In my previous post about far infrared heaters, I’ve explained my opinion on importance of heaters in an infrared sauna design. Now, my goal is to make you more confident when choosing heater type and configuration for your far infrared sauna. Understanding why you should prefer one heater over another can be extremely hard, especially when sauna companies say about excellence of their heaters without giving specific details about them (sometimes, when browsing infrared sauna site you can find it difficult to get any detail on heater, even it’s type). I’m going to give answers to more specific questions regarding infrared heaters to make you feel more comfortable in the field of far infrared sauna heaters.
In general, there are three different types of heaters used. They differ by material of which the heater’s surface is made:
- metal (incoloy or aluminium);
Ceramic is the most popular type of heaters, as it has high emissivity (degree with which material can emit electromagnetic waves), is durable, and ceramic heaters can have large surface area. However, they are more fragile than other types of heaters, so additional precautions must be taken when transporting such heaters.
Metal heaters are less fragile than ceramic ones, also durable, typically made in tubular form and have the least surface area of these three types of heaters. Metal used is usually aluminium or incoloy (special alloy, which oxide have high emissivity). On the surface this metal is highly oxide to make emissivity higher.
Carbon heaters are less common type of heaters. They are usually made as thin (about 1mm) carbon plate or film, sometimes enclosed in fiberglass. They are flexible and less fragile than ceramic infrared heaters and have largest surface area of all three types. Carbon also has high emissivity.
Heaters can also be distinguished by their shape:
- tubular heaters (metal, some ceramic heaters);
- flat heaters (ceramic, carbon).
Tubular heaters have the advantage – all infrared they emit can be reflected in one direction with reflectors in which they are usually enclosed. Tubular heaters have smaller surface area than flat heaters.
Flat heaters have larger surface area, put have the problem of heat that emitted from the back of such heater – it dissipates and lowers the overall efficiency of the heater.
Another thing to say is that quite often mixed types of heaters are used – for example, incoloy with ceramic coating, or sand-filled ceramic. By mixing and modifying different technologies infrared sauna manufacturers are trying to improve different characteristics of heaters – efficiency, durability, warm-up time and so on.
All infrared heaters get their heat from electrical current which flows through some isolated conductor inside. Typically it is a metal coil embedded in a heater material. Without current there is no heat and no intensive infrared radiation.
The technical information above gives you an idea of how far infrared heaters work and differ. More important question is: what it means for a person taking a sauna? The answer is simple: in a quality made heater, material doesn’t matter much. More important characteristics are surface area and volume of the heater.
Let’s take a tubular metal heater with small surface area and a flat ceramic heater with large surface area. They both consume the same amount of electricity, let’s say 200 watt. In both heaters almost all or this energy is emitted as infrared radiation. Amount of energy emitted from 1 sq. cm. of surface area depends on the temperature of the surface. Surface with high temperature emit more infrared than surface with low temperature. From these we can draw a conclusion: to emit the same 200 watt as a flat heater, tubular heater should have higher temperature, because it has small surface area, while the flat heater has large surface area.
So heater with smaller surface area will always be hotter than heater with larger area which consumes the same amount of electricity. Also, as I wrote in facts about infrared heaters, lower temperature means longer peak wavelength, so heater with lower temperature emits radiation closer to far infrared (not much, though). If there is a health difference between near, mid and far infrared is still in question.
On the other side, from heater volume depends how fast it will warm-up and how fast it will cool-down. If heater is massive it takes more time to heat it to the necessary temperature. Heater warm-up time should not be confused with sauna warm-up time. Sauna warm-up time depends heavily on the overall power of heaters installed, on the volume of the sauna and on speed of air circulation. Slow warm-up and cool-down can be a plus in sauna models which use turning heaters on and off to maintain constant temperature in a sauna. In such models, slow warm-up and slow cool-down lead to more gradual change in intensity of heat when heaters turn on and off.
Tubular heaters (both ceramic and metal) have, usually, short warm-up time, small surface area and high temperature, they emit rays closer to mid-infrared.
Flat ceramic heaters have slower warm-up, larger surface area, lower temperature and emit rays closer to far-infrared.
Flat thin carbon heaters have fast warm-up, largest surface area, lower temperature and emit rays closer to far-infrared.