Firebox Boilers, 10 to 250 Horsepower
Three-pass wetback firebox boilers for low-pressure steam and hot water, built to ASME Section IV in our California code shop. Hinged front and rear doors and a compact footprint for tight boiler rooms.
Code-built boilers and vessels
Code repairs and alterations
Factory-authorized Tech Center
Factory-authorized Burner Tech Center
Fifth generation, family-owned
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McKenna Boiler Works, Inc. builds three-pass wetback firebox boilers in Oceanside, California, from 10 to 250 horsepower. They are stamped to ASME Section IV for 15 psig steam and 30 or 125 psig hot water. Low NOx and ultra-low NOx designs reach as low as 2.5 ppm NOx (corrected to 3% O2) on select models. Hinged front and rear doors open for tube access, and the compact footprint fits tight boiler rooms. For boilers of 2,000,000 Btu/hr or less, McKenna has units pre-certified to South Coast AQMD Rule 1146.2. Call (323) 987-1816.
At a glance
Firebox boiler specifications.
Every McKenna firebox boiler is built to order. These are the ranges we build to; your proposal lists the exact rating, dimensions, and trim.
Type
Firebox, three-pass wetback
Size range
10 to 250 HP
Steam
15 psig
Hot water
30 or 125 psig, up to 250°F
Code
ASME Section IV (H stamp)
Access
Hinged front and rear doors for full access to the tubes and furnace. Standard, off-the-shelf replacement parts, not proprietary ones
Footprint
Compact, for tight boiler rooms
Burner and controls
A burner matched to the boiler and the emissions limit, with Autoflame controls as a standard option. Prefer a specific burner? McKenna also installs and tunes burners and controls from other manufacturers, including a brand your engineer specified
Fuels
Natural gas or propane. No. 2 oil as a backup fuel, or dual fuel. Hydrogen and hydrogen blends with a burner rated for them
Burner package
Piped, wired, and tested in our shop before the boiler ships
Built
Standard sizes or custom to your spec and room
NOx
Low NOx and ultra-low NOx, as low as 2.5 ppm NOx (corrected to 3% O2) on select models
2,000,000 Btu/hr or less
Units pre-certified to South Coast AQMD Rule 1146.2
The design
Built for tight boiler rooms.
A firebox boiler puts low-pressure steam or hot water into a small footprint. Not sure it’s the right fit? A McKenna engineer will tell you plainly.
Three-pass wetback
- The rear turnaround chamber is surrounded by water, so there is less refractory to maintain.
- Gases make three passes, through the furnace and then two banks of tubes, before the stack.
- Standard on every McKenna firebox, 10 to 250 HP.
Hinged front and rear doors
- Both doors swing open on hinges for tube and refractory inspection.
- Tube cleaning and inspections without removing and rigging a door.
- Full access at both ends of the boiler.
Compact footprint
- Sized for boiler rooms where floor space and headroom are tight.
- A practical replacement where a larger boiler won’t fit through the door.
- Laid out to your room when a standard size doesn’t fit.
Pressure and code
Low-pressure steam and hot water, Section IV.
Every McKenna firebox boiler is a Section IV heating boiler, stamped under McKenna’s H certificate. Need steam above 15 psig? See our firetube boilers, built to Section I up to 250 psig.