Right-Size Your Heat With Viessmann CU3A-160 Vitocrossal 300 160 MBH Floor-Standing Condensing Boiler

Need steady, high-temperature comfort without the fuel waste? The Vitocrossal 300 CU3A-160 is a floor-standing gas-fired condensing boiler that combines a high-mass stainless Inox-Crossal heat exchanger with a modulating MatriX dome burner for quiet, even heat and 95% AFUE—ideal for cast-iron radiator retrofits and multi-zone fin-tube systems.

• Brand: Viessmann
• MPN: CU3A-160
• Type: Floor-Standing Gas-Fired Condensing (Heat-Only) Hydronic Boiler
• Size/Capacity: 43–160 MBH input; Net AHRI 129 MBH; 95% AFUE
• Material/Finish: Stainless-steel Inox-Crossal heat exchanger; MatriX modulating dome burner
• Performance: Sound 53 dB (max) / 33 dB (min); condensate up to ~1.6 USG/h; boiler water content 18.8 USG; altitude operation to 10,000 ft (de-rate applies)
• Connections/Fit: Heating supply/return 1¼" NPTM; PRV ¾" NPTF; boiler drain 1" NPTM; gas ¾" NPTF; direct-vent; 4" flue / 3" combustion air; allowable vent lengths up to ~198 ft (layout-dependent)
• Dimensions: 61.5"–67" H × 26" W × 31.5" D
• Included: Vitotronic 200 outdoor-reset control with outdoor sensor; installation fittings with 30 psig PRV; T&P gauge (field-installed on supply); pre-wired and internally piped; NG factory-set with LP conversion labels in literature set
• Certifications: ENERGY STAR (95% AFUE); ANSI Z21.13/CSA 4.9; ASME Section IV / CSA B51; zero-clearance to combustibles when installed per instructions
• Warranty: Limited lifetime heat-exchanger warranty (residential); parts coverage up to 5 years with registration—see Viessmann warranty

Save Fuel With High Efficiency

At 95% AFUE—and up to 98% efficiency at low return temps—the CU3A-160 squeezes more heat out of every therm, reducing monthly fuel spend while keeping comfort high.

Everyday Performance You Can Feel

A 43–160 MBH input range and high-mass water volume minimize short-cycling, delivering smooth, quiet heat across changing loads—great for older radiators and mixed high-temp zones.

Built To Last

The Inox-Crossal stainless heat exchanger and MatriX burner are engineered for clean combustion and self-shedding condensate, helping maintain efficiency and resist corrosion over years of service.

Installer-Friendly Flexibility

Choose coaxial or two-pipe direct venting with long allowable runs (up to ~198 ft, layout-dependent). Standard 1¼" supply/return and ¾" gas connections simplify piping and commissioning.

Smart Controls & Compatibility

On-board Vitotronic outdoor-reset control supports multi-circuit designs and easy setup, so systems start quickly and run efficiently in day-to-day operation.

Fits Your Space

Compact footprint and a listing for zero-clearance to combustibles enable closet or alcove installs while keeping full front/rear service access.

Weight	352.0 lb
Collection	Vitocrossal 300
Height	67.00 in.
Horse Power	1/3
Length	31.50 in.
Width	26.00 in.
Inventory Number	VIESCU3A160
MPN	CU3A-160