Bosch Pro Tankless GWH-635-ES-N User manual

Water heaters for use with Natural and L.P.G.
GWH-635-ES
Temperature odulated with Electronic Ignition
Suitable for heating potable water only - Not approved for space heating purposes
(Intended for variable flow applications with multiple tapping points)
GWH-635-ES-N
GWH-635-ES-L
6 720 607 072 (16 January) JS
PRO TANKLESS
Warning: If the information in this manual is not
followed exactly. A fire or ex losion may result
causing ro erty damage, ersonal injury or death.
Do not store or use gasoline or other flammable
va or and liquids in the vicinity of this or any other
a liance.
Im ro er installation, adjustment, alteration,
service or maintenance can cause injury or
ro erty damage. Refer to this manual. For
assistance or additional information consult a
qualified installer, service agency or the gas
su lier.
In the Commonwealth of Massachusetts this
roduct must be installed by a licensed lumber or
gas fitter.
U on com letion of the installation, these
instructions should be handed to the user of the
a liance for future reference.
What to do if you smell gas
• Close gas valve. O en windows.
• Do not try to light any a liance
• Do not touch any electrical switch; do not use any
hone in your building
• If you cannot reach your gas su lier, call the fire
de artment.
• Immediately call your gas su lier from a neighbor’s
hone. Follow the gas su lier’s instructions
• Installation and service must be erformed by a
qualified installer, service agency or the gas su lier.

6 720 607 072 (16 January)
2
Index
Index
1 Warning 2
2 Appliance details 4
2.1 Features 4
2.2 GWH-635-ES S ecifications (Technical data) 4
2.3 Dimensions and Minimum installation clearances 6
2.4 General rules to follow for safe o eration 7
2.5 Pro er location for installing your heater 7
2.6 Clearances 8
2.7 Mounting installation 8
2.8 Combustion air requirements 8
2.9 Venting 9
2.9.1 Venting o tions 12
2.10 Gas i ing & connections 15
2.11 Gas line sizing 17
2.12 Measuring gas ressure 17
2.13 Water connections 18
2.14 Electrical connections 20
2.15 O erating instructions 20
2.16 For your safety read before o erating your water heater 20
2.17 Lighting and o erating instructions 20
3 Operation instructions 22
3.1 Power 22
3.2 Tem erature selection 22
3.3 New remote control registration 24
3.4 O eration 24
3.5 Reset button 24
3.6 Program button 24
3.7 Locked condition 25
4 aintenance and service 25
5 Troubleshooting 25
6 Electrical diagram 28
7 GWH-635-ES Functional scheme 29
8 Interior components diagram and parts list 30
8.1 Interior com onents 30
8.2 Com onents diagram 31
8.3 Parts list 32
9 Special adjustment for measuring and adjusting CO
2
levels 33
9.1 Adjusting the unit 33
9.1.1 CO
2
measuring ort 33
9.1.2 Selecting adjustment mode 33
10 Protecting the environment 35
11 Fifteen Year Limited Warranty 36
1Warning
Featuring
Electronic Ignition and Power Venting
For your safety
Do not store or use gasoline or other flammable,
combustible or corrosive va ors and liquids in the
vicinity of this or any other a liance.
Warning: If the information in this
manual is not followed exactly. A fire or
ex losion may result causing ro erty
damage, ersonal injury or death.
Warning: Im ro er installation,
adjustment, alteration, service or
maintenance can cause injury or
ro erty damage. Refer to this manual.
For assistance or additional information
consult a qualified installer, service
agency or the gas su lier.
U on com letion of the installation,
these instructions should be handed to
the user of the a liance for future
reference.
Warning: Carefully lan where you
install the heater. Correct combustion
air su ly and flue i e installation are
very im ortant. If a gas a liance is not
installed correctly, fatal accidents can
result from lack of air, carbon monoxide
oisoning or fire.
Warning: Exhaust gas must be vented
to outside using ro er vent material
suitable for category III vent systems
and tem eratures u to 480°F. Vent
and combustion air connector i ing
must be sealed gas-tight to revent
ossibility of flue gas s illage, carbon
monoxide emissions and risk of fire,
resulting in severe ersonal injury or
death.
Warning: Place the heater in a location
where water leaks will do NO DAMAGE
to adjacent areas or lower floors.

6 720 607 072 (16 January)
Warning
3
What to do if you smell gas
• Close gas valve. O en windows.
• Do not try to light any a liance.
• Do not touch any electrical switch; do not use any
hone in your building.
• Immediately call your gas su lier from a neighbor’s
hone. Follow the gas su lier’s instructions.
• If you cannot reach your gas su lier, call the fire
de artment.
• Installation and service must be erformed by a
qualified installer, service agency or the gas su lier.
Fig. 1
Fig. 2
Warning: Field wiring connections and
electrical grounding must com ly 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
com ly with the local codes and the
Canadian Electrical Code, CSA C22.1
Part 1.
Warning: Shock hazard line voltage is
resent. Before servicing the water
heater, turn off the electrical ower to
the water heater at the main disconnect
or circuit breaker. Failure to do so could
result in severe ersonal injury or death.
Warning: The heater must be
disconnected from the gas su ly
i ing system during any ressure
testing of that system at test ressures
equal to or more than 0.5 sig.
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.
Caution:
Any changes or modifications not expressly
approved by the party responsible for
compliance could void the user's authority to
operate the equipment.

