Weil-McLain Ultra 310
The Ultra 310 is listed on weil-mclain.ca at 310 MBH input and 289 MBH output, but it appears in no current US Series 4 document — Boilers.ca records the size from the CA page while flagging that manual 550-100-440/1025 does not cover it.
Key figures
- Max input
- 310 MBH
- Max CSA output
- 289 MBH
- AFUE
- —
- Min input
- —
Input is gas energy consumed; output is heat delivered. Never size from input alone.
Weil-McLain Ultra 310 in practice
Weil-McLain Canada's residential Ultra page lists seven input sizes — 80, 105, 155, 230, 299, 310 and 399 MBH — with 289 MBH printed against the 310. The Series 4 boiler manual (550-100-440/1025), the Series 4 brochure and the US product page all stop at 399 MBH with no 310 size, which indicates the CA page still lists a Series 1-3-era size alongside the current Series 4 set.
Because no current manual documents the 310, the only official Canadian numbers for it are the CA page's 310 MBH input and 289 MBH output figures, reproduced here. Anyone specifying or servicing a unit marked 310 should confirm the series on the rating plate and use the matching generation's literature, since the Series 4 manual's rating tables do not include this size.
Best suited to
- Documenting a size that weil-mclain.ca still lists for the Ultra
- Contractors verifying Ultra model availability against the CA product page
- Clarifying why the 310 is absent from current US Series 4 literature
Applicability and support
- Model number
- ULTRA-310
- 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 | 310 MBH | Input size listed on weil-mclain.ca; output 289 MBH per the same page. |
| Output | ||
| DOE heating capacity | 289 MBH | Output per the CA product page spec block. |
| Domestic hot water | ||
| Domestic hot water | Heating-only boiler; domestic hot water via an indirect tank or separate appliance | |
| Venting and air | ||
| Venting | Category IV: S636-certified PVC, CPVC or AL29-4C per the CA product page | Canada: install per CAN/CSA B149.1 or B149.2 with a ULC S636-compliant vent kit. |
| Operating limits and other | ||
| Turndown | 5:1 | 5:1 modulation per the CA product page (series-level claim). |
| 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
Does the Ultra 310 exist as a Series 4 model?
Only weil-mclain.ca lists it, at 310 MBH input and 289 MBH output. The US Series 4 manual, brochure and product page do not include a 310 size, so it appears to be a Series 1-3 era size carried on the CA page.
Where can I find the 310's ratings?
No Series 4 manual covers it. The CA product page prints 310 MBH input and 289 MBH output; beyond that, literature must be matched to the unit's actual series from the rating plate.
Should I specify an Ultra 310?
Confirm the current Canadian model list with Weil-McLain Canada or a distributor first — the 310 sits between documented Series 4 sizes and is not backed by the current US Series 4 ratings.
Questions about the Weil-McLain Ultra 310?
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 (lists the 310 MBH size) · accessed September 7, 2026
- Ultra Series 4 Boiler Manual 550-100-440/1025 (no 310 size) · 550-100-440/1025 · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.