Weil-McLain Ultra 80
The Ultra 80 is the smallest Series 4 Ultra: 80 MBH input with a 16 MBH low fire, 71 MBH DOE heating capacity and 93.5% AFUE from a nano-coated cast aluminum condensing block.
Key figures
- Max input
- 80 MBH
- Max CSA output
- 71 MBH
- AFUE
- 93.5 %
- Min input
- 16 MBH
Input is gas energy consumed; output is heat delivered. Never size from input alone.
Weil-McLain Ultra 80 in practice
The Ultra 80 opens the Series 4 range at 80 MBH maximum CSA input with a 16 MBH low fire — the brochure prints CSA input minimums per model at the 5:1 turndown — and delivers 71 MBH of DOE heating capacity and a 62 MBH net AHRI rating at 93.5% AFUE, the lowest efficiency figure in the series.
It vents in 2" or 3" pipe to 100 ft (the manual warns the 80 derates by up to 10% at 100 ft in 2"), uses 1" supply and return tappings with a 1/2" NPT gas connection, and holds just 0.69 gallons of boiler water. Like every Ultra it is a floor-standing or wall-hung condensing boiler with 5:1 modulation and no integrated domestic hot water.
Best suited to
- Smaller homes with calculated loads near or under 80 MBH
- Low-load hydronic systems that benefit from a 16 MBH minimum fire
- Projects where the compact, nano-coated aluminum block saves space
Applicability and support
- Model number
- ULTRA-80
- Canadian availability
- available
- Production status
- current
- ROMA supplies
- Confirmed at consultation
- ROMA services
- Confirmed at consultation
- Warranty
- Series terms
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 | 80 MBH | CSA input (maximum). |
| Input, minimum | 16 MBH | Low fire (16 MBH) per the Series 4 brochure's CSA input minimum column. |
| Output | ||
| DOE heating capacity | 71 MBH | DOE heating capacity at maximum input; the manuals also call this CSA Output. |
| Net AHRI water rating | 62 MBH | Net AHRI rating per the boiler manual ratings table. |
| Efficiency | ||
| Efficiency (AFUE) | 93.5 % | DOE seasonal efficiency (AFUE). |
| Domestic hot water | ||
| Domestic hot water | Heating-only boiler; domestic hot water via an indirect tank or separate appliance | |
| Venting and air | ||
| Venting | 2" or 3" PVC, CPVC, polypropylene or stainless steel (Category IV) | Canada: install per CAN/CSA B149.1 or B149.2 with a ULC S636-compliant vent kit. |
| Max. equivalent vent/air length | 100 ft in 2" or 3" (derates up to 10% at 100 ft in 2" per the manual) | |
| Physical and connections | ||
| Weight | 199 lb | Approx. shipping weight per the brochure. |
| Gas connection | 1/2" NPT | |
| Heating water connections | 1" NPT | Supply and return tappings 1"; minimum recommended pipe 1". |
| Operating limits and other | ||
| Turndown | 5:1 | 5:1 modulation (20-100% firing rate) per the brochure and CA page. |
| Boiler water content | 0.69 gal | |
| Altitude rating | 5,500 ft | No modifications from sea level to 5,500 ft; the control has a high-altitude selection above 5,500 ft. |
| Fuel | Natural gas or propane | Propane requires a conversion kit per the CA product page. |
Manuals
- Ultra Series 4 Boiler Manual, 550-100-440/1025550-100-440/1025 · 2025-10
Alerts documented for this model
- TEMP RISE TOO QUICKLY
- SUPPLY 58F > RETURN
- RETURN > SUPPLY
- TEMPERATURE SENSOR
- FLUE TEMP TOO HIGH
- TEMPERATURE SENSOR
- LOW WTR CUTOFF OPEN
- DISPLAY COMM
- LIMIT OPEN
- HIGH TEMP LIMIT
- FLAME FAULT
- BLOWER FAULT
- IGNITION FAULT
- GAS VALVE FAULT
- AIR PRESSURE SW FAULT
- GAS PRESSURE SW FAULT
- HW FAULT EXPANSION BRD
- GV FAULT EXPANSION BRD
- EXP BOARD COM FAULT
Frequently asked questions
What is the low fire of the Ultra 80?
16 MBH, per the Series 4 brochure's CSA input minimum column for the 80 at its 5:1 turndown.
What venting does the Ultra 80 allow?
2" or 3" pipe to 100 ft; the manual notes the 80 derates up to 10% at a full 100 ft run in 2" pipe.
Does the Ultra produce domestic hot water?
No. The Ultra is a heating-only boiler; domestic hot water comes from an indirect tank or separate appliance.
Questions about the Weil-McLain Ultra 80?
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 — Ultra · accessed September 7, 2026
- Ultra Series 4 Boiler Manual 550-100-440/1025 · 550-100-440/1025 · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.