Bosch C1210ES Instructions for use

GREENTHERM & THERM
Tankless Water Heaters
C1210ES/ESC, C1050ES, C950ES, 940ES, 940ESO, 830ES, 520HN, 520PN, 330PN
Applications Manual
WARNING:
If the information in this manual is not followed
exactly, a re or explosion may result causing
property damage, personal injury or death.
Follow each appliance's instructions precisely.
Installation and service must be performed by a
trained and certied installer, service agency or the
gas supplier.
Application drawings in this manual are conceptual
only and do not purport to address all design,
installation, code, or safety considerations.
The diagrams in this manual are for reference use by
code of cials, designers and licensed installers. It is
expected that installers have adequate knowledge of
national and local codes, as well as accepted
industry practices, and are trained on equipment,
procedures, and applications involved. Drawings are
not to scale.
Refer to the appliance and accessory installation
manuals for additional detailed information!

2
|THERM/GREENTHERM Tankless Water Heaters
Bosch Thermotechnology Corp.Data subject to change
Applications Manual

Applications Manual THERM/GREENTHERM Tankless Water Heaters | 3
Bosch Thermotechnology Corp. Data subject to change
Table of Contents
1 Explanation of symbols 4
2 Introduction 5
3 Model Certications 5
4 Tankless Water Heater Accessories 6
5 Pump sizing for circulation 7
5.1 Pressure drop curves 7
5.2 Domestic hot water circulation 8
5.3 Tank loading 9
6 Water Heater Sizing & Specications 10
6.1 Sizing tankless water heaters 10
6.2 Tankless Water Heater Specications 12
7 Water Quality 14
8 Applications Legend 15
9 Domestic Hot Water Applications 16
9.1 Low volume applications 17
9.2 Whole house applications 18
10 High Volume Potable Water Heating 22
10.1 Cascading unit applications 22
10.2 Parallel unit applications 25
11 Residential Solar Applications 26
11.1 Booster applications 27
12 Commercial Solar Applications 29
13 Commercial Water Heating Applications 30
13.1 Commercial Kitchen applications 31
13.2 Tank loading with domestic hot water
recirculation 32
13.3 Advanced tank loading commercial hot
water system 33
13.4 Common Venting 34

4
|THERM/GREENTHERM Tankless Water Heaters
Bosch Thermotechnology Corp.Data subject to change
Applications Manual
1 Explanation of symbols
Warnings
Warnings in this document are identied by a
warning triangle printed against a grey
background.
Keywords at the start of a warning indicate
the type and seriousness of the ensuing risk if
measures to prevent the risk are not taken.
The following keywords are dened and can be used in
this document:
fNOTICE indicates that damage to property may occur.
fCAUTION indicates that personal injury may occur.
fWARNING indicates that severe personal injury may
occur.
fDANGER indicates that severe personal injury or
death may occur.
Important information
Important information in cases where there is no
risk of personal injury or material losses is identi-
ed by the symbol shown on the left. It is bordered
by horizontal lines above and below the text.

Applications Manual THERM/GREENTHERM Tankless Water Heaters | 5
Bosch Thermotechnology Corp. Data subject to change
2 Introduction
This Applications Manual is intended to present some
of the most common applications of the Bosch Therm
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 specic
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 best solution for the
application.
NOTICE: All drawings are conceptual in nature
and do not address all design, installation or
safety considerations. Additional safety and/or
auxiliary equipment may be needed. Drawings
are for reference use by ofcials, 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
Corp.
This manual is not a substitute for any of the appliance
installation manuals. All specications are subject to
change.
NOTICE: 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.
3 Model Certications
The following are certication stamps and explanations
that are specic to one or more Bosch tankless water
heaters. These certications bring the appliances in ac-
cordance with the requirements of the National Fuel Gas
Code ANSI Z223.1/NFPA 54.
Energy Star qualied (models C 1050 ES,
C 950 ES, 940 ES, 940 ESO, 830 ES, 660 EF,
660 EFO).
Certied to applicable U.S. standards for
appliances using gas or other petroleum fuel.
Certied to applicable Canadian standards for
appliances using gas or other petroleum fuel.
National Sanitation Foundation International
certied.
Energy efciency certied by AHRI -
Air-Conditioning, Heating, and
Refrigeration Institute.
R
For model C 1210 ESC only.
This model is built in accordance
with the requirements of the ASME
Boiler and Pressure Vessel Code and
received the Certicate of
Authorization from the National
Board. The heat exchanger has the
NB and the HLW stamps.
Other certications:
fMeets California Energy Commission (CEC) standards.
fApproved by the Commonwealth of Massachusetts.
fSouth Coast Air Quality Management - 2012
For Models 830 ES, 940 ES, 940ESO, C 950 ES, C 1050 ES,
C 1210 ES and C 1210 ESC only.