6 720 607 072 (16 January)
4
Appliance details
2 Appliance details
2.1 Features
Parts
• Touch Pad interface control
• High ower re-mix com act burner with low Nox
emissions
• Modulating Gas Valve with constant gas:air ratio
control
• Modulating water valve for im roved comfort and
tem erature control.
Safety
• Flame sensor (ionization) rod
• Overheat sensor
• Tem erature limiter
• Fan s eed monitoring.
High Quality Materials for Long Working Life
• Co er heat exchanger
• Ceramic Burner out ut
• Automatic overheating rotection shut-off sensor
• Com act s ace saver: mounts on a wall with a
su lied bracket.
• Easily removable one- iece cover.
Features
• LCD Dis lay
• On/Off and Tem erature control switches
• Reset button
• Program Key (Selectable tem erature default)
• Failure codes for easy diagnostic and re air.
Accessories
• O tional wireless remote control accessory to
o erate with the a liance
• Vent termination kit.
2.2 GWH-635-ES Specifications
(Technical data)
A roved in US/Canada
Capacity
Maximum flow rate: 6.35 GPM (24 l/min) at a 45°F
(25°C) rise.
aximum output
142,968 Btu/h (41.8 kW)
aximum input
175,000 Btu/h (51.2 kW)
Efficiency in %
Recovery efficiency 86.5%
in. Output
31,131 Btu/h (9.1 kW)
Temperature Control
Selection range: 100°F (38°C) - 140°F (60°C)
Default tem erature: 122°F (50°C)
Stability: +/- 2°F (+/- 1°C)
Gas Requirement
Gas connection (inches) - ¾”
Inlet gas ressure under o eration (with a high hot
water flow rate)*
• Pro ane: 11” - 14” water column
• Natural Gas: 5” - 14” water column
• Gas ressure measuring oint inside the a liance
at the gas valve inlet.
* Testing with a manometer, o erate other gas
equi ment on the same gas su ly. Gas ressures
lower than 5" W.C. for Natural Gas or 11" W.C. for
LPG will result in insufficient degree rise to the hot
water being used. See Measuring Gas Pressure,
cha ter 2.12.
Fig. 3 Gas pressure measuring point
Venting
See cha ter 2.9 for Venting on age 9.
Water
• Hot water connection (inches) - ¾”
• Cold water connection (inches) - ¾”
• Water valve material: Polymer (PPS) (Poly ro ylene
Sulfid)
• Minimum water flow: 0.8 gallon/minute (3 l/m)
i
BOSCH is constantly im roving its
roducts, therefore s ecifications are
subject to change without rior notice.

6 720 607 072 (16 January)
Appliance details
5
• Minimum recommended water ressure range: 30
PSI (2.07 bar)
• Connections:
– Bottom of heater
Combustion
•NOx ≤ 55 m
•CO ≤ 200 m
•CO
2
level set from factory, see cha ter 9.1.
Dimensions
• De th (in): 8 ½” (220 mm)
• Width (in): 15 ¾” (400 mm)
• Height (in): 23 ½” (600 mm)
• Weight: 47 ounds (21 kg).
Gas types
Natural Gas.
LP Gas.
Converting the gas ty e can only be done by a certified
gas technician with a calibrated CO
2
analyzer. Call
CEC for conversion instructions.
Voltage
120 V AC (60 Hz)
Amperage
IDLE - 40 mA
O eration - ≤ 2,5 A
Noise
≤ 50 db (A)
Safety devices
• Flame failure device (ionization flame rod sensor)
• Pressure relief valve (su lied with heater)
• Over heat revention (tem erature limiter).
Water resistant
IP X4 ( rotection against water dro s)
UNPACKING THE GWH-635-ES HEATER
This heater is acked securely.
The box includes:
• Pressure relief valve
• Bracket for wall hanging the heater
• Exhaust vent ada tor (with 4 screws and gasket
rovided)
• Combustion air inlet ada tor (with 3 screws and
gasket rovided)
• Installation manual
• Product registration card.
Do not lose this manual. Please com lete and return
the enclosed roduct registration card.
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
shi ing box, and on the rating late which is located on
the right side anel of the cover.
To remove front cover
• Remove lastic decals on front anel
• Undo two Phili s head screws located behind decals
• Lift front cover anel u ward and remove.
Fig. 4 Remove front cover
Plastic decals

6 720 607 072 (16 January)
6
Appliance details
2.3 Dimensions and inimum installation clearances
Fig. 5 Dimensions
1Cover
2On/Off switch
3Reset button
4LCD dis lay
5Program button
6Tem erature buttons
Fig. 6 Minimum clearances
odel GWH-635-ES
TOP (A) 12”
FRONT (B) 4”
BACK 0”
SIDES 4”
FLOOR (C) 12”
VENT DIA ETER 3”
Table 1 Minimum clearances

