Condensing Firetube Hydronic Boiler

Size Range:
399,000 - 750,000 BTU/HR

Fuel Options:
Natural Gas

  • Energy Star
  • AHRI
  • ASME
  • ETL
  • US Green Building Council
  • Low NOx Certified

Product Overview

Hundreds of thousands of installations around the world rely on Fulton’s legendary rugged, robust and reliable boilers. Like all Fulton products, the ENDURA XE is built to last and delivers leading-edge efficiencies and utility savings.

Reduce Fuel Costs & Emissions

The ultra-high efficiency heat exchanger and fuel-saving burner reduce fossil fuel use by 15% and NOx emissions by 80% compared to conventional boilers.

Simplify Your Installation

Fully electronic combustion controls use Flame-by-Wire™ technology. This installer friendly system is simpler to learn and operate, significantly reducing commissioning time and complexity.

Trusted Long-Life Durability

Firetube architecture is recognized for superior dependability and ease of installation. The ENDURA XE envelops tubes within a large volume of water, eliminating costly buffer tanks and primary-secondary piping.

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Key Features

  • Efficiency up to 99%
  • Up to 15:1 Turndown
  • Flame-by-Wire™ Combustion Technology
  • Real-Time O2 Compensation™
  • Compact Design
  • Designed for Variable Primary Flow
Mesh Burner Flame

Reliable, Low Maintenance Burner

Fulton combines environmentally friendly low NOx emissions with the rugged durability of industrial-grade equipment. Burner maintenance has never been simpler.

  • Simpler Maintenance & Lower Cost of Ownership
  • Even Tube Heat Loading for a Longer Lasting Heat Exchanger
  • Exceptionally Durable with Low NOx Emissions

Firetube Technology

The ENDURA XE™ is engineered and built to the same rugged reliability standards as Fulton’s heavy-duty industrial boilers. Superior construction materials and water management make the ENDURA XE last longer, even in the most demanding applications.

  • Built-in Buffer Reduces Cycling
  • Lower Pump Head Requirements
  • Protects Against Scale & Corrosion

Supercharged Heating

ENDURA XE packs more performance into a smaller package, keeping your building efficiently and reliably heated while saving valuable space in the mechanical room.

Stainless Heat Exchanger

Type 439 stainless steel features 68% greater strength than 316L. There is also zero-risk of chloride stress corrosion cracking, a catastrophic mode of failure seen with boilers using 304 and 316L.

Long-Lasting Durability

Innovative water baffle technology prevents scale from forming, ensuring a long-lasting and efficient heat exchanger. This maximizes heating comfort and lowers lifetime fuel costs.


Combustion Technology

Inspired by advances in automotive and aviation, Flame-by-Wire™ technology replaces the use of conventional pneumatic (“neg-reg”) and mechanical linkage systems with a modern system of independent air and gas valves. Real-time O2 Compensation™ continuously tunes the burner air-fuel ratio, automatically optimizing for seasonality.

  • Simplifies Start-Up & Maintenance
  • Maximizes Condensing Operation
  • Reduces Fuel Bills & Emissions
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Specifications & Dimensions


EXE-399 EXE-500 EXE-650 EXE-750
Input Capacity (MBH) 399 500 650 750
Water Content (GAL) 17.9 17.9 17.9 17.9
Pressure Drop at 20°F ΔT (PSI) 0.6 0.9 1.4 1.9
AHRI Thermal Efficiency (%) 98.0 97.3 96.3 96.0
Height (IN) 73.7 73.7 73.7 73.7
Width (IN) 26.3 26.3 26.3 26.3
Depth (IN) 28.9 28.9 28.9 28.9
Operating Weight (LBS) 537 537 674 674
Sides (IN) 0 0 0 0
Front (IN) 24 24 24 24
Top (IN) 16 16 16 16
Rear (IN) 12 12 12 12

ENDURA XE Documents

3.08 M
980.21 K
4.74 M
2.43 M
1.92 M

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