Bock Water heaters OT300 Service manual

WA NING
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.
WA NING
Install in accordance with all local codes. In the
absence of local codes, refer to NFPA 54 or SA
B149.1.
CAUTION
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.
WA NING
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.
WA NING
Water heater blankets may restrict air flow to the
water heater and cause fire, asphyxiation, personal
injury or death.
THIS MANUA HAS BEEN PREPARED TO ACQUAINT
YOU WITH THE INSTA ATION, OPERATION, AND
MAINTENANCE OF YOUR WATER HEATER AND TO
PROVIDE IMPORTANT SAFETY INFORMATION.
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 ODE and the NFPA ode. 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.
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.
FAI URE TO FO OW THESE INSTRUCTIONS OR A
APP ICAB E BUI DING CODES
AND REGU ATIONS 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.
Rev2 9/2013#23402 EN
– Do ot store or use gasoli e or other flammable
vapors a d liquids i the vici ity of this or a y
other applia ce.
– WHAT TO DO IF YOU SMELL GAS
• Do ot try to light a y applia ce.
• Do ot touch a y electrical switch; do ot use
a y pho e i your buildi g.
• Immediately call your gas supplier from a eigh-
bor’s pho e. Follow the gas supplier’s i structio s.
• If you ca ot reach your gas supplier, call the fire
departme t.
–I stallatio a d service must be performed by a
qualified i staller, service age cy or the gas supplier.
WAR I G: 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 400, O 500
High Efficiency Commercial Gas Water Heater

IMPO TANT SAFETY INST UCTIONS
The 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 DANGE , WA NING, CAUTION, O NOTICE.
DANGE indicates an imminently hazardous situation which, if not
avoided, will result in serious injury or death.
WA NING indicates a potentially hazardous situation which, if not
avoided, could result in serious injury or death.
CAUTION indicates a hazardous situation which, if not avoided, could
result in minor or moderate injury.
NOTICE calls attention to observe a specified procedure.
SAVE THESE INST UCTIONS
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DANGE
Water heaters utilizing iquefied Petroleum gas ( P) are different from
natural gas models. A natural gas heater will not function safely on P 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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DANGE
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 Maintenance section for more information.
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TABLE OF CONTENTS
Section I: Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Section II: General Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Section III: Pre-Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Section IV: Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Section V: Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Section VI: Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Section VII: Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Section VIII: Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Section IX: Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
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Model
Rated Storage
apacity, GAL (L)
Rated Maximum
Input, Btu/hr (kW)
Thermal Efficiency
(%) @ Max. Input
Recovery @ 100°F
rise, GAL/HR (L/HR)
A
E
G
HOT (NPT)
Air Intake
(PV )
Rated Minimum
Input, Btu/hr (kW)
Thermal Efficiency
(%) @ Min. Input
1st Hr. Delivery @
100°F rise, GAL (L)
B
D
F
OLD (NPT)
Gas (NPT)
Exhaust
Vent (PV )
Table 1: Dimensions
Page 4
SECTION I: SPECIFICATIONS
Figure 1: All Models
DIMENSIONS, IN HES (cm)
N TE: Suffix "N" stands for NATURAL GAS and suffix "-A" denotes ASME version.
For PR PANE GAS models, change suffix "N" to "LP".
For HIGH ALTITUDE models, the following additional suffixes are defined as:
"-H28" = Approved for altitudes greater than 2,000 up to 7,800 FT
"-H25" = Approved for altitudes greater than 2,000 up to 5,400 FT
"-H58" = Approved for altitudes greater than 5,400 up to 7,800 FT
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)
119 300,000135,000 95 97 342 430 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) (1,627) (199) (81) (159) (29) (24) (156) (188) (544)
125 300,000135,000 95 97 342 430 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) (1,627) (199) (81) (159) (29) (24) (156) (188) (544)
119 399,999135,000 94 97 451 539 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)( 2,040) (199) (81) (159) (29) (24) (156) (188) (544)
125 399,999135,000 94 97 451 539 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)(2,040) (199) (81) (159) (29) (24) (156) (188) (544)
119 499,999135,000 93 97 558 646 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) (2,445) (199) (81) (159) (29) (24) (156) (188) (544)
125 500,000135,000 93 97 558 646 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)(2,445) (199) (81) (159) (29) (24) (156) (188) (544)
OT300N
OT300N-A
OT400N
OT400N-A
OT500N
OT500N-A
ONNE TION SIZES
Shipping Weight,
LBS (kg)
For LP gas:
MINIMUM GAS SUPPLY PRESSURE (at gas control) = 8" W.C. (dynamic)
MAXIMUM GAS SUPPLY PRESSURE (at gas control) = 14" W.C. (static or dynamic)
Note: Dynamic pressure is measured while gas is flowing and static pressure is measured while gas is
not flowing.
All Bock products meet or exceed current ASHRAE standards.
These products are design certified by UL (Underwriters Laboratories) and meet ANSI 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.

