Dunkirk WPSB Series 4 Gas Boiler
Mid-efficiency cast iron hot-water boiler — 7 sizes, up to 84.1% AFUE, Fuel Smart Hydrostat 3-in-1 control, and a 20-year non-prorated warranty.
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Dunkirk WPSB Series 4 — Built for Chicago Homes
The Dunkirk WPSB Series 4 is a mid-efficiency gas-fired hot-water boiler available in 7 sizes with an AFUE rating up to 84.1%. It features the advanced Fuel Smart Hydrostat 3-in-1 Control, combining temperature limit control, low-water cutoff protection, and boiler reset functionality to reduce fuel consumption and improve system efficiency.
The WPSB includes an integral draft hood and vent damper, reducing overall height and making it ideal for low-clearance or space-limited installations. Its compact footprint and Cast-to-Last 20-Year Non-Prorated Limited Warranty make it a strong choice for residential hot-water heating applications throughout Chicago.
Key Features
Fuel Smart Hydrostat 3-in-1
Combines temperature limit, low-water cutoff, and boiler reset in a single control module — no outdoor sensor required.
20-Year Non-Prorated Warranty
Dunkirk's Cast-to-Last warranty covers the heat exchanger for 20 years, non-prorated — one of the strongest in the industry.
Cast Iron Heat Exchanger
Cast iron sections with push nipples deliver long-lasting, even heat transfer and resist corrosion over decades of use.
Integral Draft Hood & Vent Damper
Built-in draft diverter and vent damper reduce overall unit height — ideal for low-clearance mechanical rooms.
Low Water Cutoff (LWCO)
Factory-installed LWCO protects the boiler from dry-fire damage — a critical safety feature for Chicago hot-water systems.
Compact Footprint
Seven sizes from 75–299 MBH (NG) fit tight Chicago basement and utility-room installations without sacrificing output.
Technical Specifications
| Efficiency | Mid-Efficiency — up to 84.1% AFUE |
| Boiler Type | Hot Water |
| Heat Exchanger | Cast Iron Sections with Push Nipples |
| Combustion | Atmospheric |
| Venting | Chimney Vent — Integral Draft Diverter + Vent Damper |
| Gas Types | Natural Gas (D models) / Propane (DP models) |
| Sizes Available | 7 (3–9 sections) |
| Warranty | 20-Year Non-Prorated Limited (Cast-to-Last) |
| Functions | Temperature limit, LWCO, Boiler Reset |
| Display | LED temperature display |
| Settings | Dial-type adjustments |
| Diagnostics | Indicator lights |
| Outdoor Sensor | Not required for boiler reset |
| Circulator Relay | Included |
| DHW Override | Domestic hot water input override |
| Ignition | 24V intermittent pilot, continuous retry |
Capacity Ranges
D models = Natural Gas · DP models = Propane
| Model | Input MBH | Output MBH | Sections |
|---|---|---|---|
| WPSB-3D | 75 | 63 | 3 |
| WPSB-4D | 112.5 | 94.5 | 4 |
| WPSB-5D | 150 | 126 | 5 |
| WPSB-6D | 187.5 | 157.5 | 6 |
| WPSB-7D | 225 | 189 | 7 |
| WPSB-8D | 262 | 220 | 8 |
| WPSB-9D | 299 | 251 | 9 |
| Model | Input MBH | Output MBH | Sections |
|---|---|---|---|
| WPSB-3DP | 70 | 58.8 | 3 |
| WPSB-4DP | 105 | 88.2 | 4 |
| WPSB-5DP | 140 | 117.6 | 5 |
| WPSB-6DP | 175 | 147 | 6 |
| WPSB-7DP | 210 | 176.4 | 7 |
| WPSB-8DP | 245 | 205.8 | 8 |
| WPSB-9DP | 280 | 235.2 | 9 |
Safety Features & Included Components
Safety Features
- Flame roll-out safety shut-off (fuse link)
- Blocked vent safety shut-off (manual reset disc thermostat)
- Built-in Low Water Cutoff (LWCO)
- Automatic redundant gas valve
- 100% shut-off on continuous retry
- Spare fuse link included
- ASME 30 lb. pressure relief valve
- Temperature/pressure gauge
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
Available Options
Installation Notes
- Most WPSB 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.
- The integral draft hood and vent damper reduce unit height — ideal for tight mechanical rooms.
- Circulator pump ships pre-wired with a 5′ harness for supply or return mounting flexibility.
- Compatible with Fill-Trol expansion tank systems for closed-loop hot-water applications.
- 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.
- All installations include startup, system pressure test, and combustion verification.
Why D's Air & Heating, Inc.
Installed pricing below includes equipment, labor, City of Chicago permits, startup, and a 1-year workmanship warranty. No hidden fees.
Small (75–112.5 MBH)
$6,950
WPSB-3D / WPSB-4D — single-family homes up to ~1,400 sq ft
Medium (150–187.5 MBH)
$7,950
WPSB-5D / WPSB-6D — single-family homes up to ~2,400 sq ft
Large (225–262 MBH)
$9,250
WPSB-7D / WPSB-8D — two-flats, larger single-family homes
XL (299 MBH)
$10,450
WPSB-9D — large two-flats, greystones, multi-zone systems
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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