Definition of control circuit.

[keithg]

Hello,

we are having a disagreement as to what actually makes up a control circuit in a control panel. The definition in art. 409.2 states that it is "The circuit of a control apparatus or system that carries the electric signals directing the performance of the controller but does not carry the main power current."

The debate is: Does this definition include power to devices such as PLCs, Power supplies, etc. that is fed from a different voltage than the supply. For example: If the incoming power is 480VAC and these devices are fed from 240vac from the secondary of a transformer when the primary is the 480 vac feed?

Thanks for any advice.

 

[Dennis Alwon]

IMO, the voltage does not matter. If the wire is directing the operation of the equipment then it is the control circuit. I don't believe the line power to the PLC would be a control circuit

 

[mgookin]

Think of a relay that has a 24vdc coil and switches a load of 120vac.

The 24vdc circuit is the control circuit.

 

[S'mise]

I think the line voltage feeding an I/O circuit is part of the control circuit. Such as the L1 terminal on an output card.
The transformer on the other hand is not if it is only delivering the power to the controls.