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|THERM/GREENTHERM Tankless Water Heaters
Bosch Thermotechnology Corp.Data subject to change
Applications Manual
4 Tankless Water Heater Accessories
Available accessories
Part number C 1210 ES /
C 1210 ESC C 1050 ES C 950 ES 940 ES 940 ESO 830 ES
Concentric vent/air intake kit stainless
steel ESHCK 
Concentric termination kit - PVC* 196016 
Exhaust/intake bird screen - PVC L2594 
Vertical vent kit ES VVT 
Horizontal vent kit 4TWHVK3SII 
Outdoor kit for Therm 7709003913  
Wireless remote control TSTAT2 
Intelligent cascading kit 7709003962 
High temperature kit 7736500074 
PVC Condensing drain tee† 196061 
Condensate neutralization cartridge kit¹ JM-2KIT 
Isolation valve kit with PRV ES ISO KIT 
Pipe Cover W2-3 Silver PTPCES 
Recess Box for 830 ES to C 1210 ES
models 7736500043 
Polypropylene up and out venting kit 7738003210 
Polypropylene common venting system
for up to 4 units
see vent
catalog 
*Meets ULC S636 Standard
†Also included in the Concentric termination kit (196016)
¹Condensate neutralization cartridge kit may be used for non-condensing product vent systems
Available accessories
Part number 520 HN 520 PN 330 PN
Freeze prevention kit 7709003775 
Isolation valve kit with PRV ES ISO KIT 
Power vent w/back draft apper AQ4 

Applications Manual THERM/GREENTHERM Tankless Water Heaters | 7
Bosch Thermotechnology Corp. Data subject to change
5 Pump sizing for circulation
The following section outlines pump sizing for domestic
hot water recirculation and tank loading. Only models
approved for such applications are listed in this section.
fPump must be bronze or stainless steel and designed
for potable water systems.
fSize the pump according to the pressure drop curve of
your Therm model (fig. 1 below) and the loop pressure
drop tables.
fMaximum flow allowed for tank loading through the
pump loop is 5 GPM.
fMaximum flow recommended for direct DHW
recirculation is 3 GPM.
fMaximum flow allowed for mini-tank DHW recirculation
is 2 GPM.
5.1 Pressure drop curves
F
0
10
20
30
40
50
60
70
0.50.40.30.20.10.0
Flow (GPM)
Pressure (Feet of Head)
C 950 ES
C 1050 ES
C 1210 series 830 ES,
940 ES / ESO
igure 1 Pressure drop curves
For direct DHW recirculation and tank loading
applications:
Run the system for 30 minutes to remove debris
from the plumbing. Then remove the unit‘s inlet
water lter to decrease pressure drop through
the system. If the inlet water lter, when remo-
ved, contains debris, it is recommended to install
a 40 mesh Y-strainer (installer supplied) on the
cold water inlet.