6 720 607 072 (16 January)
Appliance details
7
2.4 General rules to follow for safe
operation
B1. You should 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 should conform with
CGA B149.(1,2) INSTALLATION CODES and /or
local installation codes.
B2. Carefully lan where you install the heater. Correct
combustion air su ly and vent i e installation are
very imortant. If not installed correctly, fatal
accidents can be caused by lack of air, carbon
monoxide oisoning or fire.
B3. When the unit is installed indoors and ROOM
SEALED (twin i e) it is ermitted to be located in
bathrooms, bedrooms and occu ied rooms that are
normally ke t closed. See cha ter 2.9. If the unit will
be installed indoors and use indoor combustion air,
the lace where you install the heater must have
enough ventilation. The National Fire Codes do
not allow UNSEALED gas fired water heater
installations in bathrooms, bedrooms or any
occupied rooms normally kept closed. See
cha ter 2.5 and 2.8.
B4. You must vent your heater. See section on
VENTING.
B5. The a liance must be isolated from the gas
su ly i ing system by closing its individual manual
gas shutoff valve (not su lied with heater) during
any ressure testing at ressures in excess of ½ Psig
(3.5 kPa).
The a liance and its gas connection must be leak
tested before lacing the a liance in o eration.
B6. Kee 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 o timum
o eration of this heater. Gas i ing must be sized to
rovide the required ressure at the maximum out ut
of the heater, while all the other gas a liances are in
o eration. Check with your local gas su lier, and
see the section on connecting the gas su ly.
B8. Should overheating occur or the gas su ly fail to
shut off, turn off the gas su ly at the manual gas
shut off valve, on the gas line. Note: manual gas
shutoff valve is not su lied with the heater.
B9. Do not use this a liance if any art has been
underwater. Immediately call a qualified service
technician to ins ect the a liance and to re lace
any art of the control system and any gas control
which has been underwater
2.5 Proper location for installing your
heater
Carefully select the location of the water heater. For
your safety and for ro er heater o eration, you must
rovide combustion air to the heater and a ro er
exhaust vent system.
Follow the guidelines below:
B1. Locate the heater where venting, gas and
lumbing connections are feasible and convenient.
B2. It is strongly recommended that the heater be
installed as a ROOM SEALED heater (twin i e). If
the heater will be installed as an UNSEALED heater
(single i e) than National building codes require
that you do not install this a liance in bathrooms,
bedrooms or any occu ied rooms normally ke t
closed. Heaters that are UNSEALED require a
considerable amount of combustion air, see
cha ter 2.8. If installing the heater UNSEALED
within a laundry room, be certain that the dryer is
ro erly vented. Failure to ro erly vent a dryer could
result in a gradual accumulation of lint build u inside
the combustion chamber of the heater.
B3. The hot water lines should be ke t short to save
energy. Centrally locating the water heater is best. It
is always best to have hot water lines insulated.
Warning: The water in this water
heater is cold and always remains cold
exce t for the times that hot water is
being used DO NOT INSTALL IN AN
AREA WHERE IT COULD FREEZE.
Drain the heater entirely if freezing
tem eratures are antici ated in area
where heater is installed by
disconnecting both the inlet and outlet
connections at the bottom of heater.
To revent any freeze damage,
introduce short bursts of com ressed
air (20-40 si) through these
connections to remove the residual
water in the horizontal i es and water
valve.
Warning: Flammable materials,
gasoline, ressurized containers, or any
other items or articles that are otential
fire hazards must NOT be laced on or
adjacent to the heater. The a liance
area must be ke t free of all
combustible materials, gasoline and
other flammable va ors and liquids.

6 720 607 072 (16 January)
8
Appliance details
2.6 Clearances
The GWH-635-ES is design certified for installation on
a combustible wall (see 2.7 Mounting installation)
rovided 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. 6.
A. To 12 inches (306 mm)
B. Front 4 inches (102 mm)
C. 0 inches
D. Sides 4 inches (102 mm)
E. Bottom 12 inches (306 mm)
Clearances from any exhaust vent i e are de endent
u on the clearance requirements of the stainless steel
vent i e manufacturer. Single wall stainless steel
(AL29-4C) vent i e (vent ty e rated for Category III
a liances) must be used when exhaust venting this
a liance. See 2.9 Venting.
2.7 ounting installation
The GWH-635-ES is design certified for mounting on a
wall. Secure the wall mounting bracket rovided with
the heater to a wall surface. See Fig. 7.
Do not install this a liance on a car eted wall or over
floor covering which is combustible, such as car et.
The heater must be mounted on a wall using
a ro riate anchoring materials.
If the mounting bracket is unable to line u on two wall
studs it is recommended that su ort board(s), either
1x4's or ½" (minimum) lywood first be attached across
a air of studs and then the heater should be attached
to the su ort boards. The heater should be ke t level
on the wall surface. See Fig. 7.
Ex ansion and contraction of i ing due to changing
water tem erature in the i es im arts movement to the
heater which, if mounted directly to a brittle, friable
board, such as lasterboard, can cause failure of
mounting.
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
shi ing box, and on the rating late which is located on
the right side anel of the cover.
Fig. Mounting the heater
2.8 Combustion air requirements
The GWH-635-ES is a sealed water heater and it is
recommended that outdoor combustion air be i ed to
the unit. When combustion air is i ed to the unit
(TWIN PIPE SYSTEM) the combustion air i e system
may be constructed of either 3" PVC, aluminum or
galvanized i e. See Fig. 11, 12 and 13. Select a oint
for building enetration being sure that the necessary
clearance on the outside of the building, between the
combustion air i e and the exhaust vent terminator of
the a liance, can be maintained, see Fig. 16. NOTE:
Observe all local building codes when enetrating a
building wall.
The heater has the ability to o erate without
combustion air being i ed to it from the outside,
rovided there is an adequate amount of combustion air
available in the room area. Observe the following
instructions concerning combustion air when following
the SINGLE PIPE (exhaust venting only) SYSTEM only
and follow Fig. 14 and 15 for ro er setu .
• A liances located in unconfined s aces:
–a) An unconfined s ace is one whose volume is
greater than 50 cubic feet (1.42 cubic meter) er
1000 Btu er hour (292.81 Watts) of the
combined rating of all a liances installed in the
s ace. That would be 8250 cubic feet (233.6
cubic meter) for the GWH-635-ES alone.
–b) In unconfined s aces in buildings of
conventional frame, masonry, or metal
construction, infiltration air is normally adequate to
rovide air for combustion.
Warning: before starting installation:
Bcheck that there are no loose arts
inside the a liance
Bensure that gas i e, gas valve, mixer,
fan and burner have no damage and are
ro erly fitted.
i
Front cover should be removed (see
instructions on age 4) in order to ins ect
com onents visually.

