Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Smith Cast Iron Boilers · Series
The Smith 28HE RTS (Water) is the commercial high-efficiency water boiler of the 28HE cast-iron family — fifteen sizes from 931 to 4,622 MBH with forced-draft power-burner firing (oil/gas/both) and the stainless Return Temperature Stabilizer (RTS) device.
Series facts
Smith describes the 28HE RTS (Water) as its high-efficiency commercial water boiler: cast-iron wet-base sections rated 80 psi, a stainless-steel 'Return Temperature Stabilizer' (RTS) device, and forced-draft power-burner firing on oil, gas or both. The product page prints fifteen sizes ranging from 931 to 4,622 MBH; the commercial category page prints '15 sizes from 900 to 4,270 MBH' — both official, flagged rather than reconciled.
The 28HE steam sibling (28HE Steam, cast-iron sections, forced-draft) prints fifteen sizes from 900 to 4,270 MBH on the category page; steam plants are outside the hydronic scope of this hub, so only the RTS (Water) line is hubbed here.
Smith publishes the RTS brochure (RTSB-1) and warranty (CW-2) as public PDFs from the product page, with the I&O manual available through its literature library. The brochure is linked from this hub.
Highlights
Models
One canonical page per model with input, output and efficiency kept separate.
Smith Cast Iron Boilers
The Smith RTS/28HE-4 is the 4-section 27 HP size of the 28HE RTS high-efficiency water boiler — 931 MBH gross output, 810 MBH net I=B=R water, 1143 MBH gas or 7.9 GPH oil burner capacity, with 3" supply and return connections.
Smith Cast Iron Boilers
The Smith RTS/28HE-5 is the 5-section 35 HP size of the 28HE RTS high-efficiency water boiler — 1194 MBH gross output, 1038 MBH net I=B=R water, 1458 MBH gas or 10.2 GPH oil burner capacity, with 3" supply and return connections.
Smith Cast Iron Boilers
The Smith RTS/28HE-6 is the 6-section 43 HP size of the 28HE RTS high-efficiency water boiler — 1458 MBH gross output, 1268 MBH net I=B=R water, 1773 MBH gas or 12.2 GPH oil burner capacity, with 4" supply and return connections.
Smith Cast Iron Boilers
The Smith RTS/28HE-7 is the 7-section 51 HP size of the 28HE RTS high-efficiency water boiler — 1722 MBH gross output, 1497 MBH net I=B=R water, 2088 MBH gas or 14.4 GPH oil burner capacity, with 4" supply and return connections.
Smith Cast Iron Boilers
The Smith RTS/28HE-8 is the 8-section 59 HP size of the 28HE RTS high-efficiency water boiler — 1985 MBH gross output, 1726 MBH net I=B=R water, 2403 MBH gas or 16.6 GPH oil burner capacity, with 4" supply and return connections.
Smith Cast Iron Boilers
The Smith RTS/28HE-9 is the 9-section 67 HP size of the 28HE RTS high-efficiency water boiler — 2249 MBH gross output, 1956 MBH net I=B=R water, 2718 MBH gas or 18.8 GPH oil burner capacity, with 4" supply and return connections.
Smith Cast Iron Boilers
The Smith RTS/28HE-10 is the 10-section 75 HP size of the 28HE RTS high-efficiency water boiler — 2513 MBH gross output, 2185 MBH net I=B=R water, 3033 MBH gas or 21 GPH oil burner capacity, with 5" supply and return connections.
Smith Cast Iron Boilers
The Smith RTS/28HE-11 is the 11-section 83 HP size of the 28HE RTS high-efficiency water boiler — 2776 MBH gross output, 2414 MBH net I=B=R water, 3348 MBH gas or 23 GPH oil burner capacity, with 5" supply and return connections.
Smith Cast Iron Boilers
The Smith RTS/28HE-12 is the 12-section 91 HP size of the 28HE RTS high-efficiency water boiler — 3040 MBH gross output, 2643 MBH net I=B=R water, 3663 MBH gas or 25.5 GPH oil burner capacity, with 5" supply and return connections.
