Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
Both the Dunkirk WPSB-3D and the Dunkirk WPSB-4D belong to the Dunkirk Boilers WPSB Series 4 line of non-condensing boilers. The Dunkirk WPSB-3D is documented at 75 MBH input, 63 MBH heating capacity and 84% AFUE, while the Dunkirk WPSB-4D is documented at 112.5 MBH input, 94 MBH heating capacity and 84% AFUE. Dunkirk WPSB-4D lists 37.5 MBH more input than Dunkirk WPSB-3D (112.5 MBH against 75 MBH). Both list the same published AFUE of 84%. Dunkirk WPSB-4D lists 62 lb more shipping weight than Dunkirk WPSB-3D (377 lb against 315 lb).
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Dunkirk WPSB-3D | Dunkirk WPSB-4D |
|---|---|---|
| Input | 75 MBH | 112.5 MBH |
| Heating capacity | 63 MBH | 94 MBH |
| Net AHRI water rating | 55 MBH | 82 MBH |
| Efficiency (AFUE) | 84 % | 84 % |
| Domestic hot water | Heating-only boiler — domestic hot water comes from a separate indirect tank or water heater | Heating-only boiler — domestic hot water comes from a separate indirect tank or water heater |
| Boiler water content | 6.3 gal | 8.1 gal |
| Shipping weight | 315 lb | 377 lb |
| Dimensions | 11-1/4" wide x 36-3/8 in. high x 26-1/2 in. deep | 14-1/2" wide x 36-3/8 in. high x 26-1/2 in. deep |
| Gas connection | 1/2 in. NPT gas inlet; 1-1/4 in. water return/supply (all models). | 1/2 in. NPT gas inlet; 1-1/4 in. water return/supply (all models). |
| Electrical | 120 V AC / 60 Hz / 1 phase, less than 12 A (15 A circuit recommended) | 120 V AC / 60 Hz / 1 phase, less than 12 A (15 A circuit recommended) |
| Fuel | Natural gas or propane | Natural gas or propane |
Published ratings: the Dunkirk WPSB-3D is rated 75 MBH input, 63 MBH heating capacity and 84% AFUE; the Dunkirk WPSB-4D is rated 112.5 MBH input, 94 MBH heating capacity and 84% AFUE. Dunkirk WPSB-4D lists 37.5 MBH more input than Dunkirk WPSB-3D (112.5 MBH against 75 MBH). Both list the same published AFUE of 84%.
Dunkirk WPSB-4D lists 62 lb more shipping weight than Dunkirk WPSB-3D (377 lb against 315 lb). The boiler water content differs: the Dunkirk WPSB-3D lists 6.3 gal, while the Dunkirk WPSB-4D lists 8.1 gal. The dimensions differs: the Dunkirk WPSB-3D lists 11-1/4" wide x 36-3/8 in. high x 26-1/2 in. deep, while the Dunkirk WPSB-4D lists 14-1/2" wide x 36-3/8 in. high x 26-1/2 in. deep.
Both records print the same AFUE (84%), domestic-hot-water arrangement (Heating-only boiler — domestic hot water comes from a separate indirect tank or water heater), gas connection (1/2 in. NPT gas inlet; 1-1/4 in. water return/supply (all models).) and electrical requirement (120 V AC / 60 Hz / 1 phase, less than 12 A (15 A circuit recommended)), per the cited sources.
Dunkirk Boilers
The Dunkirk WPSB-3D is a current atmospheric cast-iron gas water boiler: 75 MBH natural-gas input (propane 70 MBH) for 63 MBH heating capacity and a 55 MBH net AHRI water rating at 84% AFUE, with 6.3 gallons of water content and a Fuel Smart Hydrostat control.
Dunkirk Boilers
The Dunkirk WPSB-4D is a current atmospheric cast-iron gas water boiler: 112.5 MBH natural-gas input (propane 105 MBH) for 94 MBH heating capacity and a 82 MBH net AHRI water rating at 84% AFUE, with 8.1 gallons of water content and a Fuel Smart Hydrostat control.
The Dunkirk WPSB-4D lists 112.5 MBH, against 75 MBH on the Dunkirk WPSB-3D, per the cited documentation.
Both list the same AFUE of 84%.
It ships at 377 lb against 315 lb for the Dunkirk WPSB-3D, per the cited sources.
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.