Bosch GWH 345 ESR Instructions for use

Applications manual
For GWH 345 ESR and GWH 450 ESR tankless water heaters

2| GWH 345/450 ESR applications manual
Application manual | 02.2009 BOSCH THERMOTECHNOLOGY CORPORATION

Applications manual | 02.2009BOSCH THERMOTECHNOLOGY CORPORATION
GWH 345/450 ESR applications manual | 3
Table of Contents
1 Introduction 4
2 Bosch Water Heating Models 5
2.1 Bosch GWH 345 ESR 5
2.2 Bosch GWH 450 ESR 6
3 External storage tank loading applications 7
3.1 GWH 345/450 ESR pressure drops & circulator guidelines 7
3.2 Tank loading diagrams 8
4 Open Loop Space Heating 10
5.1 External storage tank 10
5.2 Indirect tank applications 20

4| GWH 345/450 ESR applications manual
Application manual | 02.2009 BOSCH THERMOTECHNOLOGY CORPORATION
1 Introduction
The Applications Manual is intended to present some of the most
common applications of the Bosch GWH 345 ESR and GWH 450 ESR
tankless water heaters. Application drawings are shown with both
piping and corresponding electrical schematics where applicable.
Auxiliary equipment depicted does not necessarily represent any
one manufacturer or specific model number. There are a wide
variety of techniques, practices and piping strategies possible when
installing water heating appliances. It is the responsibility of the
installing contractor to determine the most suitable arrangement for
the application.
All drawings are conceptual in nature and does not address
all design, installation or safety considerations. Additional
safety and/or auxiliary equipment may be needed.
Drawings are for reference use by officials, designers and
licensed installers. It is expected that installers have
adequate knowledge of accepted industry practices for the
equipment, procedures, and applications involved. It is the
responsibiltiy of the installer to ensure that the installation
is in accordance with local building codes.
Although this manual covers many common applications for our
products, system possibilities are virtually endless. Should you
encounter an application that is not covered in this manual or have
any questions regarding any of its content, we encourage you to
contact your local sales representative or us directly at Bosch
Thermotechnology.
This is not a substitute for any of the product’s installation manuals.
All specifications subject to change.
Installation must conform with local codes or, in the absence of
local codes, the National Fuel Gas Code ANSI Z 223.1/NFPA 54.
In Canada: Installation must conform with CGA B149.(1,2)
INSTALLATION CODES and/or local installation codes.

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GWH 345/450 ESR applications manual | 5
2 Bosch Water Heating Models
2.1 Bosch GWH 345 ESR
Features:
XSpecifically designed for recirculating applications
XElectronic ignition and built in power vent
XGWH 345 ESR thermal efficiency of 82%
XVents vertically or horizontally with 3" stainless steel (AL29-4C)
XDirect vent room-sealed combustion
XComputerized temperature control — ensures temperature
stability
XModel GWH 345 ESR N for natural gas (NG) supply
XModel GWH 345 ESR L for liquid propane (LP) supply
X10-year warranty on heat exchanger
GWH 345 ESR Technical Specifications
Gas input 32,000 - 95,000 Btu/h
Maximum flow rates 3.5gpm @ 45°F rise
Thermal Efficiency 82%
Dimensions 27.5" h x 15.75" w x 11.75" d
Weight 47 lbs.
Modulating gas valve yes
Ignition Electronic
GWH 345 ESR Installation Specifications
Gas connection ¾" Male NPT
Water connections ¾" Male NPT
NG gas pressure Minimum: 5.5" W.C.
Maximum: 14" W.C.
LP gas pressure Minimum: 11" W.C.
Maximum: 14" W.C.
Electrical supply 120VAC - plugs in
Venting 3" stainless steel (AL29-4C)
direct vent
room-sealed combustion
GWH 450 ESR Installation Clearances
Top (A) 12"
Front (B) 1"
Back 0"
Sides 1"
Floor (C) 12"
Fig. 1 Venting configurations
Installation guidelines:
Venting:
XMust be 3" or 4" AL29-4C sealed stainless steel vent pipe.
XSlope horizontal runs up to termination ¼" per foot. The
horizontal section between last elbow and termination must slope
down to the termination ¼" per foot.
XDo not combination vent with any other appliance.
XAlways install an external condensate drain except when
terminating horizontally with less than 3 feet of pipe.
XSee manual for vent terminator clearances.
Gas piping:
XHeater will not function properly without adequate supply gas
pressure.
XAny appliance connector should be ¾" minimum diameter.
Plumbing:
XInstall the included pressure relief valve and pipe to suitable
drain.
XMinimum piping diameter is ¾".
XDo not solder directly to the bottom of the unit.
XUse unions to facilitate easy future maintenance.
XUse full port ball valves or isolation valves.
XPartially fill condensate drain tube loop with water prior
to start up.

