Bock Water heaters OT300-A Service manual

WARNING
Improper installation, adjustment, alteration,
service or maintenance can cause serious injury or
property damage. Refer to this manual. For
assistance or additional information, consult a
qualified installer or service agency.
WARNING
Install in accordance with all local codes. In the
absence of local codes, refer to NFPA 54 or ANSI
Z21.10.3.
CAU ION
The recommended temperature for normal
residential use is 120°F. The dial on the aquastat
does not always reflect the out-coming water
temperature and it could occasionally exceed 120°F.
Variation in out-coming temperature could be
based on factors including but not limited to usage
patterns and type of installation. Test water at the
tap nearest to the water heater. See page 37 for
measuring the out- coming water temperature.
WARNING
Hotter water increases the risk of scald injury.
Before adjusting the water temperature setting,
read this instruction manual. Temperatures at
which injury occurs vary with the person’s age and
the length of exposure. The slower reaction time of
children, elderly or physically or mentally
challenged persons increases the scalding hazard to
them. It is recommended that lower water tempera-
tures be used where these exposure hazards exist.
Households with small children or invalids may
require a temperature setting less than 120°F to
prevent accidental contact with hot water. To
produce less than 120°F, use point-of-use
temperature limiting devices.
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water system, automatic temperature limiting
devices must be used on all lines to water taps.
WARNING
Water heater blankets may restrict air flow to the
water heater and cause fire, asphyxiation, personal
injury or death.
THIS ANUAL HAS BEEN PREPARED TO ACQUAINT
YOU WITH THE INSTALLATION, OPERATION, AND
AINTENANCE OF YOUR WATER HEATER AND TO
PROVIDE I PORTANT SAFETY INFOR ATION.
Read all instructions thoroughly before attempting
installation or operation of your water heater. Keep
these instructions for future reference.
Local plumbing and electrical codes must be
followed in the installation of this water heater. In
the absence of a local code use the UNIFORM
PLUMBING CO E and the NFPA Code. Local codes
may supersede instructions in this installation
manual.
These instructions are a guide for the correct instal-
lation of the water heater. The manufacturer will
not be liable for damages caused by failure to
comply with the installation and operating instruc-
tions outlined on the following pages.
O 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.
FAILURE TO FOLLOW THESE INSTRUCTIONS OR ALL
APPLICABLE BUILDING CODES
AND REGULATIONS VOIDS THE WARRANTY ON
THIS WATER HEATER.
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Warranty, Registration Card and Parts List are included.
Owner: Please remember to return the Registration Card!
o the Consumer:
Please read these and all component
instructions and keep for future reference.
o the Installer:
Please attach these instructions
next to the water heater.
Rev1 9/2012#23402 EN
– D n t st re r use gas line r ther flammable
vap rs and liquids in the vicinity f this r any
ther appliance.
– WHAT TO O IF YOU SMELL GAS
• D n t try t light any appliance.
• D n t t uch any electrical switch; d n t use
any ph ne in y ur building.
• Immediately call y ur gas supplier fr m a neigh-
b r’s ph ne. F ll w the gas supplier’s instructi ns.
• If y u cann t reach y ur gas supplier, call the fire
department.
–Installati n and service must be perf rmed by a
qualified installer, service agency r the gas supplier.
WARNING: If the information in these instructions is not followed exactly, a
fire or explosion may result causing property damage, personal injury or death.
Installation and Operation Instructions Manual
Models: O 300, O 300-A, O 400, O 400-A, O 500, O 500-A
High Efficiency Commercial Gas Water Heater
®

IMPOR AN SAFE Y INS RUC IONS
he proper installation, use and servicing of this water heater is very
important to your safety and the safety of others.
This is the safety alert symbol. Statements following this symbol contain
important safety information. Obey all safety messages that follow this
symbol to avoid possible injury or death.
Important safety information will be preceded by the safety alert
symbol and the words DANGER, WARNING, CAU ION, OR NO ICE.
DANGER indicates an imminently hazardous situation which, if not
avoided, will result in serious injury or death.
WARNING indicates a potentially hazardous situation which, if not
avoided, could result in serious injury or death.
CAU ION indicates a hazardous situation which, if not avoided, could
result in minor or moderate injury.
NO ICE calls attention to observe a specified procedure.
SAVE HESE INS RUC IONS
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DANGER
Water heaters utilizing Liquefied Petroleum gas (LP) are different from
natural gas models. A natural gas heater will not function safely on LP gas
and vice versa. To avoid possible equipment damage, personal injury or
fire: DO NOT connect this water heater to a fuel type not in accordance
with the rating label. These units are only certified for a single fuel type.
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DANGER
Failure to properly install the vent and combustion air intake system as
outlined in this manual can result in unsafe operation of the water heater.
To avoid the risk of fire, explosion, or asphyxiation from carbon monoxide,
never operate this water heater unless it is properly vented and has
adequate air supply for combustion and dilution of flue gas. Be sure to
inspect the system for proper installation at initial start-up; and at least
annually thereafter. See the aintenance section for more information.
