Bosch 250SX NG, 250SX LP User Manual
MODEL 250SX NG and 250SX LP
Temperature Modulated with Electronic Ignition
Suitable for heating potable water only
Not approved for space heating purposes
(Intended for variable flow applications with multiple tapping points)
250 SX NG
250 SX LP
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
vapor 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.
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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.
• If you cannot reach your gas supplier, call the fire
department.
• Immediately call your gas supplier from a neighbor’s
phone. Follow the gas supplier’s instructions
• Installation and service must be performed by a
qualified installer, service agency or the gas supplier.
Index
Index
1Warning 2
2 Appliance details 4
2.1 Features 4
2.2 250 SX Specifications (Technical data) 4
2.3 Dimensions and Minimum installation clearances 6
2.4 General rules to follow for safe operation 7
2.5 Proper 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 options 11
2.10 Gas piping & connections 15
2.11 Gas line sizing 17
2.12 Measuring gas pressure 17
2.13 Water connections 18
2.14 Electrical connections 19
2.15 Operating instructions 19
2.16 For your safety read before operating your water heater 19
2.17 Lighting and operating instructions 19
3 Operation instructions 21
3.1 Power 21
3.2 Temperature selection 21
3.3 Use of remote control accessory 23
3.4 Operation 23
3.5 Reset button 23
3.6 Program button 23
3.7 Locked condition 23
1Warning
Warning: If the information in this
manual is not followed exactly. A fire or
explosion may result causing property
damage, personal injury or death.
Warning: 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.
Upon completion of the installation,
these instructions should be handed to
the user of the appliance for future
reference.
Featuring
Electronic Ignition and Power Venting
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.
4 Maintenance and service 24
5 Troubleshooting 24
6 Electrical diagram 27
7 250 SX Functional scheme 28
8 Interior components diagram and parts list 29
8.1 Interior components 29
8.2 Components diagram 30
8.3 Parts list 31
9 Special adjustment for measuring and adjusting CO2
levels 32
9.1 Adjusting the unit 32
9.1.1 CO2 measuring port 32
9.1.2 Selecting adjustment mode 32
10 Protecting the environment 34
11 Twelve Year Limited Warranty 35
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 from lack of air, carbon monoxide
poisoning or fire.
Warning: Exhaust gas must be vented
to outside using proper vent material
suitable for category III vent systems
and temperatures up to 480°F. Vent
and combustion air connector 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.
Warning: Place the heater in a location
where water leaks will do NO DAMAGE
to adjacent areas or lower floors.
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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, turn off the electrical power to
the water heater at the main disconnect
or circuit breaker. Failure to do so could
result in severe personal injury or death.
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.
Warning
Fig. 1
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.
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.
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Fig. 2
3
Appliance details
2 Appliance details
2.1 Features
Parts
• Touch 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.
Safety
• Flame sensor (ionization) rod
• Overheat sensor
• Temperature limiter
• Fan speed monitoring.
High Quality Materials for Long Working Life
• Copper heat exchanger
• Ceramic Burner output
• Automatic overheating protection shut-off sensor
• Compact space saver: mounts on a wall with a
supplied bracket.
• Easily removable one-piece cover.
Features
• LCD Display
• On/Off and Temperature control switches
• Reset button
• Program Key (Selectable temperature default)
• Failure codes for easy diagnostic and repair.
Accessories
• Optional wireless remote control accessory to
operate with the appliance
Maximum input
175,000 Btu/h (51.2 kW)
Efficiency in %
Recovery efficiency 86.5%
Min. Output
31,131 Btu/h (9.1 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: 11” - 14” water column
• Natural Gas: 5” - 14” water column
• Gas pressure measuring point inside the appliance
at the gas valve inlet.
* Testing with a manometer, operate other gas
equipment on the same gas supply. Gas pressures
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,
chapter 2.12.
• Vent termination kit.
BOSCH is constantly improving its
products, therefore specifications are
i
subject to change without prior notice.
2.2 250 SX Specifications (Technical
data)
Approved in US/Canada
Capacity
Maximum flow rate: 6.35 GPM (24 l/min) at a 45°F
(25°C) rise.
