Weil-McLain AquaBalance AB-155H
The AB-155H tops the heat-only AquaBalance Series 2 line, discontinued in Canada: 155 MBH CSA input, 144 MBH DOE heating capacity and a 125 MBH net AHRI rating at 95% AFUE, still only 67 lb in the wall-mounted stainless steel cabinet.
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-155H in practice
The AB-155H is the largest heat-only AquaBalance Series 2: 155 MBH CSA input for 144 MBH of DOE heating capacity and a 125 MBH net AHRI rating at 95% AFUE. It keeps the 67 lb shipping weight of the AB-120H while stepping the gas connection to 3/4" NPT and the heating supply and return tappings to 1" NPT, and the US Series 2 page lists a 3" vent size for the 155 against 2"-3" on the smaller sizes.
Like every Canadian AquaBalance, the AB-155H sits on weil-mclain.ca's Discontinued menu: the CA heat-only page lists inputs of 80/120/155 MBH at up to 95% AFUE and Cat. 4 S636 venting, and positions the boiler for space heating with domestic hot water from an indirect tank. Its CA-page output figure of 143 MBH trails the 144 MBH DOE heating capacity of the US Series 2 page and manual that Boilers.ca records for this Series 2 generation.
Best suited to
- The largest residential loads the AquaBalance platform covered, at 155 MBH of input
- Heat-only wall-mount installations pairing with an indirect tank for hot water
- Contractors checking discontinued-in-Canada AquaBalance ratings against Series 2 documents
Applicability and support
- Model number
- AB-155H
- 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 | Heating-only boiler; domestic hot water via an indirect tank | Per the CA discontinued "AquaBalance (Heat Only)" page, which lists its ideal use as space heating and domestic hot water with an indirect tank required. |
| 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 | 67 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 and 3/4" NPT on the 80/120 sizes, 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-155H's ratings?
155 MBH CSA input, 144 MBH DOE heating capacity, a 125 MBH net AHRI rating and 95% AFUE, at a 67 lb shipping weight per the US Series 2 product page.
Why does the CA page list 143 MBH where the US page lists 144 MBH?
The CA discontinued AquaBalance page prints outputs of 73/109/143 MBH for the 80/120/155, while the US Series 2 page and manual print DOE heating capacities of 75/112/144 MBH. Boilers.ca treats the Series 2 figures as the ratings for this generation.
What connections does the AB-155H use?
1" NPT heating supply and return, a 3/4" NPT gas connection and a 3" vent size, per the Series 2 brochure connection chart and US product page.
Questions about the Weil-McLain AquaBalance AB-155H?
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 — AquaBalance (Heat Only), 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.