Weil-McLain AquaBalance AB-155C
The AB-155C is the flagship AquaBalance Series 2 combi, discontinued in Canada: 155 MBH CSA input, 144 MBH DOE heating capacity and the line's top DHW delivery — 4 GPM at a 70°F rise per the US page — at 95% AFUE in an 87 lb wall-mounted unit.
Key figures
- Max input
- 155 MBH
- Max CSA output
- 144 MBH
- AFUE
- 95 %
- Min input
- —
Input is gas energy consumed; output is heat delivered. Never size from input alone.
Weil-McLain AquaBalance AB-155C in practice
The AB-155C tops the AquaBalance Series 2 range at 155 MBH CSA input with 144 MBH of DOE heating capacity and a 125 MBH net AHRI rating at 95% AFUE. It is the size behind Weil-McLain's DHW headline: the US Series 2 page states 4 gallons per minute of domestic hot water at a 70°F rise on the 155 combi, delivered through the built-in DHW flat plate heat exchanger, 3-way valve and internal 3-speed circulator.
The discontinued CA pages list the same 80/120/155 MBH inputs for the combi and heat-only AquaBalance entries, marketing the combi for space heating and domestic hot water at up to 4 GPM and a 70°F rise. The US Series 2 page lists a 3" vent size for the 155 — against 2"-3" on the 80/120 — and the CA page prints 143 MBH output where the Series 2 documents show 144 MBH DOE heating capacity, the discrepancy Boilers.ca flags on this record.
Best suited to
- Larger homes and small apartment buildings whose load reaches 155 MBH with real hot-water demand
- Combi installations where the 4 GPM at a 70°F rise delivery of the 155 model matters
- Owners documenting the discontinued-in-Canada AquaBalance against current Series 2 US literature
Applicability and support
- Model number
- AB-155C
- 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 | 155 MBH | CSA input (maximum). |
| Output | ||
| DOE heating capacity | 144 MBH | US Series 2 DOE heating capacity; the CA discontinued page prints 143 MBH output for this size (see the editor note). |
| Net AHRI water rating | 125 MBH | Net AHRI water rating per the US Series 2 product page table. |
| Efficiency | ||
| Efficiency (AFUE) | 95 % | 95% AFUE per the US Series 2 page; the CA discontinued page lists up to 95%. |
| Domestic hot water | ||
| Domestic hot water | Integrated combi: built-in DHW flat plate heat exchanger with a 3-way valve and an internal 3-speed circulator | The US Series 2 page states 4 gallons per minute of domestic hot water at a 70°F rise on the 155 combi; the CA discontinued combi page quotes the same figure for the range. |
| Venting and air | ||
| Venting | 3" PVC, CPVC, polypropylene or stainless steel (Category IV) — the US Series 2 page lists a 3" vent size on the 155 | Canada: install per CAN/CSA B149.1 or B149.2 with a ULC S636-compliant vent kit. |
| Physical and connections | ||
| Weight | 87 lb | Approx. shipping weight per the US Series 2 product page. |
| Gas connection | 3/4" NPT | Gas connection per the Series 2 brochure connection chart. |
| Heating water connections | 1" NPT | Heating supply and return 1" NPT on the 155, 3/4" NPT on the 80/120; DHW inlet and outlet are 3/4" NPT on this 155 combi per the Series 2 brochure connection chart. |
| Operating limits and other | ||
| Turndown | 10:1 | 10:1 modulation per the notes on both CA discontinued AquaBalance pages. |
| Fuel | Natural gas or propane | Propane requires a conversion kit per the CA product page. |
Manuals
- AquaBalance Series 2 Boiler Manual, 550-100-325/0924550-100-325/0924 · 2024-09
Alerts documented for this model
Frequently asked questions
What are the AB-155C's ratings?
155 MBH CSA input, 144 MBH DOE heating capacity, a 125 MBH net AHRI rating and 95% AFUE, at an 87 lb shipping weight per the US Series 2 product page.
How much hot water does the AB-155C deliver?
The US Series 2 page states 4 gallons per minute at a 70°F rise for the 155 combi — the model behind the CA combi page's up-to-4-GPM claim.
What venting does the AB-155C use?
The US Series 2 page lists a 3" vent size for the 155 size, with PVC, CPVC, polypropylene or stainless steel as the approved vent materials.
Questions about the Weil-McLain AquaBalance AB-155C?
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.
Compare and explore
Sources and verification
- Weil-McLain Canada — AquaBalance (Combi), discontinued · accessed September 8, 2026
- AquaBalance Series 2 Boiler Manual 550-100-325/0924 · 550-100-325/0924 · accessed September 8, 2026
Facts checked September 8, 2026. Last updated September 8, 2026. Technical reviewer: not yet assigned.