Bosch GWH C 920 ES Bedienungsanleitung

GWH C 920 ES/ESC

INDOOR RESIDENTIAL AND COMMERCIAL MODELS

Temperature Modulated with Electronic Ignition

Suitable for heating potable water - Not approved for space heating purposes

(Intended for variable flow applications)

GWH C 920 ES/ESC - Natural Gas

GWH C 920 ES/ESC - Liquefied Petroleum (LP) Gas

6 720 608 836 (2009/05) US

Warning: If the information in this manual is not

followed exactly, a fire or explosion may result

causing property damage, personal injury or death.

Do not store or use gasoline or other flammable

vapors and liquids in the vicinity of this or any other

appliance.

Improper installation, adjustment, alteration,

service or maintenance can cause injury or

property damage. Refer to this manual. For

assistance or additional information consult a

qualified installer, service agency or the gas

supplier.

In the Commonwealth of Massachusetts this

product must be installed by a licensed plumber or

gas fitter.

Upon completion of the installation, these

instructions should be handed to the user of the

appliance for future reference.

What to do if you smell gas

• Close gas valve. Open windows.

• Do not try to light any appliance.

• Do not touch any electrical switch; do not use any

phone in your building.

• Immediately call your gas supplier from a neighbor’s

phone. Follow the gas supplier’s instructions.

• If you cannot reach your gas supplier, call the fire

department.

• Installation and service must be performed by a

qualified installer, service agency or the gas supplier.

6 720 608 836

Index

1 Warning 3

2 Appliance details 4

2.1 Features 4

2.2 GWH C 920 ES and GWH C 920 ESC

Specifications (Technical data) 5

2.3 Unpacking the tankless water heater 6

2.4 General rules to follow for safe operation 7

2.5 Dimensions and minimum installation

clearances 8

3 Installation instructions 9

3.1 Specialized tools 9

3.2 Introduction 9

3.3 Venting 9

3.4 Combustion air requirements 20

3.5 Proper location for installing your heater 21

3.6 Heater placement and clearances 21

3.7 Mounting installation 21

3.8 Gas piping & connections 22

3.9 Water connections 25

3.10 Water quality 26

3.11 Domestic hot water recirculation 27

3.12 Filling the condensate trap 28

3.13 Measuring gas pressure 29

4 Electrical connections 30

4.1 Electrical power supply 30

4.2 Position of the fuses in control unit 30

5 Operation instructions 31

5.1 Description of LCD Display 31

5.2 For your safety read before operating

your water heater 32

5.3 Power 32

5.4 Temperature selection 32

5.5 Use of optional remote control accessory

(part no. TSTAT2) 33

5.6 Operation 33

5.7 Reset button 33

5.8 Program button 33

5.9 Locked condition 34

6 Maintenance and service 34

6.1 Annual maintenance 34

6.2 Winterizing for seasonal use 35

6.3 Mineral scale build-up 35

6.4 Condensing heat exchanger unit 36

6.5 Adjusting CO2 36

6.6 Program values 39

6.7 Control unit diagnostics 40

7 Troubleshooting 41

7.1 Introduction 41

7.2 Burner does not ignite when hot water

is turned on 41

7.3 Water is too hot 41

7.4 Water is not hot enough 41

7.5 Low water flow/pressure 42

7.6 Hot water temperature fluctuates at tap 42

7.7 Noisy burner/heater during operation 42

8 Error codes 44

8.1 Error code diagnostics 44

9 Electrical diagram 48

10 Sensor resistance charts 49

11 Functional scheme 51

12 Interior components diagram

and parts list 52

12.1 Interior components 52

12.2 Components diagram 54

13 Protecting the environment 61

14 Limited Warranty 62

14.1 Limited warranty for GWH C 920 ES

residential model 62

14.2 Limited warranty for GWH C 920 ESC

commercial model 63

6 720 608 836

Warning

1 Warning

For your safety

Do not store or use gasoline or other flammable,

combustible or corrosive vapors and liquids in the

vicinity of this or any other appliance.

