Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
Boilers.ca is a brand of ROMA Heating & Cooling · Licensed gas contractor LGA0202903
Comparison
Verdict in brief
The CM2-186 and CM2-246 are the two smallest Vitocrossal 200 CM2 models and share the small chassis' character: both print 95% combustion efficiency and a 5:1 turndown. The 246 fires higher at both ends — 175 to 878 MBH against the 186's 131 to 663 MBH — and weighs 759 lb against 726 lb, all within the same 186–311 size range documented by one service manual.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Viessmann Vitocrossal 200 CM2-186 | Viessmann Vitocrossal 200 CM2-246 |
|---|---|---|
| Input, minimum (natural gas) | 131 MBH | 175 MBH |
| Input, maximum (natural gas) | 663 MBH | 878 MBH |
| Combustion efficiency | 95 % | 95 % |
| Turndown ratio | 5:1 | 5:1 |
| Weight | 726 lb | 759 lb |
Both models open the Vitocrossal 200 CM2 range on the GW6B control platform with the Inox-Crossal stainless steel heat exchanger and pre-mix cylinder burner. The printed efficiency and turndown are identical — 95% combustion efficiency and 5:1 — so the comparison is capacity and its cost in minimum fire.
The 246 fires from a 175,000 BTU (51 kW) minimum up to 878,000 BTU (257 kW) maximum against the 186's 131,000 to 663,000 BTU (38.5 to 194 kW). Both the floor and the ceiling rise, so a low-load plant sees the 186 track part-load demand more closely while the 246 carries roughly 215 MBH more ceiling.
Weight steps from 726 lb (329 kg) on the 186 to 759 lb (344 kg) on the 246 — a 33 lb difference within the same chassis and the same service manual (doc 5584 109 - 16, covering the CM2-186/246/311). Both run on natural gas or propane with simple electronic conversion, and the choice follows the calculated plant load between the two firing ranges.
Viessmann
The Vitocrossal 200 CM2-186 is the smallest model of the CM2 (GW6B) line: 131 to 663 MBH natural-gas input (38.5 to 194 kW) at 95% combustion efficiency, 5:1 turndown, in a 726 lb (329 kg) floor-standing unit.
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).
They share the small CM2 chassis documented by one manual, but the printed weights differ: 726 lb (329 kg) for the 186 and 759 lb (344 kg) for the 246.
Neither — both print 95% combustion efficiency with a 5:1 turndown, the figures shared by all three small CM2 models.
When the design load needs more than the 186's 663 MBH ceiling. The 246's minimum fire is 44 MBH higher, so loads that fit the 186 idle closer to the bottom of its range.
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.