Maximum output
142,968 Btu/h (41.8 kW)
4
Fig. 3 Gas pressure measuring point
Venting
See chapter 2.9 for Venting on page 9.
Water
• Hot water connection (inches) - ¾”
• Cold water connection (inches) - ¾”
• Water valve material: Polymer (PPS) (Polypropylene
Sulfid)
• Minimum water flow: 0.8 gallon/minute (3 l/m)
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Appliance details
• Minimum recommended water pressure: 30 PSI
(2.07 bar)
• Connections:
– Bottom of heater
Combustion
•NOx ≤ 55 ppm
•CO ≤ 250 ppm
•CO
level set from factory, see chapter 9.1.
2
Dimensions
• Depth (in): 8 ½” (220 mm)
• Width (in): 15 ¾” (400 mm)
• Height (in): 23 ½” (600 mm)
• Weight: 47 pounds (21 kg).
Gas types
Natural Gas.
LP Gas.
Converting the gas type can only be done by a certified
gas technician with a calibrated CO
analyzer. Call
2
CEC for conversion instructions.
Voltage
120 V AC (50/60 Hz)
Amperage
IDLE - 40 mA
Operation - ≤ 2,5 A
Noise
≤ 50 db (A)
UNPACKING THE 250 SX HEATER
This heater is packed securely.
The box includes:
• Pressure relief valve
• Bracket for wall hanging the heater
• Exhaust vent adaptor (with 4 screws and gasket
provided)
• Combustion air inlet adaptor (with 3 screws and gasket provided)
• Plastic decal shields for covering front cover screws
and control panel, installer should affix these decals
to the front of the unit after installation is complete.
See Fig. 4
• Installation manual
• Product registration card.
Do not lose this manual. Please complete and return
the enclosed product 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
shipping box, and on the rating plate which is located on
the right side panel of the cover.
To remove front cover
• Loosen the two Philips head screws located on front
panel (beneath plastic decal shields if they are
already attached, see Fig. 4)
• Lift front cover panel upward and remove.
Safety devices
• Flame failure device (ionization flame rod sensor)
• Pressure relief valve (supplied with heater)
• Over heat prevention (temperature limiter).
Water resistant
IP X4 (protection against water drops)
Plastic decals
Fig. 4 Remove front cover
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Appliance details
2.3 Dimensions and Minimum installation clearances
Fig. 5 Dimensions
1 Cover
2 On/Off switch
3 Reset button
4 LCD display
5 Program button
6 Temperature buttons
Fig. 6 Minimum clearances
Model 250 SX
TOP (A) 12”
FRONT (B) 4”
BACK 0”
SIDES 4”
FLOOR (C) 12”
VENT DIAMETER 3”
Table 1 Minimum clearances
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Appliance details
2.4 General rules to follow for safe
operation
B 1. 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.
B 2. 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 be caused by lack of air, carbon
monoxide poisoning or fire.
B 3. 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 2.9. 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 Fire Codes do
not allow UNSEALED gas fired water heater
installations in bathrooms, bedrooms or any
occupied rooms normally kept closed. See
chapter 2.5 and 2.8.
B 4. You must vent your heater. See section on
VENTING.
B 5. 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).
The appliance and its gas connection must be leak
tested before placing the appliance in operation.
B 6. Keep water heater area clear and free from
combustibles and flammable liquids. Do not locate
the heater over any material which might burn.
B 7. Correct gas pressure is critical for the optimum
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.
B 8. 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.
B 9. 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
2.5 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:
B 1. Locate the heater where venting, gas and
plumbing connections are feasible and convenient.
B 2. It is strongly recommended that the heater be
installed as a ROOM SEALED heater (twin pipe). If
the heater will be installed as an UNSEALED heater
(single pipe) than National building codes require
that you do not install this appliance in bathrooms,
bedrooms or any occupied rooms normally kept
closed. Heaters that are UNSEALED require a
considerable amount of combustion air, see
chapter 2.8. If installing the heater UNSEALED
within a laundry room, be certain that the dryer is
properly vented. Failure to properly vent a dryer could
result in a gradual accumulation of lint build up inside
the combustion chamber of the heater.