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ABLE OF CON EN S
Section I: Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Section II: General Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Section III: Pre-Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Section IV: Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Section V: Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Section VI: Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Section VII: roubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Section VIII: Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Section IX: Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Page 3

Model
Rated Storage
Capacity, GAL (L)
Rated Maximum
Input, Btu/hr (kW)
Thermal Efficiency
(%) @ Max. Input
Recovery @ 100°F
rise, GAL/HR (L/HR)
A
C
E
G
HOT (NPT)
Air Intake
(PVC)
Rated Minimum
Input, Btu/hr (kW)
Thermal Efficiency
(%) @ Min. Input
1st Hr. elivery @
100°F rise, GAL (L)
B
F
COL (NPT)
Gas (NPT)
Exhaust
Vent (PVC)
Table 1: Dimensions
Page 4
SEC ION I: SPECIFICA IONS
Figure 1: All Models
IMENSIONS, INCHES (cm)
OTE: SUFFIX " " stands for ATURAL GAS and suffix "-A" denotes ASME version.
Working Pressure: 150 PSI (1034 kPa)
T&P valve installed
For natural gas:
MINIMUM GAS SUPPLY PRESSURE (at gas control) = 6" W.C. (dynamic)
MAXIMUM GAS SUPPLY PRESSURE (at gas control) = 14" W.C. (static or dynamic)
ote: Dynamic pressure is measured while gas is flowing and static pressure is
measured while gas is not flowing.
119 300,000135,000 95 97 342 460 78.50 32.00 62.78 11.43 9.43 61.43 74.00 2" 2" 1-1/2" 4" 4" 1200
(450) (87.9) (39.6) (1,295) (1,741) (199) (81) (159) (29) (24) (156) (188) (544)
125 300,000135,000 95 97 342 460 78.50 32.00 62.78 11.43 9.43 61.43 74.00 2" 2" 1-1/2" 4" 4" 1200
(473) (87.9) (39.6) (1,295) (1,741) (199) (81) (159) (29) (24) (156) (188) (544)
119 399,999135,000 94 97 451 568 78.50 32.00 62.78 11.43 9.43 61.43 74.00 2" 2" 1-1/2" 4" 4" 1200
(450) (117.2) (39.6) (1,707)( 2,150) (199) (81) (159) (29) (24) (156) (188) (544)
125 400,000135,000 94 97 451 568 78.50 32.00 62.78 11.43 9.43 61.43 74.00 2" 2" 1-1/2" 4" 4" 1200
(473) (117.2) (39.6) ( 1,707)(2,150) (199) (81) (159) (29) (24) (156) (188) (544)
119 499,999135,000 93 97 558 674 78.50 32.00 62.78 11.43 9.43 61.43 74.00 2" 2" 1-1/2" 4" 4" 1200
(450) (146.5) (39.6) (2,112) (2,551) (199) (81) (159) (29) (24) (156) (188) (544)
125 500,000135,000 93 97 558 674 78.50 32.00 62.78 11.43 9.43 61.43 74.00 2" 2" 1-1/2" 4" 4" 1200
(473) (146.5) (39.6) ( 2,112)(2,551) (199) (81) (159) (29) (24) (156) (188) (544)
OT300N
OT300N-A
OT400N
OT400N-A
OT500N
OT500N-A
CONNECTION SIZES
Shipping Weight,
LBS (kg)
All Bock products meet or exceed current ASHRAE standards.
These products are design certified by UL (Underwriters Laboratories) and meet A SI Z21.10.3 / CSA 4.3
requirements for operation up to 180°F (82°C).
Approved for use as a direct vent automatic storage water heater.
WARNING: Installation shall be in accordance with all national and/or local codes. In the absence of
local codes, refer to FPA 54 and/or CSA B149.1.
CAUTION: The recommended maximum hot water temperature setting for normal residential use is
120°F (49°C). Bock recommends a tempering valve or anti-scald valve be installed and used according
to the manufacturer's directions to prevent scalding.

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APPROXIMATE
TEMPERATURE/TIME
RELATIONSHIPS TO
SCAL ING
120°F (49°C) More than 5 minutes
125°F (52°C) 1 1⁄2 to 2 minutes
130°F (54°C) About 30 seconds
135°F (57°C) About 10 seconds
140°F (60°C) Less than 5 seconds
145°F (63°C) Less than 3 seconds
150°F (66°C) About 1 1⁄2 seconds
155°F (68°C) About 1 second
Table 2: Scald Temperature/Time Relationships
SEC ION II: GENERAL INFORMA ION
WHEN YOU RECEIVE YOUR NEW WA ER HEA ER
Check the new equipment to see if all components are in good condition. If damage is
observed or parts appear to be missing, contact your wholesaler.
WA ER REA MEN /FIL RA ION
In areas where poor water conditions are suspected (i.e. lime, iron, and other minerals), it is
essential that the water be tested and appropriate action taken to prevent damage to the
water heater and ensure the quality of the water.
EMPERA URE CON ROL
The water heater is equipped with a main operating control that manages the temperature
regulating and limiting functionality. For domestic hot water, the proper temperature setpoint
is 120°F. For commercial applications, the maximum approved temperature setpoint is 180°F.
Sensors in the top of the tank measure water temperature. The control constantly compares
the sensor values to the temperature setpoint and controls the burner power (on/off) and
modulation accordingly.
The automatic reset, temperature limiting safety function is managed by the main operating
control. In the event that the water temperature becomes excessive (193°F), the control will
shut off all gas to the water heater. The temperature limit safety will automatically reset when
the water temperature drops to below 193°F and normal operation will resume at the next call
for heat.
The temperature setpoint is factory set at 120°F. If hotter water is required a tempering device
or anti-scald device must be installed at the domestic hot water outlet of the heater or at the
point of use. Table 3 details the approximate relationship of water temperature and time with
regard to scald injury. It is important for the user to understand the necessity of tempering or
anti-scald devices when using hotter water in domestic water heating systems.
