Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The ALTA-120B and ALTA-150 are both 95.0% AFUE heating-only Alta boilers. The 150 steps input from 13.6–120 to 20–150 MBH (heating capacity 112 to 141 MBH, net AHRI 97 to 123 MBH) and moves from the compact 16.3 in to the 20.4 in-deep chassis at 103 lb — 27 lb heavier.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Burnham Alta ALTA-120B | Burnham Alta ALTA-150 |
|---|---|---|
| Heating input, minimum | 13.6 MBH | 20 MBH |
| Heating input, maximum | 120 MBH | 150 MBH |
| Heating capacity | 112 MBH | 141 MBH |
| Net AHRI water rating | 97 MBH | 123 MBH |
| Efficiency (AFUE) | 95 % | 95 % |
| Vent size | 2 in | 2 in |
| Boiler weight | 76 lb | 103 lb |
| Boiler depth | 16.3 in | 20.4 in |
Both are heating-only condensing Alta boilers at 95.0% AFUE on the OneTouch platform with the 316L stainless steel heat exchanger, 2" universal venting and 1/2" NPT gas connections.
The ALTA-150 raises the maximum heating input from 120 to 150 MBH (minimum 13.6 to 20 MBH), and the PDS ratings table prints 141 MBH heating capacity and a 123 MBH net AHRI rating against the 120B's 112 and 97 MBH.
The physical step is the chassis: the 120B is 16.3 in deep at 76 lb, while the 150 sits in the 20.4 in-deep chassis at 103 lb (shared with the ALTA-180 and ALTAC-200). Venting, relief-valve package (30 psi on 50 psi MAWP) and the Grundfos 26-99 circulator are unchanged.
Burnham
The Burnham Alta ALTA-120B fires 13.6 to 120 MBH heating input at 95.0% AFUE — 112 MBH heating capacity and a 97 MBH net AHRI water rating — in the compact 16.3 in-deep heating-only Alta chassis.
Burnham
The Burnham Alta ALTA-150 covers the mid-range of the heating-only Alta line: 20 to 150 MBH input at 95.0% AFUE with 141 MBH heating capacity and a 123 MBH net AHRI rating, in the 20.4 in-deep chassis.
Maximum input rises from 120 to 150 MBH, heating capacity from 112 to 141 MBH, net AHRI from 97 to 123 MBH, and boiler weight from 76 to 103 lb in the deeper 20.4 in chassis.
Yes — 95.0% AFUE for both, per the Alta Product Data Sheet ratings table.
The larger 20.4 in-deep chassis (dimension 'A'), shared with the ALTA-180 and the ALTAC-200 combi.
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.