Installation relays
An installation relay is an electrical device that responds to a change
in a certain physical quantity, such as electrical voltage or current.
It performs a step change of state in one or more output circuits due to
changing input conditions.
The task of the relay - controlling the electric circuit
The role of the relay is to control the operation of an electric
circuit (or a group of circuits) in an efficient and safe way. Relays
control lighting, ventilation systems, heating, heat pumps, but also
quite small motors that drive shutters or blinds in the windows.
Although the relays are implemented in various forms (e.g. for
installation in boxes), today installation relays are the most popular -
especially in applications in public utility facilities or residential
buildings. It is worth knowing that regardless of the type of device,
the appropriate selection of the relay is not only a key issue, but also
requires some experience and knowledge in the field of electrical
engineering.
Electromagnetic relay in installation housing
The installation relay is not some particular type of device, but simply
an electromagnetic relay enclosed in a installation box . Thanks to
this, it is possible to standardize the device dimensions and mount them
on TH35 rail in modular switchboards.
The basic electromagnetic relay performs the on-off function, that
is, it closes and opens the output electrical circuit with the use of a
signal at the device input. The task is performed by two main elements
of the device - the coil and contacts. After the control circuit is
supplied with power to the coil, the contacts close or open - depending
on whether they are make, break or changeover contacts.
Installation relays look very similar to miniature circuit breakers,
i.e. esek. A diode is installed on their housing to indicate the status
of the power supply. Most often, the correct power supply is indicated
by a green LED emitting a continuous light.
Relays in building and industrial automation
Installation relays are commonly used in electrical installations of
industrial automation. They are used in many production devices,
electrical machines or control systems, e.g. conveyor belts. However, it
is worth knowing that the relays are also responsible for controlling
escalators in shopping centers, ventilation, elevators and street
traffic lights. They are also very often used in building automation
, where they cooperate with the control clocks of administrative
circuits of multi-family buildings, switches in stairwells or other
control buttons. They are also an important element of "smart home"
systems.
How to choose the right relay?
An incorrectly selected relay will malfunction, which can easily lead to
irreparable damage to electrical devices and electronic systems.
Therefore, when replacing or installing the relay, the most important
parameters of the device must be taken into account, such as:
- type of contacts (make, break or changeover),
- rated voltage - sometimes the manufacturer allows the device to be
powered with both 24 V (alternating and direct) and 230 V
alternating voltage,
- maximum contact voltage,
- maximum switching capacity, i.e. the maximum power that can be
switched on with the relay,
- load current (maximum and rated),
- electric and mechanical durability determining the number of
switchings for which the manufacturer guarantees the correct
operation of the device,
- operating temperature (usually manufacturers guarantee stable
operation of the device at temperatures from -20 to 50 degrees
Celsius).
It is also important to choose from the offer of proven, well-known
manufacturers who guarantee that the relays made by them are of the
highest quality, just like other devices.