Warning: Carefully plan where to

install the heater. Correct combustion

air supply and flue pipe installation are

very important. If a gas appliance is not

installed correctly, fatal accidents can

result such as carbon monoxide

poisoning or fire.

Warning: Exhaust gas must be vented

to outside using approved vent material

See table 2, page 10 (For Canada use

only PVC ULC S636). Vent and

combustion air connector piping must

be sealed gas-tight to prevent

possibility of flue gas spillage, carbon

monoxide emissions and risk of fire,

resulting in severe personal injury or

death. Approved vent terminators must

be used when penetrating to the

outside.

Warning: Field wiring connections and

electrical grounding must comply with

local codes, or in the absence of local

codes, with the latest edition of the

National Electric Code, ANSI/NFPA 70,

or in Canada, all electrical wiring must

comply with the local codes and the

Canadian Electrical Code, CSA C22.1

Part 1.

Warning: Shock hazard: line voltage is

present. Before servicing the water

heater, unplug power supply cord from

outlet. Failure to do so could result in

severe personal injury or death.

Warning: The heater must be

disconnected from the gas supply

piping system during any pressure

testing of that system at test pressures

equal to or more than 0.5 psig.

Warning: The appliance should be

located in an area where water leakage

of the heat exchanger, piping or

connections will not result in damage to

the area adjacent to the appliance or to

lower floors of the structure. When such

locations cannot be avoided, it is

recommended that a suitable drain pan,

adequately drained, be installed under

the appliance. The pan must not restrict

combustion air flow.

Warning: The maximum inlet gas

pressure must not exceed the value

specified by the manufacturer and that

the minimum value listed is for the

purposes of input adjustment.

Warning: If a water heater is installed in

a closed water supply system, such as

one having a backflow preventer in the

cold water supply line, means shall be

provided to control thermal expansion.

Contact the water supplier or local

plumbing inspector on how to control

this situation.

Warning:

BEvery time there is a demand for hot

water the tankless must recognized the

activation flow, activate the burners and

raise the temperature to the set

temperature.

BThe time to reach set temperature

depends upon the inlet temperature, the

distance to the tap and the water flow.

BUse patterns with short on cycles may

not give the tankless the time to reach

the desired temperature. Examples are

commercial kitchen sprayers and some

dishwashers with short cycles.

BIn such applications a small buffer tank

may be needed to improve performance.

Contact Bosch Water Heating for

additional information.

Warning: Keep the appliance area

clear of combustible materials, gasoline

and other flammable vapors and liquids.

6 720 608 836

Appliance details

FCC:

This device complies with Part 15 of the FCC rules.

Operation is subject to the following two conditions: (1)

This device may not cause harmful interference, and (2)

this device must accept any interference received,

including interference that may cause undesired

operation.

Fig. 1

2 Appliance details

2.1 Features

Residential/commercial models

• GWH C 920 ES residential model

– maximum temperature 140° F

• GWH C 920 ESC commercial model

– maximum temperature 180° F

Parts

• Key pad interface control

• High power pre-mix compact burner with low NOx

emissions

• Modulating gas valve with constant gas:air ratio

control

• Modulating water valve for improved comfort and

temperature control.

High quality materials for long working life

• Copper heat exchanger

• High efficiency Ceramat Burner

• Compact space saver: mounts on a wall with

supplied bracket.

Features

• Easily removable one-piece cover

• LCD Display with backlight

• On/Off and Temperature control buttons

• Reset button

• Program button (Selectable temperature default)

• Error codes for easy diagnostics and repair

• Real-time diagnostics for troubleshooting/informa-

tional purposes.

Accessories (Bosch part #)

• Optional wireless remote control to operate with the

appliance (TSTAT2)

• Cascading kit (TLINK)

• Outdoor kit (PTOK)

• External water filter (part # 8 703 305 356)

• Concentric termination kit (BWH60L46)

• Freeze prevention kit (7 709 003 665).

Warning: Do not obstruct the flow of

combustion and ventilation air.

Warning: When manually operating the

relief valve, precautions must be taken

prior to operating the relief valve to avoid

contact with hot water coming out of the

relief valve and to prevent water

damage.

