Wiring of the two pressure switches
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I currently have two steam pressure switches, one for low-pressure alarm and the other for high-pressure alarm. My configuration requirement is that the signal input should be ON under normal conditions, and it should become OFF when the steam pressure is either too high or too low. So, should these two switches be connected in NC or NO configuration?
As I understand it, all of them connect to NC; there are only two options. If you’re not sure, it’s better to try both – it will also help you gain a deeper understanding
Personally, I think that whether the two switches are NO or NC, it is possible to configure them so that the signal input is ON under normal conditions. Choosing NO or NC is primarily based on safety considerations
In accordance with fail-safe requirements, it should give a low-pressure alarm when connected to NO; power is supplied when the pressure is normal, and a power-off alarm is triggered when the pressure is low. When the pressure is high, it is connected to NC; power is supplied when the pressure is normal, and an alarm is triggered when the pressure becomes too high.
In accordance with fail-safe requirements, it should give a low-pressure alarm when connected to NO; power is supplied when the pressure is normal, and a power-off alarm is triggered when the pressure is low. When the pressure is high, it is connected to NC; power is supplied when the pressure is normal, and an alarm is triggered when the pressure becomes too high.
NC/NO refers to the on/off state of a device that is not powered under normal pressure conditions. When the steam pressure is very low, the alarm signal is turned off; in other words, it is off at normal pressure, and it turns on when the pressure exceeds the very low level. Therefore, when the NO steam pressure is high, the alarm signal is turned off; in other words, it is closed at normal pressure, but turns off when the pressure exceeds a high level. So connecting to NC coincides with the 4th floor. So theoretically, the original poster’s design is quite standard.
They are all NC; this is the usual connection method for safety interlocks