Dunkirk DXL-K Cast Iron Gas Boiler
High-output atmospheric gas boiler — 10 sizes, 50–300 MBH, hot water and steam configurations, and a 20-year non-prorated cast iron warranty.
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Dunkirk DXL-K — Chicago's Workhorse Boiler
The Dunkirk DXL-K is a heavy-duty cast iron atmospheric gas boiler available in 10 sizes from 50 to 300 MBH. Designed for both hot-water and steam heating applications, it is the go-to replacement boiler for Chicago's two-flats, greystones, and older homes with cast-iron radiator systems.
Built around Dunkirk's proven cast iron section technology, the DXL-K delivers reliable, even heat through atmospheric combustion with titanium composite burners. Its wide capacity range, straightforward controls, and Cast-to-Last 20-Year Non-Prorated Limited Warranty make it one of the most trusted residential boilers in the Chicago market.
Key Features
Cast Iron Heat Exchanger
Heavy-duty cast iron sections with push nipples deliver decades of reliable, even heat transfer and superior corrosion resistance.
Integrated Boiler Control
Factory-installed control module combines temperature limit, circulator relay, and diagnostic indicator lights in a single unit.
20-Year Non-Prorated Warranty
Dunkirk's Cast-to-Last warranty covers the heat exchanger for 20 years, non-prorated — among the strongest residential boiler warranties available.
Atmospheric Combustion
Proven atmospheric burner design with titanium composite burners and automatic redundant gas valve for reliable, low-maintenance operation.
Hot Water & Steam Capable
Available in hot-water and steam configurations — ideal for Chicago two-flats, greystones, and older homes with cast-iron radiator systems.
Wide Capacity Range
10 sizes from 50–300 MBH (NG) cover everything from small single-family homes to large multi-unit buildings and commercial applications.
Technical Specifications
| Boiler Type | Hot Water & Steam configurations |
| Heat Exchanger | Cast Iron Sections with Push Nipples |
| Combustion | Atmospheric |
| Burners | Titanium composite burners |
| Venting | Chimney Vent — Integral Draft Diverter |
| Gas Types | Natural Gas (K models) / Propane (KP models) |
| Sizes Available | 10 (2–12 sections) |
| Capacity Range | 50–300 MBH input (NG) |
| Warranty | 20-Year Non-Prorated Limited (Cast-to-Last) |
| Gas Valve | Automatic redundant gas valve |
| Ignition | 24V intermittent pilot, continuous retry |
| Shut-off | 100% shut-off on continuous retry |
| Burner Assembly | Combination burner/electrode/flame sensor |
| Gas Manifold | With orifices for NG or LP |
| Circulator Relay | Included |
| Diagnostics | Indicator lights |
| Draft | Integral draft diverter + vent damper |
Capacity Ranges
K models = Natural Gas · KP models = Propane
| Model | Input MBH | Output MBH | Sections |
|---|---|---|---|
| DXL-K-050 | 50 | 42 | 2 |
| DXL-K-075 | 75 | 63 | 3 |
| DXL-K-100 | 100 | 84 | 4 |
| DXL-K-125 | 125 | 105 | 5 |
| DXL-K-150 | 150 | 126 | 6 |
| DXL-K-175 | 175 | 147 | 7 |
| DXL-K-200 | 200 | 168 | 8 |
| DXL-K-225 | 225 | 189 | 9 |
| DXL-K-250 | 250 | 210 | 10 |
| DXL-K-300 | 300 | 252 | 12 |
| Model | Input MBH | Output MBH | Sections |
|---|---|---|---|
| DXL-KP-050 | 50 | 42 | 2 |
| DXL-KP-075 | 75 | 63 | 3 |
| DXL-KP-100 | 100 | 84 | 4 |
| DXL-KP-125 | 125 | 105 | 5 |
| DXL-KP-150 | 150 | 126 | 6 |
| DXL-KP-175 | 175 | 147 | 7 |
| DXL-KP-200 | 200 | 168 | 8 |
| DXL-KP-225 | 225 | 189 | 9 |
| DXL-KP-250 | 250 | 210 | 10 |
| DXL-KP-300 | 300 | 252 | 12 |
Safety Features & Included Components
Safety Features
- Automatic redundant gas valve
- 100% shut-off on continuous retry ignition
- Flame roll-out safety shut-off (fuse link)
- Blocked vent safety shut-off (manual reset disc thermostat)
- ASME 30 lb. pressure relief valve
- Temperature/pressure gauge
- Built-in low-water cutoff (LWCO) — hot water models
- Spare fuse link included
Included Components
- Insulated boiler jacket
- Integral draft diverter
- Vent damper
- Temperature/pressure gauge
- Circulator pump (wired with 5′ harness — supply or return mounting)
- ¾″ drain valve
- 30 lb. ASME relief valve
- Combination burner/electrode/flame sensor assembly
Available Options
Installation Notes
- Most DXL-K replacements complete in a single day — minimal disruption to your home.
- D's Air pulls all required City of Chicago permits for every boiler installation.
- Available in both hot-water and steam configurations — ideal for Chicago two-flats and greystones with existing cast-iron radiator systems.
- Circulator pump ships pre-wired with a 5′ harness for supply or return mounting flexibility.
- Natural Gas and Propane conversion kits available for fuel-type changes at time of install.
- High-altitude conversion kits available for installations above 2,000 ft elevation.
- Integral draft diverter and vent damper reduce unit height — fits tight mechanical rooms.
- All installations include startup, system pressure test, and combustion verification.
Why D's Air & Heating, Inc.
Installed pricing includes equipment, labor, City of Chicago permits, startup, and a 1-year workmanship warranty. No hidden fees.
Small (50–75 MBH)
$6,450
DXL-K-050 / DXL-K-075 — single-family homes up to ~1,200 sq ft
Medium (100–125 MBH)
$7,250
DXL-K-100 / DXL-K-125 — single-family homes up to ~2,000 sq ft
Large (150–200 MBH)
$8,750
DXL-K-150 / DXL-K-175 / DXL-K-200 — two-flats, larger homes
XL (225–300 MBH)
$10,950
DXL-K-225 / DXL-K-250 / DXL-K-300 — large two-flats, greystones, multi-zone
Service Call Policy — D's Air & Heating, Inc.
- 1Fee covers travel and full diagnostics only.
- 2Fee is not deducted from repair or installation cost.
- 3After diagnostics, clear repair/replacement options with upfront itemized pricing.
- 4Once Maintenance Agreement approved, 15% discount activates and applies to repair/installation estimate.
- 515% discount does not apply to the initial service call fee.
A $95.35 Service Call Fee is Required for All Service Appointments, Including Warranty Claims.
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