What is an Electric Heater
What is an electric heater? Generally speaking they convert electricity to heat. For the purpose of our discussion, we refer to heater that is used in industrial applications.
How does an electric heater convert electricity to heat? The electric heater is basically a resistor. Base on ohms law. The power generated by the electric heater in single phase equals the square of the voltage divided by the resistance.
In troubleshooting or calculating the duty of a 3 phase heater. The next formula is use calculate the resistance of an heater
R (ohms) = 2 x V^2 / ( Power (w) * 1.05)
Electric Heater Failure
Electric Heater failure is fairly common in the electric heating industry. Most electric process heaters failed from moisture in the magnesium oxide insulator due to the poor sealing method. Electric Heater, LLC heaters are hermetically sealed to prevent this mode of failure. In over 18 years of implementing this sealing method, we have yet to have a heater failed from moisture. Hence, for long lasting heater, it is imperative that we specify that the heaters shall have hermetic sealing
Following is how the elements will look like when the heater is wet and energized. The heater elements will have to be replace. We offer electric heater repair as one of our services.
Another common mode of electric heater failure is the overheating and corrosion of the buss bar. These buss bar connects the elements together and they are located inside the heater terminal housing. Electric Heater, LLC uses tin plated copper buss. Ceramic insulators offer the best reliability. They ensure the longevity for an electric heater.
Heater Troubleshooting
Do we have a bad heater? Next are our recommended troubleshooting steps to determine if you have a good electric heater
This entire test shall be performed with qualified personnel. As a minimum the power shall be off, proper process isolation, all lock-out procedures implemented, etc to ensure personnel safety.
Visual Inspection – Look inside the heater housing. Looks for signs of overheating, broken/damage wire, process leakage, corrosion and water damage. If you remove the heater from the vessel, visually examine the heater bundle. Look for signs of physical damage.
Electrical Resistance Test –
On a 3 phase electric heater. Take a phase to phase resistance reading. Resistance reading should be within 10% of the following calculated value. An extremely low reading will indicate a shorted heater and a high reading will indicate an open heater
The following formula is use calculate the resistance of an heater
R (ohms) = 2 x V^2 / ( Power (w) * 1.05)
Electrical Insulation Test –
Utilizing an insulation resistance tester set a 500 VDC. Conduct test from phase to ground. A reading of 5 mega ohm and higher is preferred. A low reading will show a wet heater. A wet electric heater will need to be baked out in our specialized oven to remove the moisture.
Why is my heater wet? It is a common term used to describe a situation where the electrical moisture seal of the heater has failed. This failure allows water (water vapor) into the insulation of an electric heater. Electric process heater utilizes Magnesium Oxide as an insulator between the heating coil and outside sheath. Magnesium Oxide is a good head conductor and provides good dielectric properties when dry. However, Magnesium Oxide is hygroscopic and will absorb moisture from the environment if not sealed. Hence a heater that has low resistance to ground will show moisture contamination in the Magnesium Oxide insulation. Operating the heater at low resistance will cause a short to ground and permanently damage the heater elements.