Bosch 250 SXO LP User manual

MODEL 250SXO - OUTDOOR MODEL
For exterior use only
Electronic Ignition and built in Freeze protection
Suitable for heating potable water only
Not approved for space heating purposes
250 SXO NG - Natural Gas
250 SXO LP - Liquefied Petroleum (LP) Gas
6 720 607 440 US (05.03) JS
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.
What to do if you smell gas
• Close gas valve.
• 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.

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Index
Index
1 Warning 2
2 Appliance details 4
2.1 Features 4
2.2 250 SXO 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 Heater Placement and Clearances 8
2.7 Mounting installation 8
2.8 Gas piping & connections 10
2.9 Measuring gas pressure 12
2.9.1 Connecting Manometer 12
2.9.2 Static Pressure Test 12
2.9.3 Operating Pressure Test 12
2.10 Water connections 13
2.11 Electrical connections 14
2.12 Operating instructions 14
2.13 For your safety read before operating your water
heater 15
2.14 Lighting and operating instructions 15
3 Operation instructions 16
3.1 Power 16
3.2 Temperature selection 16
3.3 Use of remote control accessory 18
3.4 Operation 18
3.5 Reset button 18
3.6 Program button 18
3.7 Locked condition 18
4 Maintenance and service 19
5 Troubleshooting 19
6 Electrical diagram 22
7 250 SXO Functional scheme 23
8 Interior components diagram and parts list 24
8.1 Interior components 24
8.2 Components diagram 25
8.3 Parts list 26
9 Special adjustment for measuring and adjusting
CO2 levels 27
10 Protecting the environment 29
11 Twelve Year Limited Warranty 30
1 Warning
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.
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.
Warning: Carefully plan where you
install the heater. If a gas appliance is
not installed correctly, fatal accidents
can result from lack of air, carbon
monoxide poisoning or fire.
Warning: Place the heater in a location
where water leaks will do NO DAMAGE
to adjacent areas or 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, 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.

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Warning
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What to do if you smell gas
• Close gas valve.
• 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.
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
Fig. 2
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.
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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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
• Freeze protection.
Safety
• Flame sensor (ionization) rod
• Overheat sensor
• Temperature limiter
• Fan speed monitoring.
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.
• Easily removable two-piece cover.
Features
• Electronic Ignition
• 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.
2.2 250 SXO 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)
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 maximum operation*
• Propane: 11” - 14” water column
• Natural Gas: 5” - 14” water column.
* To measure Gas Pressure, see Measuring Gas
Pressure, chapter 2.9.
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)
• Minimum recommended water pressure: 30 PSI
(2.07 bar)
• Connections:
– Bottom of heater
i
BOSCH is constantly improving its
products, therefore specifications are
subject to change without prior notice.

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Appliance details
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Combustion
• NOx ≤55 ppm
• CO ≤250 ppm.
Dimensions
• Depth (in): 8 ½” (220 mm)
• Width (in): 15 ¾” (400 mm)
• Height (in): 26” (650 mm)
• Weight: 47 pounds (21 kg).
Gas types
Natural Gas.
LP Gas.
CO
2
analyzer is required to convert from one gas type
to another. Please contact CEC for specific
instructions.
Voltage
120 V AC (50/60 Hz)
Amperage
IDLE - 40 mA
Operation - ≤2,5 A
Noise
≤50 db (A)
Safety devices
• Flame failure device (ionization flame rod sensor)
• Pressure relief valve (supplied with heater)
• Over heat prevention (temperature limiter).
Water resistant
IP X5 (protection against water drops).
UNPACKING THE 250 SXO HEATER
This heater is packed securely.
The box includes:
• Control panel shield
• Pressure relief valve
• Bracket for wall hanging the heater
• 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. 6
• 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.
The 250SXO is not approved or designed for:
• Manufactured (mobile) homes, RV's or boats
• Heating or other recirculating/pumping applications*
• Solar/preheat backup or high temperature booster
use
* This includes domestic hot water circulator pump loop
systems that may previously exist in a home hot water
system. The use of a small electric mini-tank (4-6 gallon
size) should be used for this application; when
designed so the pump will circulate the hot water in the
mini-tank only and through the building's hot water
return loop (timed or thermostatic controlled operation
of the pump is commonly done). The 250SXO should
be plumbed in line before the mini-tank water heater,
contact CEC if further instruction is needed.

