Bosch GWH C920ESC Instructions for use

Applications manual
For tankless and point-of-use water heaters

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Bosch applications manual | 3
Table of Contents
1 Introduction 4
2 Bosch Water Heating Model Certifications 4
3 Bosch Water Heater Accessories 5
4 Water Quality 5
5 Pump Sizing 6
5.1 Pressure drop curves 6
5.2 Domestic hot water circulation 7
5.3 Tank loading 7
6 Bosch Water Heating Models & Specifications 8
6.1 Sizing tankless water heaters 8
6.2 Outdoor Installation 10
6.3 Bosch gas tankless water heater specifications 11
6.4 Bosch electric tankless water heater specifications 12
2.5 Ariston electric mini-tank water heater specifications 12
7 Domestic Water Heating Applications 13
7.1 Point-of-use applications 13
7.2 Whole house applications 16
8 High Volume Potable Water Heating 22
8.1 Cascading unit applications 23
8.2 Parallel unit applications 25
9 Residential Solar Applications 26
9.1 Tankloading 26
9.2 Booster applications 27
10 Commercial Solar Applications 29
11 Commercial Water Heating Applications 30
11.1 Commercial kitchen applications 30
11.2 Basic tank loading with domestic recirculation 32
11.3 Advanced tank loading commercial hot water system 33

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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
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 manual 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
Z223.1/NFPA 54.
In Canada: Installation must conform with CGA B149.(1,2)
INSTALLATION CODES and/or local installation codes.
2 Bosch Water Heating Model Certifications
The following are certification stamps and explanations that are
specific to one or more Bosch tankless water heaters. These
certifications bring the appliances in accordance with the
requirements of the National Fuel Gas Code ANSI Z223.1/NFPA 54.
Certified to applicable U.S. standards for
appliances using gas or other petroleum fuel.
Certified to applicable Canadian standards for
appliances using gas or other petroleum fuel.
Certified by Underwriters Laboratories Inc.
Energy efficiency certified by Gas
Appliance Manufacturers Association
(GAMA), www.gamanet.org
For Models GWH C 920 ES, GWH C 920 ESC only
These models are built in accordance with the
requirements of the ASME Boiler and Pressure
Vessel Code and received the Certificate of
Authorization from the National Board. The heat
exchanger has the NB and the HLW stamps.
Plumbing-Heating-Cooling Contractors
Association
Other certifications:
Met the California Energy Commission (CEC) standards
Approved by the Commonwealth of Massachusetts
South Coast Air Quality Management

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3 Tankless Water Heater accessories
See Table 1 for available accessories for the Bosch line of tankless
water heaters.
NOTE: Only models that have accessories available are listed in
the table below.
Available accessories Table 1
715 ES C 800 ES C 920 ES/ESC
Concentric Vent/air Intake kit - stainless steel (part# ESHCK ) √
Concentric termination kit - PVC (part# 196016) √√
Exhaust / intake bird screen (part# L2594) √√
Vertical vent kit (part# ESVVT) √
Horizontal vent kit (part# 4TWHVK3SII) √
Outdoor kit (part# PTOK) √√√
Wireless remote control (part# TSTAT2) √√√
Cascading kit (part# TLINK) √√√
Freeze prevention kit (part# 7709003665) √√√
External water filter (part# 8703305356) √√√
Gas conversion kit (part# 8719002176) √
PVC Condensate drain tee (part# 196061)* √√
Condensate neutralization cartridge kit (part# JM-2KIT) √√
* Also included in the Concentric termination kit (part# 196016)
4 Water Quality
Poor water quality will have an impact on appliance longevity and
may void the manufacturer’s warranty. For water analysis data call
your local water department, or if on a well, have well water ana-
lyzed 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.
Water quality max. levels Table 2
Description Max. Levels
pH pH 6.5 - 8.5
TDS (Total Dissolved Solids) mg/l or ppm 500
Total hardness mg/l or ppm 100 (6 grains)
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

