Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
Boilers.ca is a brand of ROMA Heating & Cooling · Licensed gas contractor LGA0202903
Comparison
Verdict in brief
The RTS/28HE-14 and RTS/28HE-18 are the top end of the fifteen-size 28HE RTS line: 3,567 versus 4,622 MBH gross output, 3,102 versus 4,019 MBH net I=B=R water, and 356 versus 462 GPM at 20 °F ΔT. Both use 5" supply and return connections and the standard RTS; the -18 is the largest size Smith prints for this water line.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Smith RTS/28HE-14 | Smith RTS/28HE-18 |
|---|---|---|
| Gas burner capacity (as printed) | 4,293 MBH | 5,553 MBH |
| Gross output (as printed) | 3,567 MBH | 4,622 MBH |
| Net I=B=R water rating | 3,102 MBH | 4,019 MBH |
| Thermal efficiency — oil | 85.7 % | 85.8 % |
| Thermal efficiency — gas | 83.1 % | 83.2 % |
| Flow at 20 °F ΔT | 356 GPM | 462 GPM |
| Supply / return connection | 5" supply / 5" return | 5" supply / 5" return |
PDRTSHE-4 covers fifteen sizes from four to eighteen sections, and these are the two largest. The fourteen-section RTS/28HE-14 prints 3,567 MBH gross, 3,102 MBH net and 106 boiler horsepower; the eighteen-section RTS/28HE-18 prints 4,622 MBH gross, 4,019 MBH net and 138 HP. Gas burner capacity moves from 4,293 to 5,553 MBH, oil from 29.5 to 38.5 GPH.
The two share 5" supply and return connections and the same printed thermal efficiency trend (85.7% oil / 83.1% gas on the -14; 85.8% / 83.2% on the -18), so the choice is entirely about the plant load. Water content rises from 392.4 to 500 gallons and water working weight from 12,467 to 16,103 lb, which affects rigging, floor loading and the expansion/air-control design.
Both sizes carry the standard Return Temperature Stabilizer. RTSB-1 states the boiler cannot be operated as a condensing boiler, so even at the top of the range a low-temperature distribution system needs the return-temperature protection described in the manual. Above the -18, Smith's larger commercial offering is the separate 28HE (Steam) line rather than a bigger water boiler.
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-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.
The RTS/28HE-18 at 4,622 MBH gross output and 138 boiler horsepower, per PDRTSHE-4 — the eighteenth and final size of the fifteen-size line (4–18 sections).
No. RTSB-1 states the boiler cannot be operated as a condensing boiler; the RTS protects the cast iron at low return temperatures instead.
Output (3,567 to 4,622 MBH gross), flow (356 to 462 GPM at 20 °F ΔT), water content (392.4 to 500 gal) and working weight (12,467 to 16,103 lb). Connections stay 5" supply and return.
A consultation includes a heat-loss review so the size is right the first time.
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.