Buderus GB312 Series User manual

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Buderus
GB312 Series
Natural Gas Condensing Boiler
High Efficiency—93.1%
Thermal Efficiency
Modulating Natural Gas
Pre-mix Burner for Extremely
Quiet Operation
Lightweight, High Performance
Aluminium Heat Exchanger
for Maximum Heat Transfer
Quick and Easy Installation
305 to 944 MBH Output:
6 Models Available

GB312: Efficiency and Performance
Buderus knows it’s important to keep costs as low as possible yet still maintain
high efficiencies, low emissions, and exceptional performance. That’s why we
have worked hard to bring all of these qualities together in the GB312 gas fired
condensing boiler from Buderus.
Powerful, Convenient, Economical
The gas fired condensing GB312 boiler offers innovative technology in a compact,
robust form with simple, space-saving, advanced condensing technology. Features
like exemplary energy efficiency, ease of handling, optional balanced flue operation
and clean combustion make the GB312 your definitive solution.
Ease of Installation and Servicing in a Compact Design
Everything about the GB312 is designed for greater simplicity and economy,
including ease of operation and installation. Matching components and factory
settings make installation quick and easy. The modulating premix gas burner is
ready for natural gas and can be quickly removed for cleaning, easy servicing, and
maintenance. Other components are equipped with their own clean-outs. Although
the GB312 delivers a lot, it takes up remarkably little space. Its compact design
makes it an ideal choice for tight installation areas, plus it easily fits through
standard doorways.
Continuous System Monitoring and Control
The EMS (Energy Management System) uses sensors to monitor the status of the
boiler. If the system values deviate greatly from the set values, the system issues a
fault or service message. When faults occur that have impact on safety, the SAFe
control triggers either a blocking or safety shutdown.
GB312 Series
Efficiency in Operation
Actual Boiler Efficiency VS. Return
Temperature at Full/Partial Load
Exhaust Gas Temperature
The exhaust gas temperature in the
vent pipe is dependent on the return
water temperature.
Exhaust gas temperatures are dependent on the boiler
return temperature GB312 (series average value)
1
2
86
95
104
113
122
131
140
149
158
176
167
86 104 122 140 158
1 2
Full Load
Full Exhaust Gas Temperature [°F ]
Return Temperature [°F ]
Partial Load

GB312 Seriess
Natural Gas Condensing Boiler
Efficient Energy Solutions
Buderus commercial boilers are designed to deliver high levels of energy
efficiency, reliable heating, and a long product life. Manufactured in Europe to
their strict safety standards, all Buderus products undergo rigorous quality tests
to ensure total safety, durability, and outstanding performance year after year.
The Buderus GB312 boiler offers a range of outputs from 305 MBH up to
955 MBH. Whether you’re planning projects for private multi-unit housing or
commercial premises, the wide range offered by the Buderus GB312 means you
are certain to find a condensing heating system to suit your needs.
The GB312 is a high performance, compact condensing boiler which provides
a high combustion rating of 93.4%. Especially well-suited for large residential
applications, multi-unit apartment dwellings, and light to moderate commercial
applications, the GB312 can be installed as a single unit or as part of a multi-
boiler cascade of up to 8 units. As a powerful floor-standing boiler, it’s remarkably
compact, lightweight, and easy to install. The GB312 is also whisper quiet, even
when running at full output.
The GB312 is designed to make servicing and maintenance as straightforward
as possible. All parts can be accessed from the front, and the burners can be
accessed without having to disturb the gas connection. The boiler is equipped
with SAFe digital ignition technology and a Buderus Energy Management
System (EMS).
Engineering Made Easy — Thanks to High Quality
Designing heating systems for medium and large buildings demands more than
just heat at the push of a button, but the added benefits of security for years to
come and greater flexibility. The innovative gas fired condensing GB312 boiler
from Buderus offers advanced condensing technology in a compact, robust
form—with high-grade components that meet every demand. All of that plus the
freedom to use the available space as you want it, thanks to compact dimensions
and the option of a balanced flue operation.
EMS Logamatic Control System:
Digital link-up with the SAFe burner
control unit
Modulating premix gas burner:
With a wide modulation range and good
accessibility
Combustion Air Fan:
Variable speed for low power consumption
High Output Aluminum Heat Exchanger:
With insulation for minimum thermal losses and
maximum energy yield
Generously Sized Clean-Out Apertures:
For easy maintenance and inspection
from the front
Neutralizing System:
Integrates under the boiler jacket*
*This is an accessory item not included with boiler
More Benefits
❚ Supplied with the BC10 and AM10
boiler controls with digital service
diagnostic and status display
❚ Insulated boiler block for low
standby loss
❚ Intelligent controls with built-in Energy
Management System (EMS)
❚ Condensate trap included
❚ Burner management technology
❚ Lightweight and compact to fit into
existing boiler rooms
❚ Modulating burner 25% to 100% for all
except the 90kW which is 33% to 100%
❚ Suitable for sealed combustion or open
vented installations
❚ Simple to service and maintain
❚ Vertical or sidewall vent up to 100 ft.
❚ CSD-1 Installation kit option available
❚ Cascade of four boilers using the
available MCM10 control module
❚ Cascade system controls up to 8 boilers
with the Logamatic 4323 Control
❚ Optional condensate neutralization tank
is available