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5 Pump sizing
The following section outlines sizing pumps for domestic hot water
circulation and tank loading. Only models approved for such
applications are listed in this section.
Pump must be bronze or stainless steel.
Size the pump according to the system pressure drop chart
below.
Maximum flow allowed through the recirc loop is 5 GPM.
If the water heater is used within an approved hot water
recirculation application and supplied with circulated
water, the heat exchanger warranty is decreased. Please
refer to the installation manual for detailed warranty
period information.
Run the system for 30 minutes to remove debris from the
plumbing. Then remove the unit‘s inlet water filter to
decrease pressure drop through the system.
If the inlet water filter, when removed, contains debris
install a Y-strainer (installer supplied) on the cold water
inlet.
5.1 Pressure drop curves
0
10
20
30
40
50
60
70
0.50.40.30.20.10.0
Flow (GPM)
Pressure (Feet of Head)
GWH C 800 ES GWH C 920 series GWH 715 ES

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5.2 Domestic hot water circulation
 Must provide a recirculation flow above 1.7 GPM. This can be
verified in the control unit diagnostics section of the installation
manual; mode P4 – 3d.
Note: The Grundfos model 15-55 has been tested and shown to
work on recirculating systems up to 120 feet of total pipe length.
System conditions vary and each pump must be sized by a profes-
sional to insure performance.
Refer to pump manufacturers flow vs pressure specifications to
select a pump that can provide the flow rate greater than 1.7 gpm
while overcoming the pressure loss through:
• Tankless water heater (see Chapter 6.1)
• All building supply and return plumbing in the circulation loop
(reference local plumbing codes, standards, or practices)
System pressure drop
Pressure drop ¾" copper (PSI)
90 degree elbow 0.088
45 degree elbow 0.053
10 ft of straight pipe ½" 1.3
10 ft of straight pipe ¾" 0.35
Source: International Plumbing Code 2003 edition.
Examples:
1) Average house (less than 2500 square feet)
a) Total loop length approximately 120 ft
b) Pump recommendation: Grundfos UP 15-55 or equivalent.
2) Large house (2500 to 5000 square feet)
a) Total loop length approximately 240 ft
b) Pump recommendation: Grundfos UP 25-64 or equivalent.
NOTE: Use only bronze or stainless steel pumps. Do not use pumps
of iron construction as they will oxidize and clog the inlet filter on
the appliance.
Recommendations for domestic hot water recirculation
An Aquastat, with a 5° F differential to control the pump, is
recommended.
 The usage of a timer is recommended to limit the energy
consumption. The timer should also limit recirculation pump
operation to the time of day when occupants are home and likely
to use hot water.
 Water heater set point must be minimum of 14° F above the
Aquastat setpoint.
Example: Tankless water heater setpoint = 122°F
Aquastat setpoint = 108°F
 Keep hot water piping insulated to limit heat loss.
 Set temperature on the GWH 920 ESC must not exceed 140°F.
5.3 Tank loading
Table 2
# of
heaters
Pressure drop vs. flow
Models: C800ES,
C920ES, C920ESC
Pressure drop vs. flow
Model: 715ES
1 4gpm @ 40 feet of head 4gpm @ 32 feet of head
2 8gpm @ 40 feet of head 8gpm @ 32 feet of head
3 12gpm @ 40 feet of head 12gpm @ 32 feet of head
4 16gpm @ 40 feet of head 16gpm @ 32 feet of head
These guidelines should be followed to maximize system output:
•Ensure flow through each water heater is between 3.5-5.0 gpm
•Isolation valves or boiler drains should installed to facilitate
descaling in applications with hard water.
•Whenever possible, plumb the system or configure the tank to
draw cold supply water into the water heater during hot water
use.
We recommend Grundfos UP26-99, Taco 009 or equivalent potable
water circulators.

