Series 400 Boilers


Wetback Scotch Marine Boilers

The Series 400 uses the latest HVACR technologies and is ideal for all commercial and industrial applications. It provides fuel efficiencies that exceed most four-pass designs. Having no large refractory rear door, these boilers allow one technician easy access to all tubes.

Steam Pressures to 15-300 PSI

Hot Water Section I and Section IV

Available with Low NOx

Series 400 Boilers

30-1500 HP


1,004-50,213 MBTU/HR

Steam To:

300 PSI

Hot Water To:

60 PSI

The Hurst 400 Series three-pass wetback scotch marine boiler is an ideal choice for all commercial and industrial applications when engineering mechanical systems using the latest HVACR technologies. The Hurst 400 Series boiler provides fuel efficiencies that exceed most four-pass designs. Having no large refractory rear door, these boilers allow one technician easy access to all tubes. The boiler's front doors can be opened without removing any burner components or controls.

Capacities range from 15 to 2,000 HP and 1,004 to 50,213 MBTU/HR. Available for 15 PSI Steam and 30 PSI Water (60 PSI Water Optional).

  • Factory assembled, prewired and tested
  • No field assembly required
  • UL listed boiler/burner packages
  • Fully assembled, prepiped, prewired, pressure tested gas trains
  • Complies with ASME, UL, CSD-1 and ASHRAE standards
  • High efficiency, low stack temperatures
  • Customer service support through national network of sales, service, start-up, training and parts by factory representatives.

Wetback Advantage

Dry backs boilers are subject to deteriorating rear refractory, leaking baffles, leaking door seals, and often found with a heat-stressed rear tube sheet. Fragile refractory baffling and door seals will require continuous monitoring, maintenance, and replacement, costing thousands of dollars in materials and specialized labor costs over the life of the boiler. In addition, broken baffles and leaking seals will short-circuit the boiler's gas flow, causing high stack temperatures and lowering efficiency until repairs can be made.

Standard Features

Built in accordance with the ASME Code, the wet back design has proven to give much longer useful life cycles than dry back boilers.

Each unit is tested and inspected and registered with the National Board of Boiler and Pressure Vessel Inspectors.

Hurst Boiler utilizes state of the art computer design techniques in every boiler. This accounts for accurate calculations of construction materials and optimum utilization of the boiler's performance criteria.

The Series 400 boiler is designed for optimum fuel efficiency and has proven in certified tests to meet, and often exceed, the efficiencies of four-pass boilers.

Low Maintenance
There are no refractory baffles to replace or maintain. Elimination of these will result in thousands of dollars in savings.

Tube Sheets
The wet back has independent tube sheets with uniform temperatures. Three and four pass dry back boilers have tube sheets with large temperature variations and this results in premature tube failure and cracks in the tube sheets.

Easy Access
Since there is no large refractory rear door, one man can easily remove the rear cover plates for access to the tubes. Front doors can be opened without removing burner components or controls.

With computer aided design, Hurst has made the wet back a space saving workhorse without sacrificing the principle of 5 sq. ft. of heating surface per BHP.

Hurst uses name brand burner components with proven reliability. Every unit is boiler/burner compatible and tested at the factory prior to shipment.

Hurst Boiler 400 Series Schematic

Standard Steam Trim

  • Operating & limit pressure control
  • Modulating pressure control (when applicable)
  • Water column with gauge glass probe typecombination low water cut-off & pump control (not shown)
  • Probe type auxiliary low water cut-off with manual reset
  • Water column drain valve
  • Safety relief valve(s) per ASME Code steam gauge
  • Stack thermometer

Standard Water Trim

  • Operating & limit temperature control
  • Modulating temperature control (when applicable)
  • Low water cut-off control with manual reset
  • Combination pressure, temperature gauge
  • Hot water return baffle for shock resistance
  • Safety relief valve(s) per ASME Code
  • Stack thermometer