GB312 with AM10: Outdoor reset, DHW and multi-zones with relay panel
GB312 with 4323 Control and the FM456 Module
GB312 with 4323 Control and Full System Functionality
GB312
Logamatic 4323 with FM456
KR
PS
FA
MAG
SA
SH2
FV2
KR
PH2
SA
FK SH1
FV1
KR
PH1
WH
PZB
PZ
FW
KR
EK
EK
FA
FK
FV
FW
KR
MAG
PH
PS
PZ
PZB
SA
SH
WH
Inlet Water
Outside Sensor
System Flow Sensor
Heating Zone Temperature Sensors
DHW Tank Sensor
Check Valve
Expansion Tank
Circulation Pump - Heating Zone
DHW Load Pump
Recirculating Pump
Boiler Pump
Shut-off Valve
(reccomended)
Mixing Valve
Low Loss Header (LLH)
GB312
PZ
KR
EK
Logamatic 4323 with FM456
KR
FW
SH2
PS
FA
SA
FV
KR
PH2
THV
FK
WH
MAG
BZPBZP
1)
EK
FA
FK
FV
FW
KR
MAG
PH
PS
PZ
PZB
SA
SH
THV
WH
Inlet Water
Outside Sensor
System Flow Sensor
Heating Zone
Temperature Sensors
DHW Tank Sensor
Check Valve
Expansion Tank
Circulation Pump - Heating Zone
DHW Load Pump
Recirculating Pump
Boiler Pump
Shut-off Valve
(reccomended)
Mixing Valve
Themostatic Head
Low Loss Header (LLH)
GB312
KR
PZ
FW
PS
FA
MAG
SA
KR
PH2
SA
THV
KR
EK KR
PH3
SA
THV
AM10
Multi-Zone
Relay Panel*
EK
FA
FW
KR
MAG
PH
PS
PZ
PZB
SA
THV
Inlet Water
Outside Sensor
DHW Tank Aquastat
Check Valve
Expansion Tank
Circulation Pump - Heating Zone
DHW Load Pump
Recirculating Pump
Boiler Pump
Shut-off Valve
(reccomended)
Thermostatic Head
* Third Party Product
PZB
GB312 Clearance Requirements
GB312 Boiler Pressure Drop
E
C
A
B
D
Top View
Dimension Min. Recommended
A 20" 28"
B 22" 28"
C 20" 28"
D 20" 28"
E 6" 14"
200-6
240-7
280-8
90-4
120-4
160-5
100
10
1
0.1
X
Y
1 10 100
XFlow Rate in Gal/Min (GPM)
YPrimary Pressure Drop in PSI

GB312 Seriess
Natural Gas Condensing Boiler
Logamatic Control
Optional integrated multi-boiler system
controller with the following features and
control modules:
❚ Control of modulating burners for up to
8 boilers with 4323 control
❚ Automatic and load/switch
dependent burner rotation
❚ Operation of boiler pumps, 2, 3, or
4-way valves and system pumps
❚ Capable of DHW and other external
on-demand loads
❚ Self diagnostics and system
parameter display
Complete Your System
Once you have a Buderus boiler, you can add a Buderus indirect fired hot water
tank, or an optional Buderus control — or both. In addition to maximizing comfort
and fuel savings, optional Logamatic control will accommodate specialized heating
applications such as radiant flooring or multiple boilers. Multiple design innovations
increase the versatility of Buderus Logamatic controls. A Buderus boiler combined
with a Logamatic control produces a premium heating system that will provide years
of exceptional comfort and economy.
Buderus Controls
Standard
❚ MC10 control assembly with BC10 controller
❚ AM10 included for single boiler installations
Options
❚ MCM10 (cascade module) for 4 boiler installations
❚ 4000 series controls
❚ Accommodates single or multiple boiler installations
❚ Can be interfaced to a building management system via LonWorks Gateway
❚ Modular construction allows for ease of field configuration and
flexibility of installation
The Convenience of a Logamatic Control
In addition to manual adjustments, Logamatic controls can be programmed for
automatic night and day functions and set to trigger automatic adjustments based
on outdoor or indoor temperature shifts. This includes adjustment by time, date,
or temperature between various modes of operation. All Logamatic controls
now include summer, winter and vacation modes to efficiently regulate energy
consumption. An optional module is available that enables direct communication
with building management systems.
Multiple or Single Boiler Control with
the 4000 Series
Logamatic controls can be used to
adjust the firing rates of burners in
multi-boiler systems. The Logamatic
control maintains precise control of
system temperature to match load
requirements, providing maximum
system efficiency. This regulation
is effective in single or multi-boiler
systems, with any heat source, and
in accordance with one or multiple
heating zones.