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6 Bosch Water Heating Models and
Specifications
This section describes the water heaters available from Bosch
Thermotechnology Corporation and provides a general overview to
the specifications of that particular model. More detailed
information is contained in the installation manuals. Download
these manuals at www.BoschPro.com.
6.1 Sizing tankless water heaters
Definitions
Major applications (2 GPM or more): Washing machine, bath tub,
shower nozzle
Minor applications(2 GPM or less): Low flow shower head, bath-
room 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 Sizing by Chart instructions
below in conjunction with the charts on the next page.
Rule of Thumb Sizing
Model Number Number of Major
Applications
Number of Minor
Applications
GWH C 920 ES/ESC 3 1
GWH 715 ES 2 0
GWH C 800 ES 2 1
GWH 425 HN/PN 1 1
GWH 425 HN/PN 0 2
GWH 260 PN 1 0
RP17PT 1 0
RP27PT 1 1
Sizing by Chart
Measure the flow rates at each fixture that will be used
simultaneously and add them together. If only one application will
be used at a time measure each fixture and use the maximum flow
rate observed
.
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.
For reference, see average ground water temperature map. Sub-
tract this temperature from the desired hot water temperature to
get the degree rise. If the desired hot water temperature is 120F
and incoming temperature is 55F, the desired degree rise is 65F.
Figure 1 Average ground water temperatures
This example requires a flow rate of 2.0 GPM at a 65˚F rise. Refer
to the graphs on the following page. Since the demand is above
the GWH 260 PN capacity, this application would require a GWH
425 HN/PN gas tankless water heater. The electrical model used
for this application would be the RP27PT electric tankless water
heater.

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0
1
2
3
4
5
6
7
8
G
WH 425 PN
/
H
N
GWH 260 PN
/
H
N
10 20 30 40 50 60 70 80 90
Degree rise (°F)
GPM
G
as Appl
i
ance S
i
z
i
ng Chart
G
WH 715 E
S
G
WH
C
800 ES
9
10
G
WH C 920 ES
/
ES
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 rise (°F)
G
P
M
Electric Appliance Sizin
g
Char
t
RP17PT
P
RP17PT
P
RP12PT
P
RP12PT
P
RP1P
P
P
P
RP7
P
RP9P
P
9P
RP3P
3
Note
:Maximum
f
low rates dependent on site condition
s

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6.2 Outdoor Installation
All models listed in this manual are designed to be installed indoors.
However, the following models are approved for outdoor installation
with the use of the Outdoor Kit (part# PTOK):
GWH 715 ES
GWH C 800 ES
GWH C 920 ES
GWH C 920 ESC
Outdoor Kit (PTOK) installation:
The installation of this outdoor kit (PTOK) is required when
installing any 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 short term freezing
conditions could exist.
Not for use in areas routinely exposed to freezing temperatures.
Minimum clearances:
Ref. Description Min.
distances
ADirectly below or adjacent to
an opening; operable
windows, doors and any fresh
air openings
≥1 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:
≥12" ≥12"
≥12"