CAUTION: Hot water in excess of 120°F can cause scalding!
Bock recommends a tempering valve or anti-scald valve be installed and used according to
the manufacturer’s directions to prevent scalding. Many state and local codes now require
installation of these devices. Point of use temperature may be hotter than the setting on the
water heater thermostat. The tempering valve or anti-scald valve will ensure potable
water temperatures at the desired set point with a higher degree of accuracy.
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SEC ION II: GENERAL INFORMA ION (cont.)
ANODE RODS
The water heater is supplied with a factory installed powered anode system to prevent corrosion of
internal tank components. Specifically, the type of anode system that is used is an impressed-
current anode system. This system uses a power supply that regulates the protective current output
based on actual conditions inside the tank. The two anode rods in the tank are not consumed over
time and, therefore, do not need to be removed and inspected. Refer to the Maintenance section of
this manual for periodic inspection instructions for the powered anode system.
NOTICE TO THE OWNER: The water heater must be connected to the power supply for the
powered anode system to operate. DO NOT DISCONNECT THE WATER HEATER FRO THE
POWER SUPPLY FOR AN EXTENDED PERIOD OF TI E. WITHOUT POWER, THE ANODE SYSTE WILL
NOT BE CAPABLE OF PROVIDING CORROSION PROTECTION. When the power switch to the
right of the display is OFF and there is a connection to the power supply, the powered
anode system will still function. If the water heater must be disconnected from the power
supply for an extended period, the tank must be drained. Refill the tank prior to reconnect-
ing the water heater to the power supply.
CAUTION
Hydrogen gas is produced in a hot water system served by the heater that has not been
used for a long period of time (2 weeks or more). Hydrogen gas is extremely flammable.
To reduce the risk of injury under these conditions, it is recommended that a hot water
faucet be opened for several minutes before using any electrical appliance connected
to the hot water system. When hydrogen is present, there will probably be an unusual
sound such as air escaping through the pipe as the water begins to flow. There should be
no smoking or open flame near the faucet at the time it is open.
EMPERA URE AND PRESSURE RELIEF VALVE ( &P)
CAUTION
To reduce the risk of excessive pressures and temperatures in this water heater, install
temperature and pressure protective equipment required by local codes and no less than
a combination temperature and pressure relief valve certified by a nationally recognized
testing laboratory that maintains periodic inspection of production of listed equipment or
materials, as meeting the requirements for Relief Valves and Automatic Gas Shutoff
Devices for Hot Water Supply Systems, ANSI Z21.22. This valve must be marked with a
maximum set pressure not to exceed the marked maximum working pressure of the
water heater. Install the valve in an opening provided and marked for this purpose in the
water heater, and orient it or provide tubing so that any discharge from the valve exits
only within 6 inches above, or at any distance below, the structural floor, and does not
contact any live electrical part. The discharge opening must not be blocked or reduced
in size under any circumstances.
CAUTION
Scalding injury and/or water damage can occur from either the manual lifting of the
lever or the normal operation of the T&P valve if it is not piped to a proper drain. If the
valve fails to flow water or reseat, call your plumber.
The T&P valve is factory installed. A discharge drain tube must be installed (responsibility
of the installer) and shall terminate plain, not threaded, 6 inches above the floor drain.
The drain tube material must be approved for temperatures of 120o F or greater and a
pressure of 150 PSI or greater.
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SEC ION II: GENERAL INFORMA ION (cont.)
BACKFLOW PREVEN ER (CLOSED SYS EM)
Some local municipal codes and ordinances require the use of these devices on potable
(domestic) water lines. Where backflow preventers, check valves, or pressure regulating valves
are required, it will be necessary to install a thermal expansion tank (designed for use with
potable water) in order to prevent pressure build up in the water heater and associated piping,
which could cause the T&P valve to discharge. Follow the expansion tank manufacturer’s
recommendations when selecting a tank for your hot water system. The expansion tank pressure
shall equal the water heater system pressure prior to initial warm up.
Note: Working pressure of the water heater is 150 SI. Do not exceed 150 SI.
CONDENSA ION
Condensation of flue gases will occur in the exhaust vent and portions of the heat exchanger
during burner operation. Condensate is considered acidic based on its typical pH range of 3.5 to 3.8
on a scale of 0 to 14 (a pH of 7 is neutral). Some installations may require the use of a condensate
neutralizer kit to reduce the acidity of the condensate prior to it entering the building's drainage
system. When possible, locate a floor drain in close proximity to the water heater to minimize the
length of the drain line. The water heater is supplied with a condensate elbow assembly that must
be installed to the water heater before the exhaust vent is connected. Horizontal sections of the
exhaust vent shall slope upward away from the water heater a minimum of 1/8" per foot. This will
allow the condensate in the vent to run back to the condensate drain on the water heater. In some
instances, condensate may form in the intake piping during periods following burner operation.
Horizontal sections of air intake piping shall slope downward away from the water heater a
minimum of 1/8" per foot. When applicable, if downward sloping is not possible or vertical
sections are used for air intake piping, a condensate drainage tube can be installed on the intake
piping (near the intake pipe connection on the water heater). See Section IV: Installation / Vent
and Combustion Air Intake / Condensate Elbow Assembly and Section IV: Installation / Vent &
Combustion Air Intake / Optional Condensate Line for installation details.
HIGH AL I UDE
Contact Bock Water Heaters for installations at altitudes greater than 2,000 feet above sea level.
