EGC for 120V Control Circuits

[jtinge]

"equipment grounding conductors of the wire type shall not
be smaller than shown in Table 250.122, but in no case
shall they be required to be larger than the circuit conductors
supplying the equipment"

So you just want to point out that smaller is conditionally permitted?

But isn't Table 250.122 used to size EGCs based on the upstream OCPD? The point of this thread was to determined the need for, type and sizing of EGCs for control conductors not directly connected to an OCPD.

 

[petersonra]

But isn't Table 250.122 used to size EGCs based on the upstream OCPD? The point of this thread was to determined the need for, type and sizing of EGCs for control conductors not directly connected to an OCPD.

Yes, but this section says the EGC never has to be larger than the circuit conductors, regardless of what table 250.122 says.

I am not sure what you mean by "not directly connected". You still have to protect the control conductor with an appropriately sized OCPD for class 1 circuits. I think there is an exception to this hidden in article 430 for class 1 motor control circuits, or at least there used to be.

 

[kwired]

As far as I can tell, here's the requirement you have to figure out first...

....(I) Remote-Control, Signaling, and Fire Alarm Circuits.Equipment supplied by Class 1 circuits shall be grounded
unless operating at less than 50 volts. Equipment supplied
by Class 1 power-limited circuits, by Class 2 and Class 3
remote-control and signaling circuits, and by fire alarm circuits
shall be grounded where system grounding is required
by Part II or Part VIII of this article....

IMO, the system grounding here refers to connecting the electrical system to earth (i.e.-creating a grounded conductor), not whether you have to route an EGC with the circuit conductors.

Just reading that subsection it would appear that way, but this is a subsection of part VI on equipment grounding conductors. Seems to need a little wordsmithing to me to get it to say what is intended here, I think they want an EGC ran in this instance and not just to connect the item in question to earth.

 

[Smart $]

But isn't Table 250.122 used to size EGCs based on the upstream OCPD? The point of this thread was to determined the need for, type and sizing of EGCs for control conductors not directly connected to an OCPD.

There is always OCPD ahead of control conductors (I'm making a general statement there, so do go all nitpicky on it). If not on the load side of the power supply, on the line side. If on the line side, it is considered a power-limited supply. Only a Class 2 supply can be 120V and power limited. See Chapter 9 Table 11(A) and (B).

 

[Smart $]

... Only a Class 2 supply can be 120V and power limited. See Chapter 9 Table 11(A) and (B).

BTW, Class 1 limitations are stipulated in 725.41.

30V and 1kVA for power limited.

Otherwise not over 600V and kVA unlimited.

 

[jtinge]

EGC for 120V Control Circuits

I am not sure what you mean by "not directly connected". You still have to protect the control conductor with an appropriately sized OCPD for class 1 circuits. I think there is an exception to this hidden in article 430 for class 1 motor control circuits, or at least there used to be.

In my example I specified 120 volt control conductors fed by a 120 volt PLC output card. Most likely some type of solid state electronics to control voltage to the conductors, although I agree there is some type of OCPD probably feeding the PLC.

I was trying to differentiate between feeders and branch circuits that are fed by an OCPD, for which the NEC has clear guidance for EGC sized and type for these circuits.