6 720 607 072 (16 January)
Appliance details
9
• A liances located in confined s aces:
The confined s ace must be rovided with two
ermanent o enings, one commencing within 12
inches (304.8mm) of the to and one commencing
within 12 inches (304.8mm) of the bottom of the
enclosure. Each o ening must have a minimum free
area of one square inch er:
– 1000 Btu/hr (292.81 Watts) if all air is taken from
inside the building
– 2000 Btu/hr (585.62 Watts) if all air is taken from
the outside by horizontal ducts
– 4000 Btu/hr (1171.24 Watts)if all air is taken from
the outside by direct o enings or vertical ducts
Or the confined s ace must be rovided with one
ermanent o ening or duct that is within 12 inches
(304.8mm) of the ceiling of the enclosure. This o ening
must have a minimum free area of one square inch er:
– 3000 Btu/hr (878.43 Watts) if all air is taken from
the outside by a direct o ening or vertical duct.
Louvers, grills and screens have a blocking effect. If the
effective free area is not known, increase the sizes of
your o enings by 75% if your louvers are wood and by
30% if your louvers are metal. Refer to the National Fuel
Gas Code for com lete information. In buildings of tight
construction all air should be taken from outside.
2.9 Venting
NOTE: This appliance's exhaust must be vented
to the outside with a sealed 3" stainless steel
vent pipe (AL29-4C). The appliance's flue gasses
are under positive pressure and must travel
through a stainless steel 3" pipe that is sealed
gas tight. Stainless steel vent pipe is equipped
with sealing gaskets for ease of installation,
proper safety and durability. The heater shall not
be vented in combination with any other
appliance; the appliance must only be vented
with a dedicated sealed vent system.
Establish vent clearances that com ly with the vent
manufacturer's s ecifications. In all cases follow local
codes. See table 2.
Warning: Do not reduce the vent
(exhaust and combustion) i e sizes
and do not common vent with any other
vented a liance or stove.
Caution: The vent system must be
installed by a qualified agency in
accordance with these instructions. If
im ro erly installed a hazardous
condition such as ex losion or Carbon
Monoxide oisoning could result. CEC
will not be res onsible for im ro erly
installed a liances.

6 720 607 072 (16 January)
10
Appliance details
The maximum flue gas exhaust temperature on the GWH-635-ES is 437°F (225°C)
Venting
Options
Exhaust
vent
diameter
and
material
* Exhaust
vent
maximum
length
* Exhaust
vent
minimum
length
Combustion
air i e
diameter
and material
Combustion
air i e
maximum
length
Vent i e
clearances
within an
unenclosed
s ace
Vent i e
clearances
within an
enclosed
s ace
Room
se a l ed
(twin pipe)
3 inch
stainless
steel
(AL29-4C)
sealed vent
i e
26 feet (8
m) with one
elbow. Less
2½ feet for
each
additional
elbow
1½ feet 3 inch PVC,
aluminum or
galvanized
i e
26 feet (8
m) with one
elbow. Less
2½ feet for
each
additional
elbow
** See vent
manufacturer's
s ecifications
** See vent
manufacturer's
s ecifications
Open
combustion
(single
pipe)
3 inch
stainless
steel
(AL29-4C)
sealed vent
i e
26 feet (8
m) with one
elbow. Less
2½ feet for
each
additional
elbow
1½ feet See
cha ter 2.8
See
cha ter 2.8
** See vent
manufacturer's
s ecifications
** See vent
manufacturer's
s ecifications
Exhaust vent is always fan assisted. Installation of exhaust vent and combustion air i ing may be run vertically or horizontally
and in se arate directions if required.
* A maximum of three 90 degree elbows are ermitted in the total vent length.
** Stainless steel (AL29-4C) vent i e is manufacturerd by Z-Flex, Protech and Heat Fab. NOTE: clearance distances are
variable de ending if the vent i e is installed in an enclosed or unenclosed s ace, the exhaust flue gas tem erature and the
orientation of the vent i e.
Never reduce i e diameter.
Table 2

