Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The CT3-17 and CT3-22 are the two smallest Vitocrossal 300 CT3 boilers and share the 684 mm shell and 8 in. vent pipe. The CT3-22 fires to 846 MBH against the CT3-17's 638 MBH, weighs 102 lb more as a shell, and prints slightly lower efficiency rows — 97.8% combustion / 97.7% thermal against 98.3% / 98.1%.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Viessmann Vitocrossal 300 CT3-17 | Viessmann Vitocrossal 300 CT3-22 |
|---|---|---|
| Input | 638 MBH | 846 MBH |
| Output | 626 MBH | 827 MBH |
| Combustion efficiency | 98.3 % | 97.8 % |
| Thermal efficiency | 98.1 % | 97.7 % |
| Weight, boiler shell | 1,012 lb | 1,114 lb |
| Overall weight (with insulation and control, less burner) | 1,228 lb | 1,352 lb |
| Boiler water content | 71.3 USG | 78.2 USG |
| Maximum operating pressure | 30 psig | 30 psig |
Both models are gas-fired floor-standing condensing boilers on the CT3 small chassis — 684 mm shell width, 8 in. (201 mm) internal vent pipe and a 30 psig maximum operating pressure at up to 210°F supply temperature. The CT3-17 prints 638 MBH (187 kW) input / 626 MBH (183 kW) output; the CT3-22 prints 846 MBH (248 kW) / 827 MBH (242 kW).
Efficiency rows ease as size grows: 98.3% combustion and 98.1% thermal on the CT3-17, against 97.8% and 97.7% on the CT3-22. The CT3-17 holds 71.3 USG (270 L) of boiler water and weighs 1,012 lb (459 kg) as a shell; the CT3-22 holds 78.2 USG (296 L) at 1,114 lb (505 kg).
Complete with insulation and control but less burner, weights are 1,228 and 1,352 lb (557 and 613 kg), and the shipping envelope grows from 1,516 to 1,594 mm long while width and height stay 684 mm and about 1,773-1,808 mm.
Viessmann
The Vitocrossal 300 CT3-17 is the smallest CT3 commercial condensing boiler: 638 MBH input (187 kW), 626 MBH output, 98.3% combustion and 98.1% thermal efficiency at 30 psig.
Viessmann
The Vitocrossal 300 CT3-22 steps the CT3 range to 846 MBH input (248 kW) with 827 MBH output at 97.8% combustion and 97.7% thermal efficiency.
They share the 684 mm shell width and 8 in. vent pipe; the CT3-22 is longer as shipped (1,594 vs 1,516 mm) and heavier (1,114 vs 1,012 lb as a shell).
The CT3-17 — 98.3% combustion and 98.1% thermal efficiency, the highest figures in the CT3 range, against 97.8% and 97.7% on the CT3-22.
638 MBH (187 kW) input on the CT3-17 and 846 MBH (248 kW) on the CT3-22, with outputs of 626 and 827 MBH.
A consultation includes a heat-loss review so the size is right the first time.
On-site service in Greater Vancouver, BC. ROMA lists “Open 7 days” on its site; call to confirm same-day availability.
Sources and verification
Facts checked September 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.