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Bosch Greenstar Combi 100 - ZBW28 - 89K BTU - 95.0% AFUE - Combi Gas Boiler - Direct Vent

Bosch Greenstar Combi 100 - ZBW28 - 89K BTU - 95.0% AFUE - Combi Gas Boiler - Direct Vent
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Model: ZWB28-3
(Based on expert analysis, manufacturer ratings and customer reviews)
5.0 out of 55.0 out of 55.0 out of 55.0 out of 55.0 out of 5
Number of Reviews (4)
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$3,149.00
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  • Product Description
  • 4
    Reviews
  • 3
    Product Q&A
  • Recommended Accessories
  • How-To Articles
  • Manuals
Product Description
+
Features
Features
    The Bosch greenstar boiler represents today's best efficiency technologies brought together in a single package. Astounding efficiency ratings can be achieved with the use of Bosch's condensing technology, squeezing every last BTU out of your home's gas supply. An included 3-speed Grundfos pump and a wide variety of pipe venting options allow the boiler to be installed in nearly any home imaginable. This boiler includes a domestic hot water coil, allowing the boiler to act as a tankless hot water heater as well as a hydronic boiler.
  • Condensing Technology Improves Efficiency
  • The ZWB28-3 is a condensing boiler, using the leftover energy in the boiler's flue exhaust to further heat your home. Keep your home warmer for less energy cost!
  • Included DHW Coil
  • This Bosch greenstar boiler contains an internal domestic hot water coil. This allows the boiler to function as a tankless hot water heater as well as a hydronic water boiler.
  • Fully Modulating Fan
  • The boiler includes a fully modulating fan to control the boiler's burning rate, allowing optimum efficiency to be achieved during a wide variety of outdoor conditions.
  • Small Size and Low Installation Clearances
  • Low installation clearances on all sides, wall mounting configuration, and small footprint translate into a boiler that can be installed almost anywhere.
Specifications
General Information
Product Line
Greenstar
Medium ? Medium refers to the substance that carries heat through the heating system. Systems are either designed to use either Hot Water or Steam as a medium, and components are usually specific to one or the other.
Hot Water
Fuel Type ? To create heat, some form of fuel is required. Fuel Type specifies what the product uses as an input to create heat.
Natural Gas
Combustion Type
Condensing
Vent Type ? Products that use combustion (burning) of fuel to create heat also create potentially dangerous gasses that need to be exhausted (AKA "Vented"). Depending on the product, venting can be done via a chimney, through a side wall, or use a second vent to provide fresh air to the appliance.
Direct Vent
DHW Production ? DHW (Domestic Hot Water) is potable water for uses other than space heat. Some boilers are able to provide DHW "out of the box", while others can do so with the purchase of optional accessories.
Yes
Modulating/Staging ? Stages are unique speeds or levels that equipment can operate at. More stages allow for better fine-tuned control of output, which improves comfort and efficiency. Modulating equipment can operate across a range of levels, giving the highest level of fine-tuned control. Learn More
Modulating
Mount Type
Wall
Minimum Altitude
0 Feet
Maximum Altitude
6000 Feet
Includes Pump
Yes
Assembly Type
Packaged
Gas Conversion Kit
Included
Performance
Maximum Input Capacity ? The Maximum Input Capacity describes how quickly the appliance will use fuel when delivering it's maximum capacity. The units may change depending on the fuel being used.
100800 BTU
Minimum Input Capacity
34600 BTU
DOE Heating Capacity ? Also referred to as Gross Output, this is the output of a boiler after accounting for combustion efficiency. We recommend sizing hot water boilers based on the DOE Heating Capacity.
89400 BTU
Net I=B=R Capacity ? I=B=R, also referred to as Net Output or AHRI Capacity, is the rated heat output of a boiler after accounting for combustion efficiency, piping loss, and an extra pickup factor. We recommend sizing steam boilers based on the I=B=R rating.
79000 BTU
AFUE ? AFUE (Annual Fuel Utilization Efficiency) measures the efficiency of combustion equipment over the entire heating season, and is calculated by dividing the amount of energy that is actually heating your home by the total energy contained in the fuel used by the boiler/furnace. Learn More
95 %
Ultra Low NOx Emissions ? NOx is a byproduct of the combustion process, and it's output is regulated in some jurisdictions. Many regulators mirror SCAQMD rules, which regulate air quality for some parts of Southern California. Ultra Low NOx appliances emit less than 10-14 ng/J (nanogram per Joule) of NOx. Learn More
Yes
Turndown Ratio
5:1
Electrical Data
Voltage
120 Volts
Phase
1
Frequency
60 Hz
Dimensions
Flue Connection Size
3 Inches
Gas Connection Size
3/4 Inch
Cold Water Inlet
3/4 Inch
Hot Water Outlet
3/4 Inch
Supply Connection
1 Inch
Return Connection
1 Inch
Product Height
33 1/2 Inches
Product Width
17 19/48 Inches
Product Depth
13 43/48 Inches
Product Weight
110.2 Pounds
Certifications
Country of Origin
United States
CSA Listed
Yes
ASME Certified
Yes
AHRI Certified
Yes
AHRI Reference Number
4444522
Warranty Information
Parts Warranty ? A warranty is a safeguard from defects in manufacturing and can vary in length and terms. To see the manufacturer's warranty statement, click on the Manuals tab. Learn More
5 Years
Heat Exchanger Warranty
Limited Lifetime Years
Features
Features
    The Bosch greenstar boiler represents today's best efficiency technologies brought together in a single package. Astounding efficiency ratings can be achieved with the use of Bosch's condensing technology, squeezing every last BTU out of your home's gas supply. An included 3-speed Grundfos pump and a wide variety of pipe venting options allow the boiler to be installed in nearly any home imaginable. This boiler includes a domestic hot water coil, allowing the boiler to act as a tankless hot water heater as well as a hydronic boiler.
