Bosch GWH 715 ES User manual

GWH 715 ES
(GWH 715 CTDR EFS)
Temperature Modulated with Electronic Ignition
Suitable for heating potable water only - Not approved for space heating purposes
(Intended for variable flow applications)
GWH 715 ES - Natural Gas
GWH 715 ES - Liquefied Petroleum (LP) Gas
6 720 608 158 US (2007.01) AL
Warning: If the information in this manual is not
followed exactly, a fire or explosion may result
causing property damage, personal injury or death.
Do not store or use gasoline or other flammable
vapors and liquids in the vicinity of this or any other
appliance.
Improper installation, adjustment, alteration,
service or maintenance can cause injury or
property damage. Refer to this manual. For
assistance or additional information consult a
qualified installer, service agency or the gas
supplier.
In the Commonwealth of Massachusetts this
product must be installed by a licensed plumber or
gas fitter.
Upon completion of the installation, these
instructions should be handed to the user of the
appliance for future reference.
What to do if you smell gas
• Close gas valve. Open windows.
• Do not try to light any appliance.
• Do not touch any electrical switch; do not use any
phone in your building.
• Immediately call your gas supplier from a neighbor’s
phone. Follow the gas supplier’s instructions.
• If you cannot reach your gas supplier, call the fire
department.
• Installation and service must be performed by a
qualified installer, service agency or the gas supplier.

6 720 608 158
2
Index
Index
1Warning 3
2 Appliance details 4
2.1 Features 4
2.2 GWH 715 ES Specifications (Technical data) 4
2.3 Unpacking the GWH 715 ES heater 5
2.4 General rules to follow for safe operation 6
2.5 Dimensions and Minimum installation
clearances 7
3 Installation instructions 8
3.1 Tools required for installation 8
3.2 Introduction 8
3.3 Proper location for installing your heater 8
3.4 Heater placement and clearances 8
3.5 Mounting installation 8
3.6 Gas piping & connections 10
3.7 Water connections 12
3.8 Water quality 12
3.9 Recirculation application 13
3.10 Combustion air requirements 13
3.11 Venting 15
3.12 Measuring gas pressure 24
4 Electrical connections 25
4.1 Electrical power supply 25
4.2 Position of the fuses in control unit 25
5 Operation instructions 26
5.1 Description LCD display 26
5.2 For your safety read before operating
your water heater 27
5.3 Power 27
5.4 Temperature selection 27
5.5 Use of optional remote control accessory
(part no. TSTAT2) 28
5.6 Operation 28
5.7 Reset button 28
5.8 Program button 28
5.9 Locked condition 28
6 Maintenance and service 29
6.1 Annual maintenance 29
6.2 Winterizing for seasonal use 29
6.3 Mineral scale build-up 30
6.4 Adjusting CO2 30
6.5 Program values 33
6.6 Control board diagnostics 34
7 Troubleshooting 35
7.1 Introduction 35
7.2 Burner do not ignite when hot water
is turned ON 35
7.3 Water is too hot 35
7.4 Water is not hot enough 35
7.5 Low water flow/pressure 36
7.6 Hot water temperature fluctuates at tap 36
7.7 Noisy burner/heater during operation 36
8 Problem solving 38
8.1 Error code diagnostics 38
9 Electrical diagram 42
10 Sensor resistance charts 43
11 GWH 715 ES Functional scheme 45
12 Interior components diagram
and parts list 46
12.1 Interior components 46
12.2 Components diagram 48
13 Protecting the environment 54
14 Limited Warranty 55

6 720 608 158
Warning
3
1 Warning
For your safety
Do not store or use gasoline or other flammable,
combustible or corrosive vapors and liquids in the
vicinity of this or any other appliance.
FCC:
This device complies with Part 15 of the FCC rules.
Operation is subject to the following two conditions: (1)
This device may not cause harmful interference, and (2)
this device must accept any interference received,
including interference that may cause undesired
operation.
Fig. 1
Warning: Carefully plan where you
install the heater. Correct combustion
air supply and flue pipe installation are
very important. If a gas appliance is not
installed correctly, fatal accidents can
result, such as carbon monoxide
monoxide poisoning or fire.
Warning: Exhaust gas must be vented
to outside using stainless steel vent
material suitable for category III vent
systems and temperatures up to 480°F.
Vent piping must be sealed gas-tight to
prevent possibility of flue gas spillage,
carbon monoxide emissions and risk of
fire, resulting in severe personal injury
or death. Approved vent terminators
must be used when penetrating to the
outside.
Warning: Place the heater in a location
where water leaks will do NO DAMAGE
to adjacent areas or lower floors.
Warning: Field wiring connections and
electrical grounding must comply with
local codes, or in the absence of local
codes, with the latest edition of the
National Electric Code, ANSI/NFPA 70,
or in Canada, all electrical wiring must
comply with the local codes and the
Canadian Electrical Code, CSA C22.1
Part 1.
Warning: Shock hazard: line voltage is
present. Before servicing the water
heater, unplug power supply cord from
outlet. Failure to do so could result in
severe personal injury or death.
Warning: The heater must be
disconnected from the gas supply
piping system during any pressure
testing of that system at test pressures
equal to or more than 0.5 psig.