8
|THERM/GREENTHERM Tankless Water Heaters
Bosch Thermotechnology Corp.Data subject to change
Applications Manual
5.2 Domestic hot water circulation
5.2.1 Ariston mini-tank DHW recirculation
Reference drawing 9.2.3 on page 20.
If recirculating through an Ariston mini-tank only, use the
smallest pump that will overcome the pressure of the loop.
Recommended ow rate within the range of 1 to 2 GPM.
This method of recirculation maintains warranty.
fThe tank and the Therm should be set at roughly the
same temperature.
fAn aquastat is required to control the recirculation
pump operation. An aquastat temperature setting of
110° F with a 10° F differential is recommended.
fThe recirculation flow must be <2 gpm. Higher flows
will waste energy and can erode the Ariston anode,
requiring frequent anode replacement to maintain its
warranty.
fTo minimize energy costs:
1. Insulate all pipes in the recirculation loop.
2. Install a timer or sensor system that will shut the
pump off when hot water will not be used.
fRecirculation loops over 200 feet in total length will
require an electric tank with a larger heating capacity
than the Ariston 8 gallon model.
5.2.2 Direct DHW recirculation
Reference drawing 9.2.4 on page 21.
If the Bosch tankless water heater provides the
heat source for recirculated water , the heat
exchanger warranty is decreased. Please refer
to the installation manual for detailed warranty
period information.
fDirect recirculation flow through the tankless water
heater must be above 1.7 gpm for best performance.
Flow can be verified in the diagnostic menu, mode
P4-3d. Refer to the Diagnostic Menu section of your
Therm installation manual for details.
System conditions vary and each pump must be
sized by a professional to insure performance.
Refer to pump manufacturers ow vs pressure
specications to select a pump that can provide ow
between 1.7 gpm and 3 gpm while overcoming the
pressure loss through the Therm and the recirculation
loop. Refer to gure 1 and table... to determine pressure
loss.
Use only bronze or stainless steel pumps. Do not
use pumps of iron construction as they will oxi-
dize and clog the inlet lter on the appliance.
fWhen properly installed in a direct recirculation
application the Therm will regulate water temperature
in a recirculation loop within a 20° F range. A
thermostatic mixing valve is required after the water
heater if no other temperature control is used.
fCloser temperature control can also be accomplished
with a recirculation pump aquastat. The Therm
temperature setting must always be at least 14° F
higher than the aquastat cut-out setting.
EXAMPLE:
— Therm temperature setting: 122° F
— Aquastat cut-out temperature setting: 108° F
— To minimize energy costs:
1. Insulate all pipes in the recirculation loop.
2. Install a timer or sensor system that will shut
the pump off when hot water will not be used.
Recirculation Loop Pressure Drop at 2GPM (Feet of Head)
10 ft Pipe 90 Elbow 45 Elbow Tee
Branch
½" Type L Copper 0.85 0.09 0.05 0.18
¾" Type L Copper 0.15 0.03 0.01 0.05
¾" Pex 0.25 0.02 N/A 0.03
" Pex 0.53 0.04 N/A 0.06
½" Pex 1.3 0.12 N/A 0.18
Source: 2009 International Plumbing Code
EXAMPLE:
Sizing a pump for a 2gpm direct DHW recirc system with a
THERM 940ES and have 150 ft total loop length.
Head Loss Loop Component
9.00 ft 940ES (See Fig.1, page 7)
1.20 ft 80 ft of ¾"copper
5.90 ft 70 ft of ½"copper return
0.24 ft 8 x ¾"90 elbows
0.10 ft 2 x ¾"Tees (branch)
0.72 ft 8 x ½"90 elbows
+ 0.18 ft 1 x ½"Tee (branch)
17.34 ft Minimum Pump Head at 2.0 gpm
Once the loop head loss has been calculated, use the
pump manufacturer’s performance curves to select the
proper potable water circulator at the required ow rate.

