Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
Weil-McLain CGa-5 and Weil-McLain CGa-6 are two non-condensing boilers from the Weil-McLain CGa (cast iron) line. The Weil-McLain CGa-5 is documented at 133 MBH input, 113 MBH output and 84% AFUE, while the Weil-McLain CGa-6 is documented at 166 MBH input, 141 MBH output and 84% AFUE. Weil-McLain CGa-6 lists 33 MBH more input than Weil-McLain CGa-5 (166 MBH against 133 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 CGa-5 | Weil-McLain CGa-6 |
|---|---|---|
| Input, maximum | 133 MBH | 166 MBH |
| DOE heating capacity | 113 MBH | 141 MBH |
| Efficiency (AFUE) | 84 % | 84 % |
| Venting | Category I, B-vent — vertical chimney venting only, natural draft | Category I, B-vent — vertical chimney venting only, natural draft |
| Fuel | Natural gas or propane | Natural gas or propane |
| Net AHRI water rating | 98 MBH | 122 MBH |
Published ratings: the Weil-McLain CGa-5 is rated 133 MBH input, 113 MBH output and 84% AFUE; the Weil-McLain CGa-6 is rated 166 MBH input, 141 MBH output and 84% AFUE. Weil-McLain CGa-6 lists 33 MBH more input than Weil-McLain CGa-5 (166 MBH against 133 MBH). Both list the same published AFUE of 84%.
Both records print the same AFUE (84%), venting (Category I, B-vent — vertical chimney venting only, natural draft) and fuel (Natural gas or propane), per the cited sources.
Weil-McLain
The CGa-5 is the first of the large-cabinet CGa Series 4 sizes, from the cast iron line discontinued in Canada in 2023: 133 MBH CSA input, 113 MBH DOE heating capacity and a 98 MBH net AHRI rating at 84% AFUE.
Weil-McLain
The CGa-6 continues the large CGa Series 4 sizes of the cast iron line discontinued in Canada in 2023: 166 MBH CSA input, 141 MBH DOE heating capacity and a 122 MBH net AHRI rating at 84% AFUE.
The Weil-McLain CGa-6 lists 166 MBH, against 133 MBH on the Weil-McLain CGa-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.