Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
Weil-McLain CGi-5 and Weil-McLain CGi-6 are two non-condensing boilers from the Weil-McLain CGi (cast iron) line. The Weil-McLain CGi-5 is documented at 119 MBH input, 102 MBH output and 84% AFUE, while the Weil-McLain CGi-6 is documented at 158 MBH input, 135 MBH output and 84% AFUE. Weil-McLain CGi-6 lists 39 MBH more input than Weil-McLain CGi-5 (158 MBH against 119 MBH). Both list the same published AFUE of 84%.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Weil-McLain CGi-5 | Weil-McLain CGi-6 |
|---|---|---|
| Input, maximum | 119 MBH | 158 MBH |
| DOE heating capacity | 102 MBH | 135 MBH |
| Efficiency (AFUE) | 84 % | 84 % |
| Venting | Category I B-vent (chimney) or Category III AL29-4C stainless steel (sidewall) | Category I B-vent (chimney) or Category III AL29-4C stainless steel (sidewall) |
| Fuel | Natural gas or propane | Natural gas or propane |
| Net AHRI water rating | 89 MBH | 117 MBH |
Published ratings: the Weil-McLain CGi-5 is rated 119 MBH input, 102 MBH output and 84% AFUE; the Weil-McLain CGi-6 is rated 158 MBH input, 135 MBH output and 84% AFUE. Weil-McLain CGi-6 lists 39 MBH more input than Weil-McLain CGi-5 (158 MBH against 119 MBH). Both list the same published AFUE of 84%.
Both records print the same AFUE (84%), venting (Category I B-vent (chimney) or Category III AL29-4C stainless steel (sidewall)) and fuel (Natural gas or propane), per the cited sources.
Weil-McLain
The CGi-5 is the first of the larger CGi Series 5 sizes, from the cast iron line Canada discontinued in 2023: 119 MBH CSA input, 102 MBH DOE heating capacity and an 89 MBH net AHRI rating at 84% AFUE.
Weil-McLain
The CGi-6 steps the CGi Series 5 line to 158 MBH CSA input with 135 MBH of DOE heating capacity — an 84% AFUE cast iron boiler from the line Canada discontinued in 2023.
The Weil-McLain CGi-6 lists 158 MBH, against 119 MBH on the Weil-McLain CGi-5, per the cited documentation.
Both list the same AFUE of 84%.
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.