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Appliance details
2.3 Dimensions and Minimum installation clearances
Fig. 3 Dimensions
1Cover
2On/Off switch
3Reset button
4LCD display
5Program button
6Temperature buttons
Fig. 4 Minimum clearances
Model 250 SXO
TOP (A) 3 ft.
FRONT (B) 4 ft.
BACK 0”
SIDES 4 ft.
BOTTOM (C) 1 ft.
Table 1 Minimum clearances

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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 plan where you install the heater. Proper
clearances must be followed.
B3. 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.
B4. Keep water heater area clear and free from
combustibles and flammable liquids. Do not locate
the heater over any material which might burn.
B5. 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.
B6. 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.
B7. 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.
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 to save
energy. Centrally locating the water heater is best. It
is always best to have the water lines insulated to
prevent the possibility of any freeze damage.
B3. The water in this heater is cold and always remains
cold except for the times that hot water is being used.
The heater is equipped with freeze prevention
equipment that will operate and prevent freezing of
the water in the heater to 5°F with no wind chill.
Electrical power must be maintained to the heater to
allow this to function.
WARNING: Proper insulation of the
water lines below the heater is required
if below freezing temperatures, below
32°F, are ever anticipated!
Danger: If the temperature drops
below 5°F, freeze damage to the water
heater itself must be prevented by
turning off the power to the heater, then
disconnecting the plumbing conne-
ctions and introducing short bursts of
compressed air (20-40 psi) through the
heater's connections. This will remove
the residual water in the horizontal
pipes and water valve..
Danger: Keep children away as the top
of the water heater vent cap will get very
hot during operation. Install in a place
that prevents the top of the heater being
reached by small children.
Danger: Flue gases will be released
through the vent cap. Flue gas is very
hot and contains carbon monoxide. The
heater cannot be installed indoors. To
prevent risk of fire and poisoning by
carbon monoxide, assure all clearances
indicated in manual.
Danger: Surface temperature around
vent cap is less than 140°F, except
highest top surface of vent cap may
reach 400°F.
Danger: Do not place or store any
combustible material within 5 feet of the
appliance. Risk of fire could be caused
by hot flue gas. Note: Exception is
made for the wall where the appliance
is installed and any adjacent walls or
overhang. In this case observe
clearances required in chapter 2.6.
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 Heater Placement and Clearances
The 250 SXO is design certified for installation directly
on a combustible wall. (see 2.7 Mounting installation)
For installation on vinyl siding see Fig. 10. Keep the area
below the heater free of combustible material.
Minimum clearances
If the appliance is installed under an overhang, there
must be a 36” clearance from the top of the appliance
and the mounting area must be open in front and on the
sides of the appliance.
Fig. 5
2.7 Mounting installation
To remove front cover.
BLoosen the two Philips head screws located on front
panel (beneath plastic decal shields if they are
already attached, see Fig. 6).
Fig. 6 Remove front cover
BRemove the two top screws securing the vent cap to
the top of the heater, being careful the washers on
the screws are not lost, see Fig. 7.
Fig. 7
BLift the top vent cap completely upward from the
heater.
BFrom the bottom of the heater, holding the sides, lift
the front cover panel of the heater upward and
slightly toward you to remove.
Danger: The top of the kit will get hot
due to the flue gases. Install away from
children.
Ref. Description Min.
distances
A Directly below or from an
opening; operable windows,
doors and any fresh air
openings
≥4 ft
B
C
DFrom any adjacent wall or tall
shruberry
≥4 ft
EBelow a gutter, sanitary
pipework, eaves or overhang ≥3 ft
F Above ground ≥1 ft
G
From a gas meter, gas
regulator, electrical box or
another 250SXO heater
≥3 ft
Table 2 Clearances
Warning: before starting installation:
Bcheck that there are no loose parts
inside the appliance
Bensure that gas pipe, gas valve, mixer,
fan and burner have no damage and are
properly fitted.
i
Front cover should be removed in order to
inspect components visually (see
instructions below).
Plastic decals