  • Condensing Technology Improves Efficiency
  • The ZWB28-3 is a condensing boiler, using the leftover energy in the boiler's flue exhaust to further heat your home. Keep your home warmer for less energy cost!
  • Included DHW Coil
  • This Bosch greenstar boiler contains an internal domestic hot water coil. This allows the boiler to function as a tankless hot water heater as well as a hydronic water boiler.
  • Fully Modulating Fan
  • The boiler includes a fully modulating fan to control the boiler's burning rate, allowing optimum efficiency to be achieved during a wide variety of outdoor conditions.
  • Small Size and Low Installation Clearances
  • Low installation clearances on all sides, wall mounting configuration, and small footprint translate into a boiler that can be installed almost anywhere.
Specifications
General Information
Product Line
Greenstar
Medium ? Medium refers to the substance that carries heat through the heating system. Systems are either designed to use either Hot Water or Steam as a medium, and components are usually specific to one or the other.
Hot Water
Fuel Type ? To create heat, some form of fuel is required. Fuel Type specifies what the product uses as an input to create heat.
Natural Gas
Combustion Type
Condensing
Vent Type ? Products that use combustion (burning) of fuel to create heat also create potentially dangerous gasses that need to be exhausted (AKA "Vented"). Depending on the product, venting can be done via a chimney, through a side wall, or use a second vent to provide fresh air to the appliance.
Direct Vent
DHW Production ? DHW (Domestic Hot Water) is potable water for uses other than space heat. Some boilers are able to provide DHW "out of the box", while others can do so with the purchase of optional accessories.
Yes
Modulating/Staging ? Stages are unique speeds or levels that equipment can operate at. More stages allow for better fine-tuned control of output, which improves comfort and efficiency. Modulating equipment can operate across a range of levels, giving the highest level of fine-tuned control. Learn More
Modulating
Mount Type
Wall
Minimum Altitude
0 Feet
Maximum Altitude
6000 Feet
Includes Pump
Yes
Assembly Type
Packaged
Gas Conversion Kit
Included
Performance
Maximum Input Capacity ? The Maximum Input Capacity describes how quickly the appliance will use fuel when delivering it's maximum capacity. The units may change depending on the fuel being used.
100800 BTU
Minimum Input Capacity
34600 BTU
DOE Heating Capacity ? Also referred to as Gross Output, this is the output of a boiler after accounting for combustion efficiency. We recommend sizing hot water boilers based on the DOE Heating Capacity.
89400 BTU
Net I=B=R Capacity ? I=B=R, also referred to as Net Output or AHRI Capacity, is the rated heat output of a boiler after accounting for combustion efficiency, piping loss, and an extra pickup factor. We recommend sizing steam boilers based on the I=B=R rating.
79000 BTU
AFUE ? AFUE (Annual Fuel Utilization Efficiency) measures the efficiency of combustion equipment over the entire heating season, and is calculated by dividing the amount of energy that is actually heating your home by the total energy contained in the fuel used by the boiler/furnace. Learn More
95 %
Ultra Low NOx Emissions ? NOx is a byproduct of the combustion process, and it's output is regulated in some jurisdictions. Many regulators mirror SCAQMD rules, which regulate air quality for some parts of Southern California. Ultra Low NOx appliances emit less than 10-14 ng/J (nanogram per Joule) of NOx. Learn More
Yes
Turndown Ratio
5:1
Electrical Data
Voltage
120 Volts
Phase
1
Frequency
60 Hz
Dimensions
Flue Connection Size
3 Inches
Gas Connection Size
3/4 Inch
Cold Water Inlet
3/4 Inch
Hot Water Outlet
3/4 Inch
Supply Connection
1 Inch
Return Connection
1 Inch
Product Height
33 1/2 Inches
Product Width
17 19/48 Inches
Product Depth
13 43/48 Inches
Product Weight
110.2 Pounds
Certifications
Country of Origin
United States
CSA Listed
Yes
ASME Certified
Yes
AHRI Certified
Yes
AHRI Reference Number
4444522
Warranty Information
Parts Warranty ? A warranty is a safeguard from defects in manufacturing and can vary in length and terms. To see the manufacturer's warranty statement, click on the Manuals tab. Learn More
5 Years
Heat Exchanger Warranty
Limited Lifetime Years
Product Specs
+
Specifications
General Information
Product Line
Greenstar
Medium ? Medium refers to the substance that carries heat through the heating system. Systems are either designed to use either Hot Water or Steam as a medium, and components are usually specific to one or the other.