Applications Manual THERM/GREENTHERM Tankless Water Heaters | 9
Bosch Thermotechnology Corp. Data subject to change
5.3 Tank loading
Refer to drawings 13.2 and 13.3 on pages 32 and 33.
Tank loading pairs tankless water heaters with storage
tanks to maximize peak ow for high demand applications.
A tank load system, because of the added storage, can
provide a high peak ow with fewer tankless units and
lower installed cost.
These guidelines should be followed to maximize system
output:
fEnsure flow through each water heater is between
3.5-5.0 gpm.
fIsolation valves or boiler drains should be installed to
facilitate descaling in applications with hard water.
fFor best performance, plumb the system or configure
the tank to draw cold supply water into the water
heater during hot water use.
fMaintain a 20 degree temperature difference between
tankless set-point and desired tank temperature.
fDo not use a cascading kit in a tank loading
application.
fWhen multiple tankless water heaters are used, the
total equivalent length of piping to each unit should
be kept roughly equal. A reverse return piping scheme
is recommended to equalize flow through each water
heater.
fFor tank temperature settings above 120° F, the Therm
C 1210 ESC is recommended. Other high capacity
Therms including the 830 ES, 940 ES/ESO, C 950 ES
and C 1050 ES can be used, but a high temperature
kit (part 7736500074) is required for each. In these
applications a thermostatic mixing valve is required.
Tank Loading Loop Pressure Drop at 4GPM (Feet of Head)
10 ft
Pipe 90 Elbow 45 Elbow Tee Branch
¾" Type L Copper 0.48 0.1 0.03 0.15
1" Type L Copper 0.14 0.04 0.02 0.07
1.25" Type L Copper 0.06 0.02 0.01 0.04
1.5" Type L Copper 0.03 0.01 <0.01 0.02
2" Type L Copper 0.01 <0.01 <0.01 0.01
Source: 2009 International Plumbing Code
Pressure drop vs. ow*
# of
Units
C 1210 ES / ESC,
C 1050 ES, C 950 ES 940 ES, 940 ESO, 830 ES
140 feet of head @ 4gpm 32 feet of head @ 4gpm
240 feet of head @ 8gpm 32 feet of head @ 8gpm
340 feet of head @ 12gpm 32 feet of head @ 12gpm
440 feet of head @ 16gpm 32 feet of head @ 16gpm
540 feet of head @ 20gpm 32 feet of head @ 20gpm
640 feet of head @ 24gpm 32 feet of head @ 24gpm
740 feet of head @ 28gpm 32 feet of head @ 28gpm
840 feet of head @ 32gpm 32 feet of head @ 32gpm
940 feet of head @ 36gpm 32 feet of head @ 36gpm
10 40 feet of head @ 40gpm 32 feet of head @ 40gpm
11 40 feet of head @ 44gpm 32 feet of head @ 44gpm
12 40 feet of head @ 48gpm 32 feet of head @ 48gpm
13 40 feet of head @ 52gpm 32 feet of head @ 52gpm
14 40 feet of head @ 56gpm 32 feet of head @ 56gpm
15 40 feet of head @ 60gpm 32 feet of head @ 60gpm
16 40 feet of head @ 64gpm 32 feet of head @ 64gpm
17 40 feet of head @ 68gpm 32 feet of head @ 68gpm
18 40 feet of head @ 72gpm 32 feet of head @ 72gpm
19 40 feet of head @ 76gpm 32 feet of head @ 76gpm
20 40 feet of head @ 80gpm 32 feet of head @ 80gpm
21 40 feet of head @ 84gpm 32 feet of head @ 84gpm
22 40 feet of head @ 88gpm 32 feet of head @ 88gpm
23 40 feet of head @ 92gpm 32 feet of head @ 92gpm
24 40 feet of head @ 96gpm 32 feet of head @ 96gpm
EXAMPLE:
Sizing a pump for a 4GPM tank loading DHW system with a
1050ES and a 20 ft total loop length.
Head Loss Loop Component
39.00 ft 1050es (See Fig.1, page 7)
1.00 ft 20 ft of ¾ copper
0.80 ft 8 x ¾” 90 elbows
+ 0.30 ft 2 x ¾” Tees (branch)
41.10 ft Minimum Pump Head at 4.0 gpm
Once the loop head loss has been calculated, use the
pump manufacturer’s performance curves to select the
proper potable water circulator at the required ow rate.
* Calculations based on 120°F Set-point temperature, 107°F shower temperature, 2.5 GPM showerhead ow rate, 1.5 GPM sink ow rate,
adequate water pressure and gas supply. Variation from these parameters may alter performance. GPM shown is the hot water ow rate
at 120°F Set-point temperature.

10 |THERM/GREENTHERM Tankless Water Heaters
Bosch Thermotechnology Corp.Data subject to change
Applications Manual
6 Water Heater Sizing &
Specications
This section describes the water heaters available from
Bosch Thermotechnology Corp. and provides a general
overview to the specications of each particular model.
More detailed information is contained in the installation
manuals. Download manuals at www.bosch-climate.us.
6.1 Sizing tankless water heaters
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.
Sizing by Chart
fMeasure 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.
fUsing a known volume container, record several fill
times. Perform 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
Hot water ow rate at 120°F Set Point temperature
Model Inlet temperature (°F)
77° 72° 67° 62° 57° 52° 47° 42° 37°
C 1210
ES /
ESC 9.8 8.8 8.0 7.3 6.7 6.2 5.8 5.4 5.1
C 1050
ES 8.5 7.6 6.9 6.3 5.8 5.4 5.0 4.7 4.4
C 950
ES 7.7 6.9 6.2 5.7 5.2 4.9 4.5 4.2 4.0
940 ES
/ ESO 7.7 6.9 6.2 5.7 5.2 4.9 4.5 4.2 4.0
830 ES 6.7 6.0 5.4 5.0 4.6 4.2 4.0 3.7 3.5
520 HN
/ PN 4.3 3.8 3.5 3.2 2.9 2.7 2.5 2.3 2.2
330 PN 2.7 2.4 2.2 2.0 1.9 1.7 1.6 1.5 1.4
Simultaneous Showers Sink Faucet
CA
OR
WA
ID
NV
MT
WY
UT
AZ
NM
CO
ND
SD
NE
TX
OK
KS
MN
IA
MO
AR
LA
MI
IN
IL
WI
GA
AL
MS
TN
KY
WV VA
NC
SC
FL
NH
VT
NY
PA
OH
NJ
RI
CT
MA
ME
MD
DE
WA
O
R
C
A
NV
ID
UT
AZ
NM
CO
WY
MT
ND
S
D
NE
K
S
OK
TX
LA
AR
M
O
IA
MN
WI
MI
IL
IN
O
H
KY
TN
M
S
AL
G
A
FL
SC
N
C
VA
WV
PA
NY
MA
A
A
VT
NH
ME
H
˚F
77˚
72˚
67˚
62˚
57˚
52˚
47˚
42˚
37˚
Figure 2 Average ground water temperatures
fUsing a thermometer, measure the incoming water
temperature. For reference, see average ground water
temperature map. Subtract 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.
EXAMPLE:
fRequired flow rate of 2.0 GPM at a 65F rise.
fRefer to the graphs on page 10.
fSince the demand is above the 330 PN capacity, this
application would require a 520 HN/PN gas tankless
water heater.