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Appliance details
9
BAfter inspection, replace front cover and tighten
screws, then replace plastic decal shields.
BFix the top vent cap on the top of the heater, as
shown in Fig. 8). Make sure the vent cap is well fitted
by taking special care that the front cover stays inside
the extended corners of the vent cap, as shown in
Fig. 8). The sides of the cover must be pressed with
your hands to ensure it fits inside those corners.
Secure it in place with its two screws.
Fig. 8
BThe water heater is design certified for mounting on
a wall. Secure the wall mounting bracket provided
with the water heater to a wall surface. See Fig. 9.
BThe installation method of the mounting bracket will
depend on what type of surface it’s being mounted
to. Due to the varying types of building surfaces, the
installer must decide on how best to support and
level the heater on an outside wall. It is always
recommended that horizontal or vertical support
boards or plywood sheathing (1/2” minimum) first be
attached to the wall surface. The heater must also be
kept level on the wall surface.
Fig. 9
Fig. 10
Vent Safety System
The 250 SXO will shut down if the intake or exhaust
louvers on the vent cap are blocked for any reason; see
troubleshooting section on page 19. See error code
table to confirm error, correct the problem and then
reset the heater before operating.
Warning: Do not mount heater directly
to vinyl siding. With vinyl siding
surfacing, a 6' x 4' area of the siding
must first be removed and then
replaced with wood or other non-plastic
made material. See Fig. 10.

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Appliance details
2.8 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 should conform with CGA
B149 INSTALLATION CODES and/or local installation
codes.
GAS LINE SIZING
The gas supply piping should be sized according to the
applicable plumbing code for a maximum draw of
175,000 BTUH. Measure the length of gas supply line
and use the tables in Fig. 12 or the gas line
manufactures sizing tables to determine the pipe
diameter necessary to accommodate the BTU demand
of the unit. If there are more gas drawing appliances on
the line, size the gas line according to the total maximum
amount of BTU draw for all appliances.
Note: Under sizing the gas line may result in diminished
output and improper operation. See chapter 2.9 for the
procedure to confirm gas pressure.
Fig. 11
BInstall a manual gas shut off valve, on the gas supply
line.
BThe use of a union when connecting gas pipe to the
gas inlet connection is important, this will facilitate
any necessary servicing and cleaning of the inlet gas
particle screen.
BThe minimum diameter required for any appliance
connector used is ¾”.
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.
The water heater must not be piped with gas supply
pressures in excess of 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.
When 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 piping
Inlet gas particle screen
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.
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.

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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. 12
Follow boxed numbers for piping just one 250 SXO (example: ¾” B.I. Natural Gas pipe for 20 ft (6.1m). will
handle 190,000 btu’s (55.7 kWh). For multiple appliances combine the total 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 .
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 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
Tube
size,
inches EHD*
10 20 30 40 50 60
1/2
18 EHD
82 58 47 41 37 34
3/4
23 EHD
161 116 96 83 75 68
1
30 EHD
330 231 188 162 144 131
1 1/4
37 EHD
639 456 374 325 292 267
Length of Flexible Corrugated Stainless Steel Tubing (CSST), Feet
Maximum Capacity of Semi-Rigid copper 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).
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 92 62 50 41 37 35 31 29 27 26
5/8 199 131 107 90 79 72 67 62 59 55
3/4 329 216 181 145 131 121 112 104 95 90
Nominal
Iron Pipe Black Iron Pipe
Size, Length 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
* EHD = Equivalent Hydraulic Diameter. The greater the
value of EHD, the greater the gas capacity of the tubing.
Tube
size
inches EHD*
10 20 30 40 50 60
1/2
18 EHD
129 91 74 64 58 53
3/4
23 EHD
254 183 151 131 118 107
1
30 EHD
521 365 297 256 227 207
1 1/4
37 EHD
971 661 528 449 397 359
Length of Flexible Corrugated Stainless Steel Tubing (CSST), Feet

