How the mattress is protected from overheating?

Ereada®  mats have double safety systems to avoid overheating.

1. First one is the thermostat type built-into controller chip with the standard thermosensors. There are 3-8 pieces in the mat, depending on size. 

These sensors measure the temperature of the mat in different spots and report to the controller. 

If the controller detects overheating, it shuts off the heating system. 

The same sensors and thermostat controller system are also used for maintaining the set temperature. 

When the mat heats up to the set temperature, the system stops heating.  And when the mat cools down approximately 5 degrees below the set level, it resumes.

2. The second safety system (emergency system) consists of bimetal sensors/auto shut-off switches. 

There are 2-6 bimetal strips in the mat. They are bridged. These strips are used to convert the temperature change into mechanical displacement. 

The strip consists of two strips of different metals, which expand at different rates as they are heated. 

The different expansions force the flat strip to bend one way if heated and in the opposite direction if cooled below its initial temperature. 

The metal with the higher coefficient of thermal expansion is on the outer side of the curve when the strip is heated and on the inner side when cooled. 

These bi-metal strips function as the power switches connecting or disconnecting electrical wires. They are fixed into the EMF-free heating cables inside the mat to go through them. 

The setpoint is around 74-77 C (165-170F). If the mat controller thermostat function fails and the temperature of the mat raises higher than the maximum temperature level of 158 F, the higher temperature will open contact, and the heating cables are cut, thus preventing the electricity flow. 

When the mat’s temperature goes down, the metal strips cool down and close the contacts.

If overheating occasionally occurs (for example, if you put an amethyst pillow on the mat’s heating surface in the area where there are no temperature sensors), bimetal sensors will do the standard shut-off, and, after cooling down, the mat will resume working properly. 

But if the temperature sensors fail or the controller chip does not work properly, bimetals will auto shut off, and the mat will not be working after this.

There are several such bimetal sensors in the mat, and each one will shut off the heating system in case of overheat. 

Based on everything said above, this emergency system is double safe.