F
0.6"-1"
1.3"
19.5"
28.2" 8.5"
45"
40.1"
8.7"
8.5"
24.2"
3.9"
AA
VK GAS
RK
ST
B
AL
RK
XRK XAA
YAA
AKO
55.1"
59.7"
A
TM
Front View Side View Rear View Top View
GB312 Series
Model GB312/90 GB312/120 GB312/160 GB312/200 GB312/240 GB312/280
Performance Data
Gas Input (MBH) 328.3 440.5 588.3 732.6 880.7 1,028.8
Gross IBR Output (MBH) 305 409 544 676 810 944
Input at Minimum Capacity 132 132 176 220 264 309
Output at Minimum Capacity 131 131 173 217 261 306
Net IBR Rating (MBH) 265 356 473 588 705 821
Thermal Efficiency 93.1% 92.8% 92.5% 92.3% 92.0% 91.7%
Combustion Efficiency 93.4% 93.1% 92.8% 92.5% 92.2% 92.0%
Boiler Horse Power 9.1 12.2 16.2 20.2 24.2 28.2
Fireside Pressure Drop (Inch WC) 0.49 0.63 0.89 0.97 1.22 1.44
MAWP (PSI) 50 50 50 50 50 50
Minimum Gas Pressure (Inch WC) 3½ 3½ 3½ 3½ 3½ 3½
Maximum Gas Pressure (Inch WC) 10½ 10½ 10½ 10½ 10 10½
Operating Temperature 180˚F 180˚F 180˚F 180˚F 180˚F 180˚F
Maximum Temperature Limit 200˚F 200˚F 200˚F 200˚F 200˚F 200˚F
Piping Connections
Flue Pipe Diameter (AA)6" 6" 6" 8" 8" 8"
Dimension (YAA)18½" 18½" 18½" 19½" 19½" 19½"
Dimension (ZAA)5¾" 5¾" 5¾" 12¼" 12¼" 12¼"
Combustion Air Pipe Diameter (AL)4" 4" 4" 4" 4" 4"
Connections (VK and RK)2½" NPT 2½" NPT 2½" NPT 2½" NPT 2½" NPT 2½" NPT
Connection (ST) (B-kit) ¾" NPT ¾" NPT ¾" NPT ¾" NPT ¾" NPT 1" NPT
GAS Connection Size 1" NPT 1" NPT 1" NPT 1¼" NPT 1¼" NPT 1¼" NPT
Physical Dimensions
# of Heat Exchanger Sections 4 4 5 6 7 8
Dimension (XAA)131/8"131/8"151/8" 17¼" 19¼" 21¼"
Dimension (XRK (= XAL = GAS)105/8"105/8"14¾" 105/8"14¾" 105/8"
Dimension (A)51½" 51½" 51¼" 51¼" 51¼" 51¼"
Height 59¾" 59¾" 59¾" 59¾" 59¾" 59¾"
Width (B)391/8" 391/8" 473/8" 473/8"55½" 55½"
Boiler Feet Spacing (F)31½" 31½" 39¾" 39¾" 48" 48"
Dry Weight (lbs.) 455 455 530 585 665 730
Approx. Water Content (gal.) 4.2 4.2 5.3 6.3 7.1 7. 9
ØAA - Flue Connection GAS - Gas Connection ST - Safety Valve Connection
AL - Combustion Air Pipe VK - Boiler Supply TM - Pressure / Temperature Gauge
AKO - Condensate Drain RK - Boiler Return