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Appliance details
2.9 Measuring gas pressure
2.9.1 Connecting Manometer
BShut off gas.
BRemove front cover and locate inlet gas pressure
measuring point (see Fig. 14).
BLoosen screw inside test point fitting (do not remove)
and connect manometer tube on test point.
2.9.2 Static Pressure Test
BTurn gas supply back on.
BOperate all other gas appliances on same gas piping
system at maximum output.
BRecord static gas pressure reading in table 3.
2.9.3 Operating Pressure Test
BON/OFF switch in position OFF (0).
BPress and hold "Program" (M) button and turn ON/
OFF switch to ON position.
Fig. 13
BAs soon as '188' is displayed, release "Program"
button and the display should read P2.
BPress , until P1 appears.
Note: While in this mode the appliance will run
constantly at maximum power and allow maximum water
flow. These program modes are for test purposes only
and not intended for normal operation.
BTurn on high volume of hot water flow (at least 6
gpm) and heater will ignite.
BRecord operating gas pressure reading in table 3.
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, and must be corrected.
See Gas Connections, chapter 2.8.
Fig. 14 Gas pressure measuring (left tapping)
HIGH ALTITUDE OPERATION
Static Gas Pressure Reading (see Chapter 2.9)
enter here: ___________________
Operating Gas Pressure Reading (see Chapter 2.9)
enter here: ___________________
Table 3
Altitude Natural
Gas:
Liquid
Propane:
0 - 4,000 ft
(0 - 1,219 m)
no
modification
no
modification
For operation at
elevations
above 2,000 ft
(610 m) the
equipment
ratings shall be
reduced at the
rate of 4% for
each 1,000 ft
(305 m) above
sea level
4,000 ft - 7,000 ft
(1,219 m - 2,134 m)
CO
2
adjustment with flue
gas analyzer required See
chapter 9 for instructions.
Above 7,000 ft
(above 2,134 m) Not approved
Table 4

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13
2.10 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 where it’s centrally close to hot
water use points if possible, and make hot water piping
runs as short as possible.
Fig. 15
BTHE USE OF A UNION WHEN CONNECTING
BOTH WATER PIPES TO THE INLET AND
OUTLET CONNECTIONS IS RECOMMENDED,
THIS WILL FACILITATE ANY NECESSARY
SERVICING AND REQUIRED CLEANING OF
THE INLET WATER PARTICLE SCREEN.
Although water piping throughout your structure may be
other than copper, we recommend that copper piping
or suitably rated stainless steel flex line piping be used
for at least three feet before and after the heater (follow
local codes if more stringent). Never sweat any rigid
piping directly to or beneath the water connections,
damage can occur to the internal water valve from
heating of the pipe. Plastics or other PEX type plumbing
line materials are not suitable for connecting directly to
the water heater. Keep water inlet and outlet pipes to no
less than ¾" (19.05mm) diameter to allow the full flow
capacity.
It is recommended that all water piping below the
heater be properly insulated to avoid heat loss. If
below freezing temperatures are ever anticipated
where the heater is located, insulation material
is required and must be capable of protecting the
piping from freezing. The freeze protection that is
equipped within the heater will not prevent any
freeze damage to the exterior water piping.
If 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.
Full port valves should be installed on both the cold
water supply and hot water outlet lines to facilitate
servicing the heater (see Fig. 16). For installation on a
private well system with the use of a pressure tank, the
lowest pressure range setting recommended is 30-50
psi (2.07 and 3.45bar).
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 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 and Pressure Relief
Valve
HOT
COLD
INLET FILTER
SCREEN

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Appliance details
2.11 Electrical connections
The 250 SXO requires an electrical power supply from
a 120VAC 60Hz circuit and must be properly
grounded.
A means for switching off the 120VAC power supply
must be provided.
The heater is wired as shown in the wiring diagram
(chapter 6, Fig. 29).
Fig. 17
2.12 Operating instructions
BRemove the control cover shield to access the
controls of the water heater.
Fig. 18
BBefore proceeding with the operation of the heater
make sure that the system is filled with water.
BTurn off power supply to heater.
BOpen the cold water inlet supply to the heater fully.
BOpen a hot water faucet to permit the water to fill the
heater and the piping and to eliminate the air trapped
in the system.
BClose the hot water faucet after the water flows freely
and all the air has escaped from the system. Turn on
power supply to heater. The water heater is now
ready to operate.
Warning: Confirm that the water
heater is appropriately grounded and
that the installation meets all electrical
codes. Outdoor electrical outlets have
special requirements.
Warning: For safety reasons,
disconnect the power supply to the
heater before any service or testing is
performed.
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 piping to ground the
metal parts of the heater.
Appliance electrical
power supply
Warning: The heater is equipped with
freeze prevention equipment that will
operate and prevent freezing of the
water in the heater to 5°F with no wind
chill. Electrical power must be
maintained to the heater to allow this to
function. WARNING: Proper
insulation of the water lines below
the heater is required if below
freezing temperatures, below 32°F,
are ever anticipated.
Warning: The control cover must be
replaced after the initial operation
begins, and must be in place at all
times.
i
NOTE: A default temperature setting of
122 F will appear on the display screen.

