230VAC vs 24VDC

For most of our simpler installations, we use 230 VAC for our hard-wired safety devices (as in independent from the PLC). This has been done for decades in our company, and one of the reasons was that in case of an defect of the cable or device, the fuse would trip, taking the safety relays with it.

That being said, we have never (as far as I know), wired these directly to the PLC. Always through relays.
 
My guess is that it just the European standard AC, compared to our 110/120 over here. As an example, I don't think siemens has any 120 only modules. Any digital AC stuff is 110-240

I agree with that. I am currently sitting in Nigeria. They use 230VAC for single phase power.
 
Its funny, they have 230 at the outlet. Americans consider 230 "danger high voltage".
All of the outlets though seem to be RCD outlets with switches on the outlet, and it seems that most/all of the plugs have fuses in them. In good ol USA we only need GFCI when required (wet locations).
 
Its funny, they have 230 at the outlet. Americans consider 230 "danger high voltage".
All of the outlets though seem to be RCD outlets with switches on the outlet, and it seems that most/all of the plugs have fuses in them. In good ol USA we only need GFCI when required (wet locations).

Atleast in Sweden we don't have RCD, fuses and switches on our outlets. We have RCD and fuses placed in the switchboard, RCD is not mandatory for all outlets but for most applications. Not due to "high voltage" but because it adds safety with a low cost.
 
How about running the long signals 220V for corrosion resistance and in the panel have a bank of 24V interposing relays going to the inputs & powered off the outputs?

This what I do in some locations.
I use 120V to control my motor starters and 120V on the motor starter aux contacts, and some other devices that will not work on 24VDC. Then i have 24vdc interfacing relays on the PLC IO.
This way I limit noise on the 24vdc system by not running near the 460V motor wiring.
 
Pleas advice to use 24 Volts, as all above 50 Volts need a lot of protection like Ground Fault, fuses, etc.
and the equipment must be shut down before opening anything.
It means complete shut down to check a simple level sensor. Also a lot of switches are not able to switch this high voltage.
 
Its funny, they have 230 at the outlet. Americans consider 230 "danger high voltage".
All of the outlets though seem to be RCD outlets with switches on the outlet, and it seems that most/all of the plugs have fuses in them. In good ol USA we only need GFCI when required (wet locations).

That is common use in the UK. The place you are working is likely to have a british colonial background.
 

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