to

ensure all air in the lines has been purged out.

B With the air purged and taps still flowing, turn on all

circuit breakers supplying the water heater.

B Close all hot water taps and proceed to the next

section.

4.6.3 Adjusting the flow

B Open fully both inlet and outlet shut-off valves at the

heater, then:

B Turn on fully the highest flowing hot water faucet

(e.g., bathtub) served by the water heater.

B Adjust 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

Before leaving the site, the installer should demonstrate the unit to the user and give them this guide.

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.

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5 Operation instructions

5.1 Before using the water heater

WARNING:

B Do 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.

B Check that the power is switched on at the circuit

breaker panel.

B Turn on the hot water faucet FULLY.

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).

Operation instructions | 19US

• 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.

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20 | Maintenance US

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:

B Disconnect electric supply. B Disconnect cold and hot water pipes from fittings on

bottom of heater. Allow water to drain out (have a catch basin ready).

B After 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

B Check that the power is switched off at the circuit

breaker panel.

B Shut off the installer supplied cold water isolation

valve to the heater. If one is not installed, install before proceeding.

B Open nearest hot water tap to relieve pressure in the

plumbing lines.

B Position a bucket under the cold water inlet

connection of the heater to catch any water that may drain.

B Disconnect the cold water plumbing connection from

the inlet (bottom right of heater) to access filter screen.

B Remove filter, clean with water and inspect for

damage. If the filter is at all damaged, it should be replaced.

B Replace the filter into the inlet housing B DO NOT leave the filter out. B DO NOT remove the flow regulator (located behind

the filter).

B DO NOT clear the filter by back flushing. B NEVER use an air line to blow out the heater (the flow

transducer will be permanently damaged).

B Before 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.

B Close all hot water taps and proceed for normal

operation.

Copyright6 720 646 951 (2011/09)

Using an ohmmeter to check for premature element failure

On WH17 model, there is no middle element

Maintenance | 21US

Fig. 12 Heating elements

Meter probes Ohm Readings

Outer to Outer 10.5 ± 0.6 Ohms

Middle to Middle 11.7 ± 0.8 Ohms

Inner to Inner 15.1 ± 1 Ohms

Tab. 8

Meter probes Ohm Readings

Outer to Outer 10.5 ± 0.6 Ohms

Middle to Middle 11.7 ± 0.8 Ohms

Inner to Inner 21.0 ± 1.2 Ohms

Tab. 9

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22 | Troubleshooting US

7 Troubleshooting

DANGER: Risk of electric shock!

B Always switch off the electricity supply to

the unit before you remove the cover.

Cold water only – Neon light off

Flow rate is too low Verify the flow rate out of fixture is at or above the minimum activation rate

required for the unit to activate. (Activation rates: WH17 = 0.6 GPM, WH27 = 0.8 GPM).

Plumbing crossover To test for a plumbing crossover, turn off power supply to the heater. Close

installer supplied cold water shut off valve (if none installed, install before proceeding). Open all hot water taps supplied by the heater. Wait 5 minutes and check all taps. Any water running is a sign of a plumbing crossover. Consult a local plumber or service person for help in correcting a plumbing crossover. To return the heater to service, reinstall cover, open the inlet water supply to the heater and open all hot water taps. Let all taps run until there is no air coming out of the fixtures. Shut off all hot water taps. Turn power supply on to the heater. Return heater to service. (This procedure will prevent the heating elements from burning out).

The flow transducer is not spinning

Turn off the power supply to the heater and remove the cover. Observe if the flow transducer "spins" when the water is turned on. Please note the flow transducer spins at a high speed and can appear to be stopped when actually spinning. It is recommended to observe the flow transducer without water flowing, then turn on a hot water tap while observing the flow transducer. If the flow transducer is not spinning, remove and flush flow transducer, noting the Do's and Dont's on page 20. See the technical support section of www.bosch-climate.us for more detailed instruction on removing the flow transducer.

Important: If you are unable to perform the tasks listed below, or need additional assistance please contact your original installer/licensed electrician.

No electricity at the heater or one of the supplies has failed

One or more of the heating module thermal cut-outs has tripped

The power supply voltage has dropped

Tab. 10

Have a licensed electrician verify proper wiring and adequate voltage on the terminal block inside the water heater. See the “Electrical connections” section on page 14 of this manual.

