Bosch Greenstar® Boilers

Gas Condensing Boilers: Waste Not Want Not

Boilers are a pretty straightforward means of providing hot water and space heating. The heat generated from burning fuel is transfered to water being pumped through the system via a heat exchanger. In a typical boiler excess hot gas is exhausted from the flue. This means a significant portion of the heat generated from fuel burning is wasted, in some cases, up to 30%. A gas condensing boiler on the other hand is able to utilize the remaining gas to pre-heat cold water as it flows into the system. High temperature exhaust gas is redirected to a second heat exchanger located near the cold water entry point of the system. Water vapor in the exhaust then condenses, releasing heat which increases the temperature of the water before it passes through the main heat exhanger. This ingenious design ensures that you get all of the energy content of the fuel you paid for.

From left to right: A standard boiler and a gas condensing boiler.

Heat and Hot Water in One Package

Bosch Greenstar Boilers come in both heat-only and combi options. A "combi" or combination boiler provides both space heating and hot water. Because the boiler is able to heat water on demand, this elimnates the need for a hot water storage tank. Under this configuration the water travels through the highly presurized mains, guaranteeing robust flow from your faucets and showerheads. Combining hot water delivery and heating in one system can save you space and installation costs.

 Reaping the Benefits of Greenstar Efficiency

Annual Fuel Utilization Efficiency or AFUE for short is the ratio of heat output to the total fuel consumed. Bosch Greenstar Boilers have an AFUE of 95%. In other words, 95% of the fuel burned is turned into useful heat. Replacing a 56% efiicient system with a Bosch Greenstar in an average cold climate home could drastically reduce your heating bills and your carbon emissions by up 1.5 tons. This high efficiency rating may also mean that you are elligible for a federal tax credit, reducing your installed costs and further increasing your potential return on investment.

Quality Design and Components

(Component descriptions courtesy of Bosch's brochure)

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. This highly durable heating block is
corrosion resistant and designed to optimize clean burning combustion over
an extra large surface area. The heat exchanger has a coating that prevents
scale build-up, reduces service, maintains high efficiency and extends the
life of the boiler."


Plated Stainless Steel Heat Exchanger

"All Greenstar Combi boilers are equipped with a high-strength stainless
steel flat plate heat exchanger with double passage ensuring consistent
DHW temperature output based on demand. This heat exchanger, with its
large surface area and advanced technology, allows the boiler to use a lower
water temperature and to condense even while producing DHW for greater
efficiency and helps reduce the build-up of scale within the heat exchanger."

Full Modulating Fan Assembly

"A full modulating fan automatically increases or decreases its speed
depending on the heat demand controlling the amount of gas coming into
the boiler. 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."



Heatronic III Boiler Control

"Bosch Heatronic III, a device integrated into the boiler, provides instant
access to the hot water and heating control buttons. Furthermore it enables
the easy setting and testing of many customized appliance functions and
applications. The exclusive keypad safety lock feature prevents unwanted
tampering with the control."


FW200 Weather Compensation Boiler Control

"The FW200 digital thermostat and outdoor reset boiler control acts as the
nerve center of a home’s heating system. Programmable up to six switching
times throughout the day, this interface can be installed within the appliance
or be wall mounted in any location throughout the home. Providing instant
feedback to the end-user along with the built-in diagnostic effortlessly
pinpoints operational issues. The FW200 is included in the wall mounted
Greenstar, and is optional on the FS models."

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