6| GWH 345/450 ESR applications manual
Application manual | 02.2009 BOSCH THERMOTECHNOLOGY CORPORATION
2.2 Bosch GWH 450 ESR
Features:
XSpecifically designed for recirculating applications
XElectronic ignition and built in power vent
XGWH 450 ESR thermal efficiency of 81%
XVents vertically or horizontally with 3" stainless steel (AL29-4C)
XDirect vent room-sealed combustion
XComputerized temperature control — ensures temperature
stability
XModel GWH 450 ESR N for natural gas (NG) supply
XModel GWH 450 ESR L for liquid propane (LP) supply
X10-year warranty on heat exchanger
GWH 450 ESR Technical Specifications
Gas input 45,000 - 120,000 Btu/h
Maximum flow rates 4.5gpm @ 45°F rise
Thermal Efficiency 81%
Dimensions 27.5" h x 15.75" w x 11.75" d
Weight 47 lbs.
Modulating gas valve yes
Ignition Electronic
GWH 450 ESR Installation Specifications
Gas connection ¾" Male NPT
Water connections ¾" Male NPT
NG gas pressure Minimum: 5.5" W.C.
Maximum: 14" W.C.
LP gas pressure Minimum: 11" W.C.
Maximum: 14" W.C.
Electrical supply 120VAC - plugs in
Venting 3" stainless steel (AL29-4C)
direct vent
room-sealed combustion
GWH 450 ESR Installation Clearances
Top (A) 12"
Front (B) 1"
Back 0"
Sides 1"
Floor (C) 12"
Fig. 1 Venting configurations
Installation guidelines:
Venting:
XMust be 3" or 4" AL29-4C sealed stainless steel vent pipe.
XSlope horizontal runs up to termination ¼" per foot. The
horizontal section between last elbow and termination must slope
down to the termination ¼" per foot.
XDo not combination vent with any other appliance.
XAlways install an external condensate drain except when termi-
nating horizontally with less than 3 feet of pipe.
XSee manual for vent terminator clearances.
Gas piping:
XHeater will not function properly without adequate supply gas
pressure.
XAny appliance connector should be ¾" minimum diameter.
Plumbing:
XInstall the included pressure relief valve and pipe to suitable
drain.
XMinimum piping diameter is ¾".
XDo not solder directly to the bottom of the unit.
XUse unions to facilitate easy future maintenance.
XUse full port ball valves or isolation valves.
XPartially fill condensate drain tube loop with water prior
to start up.

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GWH 345/450 ESR applications manual | 7
3 External storage tank loading applications
Introduction
This section outlines tank loading options for high volume water
heating for large residential and light commercial applications
including continuous flows and high volume demands of large home
and commercial applications.
3.1 GWH 345/450 ESR pressure drops and circulator
guidelines
XThe maximum amp draw for any circulator connected directly to
the appliance must not exceed 1.5 amps
XCirculator should be sized by the professional plumbing
contractor
XBronze or stainless steel circulators are required for all open loop
applications
Pressure drop curves
Note : Flow above 6 GPM is not permitted.
GWH 345 ESR
0 feet of head
10 feet of head
20 feet of head
30 feet of head
0 GPM 1 GPM 2 GPM 3 GPM 4 GPM 5 GPM 6 GPM
water flow rate
head loss
GWH 450 ESR
0 feet of head
10 feet of head
20 feet of head
30 feet of head
0 GPM 1 GPM 2 GPM 3 GPM 4 GPM 5 GPM 6 GPM
water flow rate
head loss

