Planar heating and heater wire: how the structures differ.

What heater wire is.

Heater wire is a line-shaped heating element that heats when current flows. In electric blankets and many heated floor mats the wire is laid through the body at set intervals, and the heat made along it passes into the filling and the surface fabric. The spacing, the pattern and the material around the wire are designed product by product.

What a planar heating element is.

A planar heating element is one in which the sheet itself heats. Some are made of a conductive material such as carbon formed into a sheet or a woven mesh. When current flows, heat is made across the whole surface; instead of a laid wire, the size and shape of the heating sheet set the area that heats.

Heat travels three ways.

With either structure, the heat travels in three ways: conduction between things in contact, convection through moving air, and radiation, which travels as infrared without passing through the air. [1]

A warm surface gives off infrared according to its temperature. A heated mattress pad lies on the mattress under the sheet, in contact with the body and the bedding, so conduction from the surface you touch also plays a part.

What a thermal image shows.

A thermal image captures the infrared that a surface gives off and shows the surface temperature distribution as colour. [2] With heater wire, depending on the shooting conditions, stripes may follow the layout of the wire. With a planar heating element, the area of the heating sheet shows as a surface.

The colours are a guide to the surface temperature at the moment of shooting and change with the camera settings and display range. Colours from different images cannot be compared directly, and a thermal image does not show how warm something feels or how it performs.

How to check the type of heating element.

The type of heating element is given in the product specifications, the manual or the maker’s description. The “heating element” or “heater” entry may say whether it is heater wire or a planar element, and what it is made of. If it is unclear, ask the seller.

At JPHEAT.

The two heated mattress pads JPHEAT sells in Singapore, the JPT100J (Single) and the JPT7080J (Half), use no heater wire: their heating element is ORIZUMI, a woven mesh of water-based carbon, and the pad itself runs on DC 24 V. The technology page shows the infrared thermal image from the test report and a thermal image of a working unit. JPHEAT’s four heated floor mats are Japanese AC 100 V models and are not sold in Singapore.

Questions and answers

How do heater wire and a planar heating element differ?

In the shape of the part that heats. Heater wire heats along the wire laid through the body; a planar heating element heats across its whole sheet. Which one suits you depends on the size of the product, how you use it and where.

What are planar heating elements made of?

Some are made of a conductive material such as carbon, formed into a sheet or a woven mesh. JPHEAT’s ORIZUMI is a fine woven mesh of water-based carbon.

Does a planar heating element give off far infrared too?

Anything with a temperature gives off infrared according to that temperature. Whatever the heating structure, a warm surface radiates infrared; the amount and the wavelength distribution depend on the temperature and the material.

If a thermal image shows no stripes, is it planar heating?

A thermal image alone cannot tell you. Whether stripes show depends on the wire spacing, the thickness of the fabric and filling, and the shooting conditions. Check the type of heating element in the specifications or the manual.

Where can I check that a product uses no heater wire?

In the “heating element” entry of the specifications or the manual, or in the maker’s description. JPHEAT states that the heating element of every product it sells is ORIZUMI, a planar heating element with no heater wire.

Does the structure change how warm it feels?

How warm it feels depends on many things: the set temperature, how you touch it, the mattress and bedding and the room temperature. The structure alone does not decide it.

Sources

• [1] CIE vocabulary: infrared and its bands ↗
• [9] NARO Bio-oriented Technology Research Advancement Institution: drying food with far infrared (PDF, Japanese) ↗

The public sources explain general physical principles and terms only. They do not mean that these institutions recommend JPHEAT products, and they say nothing about any action on the human body.