6 720 607 072 (16 January)
Appliance details
11
The a liance should be located as close to the oint
of termination as ossible. The maximum vent length is
26 feet (8 m) with one 90 degree elbow. Subtract 2½
feet from the total vent length for each additional 90-
degree elbow used (a maximum of three 90-degree
elbows are ermitted in the total vent length). Horizontal
sections of vent must itch ¼" for every foot of
horizontal length and be su orted at 4 foot intervals
with overhead hangers. Any vent section greater than
45 degrees is considered an elbow.
Note: The stainless steel exhaust vent i e should not
be used in concealed or unheated locations. Listed
thimbles or collars are necessary to ass through wall
and ceiling artitions. If the vent system asses through
combustible areas where the vent clearance
requirements cannot be maintained, it is ermissible to
chase straight sections of sealed 3 inch single wall vent
through 4 inch (or greater) Ty e-B vent. The distance to
combustibles using this chase technique is 1 inch.
Note: Type-B vent should never be used as the
actual exhaust vent system for the appliance, as
it is not gas tight.
inimum exhaust vent size and length
Fig. 8
aximum vent lengths
Fig. 9
Note: reduce 2½ ft for each elbow used after the first
one
Vent Safety System
The GWH-635-ES will shut down if inadequate exhaust
venting is detected or a lack of combustion air is
rovided to the unit; see troubleshooting section on
age 25. See error code to confirm error, correct the
roblem and then reset the heater before o erating.
Attaching the exhaust and air inlet connection
adaptors to the top of the heater
Fig. 10
Fig. 11
BAttach the flue gas exhaust accessory (8 705 504
114) to the to of the unit ( osition 1) using the 4
screws and gasket rovided, and fully insert 3"
stainless steel vent i e into the accessory and
tighten the clam ( osition 2).
BAttach the combustion air inlet accessory (8 705
504 115) to the to of the unit ( osition 3) using the
3 screws and gasket rovided, and fully insert 3"
combustion air i e into the accessory and tighten
the clam ( osition 4). NOTE: The a liance has the
ossibility to mount the combustion air inlet
accessory on the to right or on the to left side of
the heater. The combustion air inlet that is not used
must be ke t sealed.

6 720 607 072 (16 January)
12
Appliance details
2.9.1 Venting options
Installing this water heater as a room sealed (TWIN
PIPE SYSTEM) is the recommended method. Contact
CEC or dealer for available vent termination kits and
vent materials for this water heater.
Room sealed installation (TWIN PIPE SYSTE )
Fig. 12
Combustion air i e: ≤ 26 ft (8 m)
Exhaust vent i e: ≤ 26 ft (8 m)
Fig. 13
Combustion air i e: ≤ 26 ft (8 m)
Exhaust vent i e: A+B+C ≤ 23½ ft (7.2 m)
Note: reduce 2½ ft for each elbow used after the first
one.
Open combustion installation (SINGLE PIPE
SYSTE )
Fig. 14
Exhaust vent i e: ≤ 26 ft (8 m)
Fig. 15
Exhaust vent i e: A+B+C ≤ 23½ ft (7.2 m)
The exhaust vent system must vent directly to the
outside of the building and an adequate amount of
indoor combustion air must be rovided for this
installation. See cha ter 2.8.
Connecting a one iece 90 degree elbow i e to the
combustion air inlet ada tor is recommended, this will
revent debris or objects from ever falling into the inlet
o ening.
Note: reduce 2½ ft for each elbow used after the first
one.
i
Exhaust venting shall be done with 3”
stainless steel (AL29-4C) vent i e.
i
The exhaust vent i e and combustion air
i e can be run vertically or horizontally.
Maximum length for each individual i e is
26 feet (8 m) with one elbow, for each
additional elbow after the first elbow you
must reduce 2½ feet from the total vent
length.

6 720 607 072 (16 January)
Appliance details
13
Recommended exhaust vent terminator position
Fig. 16
* Subject to local codes and antici ated snow level
** Other equi ment that o erates with a mechanical air inlet may require greater distances, reference manufacturer's instructions
Ref. Description inimum distance
ADirectly below an o ening; o erable windows, doors and any non-
mechanical fresh air o enings 36 in
B
Below a gutter, sanitary i ework or eaves 24 in
Below a gutter, sanitary i ework or eaves, rotected by metal
shielding 12 in
CFrom any internal corner 12 in
D* Above ground 12 in
Above a aved sidewalk or driveway 7 ft
E
From an o osing wall or structure facing the termination 24 in
From any other building o ening, gas utility meter, service regulator
or the like 7 ft
FFrom a terminator facing a terminator 48 in
GVertically between two exhaust vent terminators on the same wall 60 in
HHorizontally between two exhaust vent terminators on the same wall 12 in
I**
Horizontally from combustion air inlet of 635-ES 36 in
Vertically above combustion air inlet of 635-ES
From the combustion air inlet of any a liance or below the
combustion air inlet of 635-ES 3 ft
JFrom any external corner 12 in
KHorizontally from an o ening; o erable windows, doors and any
non-mechanical fresh air o enings 12 in
LVertically from a wall, roof slo e, or obstruction (venting through a
flat or itched roof)
see ABOVE THE ROOF
requirements on following age
Table 3