6 720 608 158
4
Appliance details
2 Appliance details
2.1 Features
Parts
• Key Pad interface control
• High power pre-mix compact burner with low NOx
emissions
• Modulating Gas Valve with constant gas:air ratio
control
• Modulating water valve for improved comfort and
temperature control.
High quality materials for long working life
• Copper heat exchanger
• High efficiency Ceramat Burner
• Compact space saver: mounts on a wall with a
supplied bracket.
Features
• Real-time diagnostics for troubleshooting/
informational purposes
• LCD Display with backlight
• On/Off and Temperature control switches
• Reset button
• Program button (Selectable temperature default)
• Failure codes for easy diagnostics and repair
• Easily removable one-piece cover.
Accessories (Bosch part #)
• Optional wireless remote control accessory to
operate with the appliance (TSTAT2)
• Cascading kit (TLINK)
•Outdoorkit(PTOK)
• External water filter (8703305356).
2.2 GWH 715 ES Specifications
(Technical data)
Approved in US/Canada
Capacity
Maximum flow rate: 7.3 GPM (27 l/min) at a 45°F
(25°C) rise.
Maximum output
160,500 Btu/h (47.0 kW)
Maximum input
199,000 Btu/h (58.3 kW)
Efficiency in %
Thermal efficiency > 82%
Min. Input
19,900 Btu/h (5.8 kW)
Temperature Control
Selection range: 100°F (38°C) - 140°F (60°C)
Default temperature: 122°F (50°C)
Stability: +/- 2°F (+/- 1°C)
Gas Requirement
Gas connection (inches) - ¾”
Inlet gas pressure under operation (with a high hot
water flow rate)*
• Propane: 9” - 14” water column
• Natural Gas: 4” - 14” water column.
* To measure gas pressure, see Measuring Gas
Pressure, chapter 3.12, page 24.
Water
• Hot water connection (inches) - ¾”
• Cold water connection (inches) - ¾”
• Water valve material: Polymer (PPS) (Polypropylene
Sulfid)
• Minimum water flow: 0.65 gallon/minute (2,5 l/m).
Note: Activation varies with inlet water temperatures
from 0.65 - 1.6 gallon/minute (2.5 - 6.1 l/m).
• Minimum recommended water pressure: 30 PSI
(2.07 bar).
• Minimum well pressure 40 psi, see page 12.
• Connections:
– Bottom of heater
iBOSCH is constantly improving its
products, therefore specifications are
subject to change without prior notice.

6 720 608 158
Appliance details
5
Combustion
•NOx≤55 ppm
•CO≤190 ppm
•CO
2level set from factory, see chapter 6.4, page 30.
Dimensions
• Depth (in): 11¼” (286 mm)
• Width (in): 17 7/8” (452 mm)
• Height (in): 30½” (775 mm)
• Weight: 67 pounds (30.5 kg).
Gas types
Natural Gas.
LP Gas.
Voltage
120 V AC (60 Hz) nominal
Amperage
Idle - 40 mA
Operation - ≤2.5 A
Noise
45 - 65 db (A)
Safety devices
• Flame failure device (ionization flame rod sensor)
• Pressure relief valve (supplied with heater)
• Over heat prevention (temperature limiter)
• Inlet temperature sensor
• Outlet temperature sensor
• Back flow temperature sensor.
Water protection
IP X4 (protection against water drops)
2.3 Unpacking the GWH 715 ES heater
Before installing the unit, be certain you have the
correct heater for your type of Gas: Propane or
Natural Gas. Identification labels are found on the
shipping box, and on the rating plate which is located on
the right side panel of the cover.
Fig. 2 Rating plate
ASerial number
BType of gas
The box includes:
• GWH 715 ES
• Pressure relief valve (150 psi / 200,000 Btu rating)
• Bracket for wall hanging the heater
• Exhaust vent adaptor (with 4 screws and gasket
provided)
• Combustion air inlet adaptor (with 3 screws and gas-
ket provided)
• Installation manual (manual can be downloaded at
www.boschpro.com)
• Product registration card
• Energy Guide label.
Please complete and return the enclosed product
registration card.
The GWH 715 ES is not approved or designed for:
• Manufactured (mobile) homes, boats or any
mobile installation.
• Use above 4500ft A.S.L. altitude.
• Outdoor installation without installation of
Outdoor kit (PTOK).
• Applications where inlet water temperature is
higher than 140ºF (60°C). A 3-way valve or
mixing valve must be installed before the
appliance if inlet water temperature exceeds
this limit.
• Space heating purposes.
iIf appliance is installed at elevations
between 2000ft and 4500ft, a
combustion gas analyzer is required for
proper calibration of appliance. (see page
24).

