Heating Element FAQ

A resistance wire, usually a nickel-chrome alloy, running down the middle of a metal tube. The space around it is packed with magnesium oxide powder, which conducts heat well and does not conduct electricity. The tube is then compressed, which makes the powder dense and the element mechanically solid.

Almost always because the heat could not get away fast enough. A dry tank, a scaled sheath, a loose band, an oversized bore, a blocked fan, or a watt density that was too high from the start. The wire fails at the hottest point, but the cause is nearly always outside the element.

There is no honest single figure, because the same element lasts years in one machine and months in another. What decides it is watt density, the medium, how clean the sheath stays and how the element is controlled. An element that fails repeatedly in the same place is a design problem, not a quality problem.

Measure the overall length, the heated length, the sheath diameter and the thread or flange size. Read the voltage and wattage off the tag if there is one. If there is not, measure the cold resistance in ohms — power equals voltage squared divided by resistance — and note the termination type.

Divide the square of the rated voltage by the rated power. A 2000 W element on 220 V should read about 24 ohms cold. A reading far above that means a broken wire; a reading near zero means a short. Also measure between the pin and the body — that should read as an open circuit.

No. The failure is inside a sealed, compacted tube, and cutting it open lets moisture into the magnesium oxide powder. An element that has tripped an earth-leakage breaker after standing idle is a different case — that is damp, not failure, and drying it slowly in a low oven sometimes brings it back.

Whatever the machine supplies. Below about 3 kW, 220 V single phase is usual; above that, 380 V three phase, with the load split across three elements or three groups. An element is wound for one voltage — running it on another changes its power by the square of the difference.

The power divided by the heated surface, in watts per square centimetre. It is the number that decides how long the element lasts, and it matters more than total power. The watt density calculator on this site works it out and checks it against your medium.

Many element types can be built with a thermocouple inside the sheath or brought out beside it, which puts the measurement where the heat actually is. Ask about it before the element is built — it is not something that can be added afterwards.

By the diameter and length, the power and voltage, the sheath material, the termination and thread, whether a thermocouple is built in, and the quantity. That is why catalogue pages quote per order rather than showing a figure that would be wrong for most enquiries.

What is being heated, the working temperature, the voltage available, the power or the physical sizes, the mounting, and the quantity. A photo of the old element with a tape measure beside it answers half of those at once.

That is what the custom design and build pages are for. There are three routes — from your drawing, from your sample, or designed from your working conditions — and each page lists exactly what to send.