Caution: Label all wires prior to

disconnection when servicing controls.

Wiring errors can cause improper and

dangerous operation.

Verify proper operation after servicing.

Warning: If a relief valve discharges pe-

riodically, this may be due to thermal ex-

pansion in a closed water supply

system. Contact the water supplier or

local plumbing inspector on how to cor-

rect this situation. Do not plug the relief

valve.

HOT

BURN

D A N G E R

Water temperature over 125°F can

cause severe burns instantly or

death from scalds.

Children, disabled and elderly are

at highest risk of being scalded.

See instruction manual before

setting temperature at water

heater.

Feel water before bathing or

showering.

BOSCH is constantly improving its

products, therefore specifications are

subject to change without prior notice.

6 720 608 836

Appliance details

2.2 GWH C 920 ES and GWH C 920 ESC

Specifications (Technical data)

Approved in US/Canada

Capacity

Maximum flow rate: 9.2 GPM (35 l/min) at a 45°F

(25°C) rise. (with sufficient water pressure)

Maximum output

210,000 Btu/h (61.5 kW)

Maximum input

225,000 Btu/h (65.9 kW)

Efficiency in %

Thermal efficiency > 94%

Minimum Input

25,000 Btu/h (7.3 kW)

Temperature Control

GWH C 920 ES:

• Selection range: 100°F (38°C) - 140°F (60°C).

GWH C 920 ESC:

• Selection range: 100°F (38°C) - 180°F (82°C).

Default temperature: 122°F (50°C)

Stability: +/- 2°F (+/- 1°C)

Gas Requirement

Gas connection (inches) - ¾"

Inlet gas pressure under operation (with a high hot

water flow rate)*

• Propane: 8" - 13" water column

• Natural Gas: 3.5" - 10.5" water column.

* To measure Gas Pressure, see Measuring Gas

Pressure, chapter 3.13, page 29.

Water

• Hot water connection (inches) - ¾"

• Cold water connection (inches) - ¾"

• Water valve material: Polymer (PPS) (Polypropylene

Sulfid)

• Minimum water flow: 0.65 gallon/minute (2.5 l/m)

Note: Activation varies with inlet water temperatures

from 0.65 - 1.6 gallon/minute (2.5 - 6.1 l/m).

• Minimum recommended water pressure: 30 PSI

(2.07 bar)

• Minimum well pressure 40 psi, see page 25.

• Connections:

– Bottom of heater

Combustion

• NOx ≤55 ppm

• CO ≤290 ppm (measured)

• CO

level set from factory, see chapter 6.5, page 37.

Dimensions

• Depth (in): 11¼" (286 mm)

• Width (in): 17

" (452 mm)

• Height (in): 30½" (775 mm)

• Weight: 88 pounds (40 kg).

Gas types

Natural Gas.

LP Gas.

Voltage

120 V AC (60 Hz) nominal

Amperage

Idle - 40 mA

Operation - ≤2.5 A

Noise

45 - 65 db (A)

Safety devices

• Flame failure device (ionization flame rod sensor)

• Pressure relief valve (supplied with heater)

• Overheat prevention (temperature limiter/ECO)

• Outlet temperature sensor

• Backflow temperature sensor

• Exhaust gas temperature sensor.

Water protection

IP X4 (protection against water drops)

If appliance is installed at elevations above

2000ft, refer to table 12, page 18.

6 720 608 836

Appliance details

2.3 Unpacking the tankless water

heater

Before installing the unit, be certain you have the

correct heater for your type of Gas - Propane or

Natural Gas. Identification labels are found on the

shipping box, and on the rating plate which is located on

the right side panel of the cover.

Fig. 2 Rating plate

ASerial number

BType of gas

The box includes:

• Tankless water heater

• Pressure relief valve (150 psi / 500,000 Btu rating)

• Bracket for wall hanging the heater

• Exhaust vent adaptor (with 4 screws and gasket

provided)

• Combustion air inlet adaptor (with 3 screws and gas-

ket provided)

• Installation manual (manual can be downloaded from

www.boschpro.com)

• Product registration card.

