Bosch GWH C920ESC Instructions for use

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

2| Bosch applications manual
Bosch applications manual | 06.2009 BOSCH THERMOTECHNOLOGY CORPORATION

Bosch applications manual | 06.2009BOSCH THERMOTECHNOLOGY CORPORATION
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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Bosch applications manual | 06.2009 BOSCH THERMOTECHNOLOGY CORPORATION
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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Bosch applications manual | 06.2009 BOSCH THERMOTECHNOLOGY CORPORATION
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"