High mass condensing technology

The benefits at a glance

  • Compact, floor-standing gas condensing boiler from 19-199 MBH.
  • High efficiency of 95% AFUE on all models.
  • High temperature operation of up to 90°C (194°F).
  • Vitocrossal Pocket Design with wide water passage ways allow for system/full flow applications. No dedicated boiler pump required and eliminates primary/secondary piping.
  • MatriX dome gas burner with 5:1 turndown ratio to ensure high efficiency and extremely clean combustion.
  • High water volume extends burner run time and reduces cycling.
  • A self-calibrating Lambda Pro combustion management system ensures optimal combustion efficiency at all times regardless of gas/air quality. Simple commissioning with no field adjustments and adjusts to all fuel types (NG and LPG).
  • Durable, reliable, and long service life with Inox-Crossal stainless steel heat exchanger and high mass design.
  • Multiple venting options and configurations with vent lengths up to 198 ft.
  • Multi-boiler installation with 8 boilers up to 1592 MBH.


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.


Advanced condensing technology

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.

Where can I buy a Vitocrossal 300?


To get a quote for a new Vitocrossal 300 CU3A boiler including system installation, please contact a licensed professional heating contractor near you. You can find a contractor in your area using our Contractor Locator.


Viessmann products are available from Viessmann authorized stocking wholesalers across Canada. If you need help finding a local wholesaler, please contact a Viessmann Sales Representative via our Sales Network.

Product details


Rated input
19 to 199 MBH - 5.6 to 58 kW
Efficiency (AFUE)
Natural gas, propane gas
Application range
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For residential homes, apartment buildings and commercial applications, new buildings and retrofits
DHW heating
Additional DHW tank(s) required, for a high level of DHW convenience
Limited lifetime warranty in residential applications
Additional features
Multi-boiler installation up to 1592 MBH (464 kW) with up to 8 boilers.



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A perfect match – System technology

"The whole is greater than the sum of its parts." According to this philosophy, Viessmann does not just make individual heating equipment components that meet the high Viessmann standards for quality, reliability and effectiveness. Rather, all products are part of a matching concept, where all components complement one another. Only the perfect interaction of system integrated components draws out the maximum potential of our innovative leading technology.

Viessmann system technology includes everything you need for a reliable and economical heating system. The Vitotronic control unit with remote control, the powerful Vitocell DHW tanks for best DHW convenience, to high-quality solar thermal systems for cost-saving heating.

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