Vitocrossal 300 CU3A

Exceptional performance and flexibility

Vitocrossal 300 CU3A

Advanced condensing technology

Vitocrossal 300 CU3A is a gas-fired floor-standing boiler with stainless steel Inox-Crossal heat exchanger and MatriX dome gas burner. Rated input: 19 to 199 MBH.

Wide water passageways for full flow
Self-calibrating combustion system
Multi-boiler installation up to 1592 MBH
No dedicated boiler pump required

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Outstanding efficiency

95% AFUE rating on all models.

High temperature capability

Operating temperature up to 194°F (90°C).

High performance

High water volume extends burner run time and reduces short cycling.

Extremely clean combustion

And 5:1 turndown ratio with MatriX dome gas burner.

Durable and long service life

With Inox-Crossal stainless steel heat exchanger and high mass design.

Venting flexibility

Multiple venting options and configurations with vent lengths up to 198 ft.

The right choice for new construction or retrofits

With its combination of high temperature capability, high mass (water volume), floor standing design, condensing stainless steel construction and modulating gas burner, the Vitocrossal 300, CU3A is the ideal choice for boiler retrofits or new construction. From homes equipped with high mass cast iron radiators, to homes with multi-zone high temperature fin tube radiators, and new installations with high DHW requirements – the Vitocrossal 300, CU3A is the best choice on the market today.

Intelligent combustion control

The proven MatriX dome gas burner with Lambda Pro combustion control automatically adjusts to fluctuating gas qualities and ensures a consistently high combustion efficiency for both natural gas and propane gas.


Stainless steel MatriX dome burner

Exceptional performance and reliability

The vertical stainless steel Inox-Crossal heat exchanger offers ideal conditions for intensive utilization of hot gases, resulting in efficiencies of up to 98%. The smooth stainless steel surfaces allow the condensate created by the condensing process to simply run off downwards. This creates a permanent self-cleaning effect, ensuring high efficiency, long service life and reduced maintenance.

Lifetime warranty

With a limited lifetime warranty in residential applications, you can be sure your investment will deliver long-lasting value year after year. For detailed terms and conditions, see the warranty sheet.


Stainless steel Inox-Crossal heat exchanger

Advantages of the Vitocrossal 300 CU3A

Best value in its class with industry-leading technology and the most standard features.
Compact, floor-standing boiler with zero clearance to combustibles.
Self-calibrating Lambda Pro combustion management system ensures optimal combustion efficiency at all times regardless of gas/air quality.
Low-emission combustion for environmentally-friendly operation.
Zone circuit capabilities provide 3 input connections that allow easy integration of third party components.
Extremely quiet operation; quieter than most refrigerators.
User-friendly Vitotronic outdoor reset boiler and system control for multi-temperature space and DHW heating.
High-altitude operation up to 10,000 ft (3,000 m).

Look inside the boiler

  1. Vitotronic 200 control with graphical user interface.
  2. Water-cooled combustion chamber.
  3. Modulating MatriX dome gas burner.
  4. Inox-Crossal heat exchanger.
  5. Highly effective thermal insulation.
  6. Flue gas collector with condensate drain pipe.
  7. Combustion air inlet connection.

Product details

Fuel type

Natural gas (NG) or liquid propane gas (LPG)

Min. input

19,000 BTU (5.6 kW) for  CU3A-94
25,000 BTU (7.3 kW) for  CU3A-125
43,000 BTU (12.6 kW) for  CU3A-160 &  CU3A-199

Max. input

94,000 BTU (27.5 kW) for  CU3A-94
125,000 BTU (36.6 kW) for  CU3A-125
160,000 BTU (47 kW) for  CU3A-160
199,000 BTU (58 kW) for  CU3A-199

Efficiency (AFUE)

95% for all models


269 lbs (122 kg) for  CU3A-94
275 lbs (125 kg)  for  CU3A-125
352 lbs (160 kg) for  CU3A-160 &  CU3A-199

Overall dimensions


27 inches (684 mm)  for  CU3A-94 &  CU3A-125
31½ inches (801 mm)  for  CU3A-160 &  CU3A-199


26 inches (660 mm) for all models


61½ inches (1562 mm) for all models, with  control interface closed
67 inches (1707 mm) for all models, with  control interface open


Limited lifetime warranty in residential applications. See warranty sheet for details.

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