Bosch GWH 425 PN Instructions for use

Applications manual
For tankless and point of use water heaters

2| Applications manual
Application manual | 11.2007 Bosch Water Heating
Table of Contents
1 Introduction 3
2 Bosch Water Heating Models 3
2.1 Sizing tankless water heaters 4
2.2 Bosch GWH 715 ES 6
2.3 Bosch GWH C 800 ES 7
2.4 Outdoor Installation for GWH 715 ES and GWH C 800 ES 8
2.5 Bosch GWH 345 ESR 9
2.6 Bosch GWH 450 ESR 10
2.7 Bosch GWH 425 EF 11
2.8 Bosch GWH 425 HN 12
2.9 Bosch GWH 425 PN 13
2.10 Bosch GWH 260 PN 14
2.11 Powerstream Pro RP17PT, RP27PT 15
2.12 Powerstream Pro RP1P, RP2P, RP3P, RP7P, RP9P, RP12PT 16
2.13 Ariston Pro GL2.5Ti, GL4Ti, GL8Ti 17
3 Domestic Water Heating Applications 18
3.1 Point-of-use applications 18
3.2 Whole house applications 22
4 High Volume Potable Water Heating 26
4.1 Parallel unit applications 26
4.2 Cascade unit applications 28
4.3 External storage tank loading applications 29
5 Open Loop Space Heating 32
5.1 External storage tank 32
5.2 Indirect tank applications 42
6 Maintenance Drawings 44
6.1 Descaling procedure 44
6.1 Descaling procedure diagram 45

Applications manual | 11.2007Bosch Water Heating
Applications manual | 3
1 Introduction
The Bosch Applications Manual is intended to present some of the
most common applications of the Bosch line of tankless and point of
use water heaters. Application drawings are shown with both piping
and corresponding electrical schematics where applicable. Auxiliary
equipment depicted does not necessarily represent any one manu-
facturer 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.
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 Water
Heating.
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) INSTAL-
LATION CODES and/or local installation codes.
2 Bosch Water Heating Models
This section describes the water heaters available from Bosch Water
Heating. The information given in each section provides a general
overview to the specifications of that particular model. More detai-
led information is contained in the installation manuals. Download
these manuals at www.BoschPro.com.

4| Applications manual
Application manual | 11.2007 Bosch Water Heating
2.1 Sizing tankless water heaters
Definitions
Major applications (2 GPM or more): Washing machine, bath tub,
shower nozzle
Minor applications(1.5 GPM or less): Low flow shower head,
bathroom sink, kitchen sink
Rule of thumb sizing
The tables below provide a general rule of thumb when sizing for
most residential applications. For commercial applications or for a
more detailed sizing method, use the instructions below in conjunc-
tion with the charts on the next page.
Sizing by Chart
Measure the flow rates at each fixture that will be used simultane-
ously and add them together. If only one application will be used
at a time measure each fixture and use the maximum flow rate
observed.
Rule of Thumb Sizing
Model Number Number of Major
Applications
Number of Minor
Applications
GWH 715 ES 2 0
GWH C 800 ES 2 1
GWH 425 HN/PN/EF 1 1
GWH 425 HN/PN/EF 0 2
GWH 260 PN 1 0
RP17PT 1 0
RP27PT 1 1
Using a known volume container, record several fill times. Per-
form the calculation below to determine the flow rate (a one
gallon fill time of 30 seconds is 2.0 gallons per minute (GPM):
Flow rate (GPM) = Volume (gallons)
Fill time (sec)
sec
min
60
x
Using a thermometer, measure the incoming water temperature.
Subtract this temperature from the desired hot water temperature
to get the degree rise. So, if the desired hot water temperature is
120F and incoming temperature is 55F, the desired degree rise is
65F.
This example requires a flow rate of 2.0 GPM at a 65˚F rise. The
data point is shown on each graph. Since the demand is above
the GWH 260 PN capacity, this application would require a GWH
425 HN/PN/EF gas tankless water heater. The electrical model
used for this application would be the RP27PT electric tankless
water heater.