Hot Water
Fuel Type ? To create heat, some form of fuel is required. Fuel Type specifies what the product uses as an input to create heat.
Natural Gas
Combustion Type
Condensing
Vent Type ? Products that use combustion (burning) of fuel to create heat also create potentially dangerous gasses that need to be exhausted (AKA "Vented"). Depending on the product, venting can be done via a chimney, through a side wall, or use a second vent to provide fresh air to the appliance.
Direct Vent
DHW Production ? DHW (Domestic Hot Water) is potable water for uses other than space heat. Some boilers are able to provide DHW "out of the box", while others can do so with the purchase of optional accessories.
Yes
Modulating/Staging ? Stages are unique speeds or levels that equipment can operate at. More stages allow for better fine-tuned control of output, which improves comfort and efficiency. Modulating equipment can operate across a range of levels, giving the highest level of fine-tuned control. Learn More
Modulating
Mount Type
Wall
Minimum Altitude
0 Feet
Maximum Altitude
6000 Feet
Includes Pump
Yes
Assembly Type
Packaged
Gas Conversion Kit
Included
Performance
Maximum Input Capacity ? The Maximum Input Capacity describes how quickly the appliance will use fuel when delivering it's maximum capacity. The units may change depending on the fuel being used.
100800 BTU
Minimum Input Capacity
34600 BTU
DOE Heating Capacity ? Also referred to as Gross Output, this is the output of a boiler after accounting for combustion efficiency. We recommend sizing hot water boilers based on the DOE Heating Capacity.
89400 BTU
Net I=B=R Capacity ? I=B=R, also referred to as Net Output or AHRI Capacity, is the rated heat output of a boiler after accounting for combustion efficiency, piping loss, and an extra pickup factor. We recommend sizing steam boilers based on the I=B=R rating.
79000 BTU
AFUE ? AFUE (Annual Fuel Utilization Efficiency) measures the efficiency of combustion equipment over the entire heating season, and is calculated by dividing the amount of energy that is actually heating your home by the total energy contained in the fuel used by the boiler/furnace. Learn More
95 %
Ultra Low NOx Emissions ? NOx is a byproduct of the combustion process, and it's output is regulated in some jurisdictions. Many regulators mirror SCAQMD rules, which regulate air quality for some parts of Southern California. Ultra Low NOx appliances emit less than 10-14 ng/J (nanogram per Joule) of NOx. Learn More
Yes
Turndown Ratio
5:1
Electrical Data
Voltage
120 Volts
Phase
1
Frequency
60 Hz
Dimensions
Flue Connection Size
3 Inches
Gas Connection Size
3/4 Inch
Cold Water Inlet
3/4 Inch
Hot Water Outlet
3/4 Inch
Supply Connection
1 Inch
Return Connection
1 Inch
Product Height
33 1/2 Inches
Product Width
17 19/48 Inches
Product Depth
13 43/48 Inches
Product Weight
110.2 Pounds
Certifications
Country of Origin
United States
CSA Listed
Yes
ASME Certified
Yes
AHRI Certified
Yes
AHRI Reference Number
4444522
Warranty Information
Parts Warranty ? A warranty is a safeguard from defects in manufacturing and can vary in length and terms. To see the manufacturer's warranty statement, click on the Manuals tab. Learn More
5 Years
Heat Exchanger Warranty
Limited Lifetime Years
Reviews
(4)
+
Bosch Thermotechnology ZWB28-3 Reviews & Ratings
Product Q&A
(3)
+
Search Product Q&A's Answered by Bob, the Heating Product Expert
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I am at an altitude of 6500 ft. This unit says max 6000. Can I still use it with just less efficiency or can you recommend another similar unit? I need heat only for an in-floor radiant system.
Glenn M. 
from Connecticut 
October 26, 2016
Answer
The Bosch Greenstar models listed below offer an altitude compensation feature that allows the boiler to operate at altitudes of up to 6000' without any reduction in capacity. Beyond 6000' the boiler output will fall by 3% per 1000'. Further details on high altitude compensation and derate can be found on page 57 of the installation manual

ZBR16-3A, ZBR21-3A, ZBR28-3A, ZBR35-3A, ZWB28-3A, and ZWB35-3A
+
Can this unit be retrofitted to use propane gas?
John McNew 
from New Mexico 
May 31, 2016
Answer
Yes, it can be retrofitted for LP gas. The boiler includes an LPG conversion kit from the factory.
+
What would be the appropriate pressure setting for the relief valve?
Angie 
from New York 
September 09, 2015
Answer
Per the manufacturer, the safety valve will open if pressure exceeds 30 psi (2.07 bar) at maximum heating water temperature. Please reference page 9 of the Bosch Greenstar Owner's Manual for more details.
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Bosch Thermotechnology ZWB28-3
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