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6.3 Bosch Gas Tankless Water Heater Specifications
Technical Specifications
Model 260 PN 425 PN 425 HN 715 ES C 800 ES C 920 ES/ESC
Gas input
(BTU/hr)
Min: 30,735 Min: 31,000 Min: 30,735 Min: 19,900 Min: 19,900 Min: 25,000
Max: 74,900 Max: 117,000 Max: 117,000 Max: 199,000 Max: 199,000 Max: 225,000
Minimum flow to
activate (GPM)
0.6 0.6 0.6 0.65 0.65 0.65
Maximum flow rate
at 45° rise (GPM)
2.6 4.2 4.2 7.2 8.0 9.2
Maximum flow rate
at 90° rise (GPM)
1.3 2.1 2.1 3.6 3.9 4.6
Thermal Efficiency NG: 78%
LP: 78%
NG: 78%
LP: 78%
NG: 80%
LP: 80%
NG: 82%
LP: 82%
NG: 92%
LP: 92%
NG: 94%
LP: 94%
Dimensions
(inches)
H: 28¾
W: 12¼
D: 8½
H: 25¾
W: 16¾
D: 8½
H: 25¾
W: 16¾
D: 8½
H: 30½
W: 17⅞
D: 11¼
H: 30½
W: 17⅞
D: 11¼
H: 30½
W: 17⅞
D: 11¼
Weight (lbs.) 25 33 33 67 74 88
Modulating gas valve yes yes yes yes yes yes
Ignition Standing
pilot
Standing
pilot
Hydro-
generated
Electronic Electronic Electronic
Gas connection ½" Male NPT ¾" Male NPT ¾" Male NPT ¾" Male NPT ¾" Male NPT ¾" Male NPT
Water connections ½" Male NPT ¾" Male NPT ¾" Male NPT ¾" Male NPT ¾" Male NPT ¾" Male NPT
NG gas pressure
(inches of W.C.)
Min: 7
Max: 14
Min: 7
Max: 14
Min: 7
Max: 14
Min: 3.5
Max: 10.5
Min: 3.5
Max: 10.5
Min: 3.5
Max: 10.5
LP gas pressure
(inches of W.C.)
Min: 11
Max: 14
Min: 11
Max: 14
Min: 11
Max: 14
Min: 8
Max: 13
Min: 8
Max: 13
Min: 8
Max: 13
Water pressure
Static - (PSI)
Min: 30
Min (well): 40
Max: 150
Min: 30
Min (well): 40
Max: 150
Min: 30
Min (well): 40
Max: 150
Min: 30
Min (well): 40
Max: 150
Min: 30
Min (well): 40
Max: 150
Min: 30
Min (well): 40
Max: 150
Electrical supply N/A N/A N/A 120VAC 120VAC 120VAC
Venting options Vertical
natural draft
* horizontal
termination
not allowed
Vertical
natural draft
* horizontal
termination
only with AQ4
vent kit
Vertical
natural draft
* horizontal
termination
only with AQ4
vent kit
direct vent
room-sealed
combustion
direct vent
room-sealed
combustion
direct vent
room-sealed
combustion
Venting diameter
(inches)
4 5 5 3 or 4 3 or 4 3 or 4
Vent material Type B-vent
recommended
Type B-vent
recommended
Type B-vent
recommended
Stainless steel
(AL29-4C)
PVC, CPVC,
or ABS
(Schedule 40)
PVC, CPVC,
or ABS
(Schedule 40)
Note:
C 920 ES (residential model) has a maximum setpoint temperature
of 140°F.
C 920 ESC (commercial model) has a maximum setpoint
temperature of 180°F.
Note:
For specifications and details on the Bosch GWH 345 ESR and
GWH 450 ESR models, see the GWH 345 ESR and GWH 450 ESR
applications manual.

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6.4 Bosch Electric Tankless Water Heater Specifications
Technical Specifications
Model RP1P RP2P RP3P RP7P RP9P RP12PT RP17PT RP27PT
Volts 240 277 120 240 277 240 240 240
Kilowatts 9.50 6.00 3.40 7.20 9.50 12.00 17.25 26.85
Amps 40 22 29 30 35 50 U.S.A: 80
(2 x 40)
U.S.A: 120
(3 x 40)
Canada: 80
(1 x 80)
Canada: 120
(1 x 120)
Minimum wire size
(AWG)
810101086U.S.A: 8 U.S.A: 8
Canada: see
Canadian
Electrical Code
Canada: see
Canadian
Electrical Code
Phase Single Single Single Single Single Single Single Single
Minimum flow to
activate (GPM)
0.75 0.50 0.50 0.75 0.75 0.75 0.6 0.8
Maximum flow rate
at 45° rise (GPM)
1.4 0.9 0.5 1.1 1.4 2.0 2.6 4.0
Maximum flow rate
at 80° rise (GPM)
n/a 0.5 n/a n/a n/a n/a 1.5 2.2
Thermal Efficiency 99% 99% 99% 99% 99% 99% 90% 94%
Dimensions
(inches)
H: 6½
W: 12¼
D: 3
H: 6½
W: 12¼
D: 3
H: 6½
W: 12¼
D: 3
H: 6½
W: 12¼
D: 3
H: 6½
W: 12¼
D: 3
H: 6½
W: 12¼
D: 3
H: 15½
W: 15¼
D: 4½
H: 15½
W: 15¼
D: 4½
Weight (lbs.) 6 6 6 6 6 6 20 22
Water connections ½" Male
NPT
½" Male
NPT
½" Male
NPT
½" Male
NPT
½" Male
NPT
½" Male
NPT
¾" Male
NPT
¾" Male
NPT
6.5 Ariston Electric Mini-tank Water Heater
Specifications
Technical Specifications
Model GL2.5Ti GL4Ti GL8Ti
Volts 120 120 120
Watts 1500 1500 1500
Amps 12.5 12.5 12.5
Wire size Plug-in Plug-in Plug-in
Tank volume (gallons) 2.75 3.85 7.00
Dimensions
(inches)
H: 14
W: 14
D: 10¼
H: 14
W: 14
D: 12¼
H: 17½
W: 17½
D: 14½
Recovery at 90° F rise
(gallons per hour)
6.8 6.8 6.8
Temperature range 65 - 145° F 65 - 145° F 65 - 145° F
Water connections ½" Male NPT ½" Male NPT ¾" Male NPT
Operating pressure (PSI) 150 150 150

