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“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” upgrade for detached & terraced houses and is also suitable for apartments.

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
  • 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
  • Eligible for Tax Credit where offered

Design Features

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.

Plated stainless steel heat exchanger

All Greenstar Combi boilers are equipped with a high-strength stainless steel secondary exchanger and burner with double passage – ensuring consistent temperature output based on demand. The DHW hot water temperature control limit of 140°F helps prevent scale build-up within the heat exchanger.

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.

Product Specifications

Gas-Fired Wall Mounted Combi Condensing Boiler Greenstar Combi 100
Model Number ZWB 28-3
Input [MBH] 100
Heating Capacity [MBH] 89.4
AFUE [%] 95.0
Net Rating Water [MBH] 79
DHW Flow Max (ΔT at 72°). GPM 2.65
Tax Credit yes


Gas-Fired Wall Mounted Combi Condensing Boiler Greenstar Combi 131
Model Number ZWB 35-3
Input [MBH] 132
Heating Capacity [MBH] 118
AFUE [%] 95.0
Net Rating Water [MBH] 103
DHW Flow Max (ΔT at 72°). GPM 3.2
Tax Credit yes


Gas-Fired Wall Mounted Combi Condensing Boiler Greenstar Combi 151
Model Number ZWB 42-3
Input [MBH] 152
Heating Capacity [MBH] 135
AFUE [%] 95.0
Net Rating Water [MBH] 117
DHW Flow Max (ΔT at 72°). GPM 4.0
Tax Credit yes