SEC ION III: PRE-INS ALLA ION
LOCA ION
CAUTION
This water heater must be located in an area where leakage of the tank, water line
connections, or the temperature and pressure relief valve will not result in damage to the
area adjacent to the water heater or to lower floors of the structure. When such location
cannot be avoided, a suitable drain pan must be installed under the water heater. The
drain pan depth must be suitable for draining and collecting water. The drain pan can be
purchased from your plumbing professional. The drain pan must be piped to an
adequate drain and all drain piping must be at least 0.75” in diameter and pitched for
proper drainage.
CAUTION
DO NOT store or use gasoline or other flammable, combustible, or corrosive vapors
and/or liquids in the vicinity of the water heater or any other appliance.
IF YOU S ELL GAS:
• DO NOT try to light any appliance.
• DO NOT touch any electric switch; do not use any telephone in your building.
• Immediately call your gas supplier from a telephone in another building. Follow your
gas supplier’s instructions.
• If you cannot reach your gas supplier, call the fire department.
DO NOT OPERATE THE APPLIANCE UNTIL THE LEAKAGE IS CORRECTED!
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SEC ION III: PRE-INS ALLA ION (cont.)
LOCA ION (cont.)
CAUTION
Do not drop water heater or lay heater down on its side. ove the water heater into
position by sliding or using an appropriately sized hand truck.
CAUTION
If the water heater is installed directly on carpeting, the water heater shall be installed
on a metal or wood panel extending beyond the full width and depth of the water
heater by at least 3 inches (76.2 mm) in any direction or, if the water heater is installed
in an alcove, the entire floor shall be covered by the panel. The panel must be strong
enough to carry the weight of the heater when full of water.
NOTE: Locate the heater so it is not subject to physical damage from moving vehicles or
flooding. o not locate the water heater in a room where swimming pool chemicals or large
quantities of water softener salt are kept. Installing a water heater in this environment will
result in premature failure of tank and burner components due to corrosion caused by these
elements diffusing into the air.
The water heater can be installed on combustible or non-combustible flooring. Maintain
clearances specified in this manual and in accordance with the National Fuel Gas Code (NFPA
54, ANSI Z223.1) unless otherwise directed by state and local code requirements. Locate the
water heater such that plastic vent pipe lengths and the number of connection fittings are
minimized. Adequate downward pitch is required on the condensate line for proper drainage.
See Section IV: Installation / Vent & Combustion Air Intake / Condensate Elbow Assembly for
details. If pitch is insufficient and the use of a low profile condensate pump is not feasible, the
heater needs to be placed on a concrete slab to increase the distance between the condensate
line connection and the floor.
Minimum clearance from combustible material is 0" for the sides, top, and back of this water
heater, as shown in Figure 2. This water heater is approved for installation in an alcove with
the clearances shown in Figure 2.
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Figure 2: Minimum Clearance From Combustible Material
Page 8

Figure 3: Recommended Minimum Access Clearances
Nominal
Iron Pipe
Size
(inches)
Internal
Diameter
(inches)
Length of Pipe (feet)
10 20 30 40 50 60 70 80 90 100 125 150 175 200
1 1/4 1.380 1,050 730 590 500 440 400 370 350 320 305 275 250 225 210
1 1/2 1.610 1,600 1,100 890 760 670 610 560 530 490 460 410 380 350 320
2 2.067 3,050 2,100 1,650 1,450 1,270 1,150 1,050 990 930 870 780 710 650 610
2 1/2 2.469 4,800 3,300 2,700 2,300 2,000 1,850 1,700 1,600 1,500 1,400 1,250 1,130 1,050 980
3 3.068 8,500 5,900 4,700 4,100 3,600 3,250 3,000 2,800 2,600 2,500 2,200 2,000 1,850 1,700
4 4.026 17,500 12,000 9,700 8,300 7,400 6,800 6,200 5,800 5,400 5,100 4,500 4,100 3,800 3,500
Table 3: Gas Supply Line Capacity
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SEC ION III: PRE-INS ALLA ION (cont.)
LOCA ION (cont.)
For ease of access and proper maintenance, the clearances in Figure 3 are strongly recommended.
GAS SUPPLY LINE
Prior to installation, contact your local gas utility to confirm that sufficient gas service is available
for the water heater. The gas meter must have adequate capacity to supply the rated maximum gas
input of the water heater in addition to other gas fired equipment connected to the meter.
Minimum Gas Supply ressure
The gas supply must be capable of maintaining a minimum pressure at the inlet of the gas control
during water heater operation at maximum input. The pressure will be lowest at the gas control
during water heater operation (i.e. gas is flowing) at maximum input. At minimum, during
operation at maximum input, the supply pressure at the gas control must be at least 6" W.C.
Refer to Table 3 for gas supply line sizing. The table shows maximum input in thousands of BTU's
per hour for various pipe sizes and lengths. The table assumes gas supply pressures of 14" W.C. or
less and a pressure drop of 0.3" W.C.
At minimum, use 1-1/4" gas supply pipe for models OT300N(-A) and OT400N(-A).
For model OT500N(-A), use a minimum of 1-1/2" pipe.
Maximum Gas Supply ressure
The gas supply pressure shall never be greater than 14" W.C. Pressures greater than 14" W.C. may
damage the gas control which could cause a fire or explosion.
Refer to Section IV: Installation / Gas Connections for further installation instructions.

SEC ION III: PRE-INS ALLA ION (cont.)
