Bosch KWB42-3 Combi Water Boiler Greenstar (NG or LP)

The Bosch Greenstar KWB42‑3 combi water boiler is a premium floor‑standing condensing combination boiler engineered to deliver powerful hydronic heating and continuous domestic hot water from a single, high‑efficiency appliance. With 151,000 BTU of heating capacity, 95% AFUE, and a reliable 5:1 turndown ratio, this Greenstar NG or LP combi water boiler is ideal for homeowners seeking Bosch’s renowned performance in a traditional floor‑mount configuration. It operates on natural gas or propane, offering flexibility for a wide range of installations.

Key Features
High‑Efficiency Condensing Technology
95% AFUE for excellent energy savings

Proven aluminum‑silicon heat exchanger for long‑term durability

Low NOx emissions for cleaner, environmentally responsible operation

Combi System: Heat + Hot Water
Provides hydronic space heating and on‑demand domestic hot water

Eliminates the need for a separate water heater

Ideal for homes with moderate to high hot‑water demand

151,000 BTU Heating Output
Strong, reliable heating performance for larger homes

Smooth, consistent operation even during colder weather

5:1 Turndown Ratio
Efficient burner modulation for precise temperature control

Reduces cycling and improves overall system efficiency

Fuel Flexibility
Operates on natural gas or propane

Suitable for both urban and rural installations

Floor‑Standing Design
Stable, durable cabinet ideal for basements and mechanical rooms

Excellent replacement option for older floor‑mount boilers

Bosch Standard Controls
Simple, intuitive interface

Built‑in diagnostics streamline service and maintenance

Compatible with Bosch smart controls and outdoor reset options

Dimensions

Height: 41.0 in

Width: 17.3 in

Depth: 23.0 in

Ideal For
Homes needing both hydronic heat and domestic hot water

High‑efficiency natural gas or propane installations

Replacement of older floor‑standing boilers

Mechanical rooms where wall‑mounting isn’t practical