6 720 607 440
Appliance details
15
2.13 For your safety read before
operating your water heater
A. This appliance is equipped with electronic ignition for
lighting the main burners. When turning the heater on,
follow these instructions exactly.
B. Before operating the unit, turn the On/Off switch to
the right position.
WHAT TO DO IF YOU SMELL GAS
BDo not try to light any appliance.
BDo not touch any electric switch; do not use any
phone in your building.
BImmediately call your gas supplier from a neighbors
phone. Follow the gas supplier’s instructions.
BIf you cannot reach your gas supplier, call the fire
department.
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 supply and call
a qualified service technician. Attempted forceful repair
may result in a fire or explosion.
D. Do not use this appliance if any part has been under
water. 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
under water.
2.14 Lighting and operating instructions
B1. STOP! Read the previous safety information.
B2. The gas valve must be shut off by putting the ON/
OFF switch to the OFF position (turn to the left
position). 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 step.
B3. This appliance is equipped 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 ON position (turn to
the right position).
B5. Open a hot water tap.
B6. The burners will remain on until the hot water tap
is turned off.
When the heater is in operation you will hear its power
vent fan and burner operating. Upon turning off the hot
water flow the power vent fan will continue to operate
for up to 60 seconds to exhaust all flue gases. The
power vents fan speed is variable depending on the rate
of hot water used and the burner output.
TO TURN OFF GAS TO APPLIANCE
BTurn off the manual gas shut off valve on the supply
line to the heater and set the ON/OFF switch to the
OFF position (turn to the left position). Note: a
manual gas shut off valve is not supplied with the
heater.
Warning: If you do not follow these
instructions exactly, a fire or explosion
may result causing property damage,
personal injury or loss of life.
i
NOTE: on a first time initial
installation or after gas line work
has been done, air in the gas line
will cause ignition delay when the
hot water is turned on. This will
result in an error (EA or EC) on the
units display screen. This is
normal. When this occurs, leave
the hot water running and wait 3-5
seconds, then press reset button
to reset the unit (Fig. 19 , pos. 2).
Wait for (EA or EC) to disappear.
The heater will begin to attempt
ignition again, if the (EA or EC)
reappears then repeat this same
process until all air has been bled
from the gas line.

6 720 607 440
16
Operation instructions
3 Operation instructions
Fig. 19
1On/Off switch
2Reset button
3Program button
4Increasing temperature button
5Decreasing temperature button
6LCD display
3.1 Power
On
BTo start the appliance switch the button to the ON
position (turn to the right position).
LCD display the default temperature - temperature
factory setting 122°F (50°C).
Fig. 20
Off
BTo shut down the appliance, switch the button to the
OFF position (turn to the left position).
3.2 Temperature selection
To select water temperature outlet:
BPress buttons and in order to reach
requested temperature.
Fig. 21
If the outlet water temperature is set too high, the heater
can produce temperatures that are too hot. A
temperature balance shower valve can automatically
mix in cold water to reduce such hot water temperature.
In the event of any temperature instability with the use
of a temperature balance shower valve, refer to shower
valve manufacturer's instructions for internal adjustment
setting. Adjustments should be made to the hottest
setting in the shower valve. Additionally the temperature
control of the heater can be lowered to produce a more
comfortable hot water temperature.

6 720 607 440
Operation instructions
17
Setting the water temperature
The desired temperature of the hot water can be adjusted on the front control panel of the heater.
The 250 SXO has an electronically controlled gas valve that modulates the burner input in response to both varying
hot water flow rates and/or changes in any incoming and outgoing water temperatures.
Fig. 22 Flow/temperature charts
Hot Water Flow and Temperature with Various Inlet Temperature (lpm/Celsius)
0.00
4.00
8.00
12.00
16.00
20.00
24.00
35 40 45 50 55 60 65
Hot water temperature (ºC)
Hot Water Flow (l/min)
Inlet (ºC) 4 Inlet (ºC) 10 Inlet (ºC) 16 Inlet (ºC) 21
Hot Water Flow and Temperature with Various Inlet Temperature (gpm/Fahrenheit)
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
90 100 110 120 130 140 150
Hot water temperature (ºF)
Hot Water Flow (GPM)
Inlet (ºF) 40 Inlet (ºF) 50 Inlet (ºF) 60 Inlet (ºF) 70

