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FEATURE
ENCLOSURES
sponsored by
STEGO: THE EVOLUTION OF ENCLOSURE THERMOSTATS
M
ore than 42 years ago, before STEGO came in to existence, enclosures and panels were heated with a lit light bulb
that was, so to speak, in continuous operation. Those were the times before enclosure heaters were available. When the industry finally started using special
heaters for enclosures and cabinets, STEGO, too, took part in the business with their first enclosure heaters called ‘Heiz-Igel’ (meaning ‘heating hedgehog’ from the look of the heater). These heaters were not regulated, thus ran in continuous operation, as there were no enclosure thermostats at that time either. This has proven to be a significant disadvantage, as there is no upper temperature limit in a panel if the heater runs non- stop: permanently high temperatures limit the service life of other devices installed in the cabinet. Some enclosure manufacturers started using household or room thermostats at some point, due to the lack of adequate equipment. However, these were able to measure and control temperatures up to 25˚C only. This was the time when the idea of an enclosure thermostat by Hartmut Eisenhauer came into play. The first controller was a so-called ‘change-over’ contact and located in a metal housing.
It is quite fascinating what can be learned from the company founders of STEGO. What did enclosure climatisation look like in the old times?
and ‘normally open’ contacts, resulting in a major re-design, new thermostats KTO 111 and KTS 111 (see photo below) with Push-in terminals for tool-free connection – the re- design of our classics KTO/KTS 011. Additionally, STEGO
STEGO Small Thermostats KTO 1140 (red) and KTS 1141 (blue)
desired temperature was reached. And then, only if necessary, to switch-on a fan or filter fan using the ‘normally open’ contact that was set to a maximum temperature. This was STEGO’s first product launch of the mechanical small thermostats for enclosure
STEGO Temperature Regulator FZ 170 Series in an aluminium housing
Together with the manufacturer of the bimetal
regulator, Hartmut Eisenhauer advanced a bimetal sensor used for temperatures above 120˚C to the temperature range relevant for use in enclosures and cabinets. It was then possible to heat up an enclosure to a desired temperature, and when the desired temperature was reached, to stop the heater and to start a fan or filter fan ventilating or cooling the space. However, Eisenhauer was not yet satisfied with this solution. He divided the ‘change-over’ contact into two separate contacts – a ‘normally closed’ contact and a ‘normally open’ contact, and put them in two separate housings. Now it was possible to activate a heater for low temperatures, and to stop the heater when the
46 DESIGN SOLUTIONS MAY 2023
climatisation on the market – back then they were called KTO 1140 and KTS 1140, see photo above.
Does this mean
that everyone else has just copied STEGO’s small enclosure thermostats? Let’s just leave this question at that … STEGO is still selling re-designs of the original ‘change-over’ thermostat in large numbers, and has continuously improved the small thermostats with ‘normally closed’
complemented the product range with other types of regulators, such as hygrostats, hygrotherms (a combination of a hygrostat and a thermostat) and electronic regulators. Experts at STEGO are happy to help you to choose the right thermostat for your enclosure application.
The full range can be found on the website.
STEGO
https://en.stego.de/home
Feature
STEGO Small Thermostats KTO 111 (red) and KTS 111 (blue) w/ Push-In connection terminal
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