Viessmann Vitocrossal 300, CU3A Boilers

Viessmann Vitocrossal 300, CU3A Boiler Overview

The Viessmann Vitocrossal 300, CU3A is a gas condensing, floor mounted boiler with an efficiency of 95% AFUE. The Vitocrossal 300, CU3A was named an Energy Star Most Efficient 2016 product. It is designed to be an easy replacement for older cast iron sectional boilers, with simple connections allowing existing piping to remain intact. Exhaust and intake air flue connections are located 11.5 inches off the ground for easy connection to existing chimneys. The unit features an Inox-Crossal stainless steel heat exchanger which is self-cleaning for reduced maintenance, and multiple venting options and configurations, with vent lengths of almost 200 feet. The Vitocrossal 300, CU3A is shipped for use with natural gas but is easily convertible to liquid propane.

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Consumer Reviews of Viessmann Vitocrossal 300, CU3A


  • Very Satisfied
  • Somewhat Satisfied
  • Neutral
  • Somewhat Unsatisfied
  • Very Unsatisfied
  • #1 of 6 Viessmann Boiler
  • 50% of customers recommended

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Viessmann Vitocrossal 300, CU3A Boiler Reviews

"Not reliable for North East"

1.0 rating
Very Unsatisfied

We had a Viessmann Vitocrossell cu3a 300. 35 installed in our central Massachusetts home to replace a 70 year old cast iron bolier on December 15, 2016. We have encountered multiple instances where the boiler burner would not ignite when temperatures dropped. The latest incident was yesterday when we arrived home after a 3 day absence to find an inside temperature of 39f degrees. After going through a reset procedure, and getting the boiler to start again, the overflow valve discharged 5+ gallons of water all over the basement floor. Further, our natural gas consumption as reflected in billing year over year has not decreased appreciably. We have not received satisfactory support from the plumbing contractor that installed the equipment or the manufacturer to resolve the issues we have had with reliable, available performance from this boiler. Our plumbing contractor sold on Visemann as a premium brand that would be worth the extra cost. Our experience has been otherwise – completely unsatisfactory. I would highly recommend choosing another brand for boiler replacement in the Northeast where consistent, reliable performance is a minimum requirement.

T.R. Koehler

Westborough, MA

"Excellent boiler"

5.0 rating
Very Satisfied

Installed in Spring 2016. Installed with indirect hot water tank. This boiler is amazing. Very low chance of short cycle that occur with wall hung units. Check out the Viessmann Academy Webinars for details. I would highly recommend.

R Smochek

Punxsutawney, PA

Other Vitocrossal 300, CU3A Reviews

Among the few online comments regarding the Vitocrossal 300, CU3A is one from a homeowner on who was not happy with his Vitocrossal 300, CU3A. He was told by several members on the site that it is a top notch boiler and the problem was with the installation.

Vitocrossal 300, CU3A Warranty

The warranty for the Viessman Vitocrossal 300, CU3A boiler is comprised of the following:

  • 2-year warranty on the enclosure, combustion chamber, burner, controls and other parts
  • Limited lifetime warranty on the pressure vessel of the boiler. The warranty is prorated after the tenth year

The warranty covers only the original owner at the original site of installation. Labor costs are not included in the warranty.

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