A capillary thermostat is a useful component for measuring and regulating the temperature, used in all those industrial applications where the temperature sensor cannot be near the electrical contacts and controls, such as for example boilers, fireplaces, pellet stoves and other domestic appliances, such as air conditioning, washing machines, dishwashers, machinery for horeca & catering, medical sector…

How is a capillary thermostat made?

The capillary thermostat consists of a body, several electrical contacts and a probe, the heart of the thermostat. The probe is formed by a bulb, the actual capillary, of variable length, and by the sensitive element. The bulb is the part that detects the temperature, the capillary is the little pipe that connects the bulb to the sensitive element, also known as the expansion bellows. The bellows expands more or less according to the detected temperature, acting on the electrical contact (opening or closing it).

Principle of operation of the capillary thermostat

In order to open or close an electrical contact, the probe positioned inside the thermostat acts according to the principle of expansion of the materials based on the detected temperature. Inside the probe, which can generally be made of copper or stainless steel, a fluid (petroleum or synthetic liquid) flows and, based on the increase of temperature, and therefore pressure, expands inside the probe, going to “push” on the metal walls of the expansion bellows, which activates the electromechanical mechanism.

Depending on the function they are called to perform inside the appliance, capillary thermostats can be divided into two macro-categories: regulation capillary thermostats and safety capillary thermostats.

Capillary capillary thermoregulators

The most correct name to identify capillary regulation thermostats is “capillary thermoregulators”. They are able to trigger the electrical contact to activate/deactivate the appliance in which they are installed, based on a temperature set via the thermostat pin. In domestic ovens, for example, if the set temperature is reached, the capillary thermostat sends the signal to stop heating the resistance, opening the electrical contact.

Our products: TR2 TRZ

Capillary safety limiters

Also in this case, capillary safety thermostats are better called capillary safety limiters. Upon reaching a temperature, generally set in the factory, the thermostat opens the contact and prevents the circulation of electric current inside the appliance in which it’s installed. In this way, overheating and malfunctions, which could create very serious damage to the system or to the appliance, are avoided. Some models are also equipped with “positive safety”: an additional safety precaution which, in case of failure of the thermostat itself, keeps the electrical contact open, avoiding damage.

Our products: LS1/LS3

IMIT range of capillary thermostats

IMIT produces more than 7000 codes of capillary thermostats, differentiated according to the intervention temperatures (from -30 ° C to 300 ° C). Knowing the intervention temperature allows to choose the most suitable production material: copper for the lowest temperatures and stainless steel for the highest temperatures. The length of the bulb and capillary are defined on the basis of the degree of expansion necessary to activate / deactivate the electrical contact and of course on the basis of the precision required. It is also possible to choose the arrangement of the electrical contacts: horizontal, vertical, 45°, etc. IMIT has been producing TR2,TRZ, LS1/LS3 for over 40 years: always among our best-selling products!

To learn about the different applications of capillary thermostats, we invite you to read this article.

Produce a capillary thermostat

The production of a capillary thermostat is very complex and articulated: multiple stages of mechanical production of the probes are necessary, as many to produce and assemble the electrical contacts and micro-mechanisms, and then proceed with filling the probe with the fluid under controlled pressure. Finally, there are calibration and functional test processes, so as to have a safe, reliable and long-lasting product.

One of the production processes that our visitors find most fascinating is the welding of the expansion bellows membrane.

Each IMIT capillary thermostat is produced and certified according to the highest international standards, certified by the numerous quality marks obtained over the years: CE, ENEC, PED, TUV, UL, CSA, EAC, DIN.

To find out more, browse our website and download our catalog. For further requests or commercial information about our products for industry, send an email to info@imit.it. Our staff will reply as soon as possible.