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.

Applications manual | 02.2009BOSCH THERMOTECHNOLOGY CORPORATION
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.

Applications manual | 02.2009BOSCH THERMOTECHNOLOGY CORPORATION
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