6 720 607 440
18
Operation instructions
3.3 Use of remote control accessory
Fig. 23 Remote control
The wireless remote control accessory and the
temperature selector buttons on the front of the water
heater operate identically. Contact your distributor or
CEC to order if the remote control accessory is
preferred. Modification of the water heaters interior
control unit (Fig. 32, component 12) is required when
programming the remote control with this heater.
3.4 Operation
BWhen a hot water tap is opened, main burner ignites
and LCD displays indication .
Fig. 24
BLCD blinks until selected temperature is reached.
3.5 Reset button
If the LCD shows the error symbol .
Note: do not use the ON/OFF switch when error is
present.
See the error code on LCD and consult
“Troubleshooting” section.
Fig. 25
After following instructions indicated in
“Troubleshooting” section
Bpress reset button in order to make the appliance
ready-to-work.
Fig. 26 Reset button
If the problem persists, contact your installer.
3.6 Program button
Program button can be used/programmed in the
appliance and in the remote control.
Programming “Program” function
Programming actions are similar for both controls
(appliance control pad and wireless remote control).
Fig. 27 “Program” key
BPress buttons and to select temperature to
be memorized.
BHold “Program” button for 3 seconds to save
temperature.
When LCD stops blinking. Temperature is saved on
“Program”.
Using “Program” function
In order to select memorized temperature
BPress “Program” key.
LCD shows pre-memorized temperature, which is now
the hot water selected temperature.
3.7 Locked condition
This condition is only valid for appliances with more than
1 controller (an appliance with one or more remote
controls).
Fig. 28 Locked condition
Whenever LCD shows the temperature setting
cannot be adjusted because the appliance is in use by
a user which already selected a different temperature.
Appliance will be automatically unlocked after closing
hot water tap.
i
NOTE: up to 6 remote controls can be
programmed for one single water heater,
each with a range distance of 98 ft (30 m).

6 720 607 440
Maintenance and service
19
4 Maintenance and service
The unit should be checked once a year by a gas
technician. If repairs are needed, the repairs should be
done by a gas technician
To remove front cover
BSee instructions to remove front cover on page 8.
Systems and parts that should be checked at
least once a year
Reference diagrams on pages 24 and 25.
• Venting system
• Burners -see page 24 for observation window
• See relief valve manufacture's instruction for
pressure relief valve maintenance
• Periodic cleaning of the water filter screen, see Fig.
15, chapter 2.10.
• Flushing the heat exchanger with a descaling
solution if mineral build up is evident. Scale build up
will shorten the life of the water heater, descale heat
exchanger thoroughly and repeat annually depending
on mineral content of ground water.
5 Troubleshooting
Introduction
The 250 SXO burner is activated by a water flow valve.
Numerous water related problems can cause this water
valve to malfunction such as: Insufficient water flow
volume to activate the burners at its minimum flow
requirement; Dirt in the inlet filter screen; Sediment
build-up in faucet aerators, or shower heads; Uneven
pressures between cold and hot (with single lever mix
valves); and Plumbing crossovers. These water flow
related problems can cause the heater to deliver less
than its full output, or to fail to ignite or to shut down
completely.
Problems stated below in upper case and in bold face
should be investigated when there is a problem with the
performance of the water heater but there is NO error
code on the heater's LCD display or wireless remote
control.
Any failures that result in a displayed error code are
referenced on page 21. A Functional Scheme of the
250 SXO is detailed on page 23. If there is a problem
with the installation, venting or operation of the unit, the
heater will communicate the source by these error
codes.
BURNERS DO NOT IGNITE WHEN HOT WATER IS
TURNED ON
•Cold incoming water connection made to
wrong side of heater
Make sure cold water inlet connection is plumbed to
the right side of heater when facing unit
•Water flow rate at hot water tap is too low
A minimum of 0.8 gallon/minute (3 l/m) is required to
activate the heater
•Cold water inlet filter screen is dirty
Remove water inlet filter screen and clean. The
screen is located at the inlet connection to the water
heater, disconnecting the main cold supply line at the
heater is required. Check and clean faucet aerator
screens too.
•Crossover in plumbing
The heater activates when there is sufficient water
flow through its water valve, a minimum of 0.8 gallon/
minute (3 l/m) is required. If there is a crossover in the
plumbing, the necessary hot water flow rate through
the unit may not be reached, even though the flow at
the hot water tap is sufficient. A plumbing crossover
can be caused by a failed washer at a single lever
faucet, incorrect plumbing or a faulty mixing valve in
the piping. The crossover will create a back pressure
on the water heater and prevent an adequate flow of
water through it. To confirm there is no crossover in
the plumbing, shut off the cold water supply feed to
the water heater. Individually open each of the hot
water taps. There should be no water flowing under
a constant pressure. If there is a constant flow of
water then the plumbing crossover must be
corrected before the heater can operate properly.
WATER IS TOO HOT
•Temperature selection too high
Lower temperature adjustment on heater or wireless
remote control accessory, see chapter 3.2.
WATER IS NOT HOT ENOUGH
•Temperature selection too low
Increase temperature adjustment on heater or
wireless remote control accessory, see chapter 3.2
•Btu input is too low due to inadequate gas line
sizing
See specifications in chapter 2.8 - 2.9. The 250
SXO requires adequate gas pressure to reach
desired temperatures, to compensate for inadequate
gas supply or lack of gas pressure the 250 SXO will
effectively reach the selected output temperature by
reducing the hot water flow rate. Its motorized water
valve makes this adjustment
•Cold water is mixing with the hot water outlet
(crossover)
Warning: Always turn off the electrical
power supply, turn off the manual gas
valve and turn off the manual water
control valves whenever servicing.

