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 discontinued GB312/200 and GB312/280 are the 8"-flue sizes with 1 1/4" NPT gas connections and 50 psi MAWP. The /200 uses 6 sections and fires 219,800 to 732,600 BTU/hr for 676 MBH gross IBR output at 92.3% thermal efficiency; the /280 uses 8 sections and fires 308,600 to 1,028,800 BTU/hr for 944 MBH at 91.7%, the highest output in the line.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Buderus GB312/200 | Buderus GB312/280 |
|---|---|---|
| I-B-R input, maximum | 732.6 MBH | 1,028.8 MBH |
| I-B-R input, minimum | 219.8 MBH | 308.6 MBH |
| I-B-R gross output (180/80 °F) | 676 MBH | 944 MBH |
| I-B-R net rating (180/80 °F) | 588 MBH | 821 MBH |
| Thermal efficiency | 92.3 % | 91.7 % |
| Combustion efficiency | 92.5 % | 92 % |
| Heat-exchanger sections | 6 | 8 |
| Weight | 585 lb | 730 lb |
| Boiler water capacity | 6.3 US gal | 7.9 US gal |
| Gas connection | 1 1/4" NPT | 1 1/4" NPT |
| Vent connection | 8" | 8" |
Both sizes share the larger GB312 chassis: 8" flue connection, 1 1/4" NPT gas, 2 1/2" NPT supply/return, 3.94" combustion-air connection, 50 psi MAWP, 180 °F maximum supply and 200 °F high limit.
Ratings scale with sections: 6 sections on the /200 against 8 on the /280; gas input 219,800-732,600 against 308,600-1,028,800 BTU/hr; gross IBR output 676,000 against 944,000; net rating 588,000 against 821,000; boiler horsepower 20.2 against 28.2. Thermal efficiency is 92.3% against 91.7%, the lowest in the series.
Weights and water volumes rise from 585 lb / 6.3 gal on the /200 to 730 lb / 7.9 gal on the /280. Both are discontinued with installation/service, operating and applications manuals served from Bosch's US commercial-discontinued archive.
Bosch Thermotechnology
The Buderus GB312/200 is a discontinued commercial natural-gas condensing boiler with an aluminum heat exchanger, 6 sections, 732.6 MBH maximum input and 676 MBH gross IBR output at 92.3% thermal efficiency.
Bosch Thermotechnology
The Buderus GB312/280 is a discontinued commercial natural-gas condensing boiler with an aluminum heat exchanger, 8 sections, 1,028.8 MBH maximum input and 944 MBH gross IBR output at 91.7% thermal efficiency.
The GB312/280 with 8 heat-exchanger sections, 1,028,800 BTU/hr maximum gas input and 944,000 BTU/hr gross IBR output.
The brochure prints thermal efficiency tapering from 93.1% on the /90 to 91.7% on the /280, with combustion efficiency from 93.4% to 92.0%.
Both use 1 1/4" NPT gas connections, larger than the 1" on the /90, /120 and /160.
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.