COMBUS ION AND VEN ILA ION AIR
The water heater can be installed to utilize combustion air from either inside or outside the
building. Refer to "Section IV: Installation" for detailed venting specifications. If indoor air is
used for combustion air it is imperative that the room has an adequate air supply. Inadequate
air supplies may lead to unsafe levels of carbon monoxide (CO), condensation of flue gases,
and excessive levels of soot. See NFPA 54 or the discussions of "Unconfined Space" and
"Confined Space" below. In addition, poor ventilation will also result in hot spots around the
heater. Temperatures over 90°F near the water heater generally indicate a lack of ventilation.
UNCONFINED SPACE
Unconfined space is defined by NFPA 54 as a space with a volume greater than 50 cubic feet
(during typical use) per 1000 BTUH of the total combined input of all fuel burning appliances
in the space. Rooms leading directly to the installation space through doors that cannot be
closed can be considered part of the space. Exception: Buildings ith full vapor barriers, tight
doors and indo s or air infiltration rates of less than 0.35 air changes per hour ill be
considered a confined space and require additional air supplies.
CONFINED SPACE
Confined space is defined by NFPA 54 as a space with a volume less than 50 cubic feet (during
typical use) per 1000 BTUH of the total combined input of all fuel burning appliances in the
space. Buildings or rooms of unusually tight construction are also considered a confined space.
See “Unconfined Space: Exception”.
When installing fuel burning appliances in a confined space, air must be supplied to that
space from either inside or outside of the building as conditions allow.
A. Inside Air Supply: A confined space shall be provided with two permanent openings; one
within 12 inches of the top and one within 12 inches of the bottom of the enclosure. These
openings shall lead directly to room(s) of sufficient volume so that the combined volume of
all the space meets the criteria for unconfined space. Each opening shall have a minimum free
area of 1 square inch per 1000 Btu/hr of the combined total input of all fuel burning
appliances in the space. Each opening shall have an area of not less than 100 square inches or
a minimum dimension of not less than 3 inches.
B. Outside Air Supply: Confined spaces shall be provided with two permanent openings; one
within 12 inches of the top and one within 12 inches of the bottom of the enclosure. These
openings shall communicate directly, or by ducts, with the outdoors or spaces that
communicate with the outdoors.
1.) Leading directly to the outside or through vertical ducts: Each opening shall have a
minimum free area of one square inch per 4000 Btu/hr of total input rating of all equipment
in the enclosure.
2.) Leading to outside through horizontal ducts: Each opening shall have a minimum free
area of one square inch per 2000 Btu/hr of total input rating of all equipment in the enclosure.
Note: All ducts shall have the same cross sectional area as the free area of each opening to
which they connect. The minimum dimensions of all ducts shall not be less than three inches.
Powered combustion air supplies are also commercially available and may be used.
LOUVERS & GRILLES
In calculating the free area of an opening, consideration must be given to the blocking effects
of louvers or grilles protecting the opening. Any screens used must be no finer than 1⁄4inch
mesh. If the free area of a louver or grille is known, this should be used in calculating the size
of opening required. If free area is unknown, it may be assumed that wood louvers will have
20 to 25% free area and metal louvers and grilles will have 60 to 75% free area. Louvers and
grilles should be fixed in the open position or interlocked with the equipment so that they
open automatically during equipment operation.
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Page 11
SEC ION IV: INS ALLA ION
VEN & COMBUS ION AIR IN AKE
DANGER
Failure to properly install the vent and combustion air intake system as outlined in this
manual can result in unsafe operation of the water heater. To avoid the risk of fire,
explosion, or asphyxiation from carbon monoxide, never operate this water heater
unless it is properly vented and has adequate air supply for combustion. Be sure to
inspect the system for proper installation at initial start-up; and at least annually
thereafter. See the aintenance section for more information.
The water heater venting and combustion air intake can be installed as a power direct
vent system (combustion air from outside the building) or power vent system
(combustion air from inside the building). Vertical or horizontal (side-wall) configura-
tions may be used.
Note: If air from inside the building will be used for combustion air, the require-
ments in Section III, "Unconfined Space" must be met.
The water heater is supplied with a pre-assembled PVC condensate assembly that must be
installed to the exhaust pipe prior to connection of the exhaust venting. See instructions
in Section IV: Installation / Vent & Combustion Air Intake / Condensate Elbow Assembly.
A 4" PVC 90 deg. standard bend elbow is supplied and must be used as the combustion air
intake termination fitting for either a direct vent or power vent system. For a power vent
system, connect the elbow directly to the 4" pipe connection supplied on the water heater.
For a direct vent system, use the elbow as the outside termination fitting. For both types
of vent systems, install a protective screen in the intake elbow to block foreign debris or
small animals from entering. The screen type must be appropriate for an air intake vent
and have a low resistance to airflow. A screen that significantly restricts airflow will
reduce the performance of the water heater and could cause nuisance control lockouts.
All vent length measurements specified in this manual are in addition to the pre-
assembled piping and supplied assemblies and fittings. Equivalent pipe lengths shall not
be greater than the maximum lengths (or less than minimums) given in Tables 4 and 5.
See the notes under Tables 4 and 5 for additional information pertaining to direct vent or
power vent system lengths.
Note: DO NOT connect the water heater to an existing vent or chimney. It must
be vented separately from all other appliances.
