instrument transmitter circuit breaker 1 pole or 2 pole??? 2

[martinrelayer]

Hi all,

we are planning to install some ph, magnetic flowmeters and other instruments with powered transmitters, all of them with 230Vac supply for transmitter, this mains 230Vac coming from dedicated UPS switchboard.
All of the transmitters have own passive 4-20mA output connected to DCS.
The power supply is 230Vac for the transmitters.
Some design that I have seen uses 2-pole circuit breakers for the 230Vac supply.
The question is if we have neutral earthed in output transformer secondary from UPS, do we need to use 2 pole circuit breakers? or 1-pole is ok?
Why would they deliver a switchboard with two pole circuit breakers??

thanks!!!

 

[waross]

It depends where in the world you are.
North America would normally be a 120-240 Volt circuit and would require a 2 pole breaker for a 240 Volt circuit.
As I understand the European system, one leg of the 230 volt system is grounded and a single pole breaker may suffice.
The rule of thumb (subject to local codes and local AHJs) is that all ungrounded conductors must be disconnected by the breaker.
The ungrounded conductor MAY be disconnected simultaneously to the hot conductors.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ScottyUK]

If any of the circuits are in a hazardous area (flammable / explosive vapours or dusts) then the breaker must switch both the line and neutral simultaneously. If it's general power then largely down to client specifcation.

 

[martinrelayer]

thanks!!