Smith Cast Iron Boilers
The Smith RTS/28HE-13 is the 13-section 98 HP size of the 28HE RTS high-efficiency water boiler — 3304 MBH gross output, 2873 MBH net I=B=R water, 3978 MBH gas or 27.5 GPH oil burner capacity, with 5" supply and return connections.
Smith Cast Iron Boilers
The Smith RTS/28HE-14 is the 14-section 106 HP size of the 28HE RTS high-efficiency water boiler — 3567 MBH gross output, 3102 MBH net I=B=R water, 4293 MBH gas or 29.5 GPH oil burner capacity, with 5" supply and return connections.
Smith Cast Iron Boilers
The Smith RTS/28HE-15 is the 15-section 114 HP size of the 28HE RTS high-efficiency water boiler — 3831 MBH gross output, 3331 MBH net I=B=R water, 4608 MBH gas or 32 GPH oil burner capacity, with 5" supply and return connections.
Smith Cast Iron Boilers
The Smith RTS/28HE-16 is the 16-section 122 HP size of the 28HE RTS high-efficiency water boiler — 4095 MBH gross output, 3561 MBH net I=B=R water, 4923 MBH gas or 34 GPH oil burner capacity, with 5" supply and return connections.
Smith Cast Iron Boilers
The Smith RTS/28HE-17 is the 17-section 130 HP size of the 28HE RTS high-efficiency water boiler — 4358 MBH gross output, 3790 MBH net I=B=R water, 5238 MBH gas or 36.5 GPH oil burner capacity, with 5" supply and return connections.
Smith Cast Iron Boilers
The Smith RTS/28HE-18 is the 18-section 138 HP size of the 28HE RTS high-efficiency water boiler — 4622 MBH gross output, 4019 MBH net I=B=R water, 5553 MBH gas or 38.5 GPH oil burner capacity, with 5" supply and return connections.
| Specification | Smith RTS/28HE-4 | Smith RTS/28HE-5 | Smith RTS/28HE-6 | Smith RTS/28HE-7 | Smith RTS/28HE-8 | Smith RTS/28HE-9 | Smith RTS/28HE-10 | Smith RTS/28HE-11 | Smith RTS/28HE-12 | Smith RTS/28HE-13 | Smith RTS/28HE-14 | Smith RTS/28HE-15 | Smith RTS/28HE-16 | Smith RTS/28HE-17 | Smith RTS/28HE-18 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| input-min | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Gas burner capacity (as printed) | 1,143 MBH | 1,458 MBH | 1,773 MBH | 2,088 MBH | 2,403 MBH | 2,718 MBH | 3,033 MBH | 3,348 MBH | 3,663 MBH | 3,978 MBH | 4,293 MBH | 4,608 MBH | 4,923 MBH | 5,238 MBH | 5,553 MBH |
| output-max | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| afue | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| turndown | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| vent-max-3 | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| vent-max-2 | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Water working weight | 4,215 lb | 5,038 lb | 5,861 lb | 6,684 lb | 7,507 lb | 8,331 lb | 9,169 lb | 9,992 lb | 10,815 lb | 11,649 lb | 12,467 lb | 13,511 lb | 14,375 lb | 15,239 lb | 16,103 lb |
Read the full comparison: Smith RTS/28HE-6 vs RTS/28HE-8 →
Read the full comparison: Smith RTS/28HE-10 vs RTS/28HE-14 →
Read the full comparison: Smith RTS/28HE-14 vs RTS/28HE-18 →
Read the full comparison: Smith RTS/28HE-4 vs Smith RTS/28HE-5 →
Error codes and alerts
No alerts documented for this series yet.
Manuals
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.
Services for Smith Cast Iron Boilers boilers
No. The 28HE RTS is a non-condensing cast-iron commercial boiler with a stainless Return Temperature Stabilizer, fired by a forced-draft power burner.
The 28HE RTS product page prints fifteen sizes from 931 to 4,622 MBH; Smith's commercial category page prints '15 sizes from 900 to 4,270 MBH'. Boilers.ca quotes both official figures and flags the difference.
Yes — 28HE (Steam) is a separate official line (category copy: fifteen sizes from 900 to 4,270 MBH); this hub covers the hydronic 28HE RTS (Water) line.
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
Facts checked September 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.