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7 Domestic Water Heating Applications
Potable water
Potable water is water that is suitable for drinking. Bosch Water
Heating appliances are approved to heat potable water only. Heating
any other liquid other than potable water will void the
manufacturer’s warranty covering the appliance.
Introduction
This chapter covers the various application techniques Bosch Water
Heating recommends. The schematics are to be used by professional
contractors in designing a domestic water heating system. The
applications covered range from single sink point-of-use applications
to multi-appliance central domestic recirculation applications.
7.1 Point-of-use applications
Point-of-use applications cover the small applications in which a
large water heater would be inefficient. Installing a smaller heater at
a point-of-use puts the heater near the hot water demand and
reduces the wait for hot water. Common applications for these
appliances include homes, offices, warehouses, service stations,
stores, concession stands and summer camps.

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7.1.1 Ariston mini tank
Simply tap into the cold water line and install the water heater
directly at the sink. All models plug into a standard 120 volt outlet.
Heater can be wall mounted, or sit on the floor.
Symbols
Temperature and pressure
relief valve
Drain pan
Sink
Note:
Drawing is not to scale.
Cold water piping to fixtures not shown for clarity purposes.
Ariston Pro GL4 Ti
Ariston Pro GL2.5 Ti
Ariston Pro GL8 Ti
hot
cold
cold
Flow direction
Service valve
hot

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7.1.2 Powerstream Pro electric point-of-use tankless water heater
PowerstreamPro point-of-use water heaters come in four models to
serve a wide range of applications. Finding the right model depends
upon your desired temperature and flow rate. See Section 2.1 to
find the model best suited to your customer‘s needs. Flow controls
and faucet aerators can greatly enhance performance.
Note: Water heater must be filled with water and purged of air prior
to supplying power.
Symbols
Service valve
Sink
Flow direction
hot
hot
cold
Powerstream Pro
RP1P, RP2P, RP3P,
RP7P, RP9P
Note:
Drawing is not to scale.
RP12PT cannot be mounted sideways.
Cold water piping to fixtures not shown for clarity purposes.
hot cold supply
hot cold
Powerstream Pro
RP1P, RP2P, RP3P,
RP7P, RP9P, RP12PT
cold supply

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7.2 Whole house applications
Whole house applications cover the typical home applications up to
a 2 or 3 bedroom house. See the sizing guide (Section 6.1) to
determine the best Bosch water heater model for your application.
An enhanced design including an Ariston mini tank in line to the hot
water source will reduce the wait time for hot water and improve
temperature stability.
7.2.1 Low volume tankless water heater applications
The Bosch GWH 260 PN gas tankless water heater and the RP17PT
electric tankless water heater offer a compact and lightweight
design for easy installation.
Both appliances are intended for low volume applications
(e.g. camps, cottages, cabins).
Symbols
Pressure
relief valve
Service valves
Sink
hot cold
BOSCH
Low flow
shower
Bosch GWH 260 PN
Flow direction
Note:
Drawing is not to scale.
Cold water piping to fixtures not shown for clarity purposes.
Powerstream Pro
RP17PT
ColdHot

