Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The GS10-84 and GS10-96 are the two largest Vitogas 100 commercial boilers and top the range at 85.6% combustion efficiency. The GS10-96 adds a section and a burner tube, lifting full-load input from 340 to 380 MBH and total weight from 1,036 to 1,194 lb, with a 10 in. vent collar against 9 inches.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Viessmann Vitogas 100 GS10-84 | Viessmann Vitogas 100 GS10-96 |
|---|---|---|
| CSA input, full load | 340 MBH | 380 MBH |
| CSA input, partial load (70%) | 238 MBH | 266 MBH |
| CSA output, full load | 291 MBH | 325 MBH |
| Net I=B=R rating | 253 MBH | 283 MBH |
| Combustion efficiency | 85.6 % | 85.6 % |
| Cast iron sections | 8 | 9 |
| Overall weight (with insulation, burner, control, fittings and draft hood) | 1,036 lb | 1,194 lb |
| Boiler water content | 11.4 USG | 12.8 USG |
| Overall width | 1,120 mm | 1,220 mm |
| Vent pipe collar | 9 in | 10 in |
Both models are two-stage atmospheric cast-iron boilers with 85.6% combustion efficiency. The GS10-96 carries the range's ceiling at 380 MBH (111 kW) full-load input and 266 MBH at partial load, against the GS10-84's 340 MBH and 238 MBH; full-load outputs are 325 and 291 MBH with Net I=B=R ratings of 283 and 253 MBH.
The GS10-96 is the largest GS10 build: nine cast-iron sections and eight burner tubes against eight and seven, with a 1220 mm (48 in) overall width against 1120 mm (44 in). It also ships longer at 1057 mm against 1007 mm, while height stays 1088 mm.
Total weight rises from 1,036 to 1,194 lb (470 to 542 kg), water content from 11.4 to 12.8 USG, and the vent collar from 9 to 10 in. nominal with about 125 CFM of combustion and dilution air. Both keep the range's 60 psig maximum operating pressure.
Viessmann
The Vitogas 100 GS10-84 is the mid-size commercial GS10: 340 MBH full-load input (100 kW), 291 MBH output and 85.6% combustion efficiency with eight sections and seven burner tubes.
Viessmann
The Vitogas 100 GS10-96 is the largest commercial GS10 boiler: 380 MBH full-load input (111 kW), 325 MBH output and 85.6% combustion efficiency with nine sections.
The GS10-84 runs 340 MBH full load / 238 MBH partial and the GS10-96 runs 380 MBH / 266 MBH, both two-stage at 85.6% combustion efficiency.
1220 mm (48 in) against the GS10-84's 1120 mm (44 in), and it is 50 mm longer at 1057 mm.
The GS10-96, with a nominal 10 in. collar against the GS10-84's 9 in., per the technical data manual.
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.