Applications manual | 11.2007Bosch Water Heating
Applications manual | 5
0
1
2
3
4
5
6
7
8
GWH 425 PN/HN
4
GWH 425
4
GWH 260 PN/HN
2
10 20 30 40 50 60 70 80 90
Degree rise (°F)
GPM
G
as App
l
iance Sizing C
h
ar
t
GWH 715 ES
7
GWH C 800 ES
C
GWH C 8
C
0
.
0
0
.
5
1.
0
1.
5
2
.
0
2
.
5
3
.
0
3
.
5
4.
0
RP27PT
P
10 20 30 40 50 60 70 80 90
Degree ris
e
G
P
M
El
ectric App
l
iance Sizing C
h
art
RP17PT
P
RP17PT
P
RP12PT
P
RP12PT
P
RP1P
P
P
R
P7
P
RP9P
P
9P
RP3P
3
Note
:Maximum flow rates de
p
endant on site condition
s

6| Applications manual
Application manual | 11.2007 Bosch Water Heating
2.2 Bosch GWH 715 ES
Features:
Electronic ignition and built in power vent
82% thermal efficiency
Vents vertically or horizontally with 3" or 4" stainless steel (AL29-
4C)
Direct vent room-sealed combustion
Computerized temperature control — ensures temperature stability
Model GWH 715 ES N for natural gas (NG) supply
Model GWH 715 ES L for liquid propane (LP) supply
15-year warranty
Qualifies for $300 tax credit
GWH 715 ES Technical Specifications
Gas input Natural Gas: 19,900 - 199,000 BTU
LP Gas: 19,900 - 199,000 BTU
Minimum flow to activate 0.65 gallons per minute (gpm)
Flow rates 45˚F rise @ 7.2 gpm
55˚F rise @ 5.9 gpm
65˚F rise @ 5.0 gpm
77˚F rise @ 4.2 gpm
90˚F rise @ 3.6 gpm
Thermal Efficiency NG: 82% LP: 82%
Dimensions 30½" h x 17⅞" w x 11¼" d
Weight 67 lbs.
Modulating gas valve yes
Ignition Electronic
Accessories Outdoor kit (PTOK)
Wireless Remote (TSTAT2)
Tankless Link Cascading Kit (TLINK)
Freeze Prevention Kit (8700400022)
Water Filter Kit (8703305356)
GWH 715 ES Installation Specifications
Gas connection ¾" Male NPT
Water connections ¾" Male NPT
NG gas pressure Minimum: 4" W.C.
Maximum: 14" W.C.
LP gas pressure Minimum: 9" W.C.
Maximum: 14" W.C.
Water pressure
(Static)
Minimum: 30 PSI
Minimum well pressure: 40 PSI
Maximum: 150 PSI
Electrical supply 120VAC - plugs in
Venting 3" or 4" stainless steel (AL29-4C)
direct vent
room-sealed combustion
GWH 715 ES Installation Clearances
Top (A) 12"
Front (B) 1"
Back 0"
Sides 1"
Floor (C) 12"
3ft minimum
distance
3ft minimum
distance
Fig. 1 Venting configurations
Installation guidelines:
Venting:
Must be 3" or 4" AL29-4C sealed stainless steel vent pipe.
Slope horizontal runs up to termination ¼" per foot. The last
horizontal section of exhaust vent pipe between last elbow and
termination must slope down to the termination ¼" per foot.
Do not combination vent with any other appliance.
Install condensate drain where applicable.
See manual for vent terminator clearances.
Gas piping:
Heater will not function properly without adequate supply gas
pressure.
Any appliance connector should be ¾" minimum diameter
Plumbing:
Install the included pressure relief valve and pipe to suitable
drain.
Minimum piping diameter is ¾".
Do not solder directly to the bottom of the unit.
Use unions to facilitate easy future maintenance.
Use full port ball valves for isolation valves.
Partially fill condensate drain tube loop (where applicable) with
water prior to start up.

