Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The GS10-72 and GS10-84 are the two smaller Vitogas 100 commercial boilers, both two-stage cast-iron units at 85.6% combustion efficiency. The GS10-84 adds a section and a burner tube, raising full-load input from 300 to 340 MBH and total weight from 927 to 1,036 lb, with the vent collar growing from 8 to 9 inches.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Viessmann Vitogas 100 GS10-72 | Viessmann Vitogas 100 GS10-84 |
|---|---|---|
| CSA input, full load | 300 MBH | 340 MBH |
| CSA input, partial load (70%) | 210 MBH | 238 MBH |
| CSA output, full load | 257 MBH | 291 MBH |
| Net I=B=R rating | 224 MBH | 253 MBH |
| Combustion efficiency | 85.6 % | 85.6 % |
| Cast iron sections | 7 | 8 |
| Overall weight (with insulation, burner, control, fittings and draft hood) | 927 lb | 1,036 lb |
| Boiler water content | 9.9 USG | 11.4 USG |
| Overall width | 1,010 mm | 1,120 mm |
| Vent pipe collar | 8 in | 9 in |
Both models are two-stage atmospheric cast-iron boilers rated 85.6% combustion efficiency with partial-load values based on 70% of rated input. Full-load inputs print at 300 MBH (88 kW) for the GS10-72 and 340 MBH (100 kW) for the GS10-84, with full-load outputs of 257 and 291 MBH and Net I=B=R ratings of 224 and 253 MBH.
The GS10-84 adds a cast-iron section and a burner tube — eight sections and seven burners against seven and six — growing overall width from 1010 to 1120 mm at the same 1007 mm length and 1088 mm height. Total weight rises from 927 to 1,036 lb (420 to 470 kg) and water content from 9.9 to 11.4 USG.
The vent pipe collar grows from 8 to 9 in. nominal, with combustion and dilution air rising from about 100 to 115 CFM. Both run on natural gas or propane at 60 psig maximum operating pressure and share the same 1007 mm shipping length.
Viessmann
The Vitogas 100 GS10-72 is the smallest commercial GS10 boiler: 300 MBH full-load input (88 kW), 257 MBH output and 85.6% combustion efficiency, two-stage fired at 70% partial load.
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.
The GS10-72 runs 300 MBH full load / 210 MBH partial; the GS10-84 runs 340 MBH / 238 MBH. Both are two-stage with partial-load values at 70% of full-load input.
1,036 lb (470 kg) complete against 927 lb (420 kg) for the GS10-72; boiler shells weigh 805 vs 714 lb.
No — the GS10-72 uses a nominal 8 in. collar and the GS10-84 a 9 in. collar, 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.