The following materials are approved for use as the vent and combustion air intake
piping:
• PVC ( WV, ASTM- 2665 or CSA B181.2)
• PVC (Schedule 40, ASTM- 1785 or CSA B137.3)
• PVC (S R Series, ASTM- 2241 or CSA B137.3)
• CPVC (Schedule 40, ASTM-F441 or CSA B137.3)
• CPVC (S R Series, ASTM-F442)
• ABS (Schedule 40, WV, ASTM- 2661 or CSA B181.1)
In Canada, check local codes to ensure that SDR series is approved for use. SDR is
not approved for all installations in Canada.
The following materials are approved for use for the fittings in the vent and combustion
air intake systems:
• PVC (Schedule 40 WV, ASTM 2665)
• CPVC (Schedule 40, ASTM F438)
• ABS (Schedule 40 WV, ASTM 2661)
Please contact Bock Water Heaters for questions regarding materials that are not listed
above.
䊱
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Page 12
SEC ION IV: INS ALLA ION (cont.)
VEN & COMBUS ION AIR IN AKE (cont.)
NOTICE
Installations in Canada must conform to the requirements of CSA B149 code. Plastic
vent systems must be assembled with pipe, fittings, cements, and primers listed to ULC
S636. Components of this listed system shall not be interchanged with other vent
systems or unlisted pipe/fittings. In Canada, the primer and cement must be of the
same manufacturer as the vent system; do not mix primers and cements from one
manufacturer with a vent system from a different manufacturer. The supplied plastic
pipe/fittings are certified as part of the water heater.
Minimum and Maximum System Lengths
The water heater should be located such that plastic vent pipe lengths and the number of
connection fittings are minimized. Minimum and maximum equivalent pipe lengths for
the vent and combustion air intake systems are given in Tables 4 and 5. Either 4 in. or 6
in. plastic piping may be used. The water heater is provided with fittings that readily
adapt to 4 in. plastic pipe. O NOT use less than 4 in. diameter plastic pipe and O NOT
use unequal sizes except as shown to increase from 4 in. to 6 in. diameter at the point of
connection to the water heater. Figure 4 shows the proper connections to increase from 4"
to 6" plastic pipe.
NOTE: The equivalent straight pipe length of a 90°, 1/4 standard bend elbow and
a 45°, 1/8 standard bend elbow is 5 feet and 2.5 feet, respectively. DO NOT use
short bend elbows.
NOTE: An elbow used as an exhaust vent termination fitting must be included
when determining the total number of elbows.
Figure 4: Adapting Air Intake and Exhaust Vent for 6" Piping (optional)

Page 13
SEC ION IV: INS ALLA ION (cont.)
VEN & COMBUS ION AIR IN AKE (cont.)
Table 4: Minimum and Maximum Vent and Air Intake Pipe Lengths (4" Pipe)
1Equivalent length is measured between the 4" pipe connection on the water heater and
the required 90° elbow termination fitting.
2Equivalent length is measured after the point of connection to the condensate assembly
and includes the termination fitting (if used).
†Shown as a balanced system. Vent length may exceed air intake length if total combined
length does not exceed 100 ft.
Intake length cannot exceed exhaust length.
Table 5: Minimum and Maximum Vent and Air Intake Pipe Lengths (6" Pipe)
3Equivalent length is measured between the 4" pipe connection on the water heater and
the required 90° elbow termination fitting.
4Equivalent length is measured after the point of connection to the condensate assembly
and includes the termination fitting (if used).
‡Shown as a balanced system. Vent length may exceed air intake length if total combined
length does not exceed 240 ft.
Intake length cannot exceed exhaust length.
Model(s) Vent
Arrangement
Minimum Equivalent ipe
Length (per pipe run)
Maximum Equivalent ipe
Length (per pipe run)
Air Intake1(ft) Vent2(ft) Air Intake1(ft) Vent2(ft)
OT300N(-A),
OT400N(-A),
OT500N(-A)
irect Vent 20 20 50†50†
Power Vent 0 20 0 100
Model(s) Vent
Arrangement
Minimum Equivalent ipe
Length (per pipe run)
Maximum Equivalent ipe
Length (per pipe run)
Air Intake3(ft) Vent4(ft) Air Intake3(ft) Vent4(ft)
OT300N(-A),
OT400N(-A),
OT500N(-A)
irect Vent 50 50 120‡120‡
Power Vent 0 50 0 240

SEC ION IV: INS ALLA ION (cont.)
VEN & COMBUS ION AIR IN AKE (cont.)
The vent and combustion air intake systems must be sufficiently supported along
vertical and horizontal sections. At minimum, it is recommended that a support is placed
along the vent or air intake piping every 4 feet. For horizontal systems, the first support shall
be located immediately adjacent to the first 90-deg. elbow following the vertical section
connected to the water heater. The support method should act to isolate the vent and
combustion air intake piping from floor joists or other structural members to reduce transmis-
sion of noise and vibration.
NOTE: Do not support, pin, or secure the vent and combustion air intake pipe in a
way that restricts the normal thermal expansion and contraction of the venting
material.
For replacement installations, thoroughly inspect the existing vent and combustion air intake
systems prior to installing the new water heater. The following steps shall be taken to properly
inspect the existing vent system:
• Verify that the materials as specified in this manual have been used.
• Verify the maximum and minimum vent and combustion air intake equivalent lengths and
terminal clearances meet the specifications in this manual.
• Inspect the vent and combustion air intake systems for cracking. Pay close attention to joints
between elbows and straight pipe.
• Inspect the system for misalignment of components. This may lead to sagging and unwanted
stresses in the joints.
If any corrections are required they must be computed before installing the replacement water
heater.
