NFPA79

[fifty60]

I have a similar question posted on another thread, but the topic on that thread was not specifically NFPA79 and dealt with different voltages. I would like for this thread to be specifically NFPA79 so I hope the moderators allow it and close the other thread before closing this one.

I am trying to fully understand chapters 7 and 9 of NFPA79. Both are concerning control circuits. Chapter 7 says a control circuit can use 7.2.4.2.2 to size conductors/ocpd's if it is: "a control circuit tapped from the load side of the branch circuit short circuit and ground fault protective device and functioning to control the loads connected to the branch circuit."

There is no mention of voltage in chapter 7. Chapter 9 picks up the topic again, and says the control circuit must be 120VAC or it must use a control transformer. An exception is "other voltages shall be permitted where necessary for the operation of electronic, precision, static, or similar devices used in the control circuit."

Are timers, solenoids, control relay's considered "static"? If not, what is static and can anyone give an example?

My voltage 230V 50Hz. I understand that this is 230V to ground, and not 240V phase to phase (simplification) like here in the states. I know the NFPA79 does not have jurisdiction overseas, but I am trying to understand "essence and reasoning" behind chapters 7 and 9 so that I can better design for 240V. Ultimately I am trying to definitively discriminate between power circuits and control circuits so that I can size conductors.

The device plugs into a 15A receptacle at 240V 50Hz. I would like to use 14AWG on everything but unfortunately my control relays only take #16AWG. I would like to know if I can consider my relays, timers, and solenoids as control circuitry and use 16AWG as permitted in NFPA 79 for control circuits.

 

[james_mcquade]

this is off topic from your request, but still revelant.
are you designing systems for other countries? the UK perhaps.
if so, you should be aware of their requirements and rules, not just NFPA79.
in a lot of ways, the European rules are more restrictive than ours.
i used to work for a UK company and their practices were a lot more strick than the us.

regards,
james

 

[fifty60]

If someone could possibly name some documents, that would be helpful. Right now I use NFPA 70, NFPA 79, and IEC 61010-1 Third Edition. I know the NFPA rules do not help for European jobs, but IEC 61010-1 is relevent for UL and CE. IEC 61010 does not go into depth on exact numbers and calculations. What European document does go into this depth? Is there a European equivalent of NFPA, or is it all directives pointing to a thousand different documents.