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APPROXIMATE
TEMPERATURE/TIME
RELATIONSHIPS TO
S ALDING
120°F (49° ) More than 5 minutes
125°F (52° ) 1 1⁄2 to 2 minutes
130°F (54° ) About 30 seconds
135°F (57° ) About 10 seconds
140°F (60° ) Less than 5 seconds
145°F (63° ) Less than 3 seconds
150°F (66° ) About 1 1⁄2 seconds
155°F (68° ) About 1 second
Table 2: Scald Temperature/Time elationships
SECTION II: GENE AL INFO MATION
WHEN YOU RECEIVE YOUR NEW WA ER HEA ER
heck 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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SECTION II: GENE AL INFO MATION
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 FROM THE
POWER SUPP Y FOR AN EXTENDED PERIOD OF TIME. WITHOUT POWER, THE ANODE SYSTEM WI
NOT BE CAPAB E 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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SECTION II: GENE AL INFO MATION
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.
ote: Working pressure of the water heater is 150 PSI. Do not exceed 150 PSI.
CONDENSA ION
ondensation of flue gases will occur in the exhaust vent and portions of the heat exchanger
during burner operation. ondensate 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 ombustion Air Intake / ondensate Elbow Assembly and Section IV: Installation / Vent &
ombustion Air Intake / Optional ondensate Line for installation details.
HIGH AL I UDE
The water heaters covered in this manual are safety certified for altitudes up to 7,800 feet. For
high altitude applications (i.e. installations at altitudes greater than 2,000 feet), models that are
designated with a suffix "-H28", "-H25", or "-H58" must be used. Natural gas models for high
altitude will contain the suffix "-H28" and are certified for use at altitudes greater than 2,000 FT
up to 7,800 FT. LP gas models containing the suffix "-H25" are certified for use at altitudes
greater than 2,000 FT up to 5,400 FT. LP models that contain the suffix "-H58" are certified for
use at altitudes greater than 5,400 FT up to 7,800 FT.
Following installation at high altitudes, verify that O2readings and O levels in the exhaust
vent are within the specified ranges given in Section VI: Maintenance, “ heck the ombustion
System”.
Due to the natural reduction in input rate at higher altitudes, the actual hot water output of the
heater is gradually reduced as altitude is increased. Expect a 2.8% input rate reduction per
1,000 feet altitude. However, all high altitude models are factory adjusted to maintain the
rated sea-level minimum input at minimum fan speed.
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SECTION II: GENE AL INFO MATION
SEISMIC RES RAIN
Regions of the United States and anada that are considered earthquake zones require that the
water heater(s) is properly braced to avoid movement or falling during a seismic event. Bock
recommends a frame and strap system similar to the design shown in Figure 2.
Use heavy gauge metal framing and anchor post bases to the floor. For additional support,
connect framing to wall studs.
Locate the metal straps within the upper and lower third of the tank. The upper strap needs to
run under the plastic control cover. onnect the straps to the metal framing located behind
the water heater(s). Bock recommends the Holdrite Quick Strap® QS-120 or equivalent
strapping system. The Holdrite QS-120 is approved by the alifornia Division State Architect
and is UP /IP /IAPMO listed.