Applications manual | 11.2007Bosch Water Heating
Applications manual | 7
2.3 Bosch GWH C 800 ES
Features:
Electronic ignition and built in power vent
Condensing technology with 92% thermal efficiency
Vents vertically or horizontally with 3" or 4" PVC, CPVC or ABS
(Schedule 40) vent pipe.
Direct vent room-sealed combustion with concentric venting
option
Computerized temperature control — ensures temperature stability
Model GWH C 800 ES N for natural gas (NG) supply
Model GWH C 800 ES L for liquid propane (LP) supply
15-year warranty
Qualifies for $300 tax credit
GWH C 800 ES Technical Specifications
Gas input Natural Gas: 19,900 - 199,000 BTU
LP Gas: 19,900 - 199,000 BTU
Minimum flow to activate 0.65 gallons per minute (gpm)
Flow rates 45˚F rise @ 8.0 gpm
55˚F rise @ 6.4 gpm
65˚F rise @ 5.5 gpm
77˚F rise @ 4.6 gpm
90˚F rise @ 3.9 gpm
Thermal Efficiency NG: 92% LP: 92%
Dimensions 30½" h x 17⅞" w x 11¼" d
Weight 74 lbs.
Modulating gas valve yes
Ignition Electronic
Accessories Outdoor kit (PTOK)
Wireless Remote (TSTAT2)
Tankless Link Cascading Kit (TLINK)
Freeze Prevention Kit (8700400022)
Water Filter Kit (8703305356)
Concentic Termination Kit
(BWH60L46)
GWH C 800 ES Installation Specifications
Gas connection ¾" Male NPT
Water connections ¾" Male NPT
NG gas pressure Minimum: 4" W.C.
Maximum: 14" W.C.
LP gas pressure Minimum: 9" W.C.
Maximum: 14" W.C.
Water pressure
(Static)
Minimum: 30 PSI
Minimum well pressure: 40 PSI
Maximum: 150 PSI
Electrical supply 120VAC - plugs in
Venting 3" or 4" PVC, CPVC, or ABS
(Schedule 40) direct vent sealed
combustion
GWH C 800 ES Installation Clearances
Top (A) 12"
Front (B) 1"
Back 0"
Sides 1"
Floor (C) 12"
INTAKE
EXHAUST
COMBUSTION
AIR
MAINTAIN 12 IN.
(18IN. FOR CANADA)
MINIMUM CLEARANCE
ABOVE
HIGHEST ANTICIPATED
SNOW LEVEL.
MAXIMUM OF 24 IN.
ABOVE ROOF.
VENT
ROOF BOOT/
FLASHING (FIELD
SUPPLIED
DRAIN TEE
INTAKE
EXHAUST
MINIMUM
1”
VENT
COMBUSTION
AIR
DRAIN TEE
Fig. 1 Venting configurations
Installation guidelines:
Venting:
Must be 3" or 4" PVC, CPVC or ABS (Schedule 40) vent pipe.
Attach drain for internal condensate siphon and dispose of
according to local codes.
Do not combination vent with any other appliance.
Install an external condensate drain where applicable.
See manual for vent terminator clearances.
Gas piping:
Heater will not function properly without adequate supply gas
pressure.
Any appliance connector should be ¾" minimum diameter
Plumbing:
Install the included pressure relief valve and pipe to suitable
drain.
Minimum piping diameter is ¾".
Do not solder directly to the bottom of the unit.
Use unions to facilitate easy future maintenance.
Use full port ball valves for isolation valves.
Partially fill condensate drain tube loop (where applicable)

