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KWB 35-3 Greenstar Combi 131 103,000 BTU Gas-Fired Floor Standing Condensing Boiler
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KWB 35-3 Greenstar Combi 131 103,000 BTU Gas-Fired Floor Standing Condensing Boiler

KWB 35-3 Greenstar Combi 131 103,000 BTU Gas-Fired Floor Standing Condensing Boiler
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$4,388.28 each
Out of Stock
Out of Stock
Get it Mon, Apr 17 - Wed, Apr 26

Lift Gate

This product weighs 136.6 lbs. and may require the use of a lift gate. If you do require a lift gate at your delivery, you'll have the option to add this FREE of charge when you checkout.
Free Shipping This item ships free
Easy Returns No restocking fee for 90 days

Product Highlights

Fuel Type icon
Propane, Natural Gas
Vent Type icon
Direct Vent
Warranty icon
5 Year (Parts, Labor)/ Lifetime (Heat Exchanger) Warranty
System Type icon
Hydronic (Water)
BTU Input icon
131900 BTUs
Depth (Inches) icon
21.9" Depth


Note: Product Title reflects this boiler's IBR Net Output Rating.

The Bosch Greenstar Gas-Fired Floor-Standing (FS) 131 Condensing Boiler provides Space Heating with up to 97.5% efficiency and 36 to 131.9 MBH inputs! The new Bosch Greenstar Floor-Standing (FS) condensing boiler line is engineered to offer the ideal solution for residential heating and hot water needs at an affordable price, without compromising quality or fuel economy. The 95% AFUE Greenstar FS Series is designed to upgrade cast iron floor boilers to a ultra-high efficient condensing boiler at lower installed cost by simplifying the installation.

The Greenstar FS Series Floor Standing Condensing Boilers fit in the same footprint as existing floor boilers, with no added cost to build a wall or move the boiler to an outside wall. The Low Loss Header is pre-piped under-the-hood with no need for primary/secondary piping and they pipe just like the existing boiler. The electrical connection boxes (both high & low voltage) are conveniently located on the back of the boiler for quick and easy connections. Venting options include 2 inch polypropylene (PP), flexible PP chimney liner, concentric PP kit, PVC or CPVC. These boilers come with simplified control and no programming is required (FW200 control sold separately).

Energy-saving & environmental features
  • Aluminum-Silicon heat exchanger delivers high efficiency - 95% with low temperature applications
  • Low NOx emissions ahead of 2012 SCAQMD regulations
  • Simple, intelligent control options optimize efficiency and fuel consumption
  • Low electrical consumption when the boiler is in standby mode
  • Electronic ignition
  • Anti-cycle and modulation control

End user comfort & convenience features
  • Limited lifetime heat exchanger and 5-year parts & labor warranty
  • This Greenstar Floor-Standing condensing space heating boiler can be used for either Natural Gas or Liquid Propane installations
  • Special insulation ensures ultra-quiet operation
  • Compact dimensions and built-in frost protection offer flexibility for location of installation
  • ECO mode for energy saving fuel consumption
  • Exclusive safety feature - keypad safety lock prevents unwanted tampering with the heating controls

Al-Si heat exchanger

Each unit features an ASME approved Al-Si heat exchanger constructed of advanced Magnesium-Aluminum-Silicon alloy - offering increased flexibility versus traditional stainless steel. They are equipped with highly durable heating blocks that are corrosion resistant and designed to optimize clean burning combustion over an extra large surface area, which requires minimal servicing and reliance on spare parts during the boiler’s lifetime.

Full modulating fan assembly

A full modulating fan automatically increases or decreases its speed according to the amount of gas coming into the boiler depending on the heat demand. This process, called modulation, prevents the boiler from either having too little or too much air in the unit for optimal combustion - ensuring high efficiency.


Fuel Type:


Natural Gas

Vent Type:

Direct Vent



BTU Input:


DOE Rating:


IBR Rating:




High Efficiency

Combo DHW

System Type:

Hydronic (Water)

Depth (Inches):


Width (Inches):


Height (Inches):


Weight (lbs):



5 Year (Parts, Labor)/ Lifetime (Heat Exchanger)

Energy Star Rated:


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