Condensate Elbow Assembly
Prior to connecting the exhaust vent pipe, the condensate elbow assembly (supplied, but
not factory installed) must be connected to the exhaust pipe on the water heater.
The free end of the 3 x 3 x 1.5 PVC reducing tee slip fits over the 3" exhaust pipe on the
water heater. For maximum durability and sealing, use a high heat silicone sealant
appropriate for direct vent appliances (rated for at least 150° F). Apply a bead of silicone
around the inside of the free end of the reducing tee. o the same around the end of the
exhaust pipe on the heater. Push the end of the reducing tee onto the exhaust pipe as far
as the tee allows. The orientation of the condensate elbow assembly is critical for
proper venting of gas and drainage of condensate. See Figure 5 for proper final
orientation of the assembly.
Page 14
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Figure 5: Condensate Elbow Assembly Installation

SEC ION IV: INS ALLA ION (cont.)
VEN & COMBUS ION AIR IN AKE (cont.)
After the assembly is properly mounted to the exhaust pipe, apply more silicone caulk
between the PVC fitting and metal exhaust pipe. Caulk all the way around the pipe. If a
proper seal is not made, combustion gas will leak into the room and condensate will
collect on the floor.
The condensate trap/drain portion of the assembly is shown in Figure 5. This section
includes a 1/2" hose barb fitting for attachment of a flexible condensate hose and a 3/4"
threaded plug that can be removed for cleaning the trap. The condensate drain line must
slope down, 1/8" per foot, away from the water heater towards the drain. If there is
insufficient clearance between the condensate line connection on the water heater to
maintain downward pitch up to the drain, the heater may need to be installed several
inches above the floor on a concrete slab or use a low profile condensate pump to
facilitate drainage.
If flexible tubing is not acceptable for the condensate drain line, a rigid line assembled
from PVC Schedule 40 can be used. The supplied 1/2" hose barb fitting shall be discon-
nected and replaced with a 1/2" NPT end x 1/2" socket end adapter. The rigid line shall be
braced with floor mounted standoffs every three feet. Maintain a downward pitch of 1/8"
per foot to the drain.
Some installations require the use of a condensate neutralizer kit to reduce the acidity of
the condensate prior to reaching the drain. Figure 6 shows the connection of a rigid
condensate line to a neutralizer.
Before connecting the vent piping to the condensate elbow assembly, the condensate trap
must be primed with water. Fill the trap to the point where water starts to flow down the
condensate drain line. See Figure 5 for the minimum fill level for priming the trap.
DANGER
Failure to prime the condensate trap with water will result in combustion gas (which
may contain carbon monoxide) entering the room. To avoid the risk of asphyxiation
from carbon monoxide, never operate the water heater unless the condensate trap is
sealed with water.
䊱
!
Page 15
Figure 6: Condensate Neutralizer

SEC ION IV: INS ALLA ION (cont.)
VEN & COMBUS ION AIR IN AKE (cont.)
Horizontal Venting, Direct Vent 2-pipe termination
This water heater may be vented horizontally (through a sidewall) with a two-pipe
termination. Two holes through an exterior wall are required for the vent and
combustion air intake pipes. Minimum clearances between the terminals must be met as
specified in Figure 8. All clearances must comply with local codes or the latest edition of
NFPA 54/ANSI Z223.1 or CSA B149. See Figure 7 and Table 8 for terminal clearances.
Page 16
Figure 7: Terminal Clearances

Page 17
1 In accordance with the current CSA B149.1 Natural Gas and Propane Installation Code.
2In accordance with the current ANSI Z223.1 / NFPA 54 National Fuel Gas Code.
† A vent shall not terminate directly above a sidewalk or paved driveway that is located between two single family
dwellings and serves both dwellings.
Permitted only if veranda, porch, deck, or balcony is fully open on a minimum of two sides beneath the floor.
* Clearance in accordance with local installation codes and the requirements of the gas supplier.
In addition to the clearances specified, the following items shall be accounted for during
installation:
• o not terminate near soffit vents or crawl space or other area where condensate or
vapor could create a nuisance hazard or cause property damage.
• o not locate the exhaust vent terminal where condensate or vapor could cause damage
or could be detrimental to the operation of regulators, relief valves, or other equipment.
• o not locate the exhaust vent terminal over public area or walkways where condensate
or vapor can cause nuisance or hazard.
• o not locate the vent terminal in proximity to plants/shrubs.
• The vent and air intake shall terminate a minimum of 12 " (25.4 cm) above expected
snowfall level to prevent blockage.
CAUTION
Never install air intake terminal above vent (exhaust) terminal.
䊱
!
SEC ION IV: INS ALLA ION (cont.)
VEN & COMBUS ION AIR IN AKE (cont.)
