Weil-McLain CGi-6
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.
Key figures
- Max input
- 158 MBH
- Max CSA output
- 135 MBH
- AFUE
- 84 %
- Min input
- —
Input is gas energy consumed; output is heat delivered. Never size from input alone.
Weil-McLain CGi-6 in practice
The CGi-6 fires at 158 MBH CSA input for 135 MBH of DOE heating capacity and a 117 MBH net AHRI rating at 84% AFUE, keeping the 3" vent connection and 5" natural-draft venting shown on the US Series 5 page. It is part of the current US generation of Weil-McLain's cast iron gas-fired water boiler, with an insulated steel jacket, natural draft and direct exhaust capability, built-in low water cut-off and easy-to-service intermittent electronic ignition.
Weil-McLain Canada discontinued the CGi under the federal efficiency standard: the April 27, 2023 news release set a production cut-off of June 30, 2023, after which units sold only while inventory lasted, with parts promised for at least 20+ years. The discontinued CA page describes the Series-3-era Canadian generation at 50-233 MBH inputs; the Series 5 set documented here is the US-current successor covered by boiler manual 550-100-629/0126.
Best suited to
- Larger homes with loads in the 135-158 MBH band and chimney or sidewall venting
- Contractors documenting US CGi Series 5 models for comparison with Canadian-era CGi units
- Cast iron boiler research for larger systems with chimney or sidewall venting
Applicability and support
- Model number
- CGi-6
- Canadian availability
- historical
- Production status
- discontinued
- ROMA supplies
- Confirmed at consultation
- ROMA services
- Confirmed at consultation
- Warranty
- Not verified
Where ROMA provides on-site service
On-site service is currently offered in Greater Vancouver, BC, including Vancouver, Burnaby, Richmond, Surrey, Coquitlam, North Vancouver, West Vancouver, New Westminster, Port Coquitlam, Port Moody, Delta, Langley, Maple Ridge, Abbotsford, Chilliwack, White Rock, Pitt Meadows, Tsawwassen, Anmore, Lions Bay, Belcarra, Bowen Island, Mission. Everything else on this site is reference information you can use anywhere in Canada.
Specifications
Published specifications
Values as published by Weil-McLain. Units are shown with every value; notes flag conflicting sources or missing figures.
| Specification | Value | Note |
|---|---|---|
| Input | ||
| Input, maximum | 158 MBH | CSA input per the US Series 5 product page. |
| Output | ||
| DOE heating capacity | 135 MBH | DOE heating capacity per the US Series 5 product page. |
| Net AHRI water rating | 117 MBH | Net AHRI water rating per the US Series 5 product page. |
| Efficiency | ||
| Efficiency (AFUE) | 84 % | 84% AFUE per the US Series 5 page; the CA discontinued page lists up to 85.1% for the Series-3-era Canadian units. |
| Venting and air | ||
| Venting | Category I B-vent (chimney) or Category III AL29-4C stainless steel (sidewall) | Per the CA discontinued page, which notes Category I vent sizes increase from 3" to 4" up to the CGi-3 size and 3" to 5" on larger sizes; the US Series 5 page lists a 3" vent connection with 5" natural-draft venting for the CGi-6. |
| Operating limits and other | ||
| Fuel | Natural gas or propane | Propane requires a conversion kit per the CA product page. |
Manuals
- CGi Series 5 Boiler Manual, 550-100-629/0126550-100-629/0126 · 2026-01
Alerts documented for this model
Frequently asked questions
What are the CGi-6's ratings?
158 MBH CSA input, 135 MBH DOE heating capacity, a 117 MBH net AHRI rating and 84% AFUE per the US Series 5 product page.
Why do the Canadian CGi ratings differ from Series 5?
The CA discontinued page reflects the Series-3-era Canadian units at 50-233 MBH inputs and up to 85.1% AFUE, while the US Series 5 set runs 48-222 MBH at 84% AFUE — two different generations across the border.
Does the CGi need a chimney?
No — the CA discontinued page lists chimney venting (Category I, B-vent) or sidewall venting (Category III, AL29-4C stainless), and the Series 5 page adds direct exhaust capability.
Questions about the Weil-McLain CGi-6?
Describe what the boiler is doing and get a straight answer about the next step.
On-site service in Greater Vancouver, BC. ROMA lists “Open 7 days” on its site; call to confirm same-day availability.
Sources and verification
- Weil-McLain Canada — CGi (discontinued) · accessed September 8, 2026
- Weil-McLain Canada — Residential boiler efficiency changes (Apr 27, 2023) · accessed September 8, 2026
- CGi Series 5 Boiler Manual 550-100-629/0126 · 550-100-629/0126 · accessed September 8, 2026
Facts checked September 8, 2026. Last updated September 8, 2026. Technical reviewer: not yet assigned.