6 720 607 072 (16 January)
14
Appliance details
Supporting the exhaust vent system and the use
of an external condensate trap
External condensate traps
BA condensate tra must be used in any sidewall
exhaust vent installations when the total vent length
is ≥ 8 ft (2.5 m) OR the vent i e asses through an
unheated s ace (below 60F).
BA condensate tra must be used for any vertical
exhaust vent installations ≥ 2 ft.
BWhen installing the condensate tube at the bottom of
the drain tee, be sure to form a tra by means of a 3"
(76.2 mm) loo filled with water. This tube must be
3/8" ID high tem erature silicone for at least the first
6 inches (152 mm) and attached with a gear clam
or hose clam . The condensate must be dis osed of
according to local regulations.
Fig. 1 Horizontal side wall venting installation
(combustion air piping not being shown)
Fig. 18 Above the roof clearance requirements from
rain cap (combustion air piping not being
shown)
Fig. 19 Vertical venting installation (combustion air
piping not being shown)
i
The venting materials and accessories
required to roerly install the water
heater are available from CEC and their
distributors.

6 720 607 072 (16 January)
Appliance details
15
Fig. 20 Vertical venting installation - Masonry
Chimney (combustion air piping not being
shown)
2.10 Gas piping & connections
Before connecting the gas su ly, check the rating
late 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 should conform with CGA
B149 INSTALLATION CODES and/or local installation
codes.
GAS LINE SIZING
The gas su ly i ing should be sized according to the
A licable Plumbing Code for a maximum draw of
175,000 BTUH. First determine the effective length of
the gas su ly line by measuring the actual length of
i ing, and then adding 5 ft. (1.52m) for every elbow or
“T” to the actual length. Use the charts in Fig. 22 to
determine the i e diameter necessary to
accommodate the BTU (Wh) demand of the unit. If
there are more gas drawing a liances on the line, size
according to the maximum amount of BTU (Wh)
demand.
Note: It is im ortant that if any flexible gas line is used,
above or below ground between the gas su ly meter/
regulator and the water heater, that it be sized ro erly;
we recommend the use of non-corrugated flexible gas
line when used. Consult the gas sizing s ecification
tables rovided by the flexible gas line manufacturer.
Fig. 21
BInstall a manual gas shut off valve, on the gas su ly
line.
BThe use of a union when connecting gas i e to the
gas inlet connection is critical, this will facilitate any
necessary servicing and cleaning of the inlet gas
article screen.
BFlexible gas line connectors are not recommended
because they are commonly undersized and restrict
gas flow. Oversize the diameter of any flexible gas
line connector if one must be used.
Gas i ing
Inlet gas article screen

6 720 607 072 (16 January)
16
Appliance details
FOR NATURAL GAS
Maximum Ca acity of i e in Cubic Feet of Gas er
Hour for Gas Pressure of 0.5 Psig or less and a
Pressure dro of 0.3 in Water Column
(0.75mbar).(Based on a 0.60 S ecific Gravity Gas) Btu
numbers given in thousands.
Fig. 22
Follow boxed numbers for i ing just one GWH-
635-ES (exam le: ¾” B.I. Natural Gas i e for 20 ft
(6.1m). will handle 190,000 btu’s (55.7 kWh). For
multi le a liances combine the total btu in ut load
and then refer to a licable chart below.
Maximum Ca acity of Semi-Rigid (flexible, non
corrugated) Tubing in Thousands of BTU er Hour
of Undiluted Liquefied Petroleum Gases (at 11
inches Water Column Inlet Pressure).
(Based on a Pressure Dro 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 Ca acity of Pi e in Thousands of BTU er
Hour of Undiluted Petroleum Gases (at 11 inches
Water Column Inlet Pressure) (Based on a Pressure
Dro of 0.5 Inch Water Column).
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
5/819913110790 79 7267625955
3/4 329 216 181 145 131 121 112 104 95 90
7/8 501 346 277 233 198 187 164 155 146 138
Nominal
Iron Pipe
Black Iron Pipe
Size,
Len th of Pipe, Feet
Inches
10 20 30 40 50 60 70 80 90 100 125 150
1/2 275 189 152 129 114 103 96 89 83 78 69 63
3/4 567 693 315 267 237 217 196 185 173 162 146 132
1 107 732 590 504 448 409 378 346 322 307 275 252
1 1/4 220 149 121 103 913 834 771 724 677 630 567 511
1 1/2 330 229 185 155 141 127 118 108 102 976 866 787
2 622 433 346 299 264 239 220 204 192 1811 1606 1496
Nominal
Iron Len th of Black Iron Pipe, Feet
Pi e 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 73 63 56 50 46 43 40 38 34 31 28 26
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
2 1/2 2.469 4800 3300 2700 2300 2000 1850 1700 1600 1500 1400 1250 1130 1050 980
3 3.068 8500 5900 4700 4100 3600 3250 3000 2800 2600 2500 2200 2000 1850 1700
4 4.026 17,500 12,000 9,700 8,300 7,400 6,80 6,200 5,800 5,400 5,100 4,500 4,100 3,800 3500