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Application manual | 02.2009 BOSCH THERMOTECHNOLOGY CORPORATION
3.2 Tank Loading diagrams
3.2.1 Single unit tank loading application plumbing diagram
The GWH 345/450 ESR is specifically designed for this application
Symbols
Note: This drawing is conceptual in nature and does not address all design, installation or safety considerations.
Additional safety and/or auxiliary equipment may be needed. This diagram is for reference use by officials, designers and licensed installers.
It is expected that installers have adequate knowledge of accepted industry practices for the equipment, procedures, and applications involved.
Drawing is not to scale.
Drawing # STL CN revA 10/07
Service
valves
Bronze circulator sized
according to UPC standards
Potable water
expansion tank
Bosch GWH 345 ESR,
Bosch GWH 450 ESR
Flow
direction
Note: Piping to fixtures not shown for clarity purposes.
Cold water
feed DHW
Pressure
relief
valve
External
storage
tank
12K ohm
thermistor
with immersion
well
PS

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GWH 345/450 ESR applications manual | 9
3.2.2 Single unit tank loading application electrical diagram
The following shows the appropriate electrical connections for
plumbing diagram 3.2.1
Note: This drawing is conceptual in nature and does not address all design, installation or safety considerations.
Additional safety and/or auxiliary equipment may be needed. This diagram is for reference use by officials, designers and licensed installers.
It is expected that installers have adequate knowledge of accepted industry practices for the equipment, procedures, and applications involved.
Drawing is not to scale.
Drawing # ESTL CN revA 10/07
Single Unit Tank Loading
Electrical Diagram
PK
L N
P0
LL
PS
N L
PE
ESR control
board
Terminal box
110VAC from outlet
PS
PCB

10 | GWH 345/450 ESR applications manual
Application manual | 02.2009 BOSCH THERMOTECHNOLOGY CORPORATION
4 Open Loop Space Heating
Introduction
This section is designed to provide techniques for using a recirculat-
ing tankless water heater to heat domestic water and provide space
heating in residential applications. As with all installations, check
with the local authority having jurisdiction. Some jurisdictions may
not allow these types of applications.
Symbols
Note: This drawing is conceptual in nature and does not address all design, installation or safety considerations.
Additional safety and/or auxiliary equipment may be needed. This diagram is for reference use by officials, designers and licensed installers.
It is expected that installers have adequate knowledge of accepted industry practices for the equipment, procedures, and applications involved.
Drawing is not to scale.
Drawing # ROL CN revA 10/07
Service
valves
Bronze circulator
sized according to
UPC standards
Potable water
expansion tank
Flow
direction
Note: Piping to fixtures not shown for clarity purposes.
Bosch GWH 345 ESR,
Bosch GWH 450 ESR
Cold water
feed
DHW
Pressure
relief
valve
Storage
tank
P1
P2
PS
Thermostatic
Thermostatic
mixing
mixing
valve
valve
Radiant
piping
12K ohm
thermistor
with immersion
well
Air
separator
4.1 External storage tank
The appliances shown in this section are approved under ANSI
Z21.10.3 and CSA 4.3 as circulating gas water heaters. Only open
loop applications are approved under this standard.
4.1.1 Radiant space heating and DHW plumbing diagram

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GWH 345/450 ESR applications manual | 11
4.1.1 Radiant space heating and DHW electrical diagram
The following shows the appropriate electrical connections for plumbing diagram 4.1.1
Note: This drawing is conceptual in nature and does not address all design, installation or safety considerations.
Additional safety and/or auxiliary equipment may be needed. This diagram is for reference use by officials, designers and licensed installers.
It is expected that installers have adequate knowledge of accepted industry practices for the equipment, procedures, and applications involved.
Drawing is not to scale.
Drawing # EROL CN revA 10/07
Radiant Space Heating and DHW
Electrical Diagram
PK
L N
P0
LL
PS
N L
PE
ESR control
board
PS
Terminal box
110VAC from outlet
NPZCHX1ZR
X2
FUSE 1 AMP
24 VAC
POWER
TWO ZONE SWITCHING RELAY
SR 502 ZONE1 ZONE2
ZONE1 ZONE2
P1 P2
120Vac
Neutral
T
Stat
T
Stat
PCB

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Application manual | 02.2009 BOSCH THERMOTECHNOLOGY CORPORATION
4.1.2 Fan coil space heating and DHW plumbing diagram
Symbols
Note: This drawing is conceptual in nature and does to address all design, installation or safety considerations.
Additional safety and/or auxiliary equipment may be needed. This diagram is for reference use by officials, designers and licensed installers.
It is expected that installers have adequate knowledge of accepted industry practices for the equipment, procedures, and applications involved.
Drawing is not to scale.
Drawing # FCOL CN revA 10/07
Service
valves
Bronze circulator
sized according to
UPC standards
Potable water
expansion tank
Flow
direction
Note: Piping to fixtures not shown for clarity purposes.
Bosch GWH 345 ESR,
Bosch GWH 450 ESR
Cold water
feed
DHW
Pressure
relief
valve
Storage
tank
P1
PK
Thermostatic
mixing
valve
Air
separator
Tank
Aquastat
Fan Coil
Flow
check
valve
Fan Coil