6 720 608 158
6
Appliance details
To remove front cover
BLoosen the two Philips head screws located on
bottom rear of cover (see Fig. 3).
Fig. 3 Loosen the two screws
BLift front cover panel upward and remove.
Fig. 4 Remove the front cover
To remove combustion cover (service only)
BOpen the four clips and remove the combustion
cover see Fig. 5.
Fig. 5 Remove the combustion cover
2.4 General rules to follow for safe
operation
B1. You must follow these instructions when you install
your heater. In the United States: The 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: The Installation must conform with CGA
B149.(1,2) INSTALLATION CODES and /or local
installation codes.
B2. Carefully plan where you install the heater. Correct
combustion air supply and vent pipe installation are
very important. If not installed correctly, fatal
accidents can occur, such as carbon monoxide
poisoning or fire.
B3. When the unit is installed indoors and ROOM
SEALED (twin pipe) it is permitted to be located in
bathrooms, bedrooms and occupied rooms that are
normally kept closed. See chapter 3.11 (page 15). If
the unit will be installed indoors and use indoor
combustion air, the place where you install the heater
must have enough ventilation. The National Fuel
Gas Code does not allow UNSEALED gas fired
water heater installations in bathrooms,
bedrooms or any occupied rooms normally
kept closed. See chapter 3.3, page 8 and 3.10,
page 13.
B4. You must vent your heater. See chapter 3.11, page
15 on VENTING.
B5. The appliance and its gas connection must be leak
tested before placing the appliance in operation.
The appliance must be isolated from the gas supply
piping system by closing its individual manual gas
shutoff valve (not supplied with heater) during any
pressure testing at pressures in excess of ½ Psig (3.5
kPa).
B6. Keep water heater area clear and free from
combustibles and flammable liquids. Do not locate
the heater over any material which might burn.
B7. Correct gas pressure is critical for the proper
operation of this heater. Gas piping must be sized to
provide the required pressure at the maximum output
of the heater, while all the other gas appliances are in
operation. Check with your local gas supplier, and
see the section on connecting the gas supply, see
chapter 3.6.
B8. Should overheating occur or the gas supply fail to
shut off, turn off the gas supply at the manual gas shut
off valve, on the gas line. Note: manual gas shutoff
valve is not supplied with the heater but must be field
installed.
B9. Do not use this appliance if any part has been
underwater. Immediately call a qualified service
technician to inspect the appliance and to replace any
part of the control system and any gas control which
has been underwater.
B10. Failure to install heater correctly may lead to
unsafe operation and void the warranty.

6 720 608 158
Appliance details
7
2.5 Dimensions and Minimum installation clearances
Fig. 6 Dimensions
1On/Off button
2Reset button
3Program key
4Power ON or stand-by LED
5LCD display
6Up button
7Down button
Fig. 7 Minimum clearances
Note: For servicing access, a 2ft clearance to front
cover is recommended.
Note: Vent clearances vary per manufacturer. Consult
vent manufacturer for specific clearance information.
Model GWH 715 ES
TOP (A) 12”
FRONT (B) 1”
BACK 0”
SIDES 1”
FLOOR (C) 12”
VENT DIAMETER 3”
VENT CLEARANCES 1”
Table 1 Minimum clearances

6 720 608 158
8
Installation instructions
3 Installation instructions
3.1 Tools required for installation
• Philips head screwdriver
• Flat head screwdriver
• Adjustable wrench
• Level
• Thermometer
• Standard plumbing tools
•Manometer.
3.2 Introduction
Please follow these instructions. Failure to follow
instructions may result in:
BDamage or injury.
BImproper operation.
BLoss of warranty.
If you are unable to perform the tasks required to install
this heater properly, please contact a locally licensed
plumber or gas technician.
3.3 Proper location for installing your
heater
Carefully select the location of the water heater. For
your safety and for proper heater operation, you must
provide combustion air to the heater and a proper
exhaust vent system.
Follow the guidelines below:
B1. Locate the heater where venting, gas and
plumbing connections are feasible and convenient.
B2. The hot water lines should be kept short and
insulated to save energy. Centrally locating the water
heater is recommended to keep hot water
distribution times even throughout the structure.
3.4 Heater placement and clearances
The GWH 715 ES is approved for installation on a
combustible wall (see chapter 3.5 Mounting
installation) provided the floor covering below
the heater is noncombustible. For installations in an
alcove or closet, maintain the minimum clearances to
combustible and non-combustible materials listed
below. See also Fig. 7.
A. Top 12 inches (306 mm)
B. Front 1 inches (25 mm)
C. Back 0 inches
D. Sides 1 inches (25 mm)
E. Bottom 12 inches (306 mm)
Clearances from any exhaust vent pipe are dependent
upon the clearance requirements of the stainless steel
vent pipe manufacturer. Single wall stainless steel
(AL29-4C) vent pipe (vent type rated for Category III
appliances) must be used when exhaust venting this
appliance. See chapter 3.11 (page 15) Venting.
3.5 Mounting installation
Warning: The water in this water
heater is cold and always remains cold
except for the times the burner is on. In
the event of power outage in
conjunction with freezing temperatures,
it is recommended that the heater be
drained.
See chapter 6.2, page 29 “Winterizing”
for draining instructions.
Warning: Flammable materials,
gasoline, pressurized containers, or any
other items or articles that are potential
fire hazards must NOT be placed on or
adjacent to the heater. The appliance
area must be kept free of all
combustible materials, gasoline and
other flammable vapors and liquids.
Warning: before starting
installation
BCheck that there are no loose parts
inside the appliance
BConfirm the gas type of the heater
matches the gas supply you will be
connecting the heater, see Fig. 2,
page 5.
BEnsure that gas pipe, gas valve,
mixer, fans and burner have no
damage and are properly fitted.
iFront cover should be removed (see
instructions on page 6) in order to inspect
components visually.
Warning: Do not install this appliance
on a carpeted wall. The heater must be
mounted on a wall using appropriate
anchoring materials.

