Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
Smith 19HE-3 and Smith 19HE-4 are two non-condensing boilers from the Smith Cast Iron Boilers 19HE Series line. Published ratings: Smith 19HE-3 at 375 MBH input, 308 MBH gross output and 84.6% thermal efficiency — oil; Smith 19HE-4 at 520 MBH input, 421 MBH gross output and 84.1% thermal efficiency — oil. Smith 19HE-4 lists 145 MBH more input than Smith 19HE-3 (520 MBH against 375 MBH). Smith 19HE-3 carries the higher published thermal efficiency — oil at 84.6%, against 84.1%.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Smith 19HE-3 | Smith 19HE-4 |
|---|---|---|
| Gas burner capacity (as printed) | 375 MBH | 520 MBH |
| Gross output (as printed) | 308 MBH | 421 MBH |
| Net I=B=R water rating | 268 MBH | 366 MBH |
| Fuel | Natural gas; oil and gas/oil firing available | Natural gas; oil and gas/oil firing available |
| Oil firing rate (as printed) | 2.6 GPH | 3.6 GPH |
| Net I=B=R steam rating | 231 MBH | 316 MBH |
| Thermal efficiency — oil | 84.6 % | 84.1 % |
| Thermal efficiency — gas | 82.1 % | 81.5 % |
| Flue pipe diameter | 7" | 7" |
| Boiler tappings | 3" supply taps / 3" return tap (tapping diagram); supplied with 4" water supply tapping and 3" return tapping | 3" supply taps / 3" return tap (tapping diagram); supplied with 4" water supply tapping and 3" return tapping |
| Recommended supply / return piping | 2" supply / 2" return | 2" supply / 2" return |
| Boiler horsepower | 9.2 | 12.5 |
| Heating surface | 23.9 sq ft | 35.8 sq ft |
| Furnace volume | 2.12 cu ft | 3.5 cu ft |
| Water content — steam | 33 gal | 41 gal |
| Water content — water | 38 gal | 49 gal |
| Working weight — steam | 1,673 lb | 2,057 lb |
| Working weight — water | 1,716 lb | 2,122 lb |
| Maximum allowable working pressure | 15 psi steam / 80 psi water | 15 psi steam / 80 psi water |
Published ratings: the Smith 19HE-3 is rated 375 MBH input, 308 MBH gross output and 84.6% thermal efficiency — oil; the Smith 19HE-4 is rated 520 MBH input, 421 MBH gross output and 84.1% thermal efficiency — oil. Smith 19HE-4 lists 145 MBH more input than Smith 19HE-3 (520 MBH against 375 MBH). Smith 19HE-3 carries the higher published thermal efficiency — oil at 84.6%, against 84.1%.
The boiler horsepower differs: the Smith 19HE-3 lists 9.2, while the Smith 19HE-4 lists 12.5. The heating surface differs: the Smith 19HE-3 lists 23.9 sq ft, while the Smith 19HE-4 lists 35.8 sq ft. The furnace volume differs: the Smith 19HE-3 lists 2.12 cu ft, while the Smith 19HE-4 lists 3.5 cu ft.
Both records print the same fuel (Natural gas; oil and gas/oil firing available), flue pipe diameter (7"), boiler tappings (3" supply taps / 3" return tap (tapping diagram); supplied with 4" water supply tapping and 3" return tapping) and recommended supply / return piping (2" supply / 2" return), per the cited sources.
Smith Cast Iron Boilers
The Smith 19HE-3 is a 9.2 HP cast-iron sectional power-burner boiler rated 308 MBH gross output — 375 MBH gas or 2.6 GPH No. 2 oil burner capacity — with a 7" flue connection and printed thermal efficiencies of 84.6% (oil) and 82.1% (gas).
Smith Cast Iron Boilers
The Smith 19HE-4 is a 12.5 HP cast-iron sectional power-burner boiler rated 421 MBH gross output — 520 MBH gas or 3.6 GPH No. 2 oil burner capacity — with a 7" flue connection and printed thermal efficiencies of 84.1% (oil) and 81.5% (gas).
The Smith 19HE-4 lists 520 MBH, against 375 MBH on the Smith 19HE-3, per the cited documentation.
The Smith 19HE-3 carries the higher published thermal efficiency — oil at 84.6%, against 84.1%.
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.