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4.1.2 Fan Coil space heating and DHW electrical diagram
The following shows the appropriate electrical connections for
plumbing diagram 4.1.2
Note: This drawing is conceptual in nature and does not address all design, installation or safety considerations.
Additional safety and/or auxiliary equipment may be needed. This diagram is for reference use by officials, designers and licensed installers.
It is expected that installers have adequate knowledge of accepted industry practices for the equipment, procedures, and applications involved.
Drawing is not to scale.
Drawing # EFCOL CN revA 10/07
Fan Coil Space Heating and DHW
Electrical Diagram
PK
L N
P0
LL
PS
N L
PE
PK
Terminal box
110VAC from outlet
ESR control
board
AQUASTAT
TT
LR LS
H3 5
4
N/O
4
N/C
6
N/O
NN/C
6
SR501
1 ZONE
SWITCHING RELAY
120 VAC
INPUT
TT COM
WR 24
VAC
P1
120Vac
Neutral
T
Stat

14 | GWH 345/450 ESR applications manual
Application manual | 02.2009 BOSCH THERMOTECHNOLOGY CORPORATION
4.1.3 Baseboard/ Radiant Panel space heating and DHW plumbing
diagram
Symbols
Note: This drawing is conceptual in nature and does not address all design, installation or safety considerations.
Additional safety and/or auxiliary equipment may be needed. This diagram is for reference use by officials, designers and licensed installers.
It is expected that installers have adequate knowledge of accepted industry practices for the equipment, procedures, and applications involved.
Drawing is not to scale.
Drawing # BB OL CN revA 10/07
Service
valves
Bronze circulator
sized according to
UPC standards
Potable water
expansion tank Flow
direction
Note: Piping to fixtures not shown for clarity purposes.
Bosch GWH 345 ESR,
Bosch GWH 450 ESR
Cold water
feed
DHW
Pressure
relief
valve
Storage
tank
P1
PK
Thermostatic
Mixing
valve
Air
separator
Tank
Aquastat
Flow
check
valve
Baseboard/
Radiant
Panel

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4.1.3 Baseboard/Radiant Panel space heating and DHW electrical
diagram
The following shows the appropriate electrical connections for
plumbing diagram 4.1.3
Note: This drawing is conceptual in nature and does not purport to address all design, installation or safety considerations.
Additional safety and/or auxiliary equipment may be needed. This diagram is for reference use by officials, designers and licensed installers.
It is expected that installers have adequate knowledge of accepted industry practices for the equipment, procedures, and applications involved.
Drawing is not to scale.
Drawing # EBBOL CN revA 10/07
Baseboard Space Heating and DHW
Electrical Diagram
PK
L N
P0
LL
PS
N L
PE
Terminal box
110VAC from outlet
PK
ESR control
board
NPZCHX
1ZR
X2
ZONE1 ZONE2 ZONE3
ZONE1 ZONE2 ZONE3
FUSE 1 AMP
24 VAC
POWER
THREE ZONE SWITCHING RELAY
WITH OPTIONAL PRIORITY
SR 503
or equivalent
120Vac
Neutral
P1
T
Stat
AQUASTAT
TT
LR LS

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Application manual | 02.2009 BOSCH THERMOTECHNOLOGY CORPORATION
4.1.4 Baseboard/ Radiant Panel space heating and DHW (with Ariston mini tank) plumbing diagram
Symbols
Note: This drawing is conceptual in nature and does not address all design, installation or safety considerations.
Additional safety and/or auxiliary equipment may be needed. This diagram is for reference use by officials, designers and licensed installers.
It is expected that installers have adequate knowledge of accepted industry practices for the equipment, procedures, and applications involved.
Drawing is not to scale.
Drawing # BBAOL CN revA 10/07
Service
valves
Bronze circulator
sized according to
UPC standards Flow
direction
Note: Piping to fixtures not shown for clarity purposes.
Bosch GWH 345 ESR,
Bosch GWH 450 ESR
Cold water
feed
DHW
Pressure
relief
valve
PK
Thermostatic
mixing
valve
Aquastat
well & 12kohm
thermistor
Flow
check
valve
Baseboard/
Radiant
Panel
PS
Aquastat
well with
12k ohm
thermistor
(insulate piping
around thermistor)
Cold water
feed
Ariston GL8Ti
mini water
tank
Potable
water
expansion tank