6 720 608 158
Installation instructions
9
If wall is sheathed with plaster or drywall, it is
recommended that two support boards, either 1”x4” or
1/2" (minimum) plywood first be attached across a pair
of studs, see Fig. 8, page 9.
BSecure the wall mounting bracket provided with the
heater to the wall surface. The heater must be kept
level on the wall surface, see Fig. 9, page 9.
BHang the appliance on the bracket, see Fig. 10, page
9.
Fig. 8 Distance between support boards
Fig. 9 Leveling the mounting bracket on the studs
Fig. 10 Mounting the heater
Studs 16"
(406mm) on
center Warning: Appliance must be installed
vertically.

6 720 608 158
10
Installation instructions
3.6 Gas piping & connections
Before connecting the gas supply, check the rating
plate on the right side of the heater to be sure that the
heater is rated for the same gas to which it will be
connected.
In the United States: The 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: The Installation must conform to CSA B149
INSTALLATION CODES and/or local installation
codes.
GAS CONNECTIONS
BInstall a manual gas shut off valve on the gas supply
line.
BInstall a union when connecting gas supply.
BThe minimum internal diameter required for
any appliance connector is ¾”, see Fig. 13 for
more details on pipe sizing.
BNational Fuel Gas Code requires that a sediment
trap (drip leg) be installed on gas appliances not so
equipped. The drip leg must be accessible and not
subject to freezing conditions. Install in accordance
with the recommendations of the serving gas
supplier, see Fig. 11.
Fig. 11 Gas connection (drip leg)
Once connections are made, check for gas leaks at all
joints. Apply some gas leak detection solution to all gas
fittings. Bubbles are a sign of a leak. A combustible gas
detector may also be used to detect for leaks.
GAS LINE SIZING
The gas supply piping for a single heater should be
sized for a maximum draw of 199,000 BTUH. Measure
the length of gas supply line and use the tables in
Fig. 13, page 11 or the gas line manufacturer’s sizing
tables to determine the pipe diameter necessary to
accommodate the 199,000 BTU demand of the heater.
If there are more gas appliances on the line, size the gas
line according to the total maximum amount of BTU
input rating for all appliances.
Note: Undersizing the gas line may result in diminished
hot water flow rate and temperature. See chapter 3.12,
page 24 for the procedure to confirm gas pressure.
Proper gas pressure must be confirmed at time of
installation.
Fig. 12
Warning: DO NOT connect to an
unregulated or high pressure propane
line or to a high pressure commercial
natural gas line.
Warning: The heater must be isolated
from the gas supply piping system
during any pressure testing of that
system at test pressures equal to or
more than 0.5 psig. If overpressure has
occurred, such as through improper
testing of the gas lines or malfunction of
the supply system, the gas valve must
be checked for safe operation.
Gas supply
Cap
Minimum
3”
Danger: If you have a leak, shut off the
gas. Tighten appropriate fittings to stop
leak. Turn the gas on and check again
with a gas leak detection solution.
Never test for gas leaks using a match
or flame.
Gas piping
Inlet gas particle screen
(included)