Turn off the power to the heater, remove the cover and locate the thermal cutouts on the top of each heating module. Check for continuity through each cutout. (Less than 0.5 Ohms). A continuity value greater than 0.5 Ohms indicates that the cutout has tripped or is faulty. A cutout will only trip in exceptional circumstances and it is essential that the cause is determined and resolved. Verify the heater's inlet filter screen and all outlets served by the heater are clear of debris. Ensure the heater is not being fed preheated water. This water heater is designed for cold water feed only. Contact Technical Support 800-798-8161 for further instructions.

This is likely an issue with the incoming power supply. Have a qualified electrician measure voltage on the water heater’s terminal block while operating at maximum flow and maximum temperature setting. The WH17 & WH27 models are rated for 240V and will also operate at 220V or 208V with reduced maximum flow rate.

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Cold water only – Neon light off

Troubleshooting | 23US

The inlet water temperature is too cold

Verify the heater is sized appropriately for it’s geographic location. Turn temperature knob located on the bottom of the water all the way clockwise for maximum temperature setting. Ensure flow rates are within the heater’s specifications. Refer to Fig. 11 on page 18 of the manual. Use of an isolation valve on the hot water outlet to control flow rate is recommended.

One of the power supplies is not on

Have a licensed electrician verify adequate voltage on the terminal block inside the water heater. Verify circuit breakers serving the heater are not tripped. See the “Electrical connections” section on page 14 of this manual.

Premature element failure Shut off power to the unit and remove cover. Use an ohmmeter to verify correct

resistance on each element. If readings are different than listed specifications on page 21, contact Technical Support 800-798-8161 for further instruction.

Tab. 10

Water not hot enough - Neon light on

The water supply is connected to the outlet of

Verify plumbing connections are correct (See Fig. 2). Reconnect the water supply to the inlet of the unit (marked blue).

the unit

One or more of the heating module thermal cut-outs has tripped

Temperature dial is turned too low

Turn the temperature dial located on the bottom of the water heater clockwise for hotter temperatures. Refer to Fig. 11 for outlet temperature vs. flow rate variance.

Water flow is too high Adjust water flow to stay within the water heater’s specifications. See Fig. 11 of

this manual.

Tab. 11

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Water flow too low

There are restrictions in the plumbing

Water supply pressure too low

Outlet shut-off valves are set too low

Tab. 12

Water Temperature too Hot

Temperature dial set too high

Obstructions in the water path can restrict the flow of water through the heater. Verify the heater’s inlet filter screen, faucet aerators, showerheads and whole house filters are clear of debris. Verify proper flow on the outlet side of the heater with the hot water pipe disconnected. Maximum flow rates for each unit are as follows. WH17 = 2.3gpm, WH27 = 3.5gpm.

Verify incoming water supply is at least 30psi. For people on well systems, the recommended pressure range is 30-50psi.

Adjust installer supplied outlet valve as described below:

• Completely open both installer supplied inlet and outlet shut-off valves at the heater. (if none installed, install before proceeding).

• Completely open hot water on the highest flowing hot water fixture served by the heater (i.e. bathtub).

• Slowly close the outlet shut-off valve, slowing the water flow rate until the temperature at the hot water faucet corresponds to the values given on Fig. 11 of the manual, or desired water temperature is reached.

Turn the temperature knob located on the bottom of the water heater counterclockwise for cooler temperatures.

There are restrictions in the plumbing

Inlet water temperature is too warm

Tab. 13

Obstructions in the water path can restrict the flow of water through the heater causing overheating. Verify the heater’s inlet filter screen, faucet aerators, showerheads and whole house filters are clear of debris. Verify proper flow on the outlet side of the heater with the hot water pipe disconnected. Opening hot water isolation valve fully may be necessary. Maximum flow rates for each unit are as follows. WH17 - 2.3gpm, WH27 - 3.5gpm.

Verify the heater is being feed with cold water only. This water heater is not designed for preheated water or recirculation applications. Increase flow rate where ever possible. Replacing low flow showerheads and aerators with higher flowing (GPM) ones may be necessary.

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