6 720 607 440
20
Troubleshooting
Test by following 4th bullet under BURNERS DO
NOT IGNITE WHEN HOT WATER IS TURNED ON.
LOW WATER FLOW/PRESSURE
•Too many hot water applications are being
used simultaneously or too much flow is being
demanded
The 250 SXO will effectively support two 2.0-2.5
gpm shower heads simultaneously or multiple sink
applications. Greater draws will result in increased
pressure drop and reduced flow at taps. See flow/
temperature chart on page 17.
•Btu input is too low due to inadequate gas line
sizing
See specifications in chapter 2.8 - 2.9. The 250
SXO requires adequate gas pressure to reach
expected temperatures and flow rates, to
compensate for inadequate gas supply or lack of gas
pressure the 250 SXO will effectively reach the
selected output temperature, but only by reducing
the hot water flow rate. Its motorized water valve
makes this adjustment. Proper gas pressure will
need to be delivered before the motorized water
valve will allow greater flow rates through it. Lowering
the set temperature will also allow increased water
flow rate through the motorized water valve. See
flow/temperature chart on page 17.
•Cold water inlet filter screen is dirty
Remove water inlet filter screen and clean. The
screen is located at the inlet connection to the water
heater, disconnecting the main cold supply line at the
heater is required. Check and clean faucet aerator
screens too.
HOT WATER TEMPERATURE FLUCTUATES /
UNIT DEACTIVATED
•Unbalanced pressure in water lines
Any restriction caused by the water heater in the hot
water system can result in uneven pressures
between the cold and the hot. In such cases when
mixing cold water at the tap (manually or
automatically through a mix-type shower valve) the
lower hot water pressure may be overpowered by the
higher cold water pressure in the building and cause
the hot water flow rate to fall below the minimum rate
required. A pressure balance valve will help to
resolve this symptom.
•Temperature balance valves
If the outlet water temperature is set too high, the
heater can produce temperatures that are too hot. A
temperature balance shower valve can automatically
mix in cold water to reduce such hot water
temperature. In the event of any temperature
instability with the use of a temperature balance
shower valve, refer to shower valve manufacturer's
instructions for internal adjustment setting.
Adjustments should be made to the hottest setting in
the shower valve. Additionally the temperature
control of the heater can be lowered to produce a
more comfortable hot water temperature.
•Inlet water pressure is erratic due to
fluctuating supply water pressure
For installation on a private well system with the use
of a pressure tank, the lowest pressure range setting
recommended is 30-50 psi (2.07-3.45 bar). The use
of a pressure reducing valve after the pressure tank
is also an effective way to maintain a constant water
pressure to the water heater. Watts brand 25AUB-
¾” or N35B-¾” pressure relief valves or equivalent
are suggested.