Bundle rod heater

How to choose the right Bundle rod heaters for your furnace?


Many industrial processes require furnace heating, which usually requires temperatures exceeding 900 °C for the manufacturing process. All of this is executed through the use of electric-powered bundle rod heaters, which provide the temperature control and reliability required to complete a manufacturing process or operation by furnace heating.

What is bundle rod heater?

Bundle rod heater is a type of furnace heater that consists of rod-shaped heating elements that are supported by ceramic discs. These heaters can be installed in the furnace either vertically or horizontally. The horizontal assembly necessarily requires the use of a radiant tube to support the heating element in the furnace. Moreover, high power is delivered by heaters in combination with radiant tubes. Radiant tubes are intended to protect the elements from the furnace atmosphere, avoid corrosion, and remove gas impurities. They are designed for long life as well as maintenance-free operation. These heaters typically have higher watt densities due to the free-radiating property of the heating element design.

These heaters are widely used in a variety of furnace heating applications due to their durability and adaptability, as well as their ease of installation and replacement. Marathon Heaters has been a satisfactory and industry-leading bundle rod heater supplier for many years. We can also offer custom designed furnace heaters with the required voltage and wattage depending on the different industrial applications.

Heat Transfer through furnace heaters

Heat transfer primarily takes place via the radiation mode of heat transfer in bundle rod heaters. When BRH is installed inside the furnace, then the air in the furnace acts as a participating medium for the radiation. Bundle rod heaters are electrically powered and then transmit heat through heating elements inside the furnace. An intermediate medium is not necessary in this mode of heat transfer. The object to be heated should be kept close to the heater to maximize heat transfer. In this case, object refers to the component that we want to heat up using radiation. Watch the video at to learn how the bundle rod heater works to transfer heat inside the furnace.

Specifications of bundle rod heater by marathon

The heating elements used for bundle rod heaters are available in nearly any length starting from 300mm. Ferritic alloys, powder metallurgical heating elements, Mara FeCrAl, and NiCr 80/20 are some of the materials used for heating elements. These materials can be used for higher temperature ranges in furnace heating. Power ratings of individual heating elements are feasible up to 75 kW, with watt densities of up to 3 W/cm². Furthermore, compared to other heaters, it has the highest power rating (up to 100 KW) when combined with radiant tubes. Ferritic alloys can withstand temperatures up to 1100 °C, while NiCr alloys can withstand temperatures of up to 800 °C. Moreover, temperature control for both necessary heating as well as uniform heating can be achieved through integrating a thermocouple with the heater.

Some of the other components used are:

  • Ceramic Disc: Used to encase all of the heating elements in a complete unit. It is made up of alumina. They are available in a variety of shapes, including flower, round, conical, rectangle, as well as edge wound. Ceramic discs have holes through which the heating element passes, and these discs are used to hold the heating element and can resist very high temperatures.
  • Terminal Rod: The power supply is carried by this rod. SS 310, INCOLOY, FeCrAl, or NiCr 80:20 are common materials. The number of rods required is determined by the supply connection.
  • Center Rod: This rod provides the central support to the heater. SS 310 or INCOLOY is commonly used. 
  • Fiber Disc: Used for holding the terminal rods and central rod together. It is installed within the heater’s cold zone. It is formed of ceramic fibre.

Accessories for bundle rod heater

Radiant tubes and hangers are the two accessories available for supporting and mounting the bundle rod heaters. When used with radiant tubes, the elements are isolated from the furnace and thus protected from the harmful atmosphere of the furnace. Depending on the heater’s area, the tube’s length as well as it’s diameter can be changed. Radiant tubes can be made of cast alloys, Incoloy, stainless steel (SS), or stainless steel (SS) and have a thickness of 1.5 to 8 mm. In order to prevent impurities from the furnace atmosphere (particularly in aluminium and zinc holding and melting furnaces) from entering the tubes, Marathon coats radiant tubes and hangers with a special boron nitride coating.

Radiant tubes for bundle rod heater
Radiant Tube

Why marathon’s Bundle Rod Heater are best in the industry?

We have been a leading bundle rod heater supplier for many years owing to the use of advanced technology for heater manufacturing. Bundle rod heaters are built with the required heating element for the corresponding temperature range. We can also construct furnace heaters with varying lengths and power ratings. Our range of bundle rod heaters is used widely by many industries for furnace heating applications. These heaters have an advantage over others due to their ease of repair as well as their high temperature performance. Furthermore, bundled rod elements with a higher power output facilitate higher heat transfer rate.


  • SQF furnace
  • Carburizing furnace.
  • Galvanizing furnace in steel industries.
  • Spherodizing furnace
  • Heat treatment furnace in automotive industries.
  • Annealing furnace.
  • Primary aluminium holding as well as melting furnace.


  • Higher watt densities can be achieved.
  • Both vertical as well as horizontal mounting position for the heater is possible.
  • Temperature control for precise heating.
  • They can be installed in or withdrawn from a running furnace without necessitating the furnace to cool down.
  • Heating elements are resistant to corrosion caused by furnace gases.
  • Minimum harm to the environment.


We are recognized as one of the leading suppliers of bundle rod heating elements for wide range of furnace heating applications. Widely used in all types of heat treatment furnaces, our heaters can withstand temperatures of up to 1100°C both vertically as well as horizontally. For further queries, email us at