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4.1.4 Baseboard/Radiant Panel space heating and DHW (with Ariston mini tank) electrical diagram
The following shows the appropriate electrical connections for plumbing diagram 5.1.4
Note: This drawing is conceptual in nature and does not address all design, installation or safety considerations.
Additional safety and/or auxiliary equipment may be needed. This diagram is for reference use by officials, designers and licensed installers.
It is expected that installers have adequate knowledge of accepted industry practices for the equipment, procedures, and applications involved.
Drawing is not to scale.
Drawing # EBBAOL CN revA 10/07
Baseboard/Radiant Panel Space Heating and DHW (with Ariston mini tank)
Electrical Diagram
PK
L N
P0
LL
PS
N L
PE
Terminal box
110VAC from outlet
PS
ESR control
board
Room Thermostat
TT
LR LS
PK
PCB

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Application manual | 02.2009 BOSCH THERMOTECHNOLOGY CORPORATION
4.1.5 Baseboard / Radiant Panel space heating and DHW (without storage tank) plumbing diagram
Symbols
Note: This drawing is conceptual in nature and does not address all design, installation or safety considerations.
Additional safety and/or auxiliary equipment may be needed. This diagram is for reference use by officials, designers and licensed installers.
It is expected that installers have adequate knowledge of accepted industry practices for the equipment, procedures, and applications involved.
Drawing is not to scale.
Drawing # BBNTOL CN revA 10/07
Service
valves
Bronze circulator
sized according to
UPC standards
Flow
direction
Note: Piping to fixtures not shown for clarity purposes.
Pressure
relief
valve
Thermostatic
mixing
valve
Aquastat
well & 12kohm
thermistor
Flow
check
valve
Baseboard/
Radiant
Panel
Bosch GWH 345 ESR,
Bosch GWH 450 ESR
Insulate
piping
DHW
PK
PS
Cold
water
feed
Piping
Insulation

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GWH 345/450 ESR applications manual | 19
4.1.5 Baseboard/Radiant Panel space heating and DHW (without storage tank) electrical diagram
The following shows the appropriate electrical connections for plumbing diagram 4.1.5
Note: This drawing is conceptual in nature and does not address all design, installation or safety considerations.
Additional safety and/or auxiliary equipment may be needed. This diagram is for reference use by officials, designers and licensed installers.
It is expected that installers have adequate knowledge of accepted industry practices for the equipment, procedures, and applications involved.
Drawing is not to scale.
Drawing # BBNTOL CN revA 10/07
Baseboard/Radiant Panel Space Heating and DHW
Without Storage Tank Electrical Diagram
PK
L N
P0
LL
PS
N L
PE
ESR control
board
PK
Terminal box
110VAC from outlet
PS
PCB
Room Thermostat
TT
LR LS

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Application manual | 02.2009 BOSCH THERMOTECHNOLOGY CORPORATION
4.2 Indirect Tank Applications
4.2.1 Indirect Baseboard/ Radiant Panel space heating and DHW plumbing diagram
Note: Not suitable for space heating applications requiring high water temperature.
Symbols
Note: This drawing is conceptual in nature and does not address all design, installation or safety considerations.
Additional safety and/or auxiliary equipment may be needed. This diagram is for reference use by officials, designers and licensed installers.
It is expected that installers have adequate knowledge of accepted industry practices for the equipment, procedures, and applications involved.
Drawing is not to scale.
Drawing # IDBBOL CN revA 10/07
Service
valves
Bronze circulator
sized according to
UPC standards
Potable water
expansion tank Flow
direction
Note: Piping to fixtures not shown for clarity purposes.
Pressure
relief
valve
Indirect
hot water
tank
P1
Air
seperator
Tank
Aquastat
Flow
check
valve
Baseboard/
Radiant
Panel
Bosch GWH 345 ESR,
Bosch GWH 450 ESR
Cold water
feed DHW
PK
Cold
feed
Thermostatic
Mixing
valve
Back Flow
preventer
Pressure
reducing
valve