Does dc <50v need ground

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powersupplyguy@netzero.ne

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Warner, NH
Greetings,

I am building a machine which has a few 1kW LED drivers on board. The output voltage of these power supplies is 10v. The 10v travels down some SOOW cord to another enclosure with some LED lamps. The question is, do I need to ground the enclosure with the LED lamps in it?

Section 250.162 call out that a system over 50v must be grounded. There is an exception (#2)which further states that a rectifier-derived dc system supplied by an AC system complying with 250.20 shall not be required to be grounded.

Since my system is <50v and the voltage is a rectifier-derived (there is a high frequency transformer followed by a rectifier within the power supply) dc system, I expect I am not required to ground. Am I interpreting this correctly?

thank you
Bob
 
Since your system is under 50 volts, I don't believe it needs to be grounded. Unless something is powered by batteries or a motor generator, it is almost certainly derived from a rectifier. However, not all rectified systems are isolated from the incoming power, and if it is basically a full wave bridge on the incoming power, it can't have a common connection (ie. ground) with the input power. Otherwise, the smoke gets away.

However, your system has a transformer, which allows the incoming power to be isolated from the output. So, although I don't think you need to be grounded, most likely you may be.
 
If the enclosure is metal, it is required to be grounded by an EGC run with supply conductors. Whether a system is grounded or not has no bearing on the requirement.
 
petersonra said:
Does 250.162 have anything to do with grounding the enclosure?
Click to expand...
No.

Refer to 250.160. Grounding electrode and equipment grounding systems are required. Further supported by 250.166 requirement for a GEC, 250.167 regarding GFP, and 250.168 covering an SBJ.
 
Barbqranch said:
Since your system is under 50 volts, I don't believe it needs to be grounded. Unless something is powered by batteries or a motor generator, it is almost certainly derived from a rectifier. However, not all rectified systems are isolated from the incoming power, and if it is basically a full wave bridge on the incoming power, it can't have a common connection (ie. ground) with the input power. Otherwise, the smoke gets away.

However, your system has a transformer, which allows the incoming power to be isolated from the output. So, although I don't think you need to be grounded, most likely you may be.
Click to expand...


Ok, thank you. You have helped me to understand why the rectifier derived DC system would not be grounded.
 
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