6 720 608 158
Installation instructions
11
FOR NATURAL GAS
Maximum Capacity of pipe in Cubic Feet of Gas per Hour for Gas Pressure of 0.5 Psig or less and a Pressure drop
of 0.3” in Water Column (0.75mbar).(Based on a 0.60 Specific Gravity Gas) Btu numbers given in thousands.
Fig. 13
Follow boxed numbers for piping just one GWH 715 ES (example: ¾” B.I. Natural Gas pipe for 10 ft (3.0m).
will handle 278,000 btu’s (81.5 kWh). For multiple appliances combine the total maximum btu input load and
then refer to applicable chart below.
* EHD = Equivalent Hydraulic Diameter. The greater the
value of EHD, the greater the gas capacity of the tubing.
Maximum Capacity of Semi-Rigid (flexible, non
corrugated) Tubing in Thousands of BTU per Hour of
Undiluted Liquefied Petroleum Gases (at 11 inches
Water Column Inlet Pressure).
(Based on a Pressure Drop of 0.5 Inch Water Column)
* Source National Fuel Gas Code NFPA 54, ANSI
Z223.1 - No Additional Allowance is necessary for an
ordinary number of fittings
FOR LP GAS
Maximum Capacity of Pipe in Thousands of BTU per Hour of Undiluted Petroleum Gases (at 11 inches Water Column Inlet
Pressure) (Based on a Pressure Drop of 0.5 Inch Water Column).
* EHD = Equivalent Hydraulic Diameter. The greater the
value of EHD, the greater the gas capacity of the tubing.
Nominal
Iron Length of Black iron Pipe , Feet
Pipe Internal
Size, Diameter
inches inches 10 20 30 40 50 60 70 80 90 100 125 150 175 200
1/4 0.364 32 22 18 15 14 12 11 11 10 9 8 8 7 6
3/8 0.493 72 49 40 34 30 27 25 23 22 21 18 17 15 14
1/2 0.622 132 92 7363 56504643403834 312826
3/4 0.824 278 190 152 130 115 105 96 90 84 79 72 64 59 55
1 1.049 520 350 285 245 215 195 180 170 160 150 130 120 110 100
1 1/4 1.380 1050 730 590 500 440 400 370 350 320 305 275 250 225 210
1 1/2 1.610 1600 1100 890 760 670 610 560 530 490 460 410 380 350 320
2 2.067 3050 2100 1650 1450 1270 1150 1050 990 930 870 780 710 650 610
Tube
size,
inches EHD*
10 20 30 40 50 60
1/2 18 EH
D
82 58 47 41 37 34
3/4 23 EH
D
161 116 96 83 75 68
1 30 EH
D
330 231 188 162 144 131
1 1/4 37 EH
D
639 456 374 325 292 267
Length of Flexible Corrugated Stainless Steel Tubing (CSST), Feet
Tube
size
inches EHD*
10 20 30 40 50
1/2 18 EHD 129 91 74 64 58
3/4 23 EHD 254 183 151 131 118
1 30 EHD 521 365 297 256 227
Length of Flexible Corrugated Stainless Steel Tubing (CSST),
F
Nominal
iron Black Iron Pipe
pipe Length of Pipe, Feet
Inches 10 20 30 40 50 60 80 100 125 150 200
1/2 291 200 160 137 122 110 94 84 74 67 58
3/4 608 418 336 287 255 231 197 175 155 140 120
1 1145 787 632 541 480 434 372 330 292 265 227
Copper
Outside Length of Tubing, Feet
diameter
Inch 10 20 30 40 50 60 70 80 90 100
3/8 39 26 21 19 _ _____
1/2 9262 50 41 37 3531292726
5/8 199 131 107 90 79 72 67 62 59 55
3/4 329 216 181 145 131 121 112 104 95 90

6 720 608 158
12
Installation instructions
3.7 Water connections
BWhen facing the heater, the ¾” cold connection is on
the bottom right and the hot connection is on the
bottom left. Centrally locating the water heater is
recommended to keep hot water distribution times
even throughout the structure.
Fig. 14
Fig. 15 Water filter
1Water valve with engine
2Water filter
BThe use of unions when connecting both water
pipes to the inlet and outlet connections is
required. This will facilitate any necessary
servicing.
BPlastic or PEX type plumbing line materials are not
suitable for connecting directly to the water heater.
BAlthough water piping throughout the building may
be other than copper, we recommend that copper or
suitably rated stainless steel flex line piping be used
for the water connections for 1.5’ on either side of
the water heater (follow local codes if more
stringent).
BNever sweat any piping directly to or beneath
the water connections, as damage can occur to
the internal water valve from heating of the
pipe.
BKeep water inlet and outlet pipes to no less
than ¾" (19.05mm) diameter to allow the full
flow capacity.
BIf the cold and hot connections to the heater are
reversed, the heater will not function. Be certain there
are no loose particles or dirt in the piping. Blow out
or flush the lines before connecting to the water
heater.
BFull port shutoff valves should be installed on both
the cold water supply and hot water outlet lines to
facilitate servicing the heater (see Fig. 16).
BFor installation on a private well system with the use
of a pressure tank, the lowest pressure range setting
recommended is 40-60 psi (2.75 and 4.15 bar).
3.8 Water quality
Water quality can have an impact on appliance
longevity and may not be covered under 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
specified below, Bosch recommends installing a water
conditioner or softener.
Warning: This heater is not approved
for preheated water applications above
140°F (60°C). See chapter 3.9 for
approved recirculating application.
HOT
COLD
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
Table 2

