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Comparison
Verdict in brief
The CM2-246 and CM2-311 are the two largest models of the small Vitocrossal 200 CM2 chassis and share every efficiency figure: 95% combustion efficiency, 5:1 turndown. The 311 fires from 222 to 1112 MBH against the 246's 175 to 878 MBH and weighs 792 lb against 759 lb — the last CM2 size before the line steps to the much heavier large chassis.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Viessmann Vitocrossal 200 CM2-246 | Viessmann Vitocrossal 200 CM2-311 |
|---|---|---|
| Input, minimum (natural gas) | 175 MBH | 222 MBH |
| Input, maximum (natural gas) | 878 MBH | 1,112 MBH |
| Combustion efficiency | 95 % | 95 % |
| Turndown ratio | 5:1 | 5:1 |
| Weight | 759 lb | 792 lb |
Both boilers sit on the small CM2 chassis documented by service manual doc 5584 109 - 16 (CM2-186/246/311), with the same 95% combustion-efficiency row and 5:1 turndown. The differences sit in the firing range and the 33 lb weight step — 759 lb (344 kg) on the 246, 792 lb (359 kg) on the 311.
The 311's natural-gas range of 222,000 to 1,112,000 BTU (65 to 326 kW) crosses the one-million-BTU mark while the 246 tops out at 878,000 BTU (257 kW); the minimum fire rises in step from 175,000 to 222,000 BTU (51 to 65 kW). In part-load conditions the 246 therefore idles lower.
Both share the Inox-Crossal heat exchanger, pre-mix cylinder burner, natural-gas or propane operation with simple electronic conversion and the Vitotronic 300 GW6B control with cascade control of up to eight boilers. The 311 is the stepping point before the CM2-400's jump to the 1495 lb large chassis, so plants that may grow should weigh that jump against the 311's ceiling.
Viessmann
The Vitocrossal 200 CM2-246 is the mid-size model of the small CM2 (GW6B) chassis: 175 to 878 MBH natural-gas input (51 to 257 kW) at 95% combustion efficiency and 5:1 turndown, weighing 759 lb (344 kg).
Viessmann
The Vitocrossal 200 CM2-311 is the largest model of the small CM2 (GW6B) chassis: 222 to 1112 MBH natural-gas input (65 to 326 kW) at 95% combustion efficiency, 5:1 turndown, in a 792 lb (359 kg) unit.
The 246 fires 175 to 878 MBH and the 311 fires 222 to 1112 MBH of natural-gas input, per Viessmann Canada.
Close, but not identical: the 311 weighs 792 lb (359 kg) against the 246's 759 lb (344 kg), within the same small chassis footprint.
When the load exceeds the 311's 1112 MBH ceiling. The CM2-400 moves to the 1495 lb large chassis with its own manual (doc 5546 489 - 15) and a 95.1% efficiency row.
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.