GB312 Seriess
Natural Gas Condensing Boiler
Technical Specications
Venting Guidelines
This boiler requires a flue system approved for Category IV (condensing, positive
pressure: to ANSI Z21.13/CSA4.9.) It can be direct vented horizontally or vertically.
Combustion air can be obtained from the space or via sealed combustion. Consult
your local codes for details.
Basic Water Quality Guidelines
Water hardness
❚ Fill the system with clean water from the
municipal water supply.
❚ Consult your local water department for
the level of CaCO3 (calcium carbonate) to
determine if water treatment is necessary.
❚ Do not use water from salt bedding systems
(ion exchange) used to soften water.
❚ Approved Anti-freeze (Aluminum safe)
❚ Rhomar – Rhogard (at a concentration no
more than 60% by volume).
❚ Noble Company – Noburst-AL (at a
concentration no greater than 50% by
volume).
Maintenance
❚ Follow the instructions of the approved anti-
freeze vendor. An annual visit by a qualified
service technician is recommended.
Corrosion
❚ Damage to the system can occur when
oxygen is introduced to the heating system
water. The following must be avoided for
best system operation:
• Undersized or faulty expansion vessels
• Open vented systems
• If the system can not be constructed
as a sealed system, the use of a heat
exchanger as a means of system
separation is required.
Retrofit installations
❚ Installing a dirt trap such as a wye-strainer
is required. It must be installed in the
immediate vicinity of the boiler on the return
pipe at the lowest point in the system.
Manufacturer Flue System Material
Heat Fab Saf-T Vent EZ Seal AL29-4C
Z-Flex Z-Vent IV Special Gas Vent AL29-4C
Metal Fab Corr Guard AL29-4C
Pro-Tech Fas-N-Seal AL29-4C
Security Chimney CI-System AL29-4C
Locastion Manufacturer System
USA Spears CPVC schedule 80 pipe to ASTM D1784
Canada IPEX System 636 CPVC
GB312 Boiler Size Required Air Flow (CFM)
GB312/90 95
GB312/120 95
GB312/160 130
GB312/200 160
GB312/240 190
GB312/280 220
Approved Stainless Steel vent systems
CPVC Venting Systems
(Requires use of starter adapter. See Installation Manual for list of approved chimney manufacturers.)
CPVC Venting Systems
Vent and combustion air supply system installation must comply with Part 10, Venting of
Equipment of the National Fuel Gas Code, ANSI Z223.1 or CSA B.149 or other applicable local
building code regulations. IMPORTANT: The flue and air supply system must be designed for a
maximum pressure of 0.40 inches WC (100Pa) for the overall system (vent and combustion air
system) Vent Terminations: Approved Tee, Termination Elbow or Roof Cap for all category IV
venting systems is required.

A Tradition of Excellence
The World’s leader in heating
technologies since 1825, Buderus
produced the world’s first low-
temperature hydronic heating
systems. Today, Buderus products are
acknowledged as the world standard
in high-efficiency, low emissions
hydronic heating. All Buderus products
are designed to meet strict safety and
environmental regulations.
Buderus boilers are quick and easy to
install and will outlast and outperform
virtually any other commercial hot
water heating system. They are
designed for easy access and service.
With appropriate maintenance, Buderus
boilers deliver the highest possible
efficiencies throughout the lifespan
of operation.
In 2008 Buderus became a member
of the Bosch Group, representing
the Bosch, Buderus and FHP brands
with products that are designed to
improve efficiency, reliability and
are environmentally friendly. Bosch
Thermotechnology offers floor-standing
and wall hung boilers, water heaters,
solar systems, heat pumps, control
systems and tankless water heaters.
GB312 Benefits at a Glance
❚ Excellent value and performance
❚ Boiler sizes from 305 to 955 MBH output
❚ Modulating premix gas burner for quiet, energy efficient operation
❚ Small footprint, low weight
❚ Condensing boiler with high performance aluminium heat exchanger
❚ Thermally insulated boiler block
❚ Easy installation, fully assembled at the factory
❚ Intelligent control system (Logamatic EMS and Logamatic 4000)
❚ Maintenance made simple by easy accessibility of components requiring service
❚ Balanced flue operation
❚ Neutralizing system may be added for condensate conditioning
Bosch Thermotechnology Corp. 50 Wentworth Avenue, Londonderry, NH 03053 Tel: [phone] Fax: [phone] www.buderus.us
44499111 04/11 © 2010 Bosch Thermotechnology Corp. Subject to change without notice.
GB312 Series
Natural Gas Condensing Boiler
Approval Numbers
CRN 7834.7C
MA # G1-0409-410
Approvals and Certifications
®
Approval numbers are subject to periodic changes and updates. Please visit our web site for the most up-to-date approval numbers.