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7.2.2 Powerstream Pro whole house applications
The RP27PT must be hard wired.
Symbols
Service
valve
Sink
Powerstream Pro
RP27PT
Standard tub
fixture
Ariston Pro GL4Ti
- for pipe runs over
100 ft between
tankless heater
and Ariston, use
GL8Ti
ColdHot
Note: place Ariston close to the point of
use to reduce wait time for hot water.
cold
hot
Powerstream Pro
RP27PT
ColdHot
Note:
Drawing is not to scale.
Cold water piping to fixtures not shown for clarity purposes.
Flow
direction
Pressure &
temperature
relief valve

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7.2.3 Powerstream Pro whole house application with domestic
recirculation loop
The circulator should be controlled by an external aquastat, or with
a timer to run only during times of expected hot water usage.
Insulate piping in hot water recirculation loop to limit heat loss.
Powerstream Pro
RP17PT or RP27PT
Ariston Pro mini-tank
(2.5, 4 and 8 gallon
sizes)
ColdHot
Note:
Drawing is not to scale.
Cold water piping to fixtures not shown for clarity purposes.
Symbols
Service
valve
Sink Standard
tub fixture
Bronze or stainless steel
circulator pump sized
according to UPC standards
(Taco Bronze 007 or Grundfos 15-42B
will cover most homes up to 3 bathrooms)
Potable water
expansion tank
Flow check valve Flow direction
Timer
Aquastat
See Chapter 5.1 for recirculation pump parameters

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7.2.4 Bosch ProTankless gas water heater
Below are two examples of Bosch ProTankless gas water heater
installations for the whole house. One example shows an Ariston
mini tank in line for reduced hot water wait time and increased
temperature stability.
Symbols
Service
valve
Sink
Standard tub fixture
Flow
direction
Pressure
relief
valve
Bosch GWH 425 PN,
Bosch GWH 425 HN,
Bosch GWH 715 ES,
Bosch GWH C 800 ES,
Bosch GWH C 920 ES
ColdHot
Note: place Ariston close to the point of
use to reduce wait time for hot water.
cold
hot
Cold
Hot
Note:
Drawing is not to scale.
Cold water piping to fixtures not shown for clarity purposes.
Bosch GWH 425 PN,
Bosch GWH 425 HN,
Bosch GWH 715 ES,
Bosch GWH C 800 ES,
Bosch GWH C 920 ES
Ariston Pro GL4Ti
- for pipe runs over
100 ft between
tankless heater
and Ariston, use
GL8Ti

20 | Bosch applications manual
Bosch applications manual | 06.2009 BOSCH THERMOTECHNOLOGY CORPORATION
7.2.5 Bosch ProTankless gas water heater with domestic
recirculation loop
The circulator should be controlled by an external aquastat or with a
timer to run only during times of expected hot water usage.
Insulate piping in hot water recirculation loop to limit heat loss.
Ariston Pro mini-tank
(2.5, 4 and 8 gallon
sizes)
ColdHot
Note:
Drawing is not to scale.
Cold water piping to fixtures not shown for clarity purposes.
Symbols
Service
valve Sink Standard
tub fixture
Bronze or stainless steel
circulator pump sized
according to UPC standards
(Taco Bronze 007 or Grundfos 15-42B
will cover most homes up to 3 bathrooms)
Potable water
expansion tank
Flow check valve Flow direction
Timer
Bosch GWH 425 PN,
Bosch GWH 425 HN,
Bosch GWH 715 ES,
Bosch GWH C 800 ES,
Bosch GWH C 920 ES
Aquastat
See Chapter 5.1 for recirculation pump parameters