6 720 608 158
Installation instructions
13
Connecting the pressure relief valve (PRV)
A listed pressure relief valve supplied with the heater
must be installed at the time of installation. No valve is
to be placed between the PRV and the heater. No
reducing coupling or other restriction may be installed
in the discharge line. The discharge line must be a
minimum of 4” above a drain and installed such that it
allows complete drainage of both the PRV and the line.
The discharge line must be placed where it will not
cause any damage.
The location of the PRV must be readily accessible for
servicing or replacement, and be mounted as close to
the water heater as possible. See Fig. 16. To install the
PRV, a suitable fitting connected to an extension on a
“T” fitting can be sweated to the hot water line.
Support all piping.
Fig. 16 Plumbing Connections (with shutoff valves)
and Pressure Relief Valve
3.9 Recirculation application
The GWH 715 ES Protankless water heater is
approved for domestic hot water recirculation. The
following drawing is provided to outline one possible
recirculation design using the water heater in
conjunction with an Ariston mini tank water heater.
Recirculation directly through the tankless water heater
is also allowed. This schematic is for illustration only and
must not be used for actual installation without
appropriate engineering and technical advice from a
properly licensed professional in the locality where the
installation is made.
Fig. 17 Recirculation application
1Full port isolation valve
2Circulator (pump on timer)
3Check valve
4PRV
5Expansion tank
The use of a small electric mini-tank water heater (4-6
gallon size) should be used for this application and
designed so the pump will circulate the water through
the mini-tank and the building's hot water return loop
only. Timed or thermostatically controlled operation of
the pump is commonly done. Contact Bosch Water
Heating if further information is needed.
3.10 Combustion air requirements
Warning:
In applications where inlet water
temperature can exceed 140°F (60ºC), a
3-way valve or mixing valve must be
installed before the appliance to prevent
water exceeding 140°F (60°C) from
entering the appliance.
Warning: In areas where outside
temperatures commonly fall below
36°F, a twin pipe venting system is
required. Failure to do so may result in
cold outside air being drawn in through
the venting system due to a negative
pressure in the house and across the
heat exchanger coil causing it to freeze
and burst. This failure is not covered
under the manufacturer’s warranty.
Ariston Minitank
GWH
715
ES

6 720 608 158
14
Installation instructions
Twin pipe
The GWH 715 ES is designed as a sealed combustion
appliance. It is recommended that the combustion air
be provided by a dedicated 3” or 4” pipe from the
outside. The combustion air pipe may be PVC or any
other rigid or semi rigid sealed 3” or 4” pipe. The
combustion air inlet, whether terminating vertically or
horizontally, must be located in such a manner as
to provide a minimum 3 foot clearance from the
exhaust vent terminator. See Fig. 28 Letter I, page
21.
The maximum length of the combustion air inlet
is 26 feet with one elbow. Subtract 2.5 feet for
each additional 90° elbow and 1.25 feet for each
additional 45° elbow. Maximum number of
elbows permitted is 3.
Single pipe
Note: This appliance requires 9950 cubic feet of
available combustion air, or a minimum of 1243 square
feet of space with an 8 foot ceiling to operate. If the
large amount of air space, which equates to about half
of most average sized homes, is not available, the
appliance must pull air from the outside (see twin pipe
above).
Although it is permissible to draw combustion air from
inside the structure, it is not the manufacturer’s
recommended installation method. Always install a 3
inch elbow on the top of the combustion air inlet
adaptor to prevent foreign objects from falling into the
unit.
If a single pipe installation is utilized, follow guidelines
below for providing adequate combustion air for the
water heater as well as any other appliances that may
consume air in the space. Always follow local codes if
they are more stringent.
This Installation Manual specifies the minimum vertical
vent pipe and the amount of combustion air required for
this unit. When all requirements are followed, the unit
will operate properly and safely. However, there may still
be a risk of freezing due to negative draft if the other
combustion appliances in the building are not supplied
with sufficient combustion air. A wood stove or furnace
can pull its combustion air from the heater's vent pipe,
allowing the cold incoming air to freeze the cold water
in the heat exchanger. Supplying more combustion air
for all combustion appliances is the solution. A HVAC
specialist should be consulted to design solutions for
providing more combustion air.
Observe the following guidelines:
Installations in structures that have been tightly
constructed (air infiltration rate of 0.40 ACH or less)
must be provided with combustion air per the National
Fuel Gas Code. Consult a HVAC specialist if your air
infiltration rate is questionable.
The space must have two permanent openings, one
commencing within 12 inches of the top and one
commencing within 12 inches of the bottom of the
enclosure.
Each opening must have a minimum free area of one
square inch per:
• 1000Btu/hr if all air is taken from inside the building
• 2000Btu/hr if all air is taken from the outside by
horizontal ducts
• 4000Btu/hr if all air is taken from the outside by
direct openings or vertical ducts.
Or the space must be provided with one permanent
opening or duct that is within 12 inches of the ceiling of
the enclosure.
This opening must have a minimum free area of one
square inch per:
• 3000Btu/hr if all air is taken from the outside by a
direct opening or vertical duct.
Warning: When installed in an
environment where corrosive chemicals
or dirty air are present the twin pipe
system is required.
Warning: Terminations must prevent
rain and debris from entering the
combustion air and exhaust vent piping.