Figure 2: Seismic Straps and Framing

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SECTION III: P E-INSTALLATION
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 SME 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 APP IANCE UNTI THE EAKAGE IS CORRECTED!
CAUTION
Do not drop water heater or lay heater down on its side. Move 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.
Locate the heater so it is not subject to physical damage from moving vehicles or flooding. Do
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.
NOTE: To comply with the installation requirements in NSF Standard 5, the bottom of this
water heater must be sealed to the floor with a silicone based sealant.
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 ode (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 & ombustion Air Intake / ondensate 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.
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Figure 3: Minimum Clearance From Combustibles Figure 4: equired Minimum Access Clearances
Nominal
Iron Pipe
Size
(inche )
Internal
Diameter
(inche )
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
SECTION III: P E-INSTALLATION
Minimum clearance from combustible material is 0" for the sides, top, and back of this water
heater, as shown in Figure 3. This water heater is approved for installation in an alcove with
the clearances shown in Figure 3. For ease of access and proper maintenance, the clearances in
Figure 4 are required.
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 Pressure
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. For natural gas models,
during operation at maximum input, the supply pressure at the gas control must be at least 6" W. .
For LP gas models, during operation at maximum input, the supply pressure at the gas control
must be at least 8” W. .
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. . or
less and a pressure drop of 0.3" W. .
At minimum, use 1-1/4" gas supply pipe for models OT300 and OT400.
For model OT500, use a minimum of 1-1/2" pipe.
Maximum Gas Supply Pressure
The gas supply pressure shall never be greater than 14" W. . Pressures greater than 14" W. . may
damage the gas control which could cause a fire or explosion.
Refer to Section IV: Installation / Gas onnections for further installation instructions.

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SECTION III: P E-INSTALLATION
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 ( O) and excessive levels of soot.
See NFPA 54 or the discussions of "Unconfined Space" and " onfined 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
onfined 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: onfined 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.
ote: 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.

Page 12
SECTION IV: INSTALLATION
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 Maintenance 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.
ote: 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 PV condensate assembly that must be
installed to the exhaust pipe prior to connection of the exhaust venting. See instructions
in Section IV: Installation / Vent & ombustion Air Intake / ondensate Elbow Assembly.
A 4" PV 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. The supplied 90
deg. elbow contains a protective screen to block foreign debris or small animals from
entering the pipe. If a screen is preferred at the exhaust termination, it must have a low
resistance to airflow. Refer to the type of screen used in the supplied elbow. A screen that
significantly restricts airflow will reduce the performance of the water heater and could
cause nuisance control lockouts.
Prior to connecting intake piping to the water heater, look down the end of the air intake
assembly (see Item 6, page 47) to make sure damper is oriented such that the pins on
opposing sides of the swinging gate are level. If not, adjust orientation of the air intake
assembly by loosening the flexible coupling from the blower and turning the intake
assembly until the pins are level.
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.
ote: DO OT 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:
• PV (DWV, ASTM-D2665 or SA B181.2)
• PV (Schedule 40, ASTM-D1785 or SA B137.3)
• PV (SDR Series, ASTM-D2241 or SA B137.3)
• PV (Schedule 40, ASTM-F441 or SA B137.3)
• PV (SDR Series, ASTM-F442)
• ABS (Schedule 40, DWV, ASTM-D2661 or SA 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.
䊱
!

SECTION IV: INSTALLATION
The following materials are approved for use for the fittings in the vent and combustion
air intake systems:
• PV (Schedule 40 DWV, ASTM D2665)
• PV (Schedule 40, ASTM F438)
• ABS (Schedule 40 DWV, ASTM D2661)
Please contact Bock Water Heaters for questions regarding materials that are not listed
above.
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 U C
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. DO NOT use less than 4 in. diameter plastic pipe and DO 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 5 shows the proper connections to increase from 4"
to 6" plastic pipe.
OTE: 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 OT use
short bend elbows.
OTE: An elbow used as an exhaust vent termination fitting must be included
when determining the total number of elbows.
Page 13
Figure 5: Adapting Air Intake and Exhaust Vent for 6" Piping (optional)