Applications Manual THERM/GREENTHERM Tankless Water Heaters | 11
Bosch Thermotechnology Corp. Data subject to change
10 20 30 40 50 60 70 80 90
9
10
11
8
12
13
100 110 120 130 140
7
6
4
3
2
1
0
5
Temperature rise (°F)
Flow
Rate
(GPM)
C 1210 ES/
C 1210 ESC
C 950 ES
C 1050 ES
Figure 3 Flow rate vs. temperature rise - condensing models
10 20 30 40 50 60 70 80 90
9
10
11
8
100 110 120 130 140
7
6
4
3
2
1
0
5
Temperature rise (°F)
Flow
Rate
(GPM)
830 ES
520 HN/
520 PN
330 PN
940 ES/
940 ESO
Figure 4 Flow rate vs. temperature rise - non-condensing models
Flows above 10 GPM require installation of a
mixing valve to help mitigate pressure drop in the
water heater and plumbing system
Temperature rises above 110 °F or more,
or output temperatures above 140 °F require
either a commercial unit or optional accessories
such as a high temperature kit.

12 |THERM/GREENTHERM Tankless Water Heaters
Bosch Thermotechnology Corp.Data subject to change
Applications Manual
6.2 Tankless Water Heater Specications
Technical Specications
Unit
Models
C 1210 ES /
C 1210 ESC C 1050 ES C 950 ES 940 ES 940 ESO 830 ES
Gas input BTU/hr Max: 225,000
Min: 25,000
Max: 199,000
Min: 19,900
Max: 175,000
Min: 19,900
Max: 199,000
Min: 19,900
Max: 199,000
Min: 19,900
Max: 175,000
Min: 19,900
Minimum ow to activate GPM 0.5 0.5 0.5 0.5 0.5 0.5
Maximum ow rate at 35° rise GPM 12.1 10.5 9.2 9.4 9.4 8.3
Maximum ow rate at 90° rise GPM 4.6 3.9 3.6 3.6 3.6 3.6
Thermal efciency % NG: 94
LP: 94
NG: 94
LP: 94
NG: 93
LP: 93
NG: 82
LP: 82
NG: 82
LP: 82
NG: 82
LP: 82
Energy factor  N/A .94 .93 .83 .83 .83
Dimensions Inches
H: 30½
W: 17
D: 11¼
H: 30½
W: 17
D: 11¼
H: 30½
W: 17
D: 11¼
H: 30½
W: 17
D: 11¼
H: 30½
W: 17
D: 11¼
H: 30½
W: 17
D: 11¼
Weight LBS 88 74 74 67 67 67
Modulating gas valve  Electronic Electronic Electronic Electronic Electronic Electronic
Ignition  Electronic Electronic Electronic Electronic Electronic Electronic
Gas connection Inches ¾Male NPT ¾Male NPT ¾Male NPT ¾Male NPT ¾Male NPT ¾Male NPT
Water connections Inches ¾Male NPT ¾Male NPT ¾Male NPT ¾Male NPT ¾Male NPT ¾Male NPT
NG gas pressure
Inches
of
W.C.
Min: 3.5
Max: 10.5
Min: 3.5
Max: 10.5
Min: 3.5
Max: 10.5
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: 8.0
Max: 13.0
Min: 8.0
Max: 13.0
Min: 8.0
Max: 13.0
Min: 8.0
Max: 13.0
Min: 8.0
Max: 13.0
Min: 8.0
Max: 13.0
Water pressure- static PSI
Min: 30
Min (well): 40
Max: 145
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 VAC 120 120 120 120 120 120
Venting options 
direct vent,
room-sealed,
combustion
direct vent,
room-sealed,
combustion
direct vent,
room-sealed,
combustion
direct vent,
room-sealed,
combustion
outdoor
installation
only
direct vent,
room-sealed,
combustion
Venting diameter Inches 3 or 4 3 or 4 3 or 4 3 or 4 N/A 3 or 4
Vent material 
PP common
vent, PP twin
pipe, PVC,
CPVC,
or ABS
(Schedule 40)
PP common
vent, PP
up and out
concentric
vent, PP twin
pipe, PVC,
CPVC,
or ABS
(Schedule 40)
PP common
vent, PP
up and out
concentric
vent, PP twin
pipe, PVC,
CPVC,
or ABS
(Schedule 40)
Stainless
steel
(AL29-4C)
Outdoor vent
cap supplied
Stainless
steel
(AL29-4C)
Temperature range °F
100-180°F
(ESC)
100-140°F
(ES)
100-140°F
100-184°F
(requires HT
kit)
100-140°F
100-184°F
(requires HT
kit)
100-140°F
100-184°F
(requires HT
kit)
100-140°F
100-184°F
(requires HT
kit)
100-140°F
100-184°F
(requires HT
kit)