B 3. The hot water lines should be kept 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
except 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
temperatures are anticipated in area
where heater is installed by
disconnecting both the inlet and outlet
connections at the bottom of heater.
To prevent any freeze damage,
introduce short bursts of compressed
air (20-40psi) through these
connections to remove the residual
water in the horizontal pipes and water
valve.
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.
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Appliance details
2.6 Clearances
The 250 SX is design certified for installation on a
combustible wall (see 2.7 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. 6.
A. Top 12 inches (306 mm)
B. Front 4 inches (102 mm)
C. Back 0 inches
D. Sides 4 inches (102 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 2.9 Venting.
2.7 Mounting installation
Warning: before starting installation:
B check that there are no loose parts
inside the appliance
B ensure that gas pipe, gas valve, mixer,
fan and burner have no damage and are
properly fitted.
Front cover should be removed (see
instructions on page 4) in order to inspect
i
components visually.
The 250 SX is design certified for mounting on a wall.
Secure the wall mounting bracket provided with the
heater to a wall surface. See Fig. 7.
Do not install this appliance on a carpeted wall or over
floor covering which is combustible, such as carpet.
The heater must be mounted on a wall using
appropriate anchoring materials.
If the mounting bracket is unable to line up on two wall
studs it is recommended that support board(s), either
1x4's or ½" (minimum) plywood first be attached across
a pair of studs and then the heater should be attached
to the support boards. The heater should be kept level
on the wall surface. See Fig. 7.
Expansion and contraction of piping due to changing
water temperature in the pipes imparts movement to the
heater which, if mounted directly to a brittle, friable
board, such as plasterboard, 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
shipping box, and on the rating plate which is located on
the right side panel of the cover.
Fig. 7 Mounting the heater
2.8 Combustion air requirements
The 250 SX is a sealed water heater and it is
recommended that outdoor combustion air be piped to
the unit. When combustion air is piped to the unit
(TWIN PIPE SYSTEM) the combustion air pipe system
may be constructed of either 3" PVC, aluminum or
galvanized pipe. See Fig. 11, 12 and 13. Select a point
for building penetration being sure that the necessary
clearance on the outside of the building, between the
combustion air pipe and the exhaust vent terminator of
the appliance, can be maintained, see Fig. 16. NOTE:
Observe all local building codes when penetrating a
building wall.
NOTE: The combustion air inlet location on the
side of a building must never be less than 3 feet
away from the units exhaust vent terminator, see
Fig. 16 Table 3.
The heater has the ability to operate without
combustion air being piped to it from the outside,
provided 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 proper setup.
• Appliances located in unconfined spaces:
– a) An unconfined space is one whose volume is
greater than 50 cubic feet (1.42 cubic meter) per
1000 Btu per hour (292.81 Watts) of the
combined rating of all appliances installed in the
space. That would be 8750 cubic feet (247.8
cubic meter) for the 250 SX alone.
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Appliance details
– b) In unconfined spaces in buildings of
conventional frame, masonry, or metal
construction, infiltration air is normally adequate to
provide air for combustion.
• Appliances located in confined spaces:
The confined space must be provided with two
permanent openings, one commencing within 12
inches (304.8mm) of the top and one commencing
within 12 inches (304.8mm) of the bottom of the
enclosure. Each opening must have a minimum free
area of one square inch per:
– 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 openings or vertical ducts
Or the confined space must be provided with one
permanent opening or duct that is within 12 inches
(304.8mm) of the ceiling of the enclosure. This opening
must have a minimum free area of one square inch per:
– 3000 Btu/hr (878.43 Watts) if all air is taken from
the outside by a direct opening or vertical duct.
Louvers, grills and screens have a blocking effect. If the
effective free area is not known, increase the sizes of
your openings by 75% if your louvers are wood and by
30% if your louvers are metal. Refer to the National Fuel
Gas Code for complete information. In buildings of tight
construction all air should be taken from outside.
Establish vent clearances that comply with the vent
manufacturer's specifications. In all cases follow local
codes. See table 2.
