HEATER ELEMENT LIFE CURVE

Sylvania air heater element life is directly related to the filament wire temperature.  The graph below illustrates that 5000 hours of air heater life is obtainable, if the filament temperature remains below 1900°F.  PLEASE ALSO REALIZE THAT THE HEATER ELEMENT DOES NOT FAIL UNTIL IT REACHES MORE THAN 2200°F.

HEATER PERFORMANCE CURVE

The Sylvania air heater element’s temperature is controlled by the airflow and applied voltage.  Look below at the Sylvania Hot Air Tool’s performance curve showing the safe operating airflow rates and voltages.

 ClICK HERE for pictures of burnt up heater elements due to voltage overshoot or zero airflow with the power was turned on.

HOW TO PREVENT TEMPERATURES ABOVE 1900°F

Because the heater element has an extremely high watt density, a fast closed-loop controller and adequate voltage control are required for safe operation.  Please note the following process recommendations from Osram Sylvania:

  1. Ensure airflow is always turned on BEFORE and AFTER the heater is powered on or off.
  2. Use a type K thermocouple with an exposed junction, and locate the thermocouple within 1″ of the heater’s air outlet.
  3. Using a temperature controller with a 100 ms or faster cycle time to ensure fast response to changing process conditions.  Be sure the power controller and solid state relay are equally fast in regulating the AC voltage to the heater.
  4. Start the heater with a 0° (F or C) Set-Point (SV) to ensure the output signal to the power controller starts off low (0% Output) before the contactor is engaged and immediately applies full power.
  5. Sylvania recommends using the following closed loop Proportional, Integral and Derivative (PID) settings as a starting point for stable temperature control.  Some manual tuning may be required for even more precise process control:
DescriptionSetting RangeDefault
Proportional90-250131
Integral8-209
Derivative0-22
Scan/Refresh Rate≤500ms200msec
  1. Ensure airflow is always turned on BEFORE and AFTER the heater is powered on or off.
  2. Use a type K thermocouple with an exposed junction, and locate the thermocouple within 1″ of the heater’s air outlet.
  3. Using a temperature controller with a 100 ms or faster cycle time to ensure fast response to changing process conditions.  Be sure the power controller and solid state relay are equally fast in regulating the AC voltage to the heater.
  4. Start the heater with a 0° (F or C) Set-Point (SV) to ensure the output signal to the power controller starts off low (0% Output) before the contactor is engaged and immediately applies full power.
  5. Sylvania recommends using the following closed loop Proportional, Integral and Derivative (PID) settings as a starting point for stable temperature control.  Some manual tuning may be required for even more precise process control:
  6. Include a controller ramp rate for starting up the air heater element.  The slower the controller ramps up to the final set-point, the less likely the process will have temperature overshooting problems.  It is recommended the Sylvania air heaters are ramped up to the desire set-point temperature over a period of several minutes.  The following are basic ramp rate recommendations based on the final required set-point temperature, but Sylvania technical support can be contacted for custom temperature ramp rates:
SET-POINT TEMPERATUREDEGREES PER MINUTE
Up to 600°F (300°C)360°F (150°C)
601-1000°F (301-500°C)240°F (100°C)
1001-1400°F (501-760°C)120°F (50°C)
Up to 1650°F (900°C)60°F (25°C)
  1. Reduce the high limit value output of the temperature controller.  Usually the default high limit value is 100%, but this value can be reduced since most air heaters are oversized in wattage for the application. 100% power output normally isn’t necessary to achieve the desired process set-point temperature.  The heater can be manually controlled to determine the approximate fixed output that is required from the power controller for achieving the desired set-point temperature.  This determined value can then be set as the high limit output for the temperature controller.
Osram Sylvania ZTT 2208272 [05] 10/29/13 Supersedes: 03/28/13