Table 8: Direct Vent Terminal Clearances
Canadian Installations1US Installations2
A = Clearance above grade, veranda,
porch, deck, or balcony 12 inches (30 cm) 12 inches (30 cm)
B = Clearance to window or door that
may be opened 36 inches (91 cm) 12 inches (30 cm)
C = Clearance to permanently closed
window * *
= Vertical clearance to ventilated
soffit located above the terminal within
a horizontal distance of 2 feet (61 cm)
from the centerline of the terminal
* *
E = Clearance to unventilated soffit * *
F = Clearance to outside corner * *
G = Clearance to inside corner * *
H = Clearance to each side of centerline
extended above meter/regulator
assembly
3 feet (91 cm) within a height 15 feet
above the meter/regulator assembly *
I = Clearance to service regulator vent
outlet 3 feet (91 cm) *
J = Clearance to non-mechanical air
supply inlet to building or the
combustion air inlet to any other
appliance
36 inches (91 cm) 12 inches (30 cm)
K = Clearance to a mechanical air
supply inlet 6 feet (1.83 m) 3 feet (91 cm) above if within 10 feet (3 m) horizontally
L = Clearance above paved sidewalk or
paved driveway located on public
property
7 feet (2.13 m)† *
M = Clearance under veranda, porch,
deck, or balcony 12 inches (30 cm) *
†
†
†
†

Install piping through the wall as shown in Figure 8. Adequate length of pipe must protrude
beyond the exterior wall for attachment of the termination fitting. The recommended distance
between the terminal fitting and the exterior wall is 1 in. (2.5 cm). irections for cementing joints
(such as the terminal fittings to the straight pipe) can be found on page 25. A single 90°elbow is
supplied with the water heater for the termination fitting on the air intake. If other fittings are
required they must be purchased separately. Install a screen inside the air intake termination fitting
to prevent items from entering the system. The screen type must be appropriate for an air intake
vent and have a low resistance to airflow. A screen that significantly restricts airflow will reduce
the performance of the water heater and could cause nuisance control lockouts. Complete the
installation of the remainder of the vent and air intake system and attach to the water heater as
shown in Figure 9. Horizontal sections of the exhaust vent shall slope upward away from the water
heater a minimum of 1/8" per foot (10 mm per meter). This will allow the condensate in the vent
to run back to the condensate drain on the water heater. Horizontal sections of air intake piping
shall slope downward away from the water heater a minimum of 1/8" per foot.
CAUTION
Annular spaces around vent pipe wall penetrations shall be permanently sealed using
approved materials to prevent entry of combustion products into the building.
䊱
!
SEC ION IV: INS ALLA ION (cont.)
VEN & COMBUS ION AIR IN AKE (cont.)
Figure 8: Horizontal Venting, 2-pipe termination
Figure 9: Horizontal Direct Vent Arrangement
Page 18

Horizontal Venting, ower Vent 1-pipe termination
This water heater may be vented horizontally (through a sidewall) with a one-pipe
termination. In this case, the water heater will be utilizing air from inside the building for
combustion air. A single hole through the exterior of the building is required for the vent
pipe.
Note: If air from inside the building will be used for combustion air, the require-
ments in Section III, “Unconfined Space” must be met.
All clearances must comply with local codes or the latest edition of NFPA 54/ANSI Z223.1
or CSA B149. See Figure 10 and Table 9 for vent terminal clearances.
SEC ION IV: INS ALLA ION (cont.)
VEN & COMBUS ION AIR IN AKE (cont.)
Figure 10: Terminal Clearances
Page 19

SEC ION IV: INS ALLA ION (cont.)
VEN & COMBUS ION AIR IN AKE (cont.)
Table 9: Power Vent Terminal Clearances
1 In accordance with the current CSA B149.1 Natural Gas and Propane Installation Code.
2In accordance with the current ANSI Z223.1 / NFPA 54 National Fuel Gas Code.
† A vent shall not terminate directly above a sidewalk or paved driveway that is located between two single family
dwellings and serves both dwellings.
Permitted only if veranda, porch, deck, or balcony is fully open on a minimum of two sides beneath the floor.
* Clearance in accordance with local installation codes and the requirements of the gas supplier.
In addition to the clearances specified, the following items shall be accounted for during
installation:
• o not terminate near soffit vents or crawl space or other area where condensate or
vapor could create a nuisance hazard or cause property damage.
• o not locate the exhaust vent terminal where condensate or vapor could cause damage
or could be detrimental to the operation of regulators, relief valves, or other equipment.
• o not locate the exhaust vent terminal over public area or walkways where condensate
or vapor can cause nuisance or hazard.
• o not locate the vent terminal in proximity to plants/shrubs.
• The vent and air intake shall terminate a minimum of 12 " (25.4 cm) above expected
snowfall level to prevent blockage.
CAUTION
Never install air intake terminal above vent (exhaust) terminal.
䊱
!
†
†
Canadian Installations1US Installations2
A = Clearance above grade, veranda,
porch, deck, or balcony 12 inches (30 cm) 12 inches (30 cm)
B = Clearance to window or door that
may be opened 36 inches (91 cm)
4 feet (1.2 m) below or to side
of opening; 1 foot (300 mm)
above opening
C = Clearance to permanently closed
window * *
= Vertical clearance to ventilated
soffit located above the terminal within
a horizontal distance of 2 feet (61 cm)
from the centerline of the terminal
* *
E = Clearance to unventilated soffit * *
F = Clearance to outside corner * *
G = Clearance to inside corner * *
H = Clearance to each side of centerline
extended above meter/regulator
assembly
3 feet (91 cm) within a height 15 feet
above the meter/regulator assembly *
I = Clearance to service regulator vent
outlet 3 feet (91 cm) *
J = Clearance to non-mechanical air
supply inlet to building or the
combustion air inlet to any other
appliance
36 inches (91 cm)
4 feet (1.2 m) below or to side
of opening; 1 foot (300 mm)
above opening
K = Clearance to a mechanical air
supply inlet 6 feet (1.83 m) 3 feet (91 cm) above if within 10 feet (3 m) horizontally
L = Clearance above paved sidewalk or
paved driveway located on public
property
7 feet (2.13 m)† *
M = Clearance under veranda, porch,
deck, or balcony 12 inches (30 cm) *
†
†
Page 20