6 720 608 158
Installation instructions
15
3.11 Venting
3.11.1 Vent material and specifications
Establish vent clearances that comply with the vent
manufacturer's specifications. In all cases, follow local
codes. See Table 3.
The appliance should be located as close to the point
of vent termination as possible. The maximum vent
length is 26 feet (8 m) with one 90 degree elbow and
approved terminator. Subtract 2.5 feet from the total
vent length for each additional 90° elbow used (a
maximum of three 90° elbows are permitted in the
total vent length), or subtract 1.25 feet for every 45°
elbow used. Horizontal sections of vent must pitch
upwards towards termination ¼" for every foot of
horizontal length, to prevent the pooling of condensate,
and be supported at 4 foot intervals with overhead
hangers. Exception: horizontal run between last
elbow and termination must pitch down to
termination 1/4" per foot.
Note: For horizontal terminations, venting must
terminate once it penetrates to the outside of the
structure. There must be no sections of vent pipe
exposed to the outdoors other than the
termination.
Note: Listed thimbles or collars are necessary where
venting passes through wall and ceiling partitions. If the
vent system passes through combustible areas where
the vent clearance requirements cannot be maintained,
it is permissible to chase straight sections of sealed 3
inch single wall vent through 4 inch (or greater) Type-B
vent. The distance to combustibles using this chase
technique is 1 inch1). Note: Type-B vent must never
be used as the actual exhaust vent system for the
appliance, as it is not gas tight and illegal for use
with this appliance. This will create a serious
health hazard and void the warranty.
For specific questions concerning vent material,
specifications, usage or installation, please contact the
vent manufacturer directly.
Warning: Do not reduce the vent
(exhaust and combustion) pipe sizes
and do not common vent with any other
vented appliance or stove.
Warning: Failure to vent the exhaust
gases to the outside with sealed
stainless steel vent pipe (AL29-4C)
may result in dangerous flue gases
filling the structure in which it is
installed.
Warning: Do not mix vent pipe or
joining methods from different
manufacturers.
Warning: Proper end terminal / rain
cap must be used. Failure to do so may
result in damage to the appliance.
This damage is not covered under
the manufacturer's warranty.
Caution: The vent system must be
installed by a qualified installer in
accordance with these instructions. If
improperly installed, a hazardous
condition such as explosion or carbon
monoxide poisoning could result.
Bosch Water Heating will not be
responsible for improperly installed
appliances.
Diam. Min.
lenght
Max.
length
Material
Exhaust
Vent
3 or 4
inches
3 feet 26 feet with
1 90° elbow
and terminal
Sealed single wall
stainless steel
(AL29-4C)
Intake
Vent
3 or 4
inches
1 90°
elbow
26 feet with
1 90°elbow
and terminal
Sealed PVC or
any other rigid or
semi rigid pipe
Table 3 Venting Specifications
iNote:
Maximum combination length for separate
(twin) tubes:
• 52 ft + two 90° elbows + two terminals. 1) in all cases, follow local codes.
3”
VENTING
Z flex Protech Heat Fab
3”
Horizontal
Terminal
2SVSTB03 FSTB3 9390 TEE
3” Vertical
terminator 2SVSRCF03 FSRC3 5300CI
Table 4 Terminator Part Numbers
Fittings or Piping Equivalent
feet m
45 degree elbow 1.25 0.38
90 degree elbow 2.5 0.76
pipe per foot 1 0.30
Table 5 Friction Loss Equivalent in piping and fittings

6 720 608 158
16
Installation instructions
Minimum exhaust vent size and length
Fig. 18
Maximum exhaust vent and combustion air inlet
lengths
Fig. 19 Maximum vent and combustion air lenghts
Note: reduce 2.5 ft for each 90° elbow used after the
first one, reduce 1.25 ft for each 45° elbow, see table 3,
page 15.
Refer to chapter 3.11.3 for condensate drain
requirements.
Vent Safety System
The GWH 715 ES will shut down if inadequate exhaust
venting is detected or a lack of combustion air is
provided to the unit; see troubleshooting section on
page 35. See error code to confirm error, correct the
problem and then reset the heater before operating.
3.11.2 Vent connections
BAttach the flue gas exhaust accessory (8 705 504
151) to the top of the unit (position 1) using the 4
screws and gasket provided. Fully insert stainless
steel vent pipe 1.5” minimum into the accessory and
tighten the clamp (position 2).
Fig. 20
BAttach the combustion air inlet accessory (8 705
504 154) to the top of the unit (position 3) using the
3 screws and gasket provided, and install air intake
pipe over the accessory. NOTE: The appliance has
the option to mount the combustion air inlet acces-
sory on the top right or on the top left side of the
heater. The combustion air inlet that is not used must
be kept sealed.
Fig. 21
BEnsure that exhaust vent pipe is fully inserted in collar
to enable proper connection.
Company Contact info
Z-flex www.z-flex.com
800-654-5600
ProTech Industries www.protechinfo.com
800-766-3473
Heat-Fab www.heatfab.com
800-772-0739
Table 6 Vent manufacturers
iNote:
Maximum combination length for separate
tubes:
• 52 ft + two 90° elbows + two terminals.
The minimum exhaust vent length is
3 feet (1 m) with one 90 degree
elbow.
iExhaust venting must be 3" or 4" sealed
single wall stainless steel (AL29-4C) vent
pipe.