Applications Manual THERM/GREENTHERM Tankless Water Heaters | 13
Bosch Thermotechnology Corp. Data subject to change
- C 1210 ES (residential model) has a maximum
set-point temperature of 140°F.
- C 1210 ESC (commercial model) has a maximum
set-point temperature of 180°F.
- To achieve temperatures up to 184°F with C
1050 ES, C950 ES, 940 ES, 940 ESO, and 830 ES,
the optional High Temperature kit #7736500074
is required.
Technical specications
Unit 520 HN 520 PN 330 PN
Gas input BTU/hr Max: 117,000
Min: 30,735
Max: 117,000
Min: 30,735
Max: 74,900
Min: 30,735
Minimum ow to activate GPM 0.5 0.5 0.5
Maximum ow rate at 35° rise GPM 5.2 5.2 3.3
Maximum ow rate at 90° rise GPM 2.0 2.0 1.3
Thermal efciency % NG: 80
LP: 80
NG: 78
LP: 78
NG: 78
LP: 78
Energy factor  N/A N/A N/A
Dimensions Inches
H: 25.79
W: 17.11
D: 8.66
H: 25.79
W: 18.11
D: 8.66
H: 22.83
W: 12.20
D: 8.66
Weight LBS 35 35 36
Modulating gas valve  Mechanical Mechanical Mechanical
Ignition  Hydro-
generated
Standing
pilot
Standing
pilot
Gas connection Inches ¾Male NPT ¾Male NPT ½Male NPT
Water connections Inches ½Male NPT ½Male NPT ½Male NPT
NG gas pressure Inches of W.C. Min: 5.7
Max: 14.0
Min: 5.7
Max: 14.0
Min: 5.7
Max: 14.0
LP gas pressure Inches of W.C. Min: 10.5
Max: 14.0
Min: 10.5
Max: 14.0
Min: 10.5
Max: 14.0
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
Electrical supply VAC N/A N/A N/A
Venting options 
Vertical
natural draft,
Horizontal
termination
only with AQ4
vent kit
Vertical
natural draft,
Horizontal
termination
only with AQ4
vent kit
Vertical
natural draft,
Horizontal
termination
not allowed
Venting diameter Inches 5 5 4
Vent material  Type B-vent
recommended
Type B-vent
recommended
Type B-vent
recommended
Temperature range °F High to low High to low High to low
The following models are designed to be installed
indoors but may be installed outdoors with the
Outdoor Kit: 830 ES, 940 ES, C 950 ES, C 1050 ES,
C 1210 ES / ESC. Please refer to the installation
manuals for details.

