Viessmann CU3A-125 Vitocrossal 300 CU3A 125,000 BTU Gas Condensing Boiler
- SKU #: VIESCU3A125
- MPN #: CU3A-125
MSRP:
$8,544.00
$6,798.83
In Stock
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Elevate Your Heat With Viessmann CU3A-125 Vitocrossal 300 125 MBH Floor-Standing Condensing Boiler
Looking for high-output comfort with lower fuel bills and fewer callbacks? The Vitocrossal 300 CU3A-125 is a floor-standing gas-fired condensing boiler that pairs Viessmann’s stainless Inox-Crossal heat exchanger with a self-calibrating MatriX dome burner for quiet, steady heat and 95% AFUE performance—ideal for radiator retrofits or multi-zone fin-tube systems.
- Brand: Viessmann
- MPN: CU3A-125
- Type: Floor-Standing Gas-Fired Condensing (Heat-Only) Hydronic Boiler
- Size/Capacity: 25–125 MBH input; Net AHRI 101 MBH; 95% AFUE
- Material/Finish: Stainless-steel Inox-Crossal heat exchanger; MatriX dome modulating burner
- Performance: High-mass design with ~13.0 USG water content; sound rating ~55 dB max / 33 dB min; condensate up to ~1.2 USG/h
- Connections/Fit: 1¼" NPTM heating supply & return; ¾" NPTF gas; ¾" NPTF PRV; 3" (80 mm) flue & 3" combustion air; ¾" hose condensate
- Dimensions: 61.5" H (closed) / 67" H (open) × 26" W × 27" D
- Included: Vitotronic outdoor-reset control with outdoor sensor; 30 psig PRV & fittings; T&P gauge (field-installed on supply); factory pre-wired/piped internals; NG factory-set with LP conversion labels in literature set
- Certifications: ENERGY STAR; ANSI Z21.13/CSA 4.9; ASME Section IV / CSA B51 construction
- Warranty: Limited lifetime heat-exchanger warranty (residential)—see Viessmann warranty sheet
Save Fuel With High Efficiency
At 95% AFUE and up to 98% efficient under low-return temps, the CU3A condenses deeply to turn more of every therm into usable heat—cutting operating costs season after season.
Everyday Performance You Can Feel
A 25–125 MBH modulating input and high-mass water volume smooth out cycling and deliver quiet, even heat across changing loads—perfect for cast-iron radiators or mixed high-temp zones.
Built To Last
The Inox-Crossal stainless heat exchanger is constructed to ASME Section IV/CSA B51 and designed for a self-cleaning condensate “sheen,” helping maintain efficiency and resist corrosion over time.
Installer-Friendly Flexibility
Direct-vent coaxial or two-pipe options with long allowable runs (layout-dependent, up to ~198 ft per Viessmann guidelines) make venting straightforward. Standard 1¼" supply/return and ¾" gas keep piping simple.
Smart Controls & Compatibility
The integrated Vitotronic control with outdoor reset, zone-circuit capability, and start-up wizard speeds commissioning. High-altitude operation is supported up to 10,000 ft (electronic adjustment; de-rate applies).
Fits Your Space
A compact footprint (26" × 27") and zero-clearance to combustibles rating allow closet or alcove installs while keeping full front/rear service access.