6 720 607 072 (16 January)
Appliance details
17
2.11 Gas line sizin
BIt is strongly recommended that the Natural Gas i e
be Black Iron i e the entire distance from the
outside meter to the inlet of the gas connection. ¾”
Black Iron i e u to 20 feet (6.1m) and 1” Black Iron
i e u to 70 feet (21.34m) distances. Flex line is
NOT recommended, but if used, then oversize the
diameter of the flex i e, kee the length to a
minimum and try to kee the flex line as straight as
ossible.
BIt is strongly recommended that the LP Gas i e be
semi-rigid co er or Black Iron i e from the outside
regulator to the inlet of the gas connection. For semi-
rigid co er i ing: 5/8” u to 10 feet (3.05m) and
¾” u to 30 feet (9.14m) distances. For Black Iron
i ing: ½” u to 20 feet (6.1m) and ¾” u to 80 feet
(24.38m) distances. Flex line is NOT recommended,
but if used, then oversize the diameter of the flex
i e, kee the length to a minimum and try to kee
the flex line as straight as ossible.
National Fuel Gas Code requires that a sediment tra
(dri leg) be installed on gas a liances not so
equi ed. Also, a manual gas shut off valve must be
installed on the gas su ly line within close roximity of
the water heater and be visible from the water heater.
The water heater must not be i ed with gas su ly
ressures in excess of 0.5 sig. If over ressure has
occurred, such as through im ro er testing of the gas
lines or malfunction of the su ly system, the gas valve
must be checked for safe o eration.
When connections are made, check for gas leaks at all
joints. A ly some soa y water to all gas fittings. Soa
bubbles are a sign of a leak.
2.12 Measurin as pressure
To measure and verify if adequate gas ressure is being
delivered to the water heater, first run a high hot water
flow rate and o erate other gas equi ment on the same
load. Using a manometer, then measure the inlet gas
ressure at the inlet gas ressure test ort. See Fig. 23.
Gas ressures lower than 5" W.C. for Natural Gas or
11" W.C. for LPG will result in insufficient degree rise
to the hot water being used. See Gas Connections,
cha ter 2.10.
Fig. 23 Gas pressure measuring (left tapping)
HIGH ALTITUDE OPERATION
Due to the lower density of air at high altitudes, out ut
must be reduced in installations above 4000 ft (1219
m).
Burner out ut at altitudes greater than 4000 ft (1219
m) will be electronically reduced once the control board
has been ro erly adjusted. Follow instruction below.
High altitude adjustment
BDisconnect ower su ly to heater.
BRemove front cover of heater.
BRemove control box auxiliary cover (Fig. 24, os. 4).
Fig. 24
i
THESE FIGURES ARE FOR GWH-635-
ES SUPPLY ONLY, ALL OTHER
APPLIANCES IN THE BUILDING MUST
BE INCLUDED IN THE PIPE SIZING.
Warning: The heater must be
disconnected from the gas su ly
i ing system during any ressure
testing of that system at test ressures
equal to or more than 0.5 sig.
Danger: If you have a leak, shut off the
gas. Tighten a ro riate fittings to sto
leak. Turn the gas on and check again
with a soa y solution. Never test for gas
leaks using a match or flame.
Altitude Natural Gas: Liquid
Pro ane:
0 - 4,000 ft
(0 - 1,219 m)
no
modification
no modification
4,000 ft - 8,000 ft
(1,219 m - 2,438 m)
insert jum er
JP3
insert jum er
JP3
Table 4

6 720 607 072 (16 January)
18
Appliance details
BRemove the 5 screws on the front retaining bar (see
Fig. 24, os. 1 and 2) being careful not to damage
the foam sealant material on it.
BRemove the two electrical stri connectors inside the
board (Fig. 25) and then loosen the 120V ower
su ly cord retaining nut located underneath the
heater. Once loosened, the ower cord can be
ulled u through the heater to rovide sufficient
slack.
Fig. 25 Electrical strip connectors
BAt the ignition electrodes, ull off the 2 yellow igniter
wires that come from the to of the control board
(Fig. 24, os. 3). Then ull the com lete control
board forward and out of the heater, ull u the
ower su ly cord further if more slack is needed.
BWhile holding the board in one hand or resting it on
a flat surface, remove the front cover of the control
board by removing its 4 screws.
BOnce o en, locate JP3 on the rinted circuit board
(see Fig. 26). The board is su lied with a jum er
laced on one JP3 in, this means that one of the
jum er sockets is connected to a JP3 in and the
other socket of the jum er is in the air. To make the
high altitude adjustment com lete, the jum er must
be connected to both ins.
BRemove the jum er from the JP3 in (see Fig. 26).
BLine u the two jum er sockets with the two JP3
ins.
BInsert the jum er.
BRe lace the front cover to the control board and re-
insert into heater and then roceed with revious
ste s in reverse order. Be sure that the rubber
grommets of the electrical stri connectors are in
lace and the 2 yellow igniter wires get re-
connected.
Fig. 26 Control board adjustment for high altitudes
(above 4000 ft)
2.13 Water connections
When facing the heater, the ¾” cold water inlet is on the
bottom right and the hot water outlet is on the bottom
left. Install the heater centrally in the building if ossible
and make hot water i ing runs as short as ossible.
Fig. 2
BThe use of a union when connecting both water
i es to the inlet and outlet connections is
recommended, this will facilitate any necessary
servicing and required cleaning of the inlet water
article screen.
Although water i ing throughout the building may be
other than co er, we recommend that co er,
galvanized or suitably rated stainless steel flex line
i ing be used for the water heater connections (follow
local codes if more stringent). Plastics or other PEX
ty e lumbing line materials are not suitable for
connecting directly to the water heater. Kee water inlet
and outlet i es to no less than ¾” (19.05mm) diameter
to allow the full flow ca acity.
If the cold and hot connections to the heater are
Once auxiliary cover is
off, ull off the two
electrical stri connec-
tors inside the board.
Once off, the wiring
strands can be removed
from the area of the
board by ulling their
rubber grommets
outward.
Rubber
grommets i
For altitudes greater than 8000 ft (2438 m),
a s ecial adjustment and CO
2
measurement needs to be done. Please
contact CEC for detailed instructions.
High altitude adjustment
(above 4 000 ft)
HOT COLD
INLET FILTER
SCREEN