14 |THERM/GREENTHERM Tankless Water Heaters
Bosch Thermotechnology Corp.Data subject to change
Applications Manual
7 Water Quality
Water quality can 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 analyzed periodically. If
water quality exceeds one or more of the values
specied below, Bosch recommends installing a water
conditioner or softener. If the tankless water heater is
operating in applications where the outlet temperature
exceeds 140°F, a water softening system is strongly
recommended. The higher the set temperature is on the
appliance, the greater the risk for scale/mineral
deposits. Damage from scale/mineral deposits is not
covered under warranty. Refer to manufacturer’s limited
warranty.
Water quality limits
Description Unit 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

Applications Manual THERM/GREENTHERM Tankless Water Heaters | 15
Bosch Thermotechnology Corp. Data subject to change
8 Applications Legend
Thermostatic 3-way valve
Gauge
Shutoff valve with drain
Check valve
Two way shutoff valve
Safety relief valve
Y-Strainer
Temperature sensor
Aquastat
Cold water pipe
Hot water pipe
Shutoff valve with
temperature gauge
Pump
Automatic air vent valve
Manual air vent valve
Timer
Expansion tank
Sink
Standard tub
Shower
Solar supply pipe
Line voltage connection
Sensor connection
Intelligent cascade kit
Tank drain valve
Solar return pipe
NOTICE: These drawings are conceptual in nature, not to scale and for reference only. Additional functional,
installation, and safety devices may be needed or required. All work pertaining to the installation shall be in full
compliance with all legal requirements, including national and local codes. Best installation practices should be
followed.

16 |THERM/GREENTHERM Tankless Water Heaters
Bosch Thermotechnology Corp.Data subject to change
Applications Manual
9 Domestic Water Heating
Applications
Potable water
Potable water is water that is suitable for drinking. Bosch
Thermotechnology Corp. appliances are approved to heat
potable water only. Heating any other liquid other than po-
table water will void the manufacturer’s warranty covering
the appliance.
Introduction
This chapter covers the various application techniques
Bosch Thermotechnology Corp. recommends. The
schematics are to be used by professional contractors
in designing a domestic water heating system. The
applications covered range from single appliance low
volume to multi-appliance central domestic recirculation.

Applications Manual THERM/GREENTHERM Tankless Water Heaters | 17
Bosch Thermotechnology Corp. Data subject to change
9.1 Low volume applications
Low volume applications cover the small applications in
which a large water heater would be inefcient. Common
applications for these appliances include cottages, cabins,
and summer camps. The Bosch THERM 520HN, 520PN
and 330PN gas tankless water heaters offers compact
and lightweight design for easy installation in these
applications.
Applicable models: Bosch 330 PN, 520 PN, 520 HN.

18 |THERM/GREENTHERM Tankless Water Heaters
Bosch Thermotechnology Corp.Data subject to change
Applications Manual
9.2 Whole house applications
Whole house applications cover the typical home
applications up to a 2 to 4 bathroom house. See the sizing
guide (page 9) to determine the best Bosch water heater
model for your application. An enhanced design combining
an Ariston mini tank in line after the Bosch water heater
will reduce wait times and improve temperature stability.
9.2.1 Bosch gas water heater
Below is an example of a basic Bosch gas tankless water
heater installation for the whole house.
Applicable models: Bosch 830 ES, 940 ES, 940 ESO,
C 950 ES, C 1050 ES, C 1210 ES.

Applications Manual THERM/GREENTHERM Tankless Water Heaters | 19
Bosch Thermotechnology Corp. Data subject to change
9.2.2 Bosch gas water heater with buffer tank
Below is an example of a Bosch gas tankless water heater
installation for the whole house. A Bosch Tronic 3000T
mini tank (model ES8) is installed in line for reduced hot
water wait time and increased temperature stability.
Bosch
Applicable models: Bosch 520 PN, 520 HN, 830 ES,
940 ES, 940 ESO, C 950 ES, C 1050 ES, C 1210 ES.

20 |THERM/GREENTHERM Tankless Water Heaters
Bosch Thermotechnology Corp.Data subject to change
Applications Manual
9.2.3 Bosch gas water heater with domestic
recirculation loop
The circulator should be controlled by an external aq-
uastat and/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.
Bosch
See Chapter 5.2 for recirculation pump
parameters
Applicable models: Bosch 520 PN, 520 HN, 830 ES,
940 ES, 940 ESO, C 950 ES, C 1050 ES, C 1210 ES,
Mini tank: Bosch Tronic 3000T ES8.