Crown Boiler Co. · Cayman (legacy)
Crown Cayman CWI311
The Crown Cayman CWI311 is a legacy cast-iron gas water boiler with an integrated tankless domestic coil: 310 MBH input over 10 sections with 252 MBH heating capacity and a 219 MBH AHRI net rating at 81.4% thermal efficiency.
Key figures
- Max input
- 310 MBH
- Max CSA output
- —
- AFUE
- —
- Min input
- —
Input is gas energy consumed; output is heat delivered. Never size from input alone.
Crown Cayman CWI311 in practice
The Cayman CWI311 is documented in the CWI specification table (Table 1) as a Category I, natural-draft cast-iron hot water boiler: 310 MBH input over 10 sections, 252 MBH heating capacity, a 219 MBH AHRI net rating (1.15 allowance) and 81.4% thermal efficiency (CWI311–CWI380 print thermal efficiency rather than AFUE). Boiler water volume is 23.2 US gallons.
The model carries an integrated tankless domestic-water coil in the boiler body — rated 4 / 5.25 GPM (standard / optional high-capacity tankless heater) at the specification-table conditions (40°F inlet, 140°F outlet, 190°F boiler water) — and is natural gas only. The tankless heater is included on CWI103–CWI276 and optional on CWI311–CWI380.
The Cayman is legacy — absent from the current Velocity Boiler Works menu — so productStatus is 'discontinued'. Boilers.ca documents this model at model level from the hosted CWI manual; no official Canadian-sales statement was found, so canadianStatus stays 'unknown', and gas, combustion and venting work belongs with a licensed contractor.
Best suited to
- Owners documenting an installed Cayman against the CWI specification table
- Service planning for cast-iron natural-draft boilers with integrated tankless coils
- Legacy-replacement research in the 310-MBH-input class
Applicability and support
- Model number
- CWI311
- Canadian availability
- unknown
- 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 Crown Boiler Co.. Units are shown with every value; notes flag conflicting sources or missing figures.
| Specification | Value | Note |
|---|---|---|
| Input | ||
| Input | 310 MBH | Input per the CWI specification table (Table 1). |
| Output | ||
| Heating capacity | 252 MBH | Heating capacity per the CWI specification table (Table 1). |
| AHRI net rating | 219 MBH | AHRI net rating based on a piping and pickup allowance of 1.15 per the specification table note. |
| Efficiency | ||
| Thermal efficiency | 81.4 % | 81.4% thermal efficiency per the specification table (footnote 2) — CWI311–CWI380 print thermal efficiency rather than AFUE. |
| Domestic hot water | ||
| Tankless heater rating | 4 / 5.25 GPM | Tankless heater rating (standard / with optional high-capacity tankless heater) per the specification table — based on 40°F inlet water, 140°F outlet water and 190°F boiler water, with 5-minute intermittent draws and 10 minutes between draws. The tankless heater is included on CWI103–CWI276 and optional on CWI311–CWI380. |
| Domestic hot water | Integrated tankless coil in the boiler body (water boiler, not a combi burner) | CWI103–CWI276 include a tankless heater for domestic hot water generation; it is optional equipment on CWI311–CWI380. A mixing valve is required in the tankless piping per the manual. |
| Venting and air | ||
| Venting | Category I natural draft into a lined masonry or listed metal chimney | Draft-diverter-equipped Category I appliance per the CWI installation manual product description. |
| Physical and connections | ||
| Cast-iron sections | 10 | Number of sections per the CWI specification table (Table 1). |
| Dimensions (A × B × C) | 35-1/2 × 30 × 45-7/16" | Boiler dimensions A, B and C (inches) per the CWI specification table (Table 1). |
| Water volume | 23.2 gal | Boiler water volume per the CWI specification table (Table 1). |
| Operating limits and other | ||
| Fuel | Natural gas only | CWI311–CWI380 are not available for use with LP gas (specification table footnote 1). |
Alerts documented for this model
None documented yet.
Frequently asked questions
What are the CWI311's ratings?
310 MBH input, 252 MBH heating capacity and a 219 MBH AHRI net rating at 81.4% thermal efficiency per the CWI specification table.
Can the CWI311 run on propane?
No — CWI311–CWI380 are not available for use with LP gas per the specification table's footnote 1.
Is the Cayman a combi boiler?
It is a cast-iron water boiler with an integrated tankless domestic coil — not a modulating combi. The tankless heater is standard on CWI103–CWI276 and optional on CWI311–CWI380.
Questions about the Crown Cayman CWI311?
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
- crownboiler.com — Cayman (CWI) legacy product page · accessed September 9, 2026
- CWI Series Gas-Fired Natural Draft Water Boilers — Installation Instructions (PDF) · accessed September 9, 2026
Facts checked September 8, 2026. Last updated September 8, 2026. Technical reviewer: not yet assigned.