No chance for dust and water
Most of the time, circuit breakers stay inconspicuously in the background. But if a situation becomes dangerous, they immediately have everything under control and disconnect overcurrent in a flash. A requirement for circuit breakers to functional smoothly is that they do not get damaged during operation. Harsh environmental conditions put breakers at risk. Without a suitable seal, dust and liquids find ways to ingress into the circuit breakers’ interior. Subsequently, bimetals start to corrode, contacts get dirty and latching mechanisms work very sluggishly. It is difficult to know if the breaker will reliably trip when the next overcurrent occurs.
Major risk zone: actuating area
In most cases, the following is true: The actuating area of a circuit breaker has the highest risk. If it is not properly sealed, dust and liquids such as rain, detergents or blood (in medical equipment) can penetrate into the circuit breaker. This is because all actuators, like toggles or reset buttons, have an air slot on the rear. Even if it is very small, it allows dust and liquids to enter freely. Therefore, E-T-A offers a range of optional water splash covers for many of its circuit breakers. They are typically made of PVC or silicone and can either be snapped or screwed on. Some circuit breaker series are even available with seals pre-mounted in the factory.
Additional sealing of the mounting hole
Another weak spot is the circuit breaker mounting cut-out. If this hole is not also sealed, dust and liquids can penetrate into the interior of equipment and machinery and cause considerable damage. As a solution, E-T-A offers seals which protect both the circuit breaker mounting cut-out and the actuating area. As an example, look at the 3120 snap-in model with accordion-style seal. When installing the circuit breaker, an all-round rubber lip is firmly pressed against the housing, thus reliably protecting the mounting hole against ingress of water or dust. We can achieve protection degrees of up to IP65 with this solution. If this value is not sufficient, a seal with screws is required. Only mounting with screws is suitable to provide reliable double protection (actuating and installation area) with ratings of IP66 or IP67.
Rear-side protection of the terminal area
Even with a very good seal for the circuit breaker actuation and installation area it may not serve its purposes, if dust and liquids can penetrate into the breaker’s interior via other ways during operation. In these cases, an additional terminal shroud is required to protect the circuit breaker’s terminal area. Generally, dust and water can also penetrate from this side. In this case, E-T-A offers a choice of sealing solutions, for instance for the 1110 circuit breaker/switch combination.