Please complete and return the enclosed product

registration card.

The tankless water heater is not approved or

designed for:

•Manufactured (mobile) homes, boats or any

mobile installation. (Modular homes are

acceptable for installation).

•Use above 8000 ft A.S.L. altitude (see page 18).

•Outdoor installation without installation of

Outdoor kit (PTOK).

• Applications where inlet water temperature is

higher than 140°F (60°C). A thermostatic

mixing valve must be installed before the

appliance.

• Space heating purposes.

To remove front cover

BLoosen the two Philips head screws located on

bottom rear of cover (see Fig. 3).

Fig. 3 Loosen the two screws

BLift front cover upward and remove.

Fig. 4 Remove the front cover

To remove combustion cover (service only;

unplug appliance before removing cover)

BOpen the four clips and remove the combustion

cover (see Fig. 5).

Fig. 5 Remove the combustion cover

6 720 608 836

Appliance details

2.4 General rules to follow for safe

operation

B1. You must follow these instructions when you

install your heater. In the United States: The

installation must conform with local codes or, in the

absence of local codes, the National Fuel Gas Code

ANSI Z223.1/NFPA 54.

In Canada: The Installation must conform with CSA

B149.(1,2) INSTALLATION CODES and /or local

installation codes.

B2. Carefully plan where to install the heater. Correct

combustion air supply and vent pipe installation are

very important. If not installed correctly, fatal

accidents can occur, such as carbon monoxide

poisoning or fire.

B3. When the unit is installed indoors and ROOM

SEALED (twin pipe) it is permitted to be located in

bathrooms, bedrooms and occupied rooms that are

normally kept closed. See chapter 3.3 (page 9). If the

unit will be installed indoors and use indoor

combustion air, the place where you install the heater

must have enough ventilation. The National Fuel

Gas Code does not allow UNSEALED gas fired

water heater installations in bathrooms,

bedrooms or any occupied rooms normally

kept closed. See chapter 3.4 (page 20).

B4. You must correctly vent your heater. See

chapter 3.3 (page 9) on VENTING.

B5. The appliance and its gas connection must be leak

tested before placing the appliance in operation.

The appliance must be isolated from the gas supply

piping system by closing its individual manual gas

shutoff valve (not supplied with heater) during any

pressure testing at pressures in excess of ½ Psig

(3.5 kPa).

B6. Keep water heater area clear and free from

combustibles and flammable liquids. Do not locate

the heater over any material which might burn.

B7. Correct gas pressure is critical for the proper

operation of this heater. Gas piping must be sized to

provide the required pressure at the maximum output

of the heater, while all the other gas appliances are in

operation. Check with your local gas supplier, and

see the section on connecting the gas supply. See

chapter 3.8 (page 22).

B8. Should overheating occur or the gas supply fail to

shut off, turn off the gas supply at the manual gas

shut off valve, on the gas line. Note: manual gas

shutoff valve is not supplied with the heater but must

be field installed.

B9. Do not use this appliance if any part has been

underwater. Immediately call a qualified service

technician to inspect the appliance and to replace

any part of the control system and any gas control

which has been underwater.

B10. Failure to install heater correctly may lead to

unsafe operation and void the warranty.

B11. Water temperatures over 125°F can cause

severe burns instantly. If the outlet temperature is set

above 125°F, a thermostatically controlled mixing

valve or temperature limiting valve should be

considered to reduce the risk of scalding. Contact a

licensed plumber or the local plumbing authority for

further information.

6 720 608 836

Appliance details

2.5 Dimensions and minimum installation clearances

Fig. 6 Dimensions

1On/Off button

2Reset button

3Program button

4Power ON or stand-by LED

5LCD display

6Up button

7Down button

Fig. 7 Minimum clearances

Note: For servicing access, a 2 foot clearance is

recommended to the front cover.