8| Applications manual
Application manual | 11.2007 Bosch Water Heating
2.4 Outdoor Installation for GWH 715 ES,
and GWH C 800 ES
Outdoor Kit (PTOK) installation:
The installation of this outdoor kit (PTOK) is required when
installing either of the above appliances outdoors
Outdoor cap easily retrofits to these indoor models
Outdoor kit comes with Freeze Prevention which must be installed
Exterior water piping should be protected if freezing conditions
could exist
Minimum clearances:
Ref. Description Min.
distances
ADirectly below or adjacent to
an opening; operable
windows, doors and any fresh
air openings
≥4 ft
B
C
D From any adjacent wall ≥4 ft
EBelow a gutter, sanitary
pipework, eaves or overhang ≥3 ft
F Above ground ≥1 ft
GFrom a gas meter or gas
regulator
≥5 ft
Outdoor Installation Clearances
Source: NFPA 54 National Fuel Gas Code
ANSI Z223.1
Installation on wood siding
Installation on vinyl siding:

Applications manual | 11.2007Bosch Water Heating
Applications manual | 9
2.6 Bosch GWH 345 ESR
Features:
Specifically designed for recirculating applications
Electronic ignition and built in power vent
GWH 345 ESR thermal efficiency of 82%
Vents vertically or horizontally with 3" stainless steel (AL29-4C)
Direct vent room-sealed combustion
Computerized temperature control — ensures temperature
stability
Model GWH 345 ESR N for natural gas (NG) supply
Model GWH 345 ESR L for liquid propane (LP) supply
10-year warranty
GWH 345 ESR Technical Specifications
Gas input GWH 345 ESR: 32,000 - 95,000 Btu/h
Maximum flow rates GWH 345 ESR: 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:
Must be 3" or 4" AL29-4C sealed stainless steel vent pipe.
Slope horizontal runs up to termination ¼" per foot. The horizon-
tal section between last elbow and termination must slope down
to the termination ¼" per foot.
Do not combination vent with any other appliance.
Always install an external condensate drain except when termi-
nating horizontally with less than 3 feet of pipe.
See manual for vent terminator clearances.
Gas piping:
Heater will not function properly without adequate supply gas
pressure.
Any appliance connector should be ¾" minimum diameter
Plumbing:
Install the included pressure relief valve and pipe to suitable
drain.
Minimum piping diameter is ¾".
Do not solder directly to the bottom of the unit.
Use unions to facilitate easy future maintenance.
Use full port ball valves for isolation valves.
Partially fill condensate drain tube loop with water prior to start
up.

10 | Applications manual
Application manual | 11.2007 Bosch Water Heating
2.6 Bosch GWH 450 ESR
Features:
Specifically designed for recirculating applications
Electronic ignition and built in power vent
GWH 450 ESR thermal efficiency of 81%
Vents vertically or horizontally with 3" stainless steel (AL29-4C)
Direct vent room-sealed combustion
Computerized temperature control — ensures temperature
stability
Model GWH 450 ESR N for natural gas (NG) supply
Model GWH 450 ESR L for liquid propane (LP) supply
10-year warranty
GWH 450 ESR Technical Specifications
Gas input GWH 450 ESR: 45,000 - 120,000 Btu/h
Maximum flow rates GWH 450 ESR: 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:
Must be 3" or 4" AL29-4C sealed stainless steel vent pipe.
Slope horizontal runs up to termination ¼" per foot. The horizon-
tal section between last elbow and termination must slope down
to the termination ¼" per foot.
Do not combination vent with any other appliance.
Always install an external condensate drain except when termi-
nating horizontally with less than 3 feet of pipe.
See manual for vent terminator clearances.
Gas piping:
Heater will not function properly without adequate supply gas
pressure.
Any appliance connector should be ¾" minimum diameter
Plumbing:
Install the included pressure relief valve and pipe to suitable
drain.
Minimum piping diameter is ¾".
Do not solder directly to the bottom of the unit.
Use unions to facilitate easy future maintenance.
Use full port ball valves for isolation valves.
Partially fill condensate drain tube loop with water prior to start
up.