Model Numbers Pertaining to the Bosch Greenstar Combi and Straight Boilers

Below is a table describing the model numbers that pertain to the Bosch Greenstar gas-fired wall-hung boilers and combination boilers.

Z - Central heating appliance
W - DHW heating
B - Condensing technology
R - Constant temperature control
16 - Output up to 54,600 BTU/hr (16 kW)
21 - Output and DHW output up to 71,600 BTU/hr (21 kW)
28 - Output and DHW output up to 95,500 BTU/hr (28 kW)
35 - Output and DHW output up to 119,400 BTU/hr (35 kW)
42 - Output and DHW output up to 143,300 BTU/hr (42 kW)
-3 - Version
A - Fan-supported appliance
23 - Natural gas (NG) conversion to Liquid Propane (LP) comes with boiler

So if you wanted to reference model number "ZWB42-3" this would be the model number for the Bosch Combi 151 Gas-Fired Wall-Hung Boiler for space heating and domestic hot water (DHW).
Z - Central heating appliance
W - DHW heating
B - Condensing technology
42 - Output and DHW output up to 143,300 BTU/hr (42 kW)
-3 - Version

All Greenstar boilers and Combi units are fan assisted "A" and they all come preset for Natural Gas NG "23" but also come with the conversion kit for Liquid Propane LP.

Conversion:
Model #               Description
ZBR16-3             Bosch Greenstar Wall-Hung 57 Boiler
ZBR21-3             Bosch Greenstar Wall-Hung 79 Boiler
ZBR28-3             Bosch Greenstar Wall-Hung 100 Boiler
ZBR35-3             Bosch Greenstar Wall-Hung 131 Boiler
ZBR42-3             Bosch Greenstar Wall-Hung 151 Boiler
ZWB28-3            Bosch Greenstar Wall-Hung Combi 100 Boiler
ZWB35-3            Bosch Greenstar Wall-Hung Combi 131 Boiler
ZWB42-3            Bosch Greenstar Wall-Hung Combi 151 Boiler

Greenstar Combi 100 & 151 Gas Fired Condensing Boilers

The New Bosch Greenstar Combi 100 (100K BTU) & Bosch Greenstar Combi 151 (151K BTU) Gas Fired Condensing Boilers are new to the American market but have been in use for years in Europe.  The combi 100 is 98.5% efficient as the combi 151 is 96.5% efficient.  The new Bosch Greenstar 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.

"Combi" (combination) unit with space heating and integrated water heating in one highly efficient, compact unit. With special insulation to ensure ultra quiet operation and the exclusive keypad safety lock feature to prevent unwanted tampering with heating controls, this unit is the ideal "green" unit.

Limited lifetime heat exchanger and 5-year parts & labor warranty

All models available as NG or LP

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 heating controls.

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.  The Greenstar units come set for Natural Gas (NG) and there is a conversion kit that is included with the unit if it has to be converted to Liquid Propane (LP).

The Greenstar Combi units are designed for heating such as radiant floor heat or baseboard heating with multiple zones depending on the size of the unit and also for domestic hot water (DHW).  

The combi 100 unit besides being used for heating applications is also designed for DHW for 1 major application at a time - 72 degree rise at 2.4 gpm while the combi 151 could possibly do 2 applications at a time and will deliver - 72 degree rise at 4 gpm.

Depending on the size of your home and the heating and DHW applications you are looking for, you would need to get an HVAC or gas technician to size the unit properly as they would have to factor in,  size of home, insulation "R" factor, windows, etc..

Gas Conversion of Pro Gas Tankless Water Heaters

Some of the Bosch Professional gas tankless water heaters can be converted from one gas type to the next, i.e. from Natural Gas (NG) - Liquid Propane (LPG) and also from LPG - NG.  The Gas Conversion Kit, part #8719002176 includes a jumper for placement on the control board, a set of instructions for calibrating the gas and air mix and also some stickers to be placed on the heater stating it has been converted. 

The tools required for the gas conversion are:

• Flat and Phillips Screwdrivers
• #40 torx driver
• Digital CO2 Gas Combustion Analyzer
• This procedure must be performed by a licensed gas technician

The Bosch Professional Non-condensing heaters such as the 940ES/940ESO/830ES/715ES/635ES and the Evolution 500 CAN be converted using the gas conversion kit.

All of the Bosch Therm condensing heaters such as the C1210ESC/C1210ES/C1050ES/C950ES/C800ES and Integra 500 CANNOT be converted as the units have a special plate built into the burner tray.  This extra plate in the burner tray was designed and instlled to give the heater the ability to be installed at higher elevations up to 8000'.

Also the Bosch Therm 660EF/660EFO/520PN/520HN/425HN/425EF/330PN CANNOT be converted as they are not designed at all for gas conversion.