6 720 607 072 (16 January)
Appliance details
19
reversed, the heater will not function. Be certain there
are no loose articles or dirt in the i ing. Blow out or
flush the lines before connecting to the water heater.
Full ort valves should be installed on both the cold
water su ly and hot water outlet lines to facilitate
servicing the heater (see Fig. 28). For installation on a
rivate well system with the use of a ressure tank, the
lowest ressure range setting recommended is 30-50
si (2.07 and 3.45bar).
Connectin the pressure relief valve (PRV)
A listed ressure relief valve su lied with the heater
must be installed at the time of installation. No valve is
to be laced between the PRV and the heater. No
reducing cou ling 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 com lete drainage of both the PRV and the line.
The location of the PRV must be readily accessible for
servicing or re lacement, and be mounted as close to
the water heater as ossible. See Fig. 28. To install the
PRV, a suitable fitting connected to an extension on a
“T” fitting can be sweated to the hot water line.
Su ort all i ing.
Fig. 28 Plumbing Connections and Pressure Relief
Valve

6 720 607 072 (16 January)
20
Appliance details
2.14 Electrical connections
The GWH-635-ES requires an electrical ower su ly
from a 120VAC 60Hz circuit and must be ro erly
grounded.
A means for switching off the 120VAC ower su ly
must be rovided.
The heater is wired as shown in the wiring diagram
(cha ter 6, Fig. 39).
2.15 Operating instructions
BBefore roceeding with the o eration of the heater
make sure that the system is filled with water.
BTurn off ower su ly to heater.
BO en the cold water inlet su ly to the heater fully.
BO en a hot water faucet to ermit the water to fill the
heater and the i ing and to eliminate the air tra ed
in the system.
BClose the hot water faucet after the water flows freely
and all the air has esca ed from the system. Turn on
ower su ly to heater. The water heater is now
ready to o erate.
2.16 For your safety read before
operating your water heater
A. This a liance is equi ed with electronic ignition for
lighting the main burners. When turning the heater on,
follow these instructions exactly.
B. Before o erating the unit, set the On/Off switch to
the On ( I ) osition.
WHAT TO DO IF YOU SMELL GAS
BDo not try to light any a liance.
BDo not touch any electric switch; do not use any
hone in your building.
BImmediately call your gas su lier from a neighbors
hone. Follow the gas su lier’s instructions.
BIf you cannot reach your gas su lier, call the fire
de artment.
C. Use only your hand to turn the on/off control switch.
Never use tools. Follow these instructions exactly. If
control switch is jammed, close the gas su ly and call
a qualified service technician. Attem ted forceful re air
may result in a fire or ex losion.
D. Do not use this a liance if any art has been under
water. Immediately call a qualified service technician to
ins ect the a liance and to re lace any art of the
control system and any gas control which has been
under water.
2.17 Li htin and operatin instructions
B1. STOP! Read the revious safety information.
B2. The gas valve must be shut off by utting the ON/
OFF switch to osition (0). Wait five (5) minutes to
clear out any gas. If you smell gas, STOP! Follow “B”
in the safety information above. If you do not smell
gas, go to the next ste .
B3. This a liance is equi ed with electronic ignition
for lighting the main burners. When turning the
heater on, follow these instructions exactly.
B4. Set the ON/OFF switch to the (I) osition. In this
osition, the water heater is ready to use.
B5. O en a hot water ta .
B6. The burners will remain on until the hot water ta
is turned off.
Warning: For safety reasons,
disconnect the ower su ly to the
heater before any service or testing is
erformed.
Warning: This heater must be
electrically grounded in accordance
with the most recent edition of the
National Electrical Code. NFPA 70. In
Canada, all electrical wiring to the
heater should be in accordance with
local codes and the Canadian Electrical
Code, CSA C22.1 Part 1. Do not rely
on the gas or water i ing to ground the
metal arts of the heater.
i
NOTE: when the heater is turned on its
motorized water valve will check its
osition at minimum and maximum
settings and rest, this rocess lasts about
10 seconds and the noise of it will sto
afterwards. Additionally a default
tem erature setting of 122 F will a ear
on the dis lay screen.
Warning: If you do not follow these
instructions exactly, a fire or ex losion
may result causing ro erty damage,
ersonal injury or loss of life.