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 Pennco FSB-3 and Pennco FSB-4 are both non-condensing boilers in the Pennco FSB Series line. The Pennco FSB-3 is rated 75 MBH input, 63 MBH heating capacity and 84% AFUE, and the Pennco FSB-4 is rated 112.5 MBH input, 95 MBH heating capacity and 84% AFUE. Pennco FSB-4 lists 37.5 MBH more input than Pennco FSB-3 (112.5 MBH against 75 MBH). Both list the same published AFUE of 84%. Pennco FSB-4 lists 57 lb more shipping weight than Pennco FSB-3 (322 lb against 265 lb).
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Pennco FSB-3 | Pennco FSB-4 |
|---|---|---|
| Input | 75 MBH | 112.5 MBH |
| Heating capacity | 63 MBH | 95 MBH |
| Net 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 |
| Approx. shipping weight | 265 lb | 322 lb |
| Dimensions (width × height × depth) | 14-1/4" × 29" × 23-1/4" | 17-1/2" × 29" × 23-1/4" |
| Venting | Chimney or sidewall vented | Chimney or sidewall vented |
| Supply/return tappings | 1-1/4" supply and return tappings | 1-1/4" supply and return tappings |
| Gas connection | 1/2" gas inlet | 1/2" gas inlet |
| Control | Control delays burner start until residual heat is transferred | Control delays burner start until residual heat is transferred |
| Fuel | Natural gas or propane | Natural gas or propane |
| Venting (chimney / sidewall) | 4" chimney / 3" sidewall | 4" chimney / 3" sidewall |
Published ratings: the Pennco FSB-3 is rated 75 MBH input, 63 MBH heating capacity and 84% AFUE; the Pennco FSB-4 is rated 112.5 MBH input, 95 MBH heating capacity and 84% AFUE. Pennco FSB-4 lists 37.5 MBH more input than Pennco FSB-3 (112.5 MBH against 75 MBH). Both list the same published AFUE of 84%.
Pennco FSB-4 lists 57 lb more shipping weight than Pennco FSB-3 (322 lb against 265 lb). The dimensions differs: the Pennco FSB-3 lists 14-1/4" × 29" × 23-1/4", while the Pennco FSB-4 lists 17-1/2" × 29" × 23-1/4".
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), venting (Chimney or sidewall vented) and water connections (1-1/4" supply and return tappings), per the cited sources.
Pennco
The Pennco FSB-3 is the second FSB size: 75 MBH input with 63 MBH heating capacity and a 55 MBH net water rating at 84% AFUE, vented through a 4" chimney or 3" sidewall connection.
Pennco
The Pennco FSB-4 is the mid-size FSB: 112.5 MBH input with 95 MBH heating capacity and a 82 MBH net water rating at 84% AFUE, vented through a 4" chimney or 3" sidewall connection.
The Pennco FSB-4 lists 112.5 MBH, against 75 MBH on the Pennco FSB-3, per the cited documentation.
Both list the same AFUE of 84%.
It ships at 322 lb against 265 lb for the Pennco FSB-3, 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.