6 720 608 158
Installation instructions
17
3.11.3 Condensate drain requirements
A condensate drain must be installed under the
following conditions:
• All vertical terminating vent installations
• Horizontal terminating vent installations where the
total vent length is greater than 10 feet
• Vent installations where any section of the exhaust
vent pipe passes through an unconditioned space.
Note: Do not install condensate drain in areas where it
may freeze.
1. Install condensate drain as close to heater as
possible.
2. Use 3/8" ID high temperature silicone tube to
connect to condensate drain port. Do not use copper
piping for any portion of the condensate drain.
3. Form a condensate trap by means of a 3" loop
partially filled with water.
4. To increase the tube length, connect to end of the
high temperature silicon tubing with vinyl tubing, PVC or
CPVC pipe. Do not reduce the internal diameter at any
point.
5. Dispose of condensate according to local codes.
Fig. 22 Condensate drain installation
Room sealed installation (TWIN PIPE SYSTEM)
Installing this water heater as a room sealed (TWIN
PIPE SYSTEM) is the recommended method. Contact
your dealer for available vent termination kits and vent
materials for this water heater.
The exhaust and combustion air piping must vent
directly to the outside of the structure.
Fig. 23
Combustion air pipe: ≤26 ft (8 m) from collar
Exhaust vent pipe: ≤26 ft (8 m) from collar
Fig. 24
3" Venting Z-flex ProTech Heat Fab
90°
Condensate
Drain Tee
2SVEVWCF03 FST3 &
FSDF3
93PPLSTEE
Horizontal
Condensate
Drain
2SVEDWCF03 FSHDT3 9321
Condensate
Drain Tube
2SVEDTK24 N/A 7000TUBE
Table 7 Approved Condensate Drain Part Numbers
Warning: In areas where outside
temperatures commonly fall below
36°F, a twin pipe venting system is
required. Failure to do so may result in
cold outside air being drawn across the
heat exchanger coil causing it to freeze
and burst. This failure is not covered
under the manufacturer's warranty.

6 720 608 158
18
Installation instructions
Fig. 25
Open combustion installation (SINGLE PIPE
SYSTEM)
Not recommended in cold climate areas, see
chapter 3.10, page 13.
Fig. 26
Connecting a one piece 90 degree elbow pipe to the
combustion air inlet adaptor is necessary. This will
prevent debris or objects from falling into the appliance.
The exhaust vent system must vent directly to the
outside of the building and an adequate amount of
indoor combustion air must be provided for this
installation. See chapter 3.10.
Note: reduce 2.5 ft for each 90° elbow used after the
first one, reduce 1.25 ft for each 45° elbow.
A maximum of three 90-degree elbows are permitted.
Warning: Approved terminators must
be used for inlet and exhaust vent
systems to prevent rain from entering
the appliance, failure to do so may result
in damage to the appliance. This failure
is not covered under the manufacturer’s
warranty.

6 720 608 158
Installation instructions
19
3.11.4 Vent length calculation
Adjusting the minimum power (P2) based on the total
combined vent length.
After installing the GWH 715 ES, the minimum power
fan speed must be selected to compensate for variation
in vent pipe length.
Total vent length calculation
BDetermine the total length of all straight sections of
vent pipe and enter in table 8, line 1.
BCount the number of 90° elbows used and enter that
value in line 2. (Do not count end terminal and first
elbow after the appliance).
BCount the number of 45° elbows used and enter that
value in line 3.
BRepeat steps 1 through 3 for air intake pipe and enter
those values in the intake section of table 8.
BAdd line 4 from Exhaust to line 4 of Intake and enter
result in line 5.
This is the total equivalent vent length.
NOTE: If total equivalent vent length calculated
is 19 feet or less, no P2 adjustment is needed.
Example
Exhaust
• 7 - 3' straight sections
• 1 - 1' straight section
Total length 22'
• 1 - 90° elbow.
Intake
• 5 - 3' straight sections
Total length 15'
• 1 - 90° elbows.
Example
Exhaust
1Straight section length __ = ____
290° elbows (qty) __ x 2.5 = ____
345° elbows (qty) __ x 1.25 = ____
4Total: ____
Intake
1Straight section length __ = ____
290° elbows (qty) __ x 2.5 = ____
345° elbows (qty) __ x 1.25 = ____
4Total: ____
5Total equivalent vent length = ____
Table 8 Determining vent length combination (see
example in Table 9)
Exhaust
Straight section length 22 =22
90° elbows (qty) 1 x 2.5 = 2.5
45° elbows (qty) 0 x 1.25 = 0
Total: 24.5
Intake
Straight section length 15 =15
90° elbows (qty) 1 x 2.5 = 2.5
45° elbows (qty) 0 x 1.25 = 0
Total: 17.5
Total equivalent vent length = 42
Table 9 Determining vent length combination example
iTotal maximum length not to exceed 52 ft.

6 720 608 158
20
Installation instructions
To select fan speed:
BPress ON/OFF button into OFF.
BPress and hold "Program" button and press
ON/OFF button to turn appliance ON.
Fig. 27
BAs soon as '188' is displayed, release "Program"
button , and the display should read P2.
BPress or to choose the fan speed suitable
with your installation, see Table 10.
BPress and hold (±5 sec.) “Program” button until
the display flashes, then the selected value is
memorized.
Mode Pipe Length1)
1) Full equivalent length (inlet + outlet piping + fittings)
Fan speed
“P2”
3 - 19 ft pick 6
20 - 46 ft pick 7
47 - 52 ft pick 8
Table 10Fan speed adjustment
iDo not set P2 to greater then 8.