Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
Dunkirk PSB-5D and Dunkirk PSB-6D are two non-condensing boilers from the Dunkirk Boilers PSB Plymouth Steam Boiler line. Published ratings: Dunkirk PSB-5D at 150 MBH input, 122 MBH heating capacity and 82% AFUE; Dunkirk PSB-6D at 187 MBH input, 153 MBH heating capacity and 82% AFUE. Dunkirk PSB-6D lists 37 MBH more input than Dunkirk PSB-5D (187 MBH against 150 MBH). Both list the same published AFUE of 82%. Dunkirk PSB-6D lists 72 lb more shipping weight than Dunkirk PSB-5D (512 lb against 440 lb).
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Dunkirk PSB-5D | Dunkirk PSB-6D |
|---|---|---|
| Efficiency (AFUE) | 82 % | 82 % |
| Shipping weight | 440 lb | 512 lb |
| Dimensions (W x H x D) | 17-3/4" x 36-3/8 in. x 26-1/2 in. | 21" x 36-3/8 in. x 26-1/2 in. |
| 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 |
| Input (natural gas) | 150 MBH | 187 MBH |
| Input (propane) | 140 MBH | 175 MBH |
| Heating capacity (natural gas) | 122 MBH | 153 MBH |
| Heating capacity (propane) | 114 MBH | 143 MBH |
| Net AHRI steam rating (natural gas) | 92 MBH | 115 MBH |
| Net AHRI steam rating (propane) | 86 MBH | 107 MBH |
| Flue diameter | 6" | 7" |
| Connections | Return/supply 2-1/2 in. NPT; gas 1/2 in. NPT (75/112/150) or 3/4 in. NPT (187 MBH and larger) | Return/supply 2-1/2 in. NPT; gas 1/2 in. NPT (75/112/150) or 3/4 in. NPT (187 MBH and larger) |
| Control | Electronic low-water cut-off with 3/4 in. probe, pressure limit control, steam pressure gauge and glass water level gauge | Electronic low-water cut-off with 3/4 in. probe, pressure limit control, steam pressure gauge and glass water level gauge |
Published ratings: the Dunkirk PSB-5D is rated 150 MBH input, 122 MBH heating capacity and 82% AFUE; the Dunkirk PSB-6D is rated 187 MBH input, 153 MBH heating capacity and 82% AFUE. Dunkirk PSB-6D lists 37 MBH more input than Dunkirk PSB-5D (187 MBH against 150 MBH). Both list the same published AFUE of 82%.
Dunkirk PSB-6D lists 72 lb more shipping weight than Dunkirk PSB-5D (512 lb against 440 lb). The dimensions differs: the Dunkirk PSB-5D lists 17-3/4" x 36-3/8 in. x 26-1/2 in., while the Dunkirk PSB-6D lists 21" x 36-3/8 in. x 26-1/2 in. The flue diameter differs: the Dunkirk PSB-5D lists 6", while the Dunkirk PSB-6D lists 7".
Both records print the same AFUE (82%), electrical requirement (120 V AC / 60 Hz / 1 phase, less than 12 A (15 A circuit recommended)), fuel (Natural gas or propane) and connections (Return/supply 2-1/2 in. NPT; gas 1/2 in. NPT (75/112/150) or 3/4 in. NPT (187 MBH and larger)), per the cited sources.
Dunkirk Boilers
The Dunkirk PSB-5D is a current cast-iron gas steam boiler: 150 MBH natural-gas input (140 MBH propane) for 122/114 MBH NG/LP heating capacity, a 92/86 MBH net AHRI steam rating (383/358 sq ft) at 82% AFUE, with a 6" flue and 440 lb shipping.
Dunkirk Boilers
The Dunkirk PSB-6D is a current cast-iron gas steam boiler: 187 MBH natural-gas input (175 MBH propane) for 153/143 MBH NG/LP heating capacity, a 115/107 MBH net AHRI steam rating (479/446 sq ft) at 82% AFUE, with a 7" flue and 512 lb shipping.
The Dunkirk PSB-6D lists 187 MBH, against 150 MBH on the Dunkirk PSB-5D, per the cited documentation.
Both list the same AFUE of 82%.
It ships at 512 lb against 440 lb for the Dunkirk PSB-5D, 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.