Page 14
SECTION IV: INSTALLATION
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) Fuel
Type
Vent
Arrangement
Minimum Equivalent Pipe
Length (per pipe run)
Maximum Equivalent Pipe
Length (per pipe run)
Air Intake1(ft) Vent2(ft) Air Intake1(ft) Vent2(ft)
OT300, OT400,
OT500
NAT or
LP
Direct Vent 20 20 50†50†
Power Vent 0 20 0 100
Model(s) Fuel
Type
Vent
Arrangement
Minimum Equivalent Pipe
Length (per pipe run)
Maximum Equivalent Pipe
Length (per pipe run)
Air Intake3(ft) Vent4(ft) Air Intake3(ft) Vent4(ft)
OT300, OT400,
OT500
NAT or
LP
Direct Vent 50 50 120‡120‡
Power Vent 0 50 0 240

Page 15
SECTION IV: INSTALLATION
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.
OTE: 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 PV 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. Do 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 6 for proper final
orientation of the assembly.
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Figure 6: Condensate Elbow Assembly Installation

Page 16
SECTION IV: INSTALLATION
After the assembly is properly mounted to the exhaust pipe, apply more silicone caulk
between the PV fitting and metal exhaust pipe. aulk 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 6. 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 to the drain, the heater may need to be installed 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 PV 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 7 shows the connection of a condensate
line to a neutralizer. It is recommended that a low profile condensate pump is installed
between the heater and the neutralizer to facilitate flow through the neutralizer. For
further installation details, refer to the instructions provided with the pump and
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 6 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
!
Figure 7: Condensate Pump and Neutralizer

SECTION IV: INSTALLATION
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 9. All clearances must comply with local codes or the latest edition of
NFPA 54/ANSI Z223.1 or SA B149. See Figure 8 and Table 9 for terminal clearances.
Page 17
Figure 8: Terminal Clearances

Page 18
1 In accordance with the current SA 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.
* learance 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:
• Do not terminate near soffit vents or crawl space or other area where condensate or
vapor could create a nuisance hazard or cause property damage.
• Do 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.
• Do not locate the exhaust vent terminal over public area or walkways where condensate
or vapor can cause nuisance or hazard.
• Do 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.
• It is best practice to locate the intake and exhaust terminations on a common plane.
CAUTION
Never install air intake terminal above vent (exhaust) terminal.
䊱
!
SECTION IV: INSTALLATION
Table 8: Direct Vent Terminal Clearances
anadian Installations1US Installations2
A = learance above grade, veranda,
porch, deck, or balcony 12 inches (30 cm) 12 inches (30 cm)
B = learance to window or door that
may be opened 36 inches (91 cm) 12 inches (30 cm)
= learance to permanently closed
window * *
D = 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 = learance to unventilated soffit * *
F = learance to outside corner * *
G = learance to inside corner * *
H = learance 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 = learance to service regulator vent
outlet 3 feet (91 cm) *
J = learance 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 = learance to a mechanical air
supply inlet 6 feet (1.83 m) 3 feet (91 cm) above if within 10 feet (3 m) horizontally
L = learance above paved sidewalk or
paved driveway located on public
property
7 feet (2.13 m)† *
M = learance under veranda, porch,
deck, or balcony 12 inches (30 cm) *
†
†
†
†

Page 19
Install piping through the wall as shown in Figure 9. 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). Directions 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. The supplied 90°elbow contains a protective screen to
block foreign debris or small animals from entering the pipe. If a screen is preferred at the exhaust
termination, it must have a low resistance to airflow. Refer to the type of screen used in the
supplied elbow. A screen that significantly restricts airflow will reduce the performance of the
water heater and could cause nuisance control lockouts. omplete the installation of the
remainder of the vent and air intake system and attach to the water heater as shown in Figure 10.
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.
NOTE: If the air intake and exhaust vent terminations will be located on a side of the building
that is frequently subjected to high winds, it is recommended that the air intake termination is
located 24” (center-to-center) below the exhaust vent termination.
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
!
SECTION IV: INSTALLATION
Figure 9: Horizontal Venting, 2-pipe termination
Figure 10: Horizontal Direct Vent Arrangement

Page 20
Horizontal Venting, Power 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.
ote: 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 SA B149. See Figure 11 and Table 9 for vent terminal clearances.
SECTION IV: INSTALLATION
Figure 11: Terminal Clearances