Unilux Boilers


Unilux Boilers is home to the world’s original 5-pass forced draft bent tube design. With over thirty years of manufacturing and operational experience, Unilux has products for just about every application in the boiler industry.

  • The Unilux steel bent water tube boiler design was patented in 1981.
  • The Unilux Boiler is the second oldest bent tube boiler available on the market today.
  • Unilux became American owned in year 2000.
  • In 2004, corporate expansion increased manufacturing to a new state of the art 67000 sq. ft. production US plant.

Design features include natural internal circulation, service friendly design, and thermal shock proof with a standard twenty-year warranty, fast recovery rate, and a four (4) sided water wall furnace.

  • 81% Efficiency Low Pressure Steam Boilers
  • 81% Efficiency High Pressure Steam Boilers
  • 85% Efficiency 5-pass Hot Water Boilers

Unlike other bent tube boilers, Unilux has a large volume furnace of tangent tube design, allowing for a 4-sided water wall heat release and a positive flow through all boiler tubes, as each is exposed to direct radiant heat. Therefore, the radiant heat from the burner flame is not absorbed by refractory and lost to ambient; it is transferred directly to the tube side fluid.

The volumetric furnace heat release of the Unilux boiler is no more than 80,000 BTU/HR/CU.FT. depending on boiler size. Equally or more importantly, the heat release per sq. ft. of heating surface in the Unilux design is never greater than 45,000 BTU/HR/SQ.FT. This value represents the lowest furnace heat release of all steel boiler designs in the market today. 

This inherently provides the greatest protection against metal fatigue as well as being an integral design feature, which helps the Unilux (5) pass design achieve the highest available operating efficiencies.

Unilux Hot Water Boiler

The Unilux 5 pass boiler is a true forced draft design encased in a heavy duty insulated steel housing. Industrial grade housing panels are well insulated with 3″ of high temperature fiberwool. The entire casing, when completed allows for up to +5″ water column pressure. The housing is further insulated with a steel jacket employing a 2″ air insulator space between the inner and outer panels for maximum insulating effect. The front and rear boiler walls are made with our exclusive 3-tier process. First, a 4″ layer of insulating refractory is poured, second a 1″ layer of high temperature fiberboard installed, and third, a 4″ layer of 2700 deg. F refractory is poured. All this is tied together with stainless steel anchors closely spaced and welded to the outer steel housing.Operating radiant losses are calculated at ¼ of 1% of maximum input. Larger boilers (model 2000 and up) have industrial grade 12″ and 10″ walls for ultimate dependability.

Unilux features large volume down comers (one for water designs and two for steam designs) totally isolated from the fireside to provide maximum positive circulation within the pressure vessel. Water flow resistance is minimal, as such; external circulating devices are not required with the Unilux design.

Both the fireside and waterside are easily accessed for inspection and maintenance though strategically located ports on the assembly.
Unilux boiler tubes are no less than 1 ½” SA178A, electric resistance, welded carbon steel high quality construction. Tubes are generally fitted with a precision machined, tapered ferrule that is driven into the machined boiler drums. There is no welding or rolling required. Tube replacement, if required is easily achieved without major disassembly of the boiler.

The Unilux UL/FE boiler is another Unilux first. We are proud to have tackled the job of producing theworld’s first and only line of Underwriters Laboratories Listed and Labeled field erect boiler assemblies. The specifying of a Unilux UL/FE provides the highest available safety and accountability procedure for the field erect market.

  • High thermal efficiencies due to the high number of Gas Passes (5)
  • Field erect design for getting into tight spaces
  • Modulating turndown ratio from 4 to 8:1 depending on the type of burner selected
  • Firing on Natural Gas or # 2 Oil, exceeding environmental regulations
  • Flexible tube design, eliminating the possibility of thermal shock
  • Large Steam drum, capable of handling large load swings
  • Excellent steam quality, due to better internal circulation
  • Natural boiler circulation, eliminating the need of an extra pump. No circulating pump required.
  • No tube welding required, making repairs easy and having the lowest repair cost. Tubes are ferruled fitted
  • Low electrical, maintenance and fuel operating cost. Request a Free Evaluation
  • Lower Installation Cost – Low replacement parts cost, as most parts are available from any supplier
  • Most comprehensive Warranty’s available, including Thermal Shock (25 Years) & refractory warranty of 5 yrs.

If you’d like more information on Unilux or any of our other products, or would like to schedule a lunch and learn at your company, please contact Andrew Fleck (andyf@fluidh.com) or at 414-358-2646.