2.9 Venting
Warning: Do not reduce the vent
(exhaust and combustion) pipe sizes
and do not common vent with any other
vented appliance or stove.
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.
Caution: The vent system must be
installed by a qualified agency in
accordance with these instructions. If
improperly installed a hazardous
condition such as explosion or Carbon
Monoxide poisoning could result. CEC
will not be responsible for improperly
installed appliances.
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Appliance details
The maximum flue gas exhaust temperature on the 250 SX is 437°F (225°C)
Venting
Options
Room
s ea l ed
(twin pipe)
Open
combustion
(single
pipe)
Exhaust vent is always fan assisted. Installation of exhaust vent and combustion air piping may be run vertically or horizontally
and in separate directions if required.
* A maximum of three 90 degree elbows are permitted in the total vent length. The total vent length must be reduced by 1 ¼
feet for every 45° elbow used in the vent system.
** Stainless steel (AL29-4C) vent pipe is manufacturerd by Z-Flex, Protech and Heat Fab. NOTE: clearance distances are
variable depending if the vent pipe is installed in an enclosed or unenclosed space, the exhaust flue gas temperature and the
orientation of the vent pipe.
Exhaust
vent
diameter
and
material
3 inch
stainless
steel
(AL29-4C)
sealed vent
pipe
3 inch
stainless
steel
(AL29-4C)
sealed vent
pipe
* Exhaust
vent
maximum
length
26 feet (8
m) with one
elbow. Less
2½ feet for
each
additional
90° elbow
26 feet (8
m) with one
elbow. Less
2½ feet for
each
additional
90° elbow
* Exhaust
vent
minimum
length
3 feet 3 inch PVC,
3 feet See
Combustion
air pipe
diameter
and material
aluminum or
galvanized
pipe
chapter 2.8
Combustion
air pipe
maximum
length
26 feet (8
m) with one
elbow. Less
2½ feet for
each
additional
90° elbow
See
chapter 2.8
Vent pipe
clearances
within an
unenclosed
space
** See vent
manufacturer's
specifications
** See vent
manufacturer's
specifications
Vent pipe
clearances
within an
enclosed
space
** See vent
manufacturer's
specifications
** See vent
manufacturer's
specifications
Table 2
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Appliance details
The appliance should be located as close to the point
of termination as possible. 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°
elbow used (a maximum of three 90° elbows are
permitted in the total vent length), or subtract 1 ¼ feet
for every 45° elbow used. Horizontal sections of vent
must pitch ¼" for every foot of horizontal length and be
supported at 4 foot intervals with overhead hangers.
Note: Listed thimbles or collars are necessary to pass
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 inch. Note: Type-B vent should never
be used as the actual exhaust vent system for the
appliance, as it is not gas tight.
Minimum exhaust vent size and length
The use of a 90 degree elbow
is equivalent to 2 ½ ft in vent
length.
The use of 45 degree elbow is
equivalent to 1 ¼ ft in vent
length.
page 24. See error code to confirm error, correct the
problem and then reset the heater before operating.
Attaching the exhaust and air inlet connection
adaptors to the top of the heater
Fig. 10
Fig. 8
Maximum exhaust vent and combustion air inlet
lengths
Fig. 9
Note: reduce 2½ ft for each 90° elbow used after the
first one, reduce 1 ¼ ft for each 45° elbow.
Vent Safety System
The 250 SX will shut down if inadequate exhaust
venting is detected or a lack of combustion air is
provided to the unit; see troubleshooting section on
Fig. 11
B Attach the flue gas exhaust accessory (8 705 504
114) to the top of the unit (position 1) using the 4
screws and gasket provided, and fully insert 3"
stainless steel vent pipe into the accessory and
tighten the clamp (position 2).
B Attach the combustion air inlet accessory (8 705
504 115) to the top of the unit (position 3) using the
3 screws and gasket provided, and fully insert 3"
combustion air pipe into the accessory and tighten
the clamp (position 4). NOTE: The appliance has the
possibility to mount the combustion air inlet
accessory 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.
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.
Exhaust venting shall be done with 3”
stainless steel (AL29-4C) vent pipe.
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