Smith Cast Iron Boilers · 28HE Series
Smith RTS/28HE-4
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.
Key figures
- Max input
- 1,143 MBH
- Max CSA output
- —
- AFUE
- —
- Min input
- —
Input is gas energy consumed; output is heat delivered. Never size from input alone.
Smith RTS/28HE-4 in practice
The RTS/28HE-4 is a 4-section cast-iron wet-base water boiler in Smith's 28HE RTS line, documented in the PDRTSHE-4 product data sheet. It prints 931 MBH gross output, 810 MBH net I=B=R water, 81.2 sq ft of heating surface, a 12.04 cu ft furnace volume and a water working weight of 4,215 lb. Burner capacity is 1143 MBH on gas or 7.9 GPH on light oil, with thermal efficiencies of 83.9% (oil) and 81.4% (gas).
The water piping diagram prints 3" supply and 3" return connections and 90 GPM at a 20 °F ΔT. The RTS (Return Temperature Stabilizer) is standard on all 28HE water boilers and is not a condensing device — the bulletin states the boiler cannot be operated as a condensing boiler. The model number denotes the section count; ordering adds a fuel prefix (LO for light oil, G for gas, GO for gas/oil). Smith lists the 28HE RTS as current; Canadian availability is not stated on the captured pages.
Best suited to
- Commercial hydronic plants whose calculated load fits 931 MBH gross output
- Buildings that need the Return Temperature Stabilizer for low-temperature return water protection
- Oil, gas or gas/oil power-burner installations with a chimney
Applicability and support
- Model number
- RTS/28HE-4
- Canadian availability
- unknown
- Production status
- current
- 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 Smith Cast Iron Boilers. Units are shown with every value; notes flag conflicting sources or missing figures.
| Specification | Value | Note |
|---|---|---|
| Input | ||
| Gas burner capacity (as printed) | 1,143 MBH | I=B=R gas burner capacity printed in PDRTSHE-4. |
| Oil firing rate (as printed) | 7.9 GPH | Light oil at 140,000 BTU/gal, printed in PDRTSHE-4. |
| Output | ||
| Gross output (as printed) | 931 MBH | I=B=R gross output printed in PDRTSHE-4 and BSG-10. |
| Net I=B=R water rating | 810 MBH | Net water rating (allowance 1.15) printed in PDRTSHE-4. |
| Efficiency | ||
| Thermal efficiency — oil | 83.9 % | Printed in PDRTSHE-4. |
| Thermal efficiency — gas | 81.4 % | Printed in PDRTSHE-4. |
| Combustion efficiency — oil | 86.2 % | Printed in PDRTSHE-4. |
| Combustion efficiency — gas | 83.6 % | Printed in PDRTSHE-4. |
| Physical and connections | ||
| Supply / return connection | 3" supply / 3" return | Printed in the PDRTSHE-4 water piping diagram (SIOM-98). |
| Cast-iron sections | 4 | The model number denotes the section count, per PDRTSHE-4 ordering notes. |
| Heating surface | 81.2 sq ft | Printed in PDRTSHE-4. |
| Furnace volume | 12.04 cu ft | Printed in PDRTSHE-4. |
| Water content | 123.4 gal | Printed in PDRTSHE-4. |
| Water working weight | 4,215 lb | Printed in PDRTSHE-4. |
| Maximum allowable working pressure | 80 psi water | Printed in PDRTSHE-4 (ASME Section IV). |
| Operating limits and other | ||
| Flow at 20 °F ΔT | 90 GPM | Printed in the PDRTSHE-4 water piping diagram. |
| Boiler horsepower | 27 | Printed in PDRTSHE-4 and BSG-10. |
| Fuel | Natural gas; oil and gas/oil firing available | PDRTSHE-4 prints oil (LO) and gas (G) prefixes plus gas/oil (GO) ordering; the product page says 'fired with oil, gas or both'. Oil capability is carried here because the schema's fuel enum has no oil value. |
Manuals
Alerts documented for this model
None documented yet.
Frequently asked questions
What is the output of the Smith RTS/28HE-4?
PDRTSHE-4 prints 931 MBH gross output and 810 MBH net I=B=R water for this size, with 90 GPM at 20 °F ΔT.
Is the 28HE RTS a condensing boiler?
No. RTSB-1 states plainly that the boiler cannot be operated as a condensing boiler; the RTS device protects the cast iron from thermal shock at low return temperatures.
What size connections does RTS/28HE-4 use?
The PDRTSHE-4 water piping diagram prints 3" supply and 3" return connections for this size.
Questions about the Smith RTS/28HE-4?
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.
Compare and explore
- Smith RTS/28HE-4 vs Smith RTS/28HE-5Comparison
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- Smith RTS/28HE-6Same series
- Smith RTS/28HE-7Same series
- Smith RTS/28HE-8Same series
- Smith RTS/28HE-9Same series
- Smith RTS/28HE-10Same series
- Smith RTS/28HE-11Same series
- Smith RTS/28HE-12Same series
- Smith RTS/28HE-13Same series
- Smith RTS/28HE-14Same series
- Smith RTS/28HE-15Same series
- Smith RTS/28HE-16Same series
- Smith RTS/28HE-17Same series
- Smith RTS/28HE-18Same series
- 28HE Series series hub
- Buying guide
Sources and verification
- Smith Cast Iron Boilers — 28HE RTS (Water) product page · accessed September 9, 2026
- Smith Cast Iron Boilers — Commercial catalogue · accessed September 9, 2026
- Smith — RTS HE Series Water Boilers product data PDRTSHE-4 (ratings, burner capacities, water piping diagram) · PDRTSHE-4 · accessed September 9, 2026
- Smith — Return Temperature Stabilizer bulletin RTSB-1 · RTSB-1 · accessed September 9, 2026
Facts checked September 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.