Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The discontinued GB312/90 and GB312/160 are aluminum-heat-exchanger condensing boilers at 50 psi MAWP with 1" NPT gas and 2 1/2" NPT water connections. The /90 uses 4 sections, fires 132,200 to 328,300 BTU/hr and delivers 305 MBH gross IBR output at 93.1% thermal efficiency; the /160 adds a fifth section, fires 176,500 to 588,300 BTU/hr and delivers 544 MBH at 92.5%.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Buderus GB312/90 | Buderus GB312/160 |
|---|---|---|
| I-B-R input, maximum | 328.3 MBH | 588.3 MBH |
| I-B-R input, minimum | 132.2 MBH | 176.5 MBH |
| I-B-R gross output (180/80 °F) | 305 MBH | 544 MBH |
| I-B-R net rating (180/80 °F) | 265 MBH | 473 MBH |
| Thermal efficiency | 93.1 % | 92.5 % |
| Combustion efficiency | 93.4 % | 92.8 % |
| Heat-exchanger sections | 4 | 5 |
| Weight | 455 lb | 530 lb |
| Boiler water capacity | 4.2 US gal | 5.3 US gal |
| Gas connection | 1" NPT | 1" NPT |
| Vent connection | 6" | 6" |
The GB312/90 and /160 share the manual's gas condensing design and most connection data: 1" NPT gas, 2 1/2" NPT supply and return, 3.94" balanced-flue combustion-air connection, 50 psi MAWP, 180 °F maximum supply temperature and a 200 °F manual-reset high limit. Both use the same 6" flue connection and the same G1G 170 fan.
The capacity rows scale with sections: 4 sections on the /90 against 5 on the /160. Gas input is 132,200-328,300 BTU/hr against 176,500-588,300; I-B-R gross output 305,000 against 544,000 BTU/hr; net rating 265,000 against 473,000. Thermal efficiency eases from 93.1% to 92.5% and combustion efficiency from 93.4% to 92.8%.
Physical data: 455 lb and 4.2 gal boiler water on the /90; 530 lb and 5.3 gal on the /160. The /90's 33%-100% modulation (per the brochure) contrasts with the wider range of larger sizes. Both are discontinued with manuals in Bosch's US commercial-discontinued archive.
Bosch Thermotechnology
The Buderus GB312/90 is a discontinued commercial natural-gas condensing boiler with an aluminum heat exchanger, 4 sections, 328.3 MBH maximum input and 305 MBH gross IBR output at 93.1% thermal efficiency.
Bosch Thermotechnology
The Buderus GB312/160 is a discontinued commercial natural-gas condensing boiler with an aluminum heat exchanger, 5 sections, 588.3 MBH maximum input and 544 MBH gross IBR output at 92.5% thermal efficiency.
The series brochure prints 93.1% thermal / 93.4% combustion efficiency for the /90 and 92.5% / 92.8% for the /160.
Yes - both use a 6" flue connection (the /200, /240 and /280 move to 8").
No. The GB312 line is discontinued and documented in Bosch's US commercial-discontinued archive and the discontinued Buderus products library.
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.