6720608000-03.2AL

Model GWH C 920 ES

TOP (A) 12

FRONT (B) 1

BACK 0

SIDES 1

FLOOR (C) 12

Table 1 Minimum clearances

6 720 608 836

Installation instructions

3 Installation instructions

3.1 Specialized tools

The following specialized tools may be required for

installation:

• Manometer

• Multi-meter

• Combustion Gas Analyzer.

3.2 Introduction

Please follow these instructions. Failure to follow

instructions may result in:

BDamage or injury.

BImproper operation.

BLoss of warranty.

3.3 Venting

Warning:

The water heater must be installed by a

qualified installer in accordance with these

instructions. If improperly installed, a

hazardous condition such as explosion or

carbon monoxide poisoning could result.

Bosch Thermotechnology Corp. is not

responsible for improperly installed

appliances.

Common installation practice is to

first determine the venting/

combustion air point of termination,

then design the piping layout back to

the heater.

Warning:

BDo not reduce the exhaust or

combustion air vent pipe sizes.

BDo not common vent with any other

vented appliance or stove.

BDo not use Type-B vent as the actual

exhuast vent system for the appliance.

Warning: Failure to vent the exhaust

gases to the outside (see Table 2 for

proper material) may result in

dangerous flue gases filling the

structure in which it is installed.

Warning: In areas where outside

temperatures routinely come close to

freezing, sealed combustion operation

is required. Concentric termination or

separate terminations for combustion

and vent, must be installed on the same

wall or roof surface; however, never

facing the direction of prevailing winds.

Failure to do so may result in heat

exchanger freezing and bursting. This

failure is not covered under the

manufacturer's warranty.

Warning: Protect the exhaust and inlet

from leaves and debris by installing a

screen on the end of the terminator.

¼" mesh minimum opening

recommended on screen.

6 720 608 836

Installation instructions

3.3.1 Vent material

All combustion air and vent pipe materials and fittings

must comply with the following:

For specific questions concerning vent material,

specifications, usage or installation, please

contact the vent manufacturer directly.

All vent connections must be glued, except for the

exhaust accessory (see section 3.3.4) which is

screwed into place on the top of the appliance. Slide

the vent pipe into the exhaust accessory. The exhaust

pipe must be properly supported and must be pitched

a minimum of a ¼ inch per foot back to the appliance.

This allows the condensate to drain properly.

An optional concentric vent/air intake termination can

be used for the installation of a vertical or horizontal

venting system. (see Fig. 8).

The concentric vent/air intake body can be ordered

from your local wholesaler. (Part# BWH60L46).

The appliance can also be installed with separate air

intake and exhaust piping (see Fig. 11, Fig. 17 and Fig.

18, page 16).

Fig. 8 Concentric vent kit example

Item Material United States Canada

Vent or

air pipe

and

fitting

PVC schedule 40 ANSI/ASTM D1785

CSA or ULC

certified only

(ULC-S636)

PVC-DWV ANSI/ASTM D2665

CPVC schedule 40 ANSI/ASTM F441

ABS-DWV schedule 40 ANSI/ASTM D2661

Pipe

cement /

primer

PVC ANSI/ASTM D2564

CPVC ANSI/ASTM F493

ABS ANSI/ASTM D2235

Table 2 Approved vent material

Do not use cellular foam core pipe.

Description Length

Kit part no. and

quantity

BWH60L46

3- In. Rain Cap N/A 1

4- In. Diameter

SDR-26 Pipe 24 In. long 1

3- In. Y

Concentric Fitting N/A 1

2- ½ In. Diameter

SDR-26 Pipe 37-1/8 in. long 1

Table 3 Concentric vent part breakdown

6720608836-27.1Av

3 (76mm)"

INTAKE

EXHAUST

COMBUSTION

AIR

MAINTAIN 12 IN. (18 IN. FOR CANADA)

MINIMUM CLEARANCE ABOVE

HIGHEST ANTICIPATED SNOW LEVEL.

MAXIMUM OF 24 IN. ABOVE ROOF.

EXHAUST

ROOF BOOT/

FLASHING (FIELD

SUPPLIED

DRAIN TEE

CONCENTRIC

VENT KIT

(BWH60L46)

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