# Can AC and DC be grounded at the same ground rod?



## Owism (Dec 15, 2016)

Any references to NEC to support this is much appreciated.

From my own searching in NEC: 

[SIZE=11pt]The NEC doesn’t say to not connect ac and dc ground.[/SIZE]

[SIZE=11pt]If there is noise, NEC does state that mitigation devices can be installed to remove the DC noise on the system, or just get a separate ground rod to isolate the two systems. 250.6 (E) [/SIZE]

[SIZE=11pt][/SIZE]

Thanks in advance


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## knight1fox3 (Dec 15, 2016)

Interesting question. But I'd have to say one would really need to closely examine both sources for the different power supplies and what their grounding configuration looks like.


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## mudpuppy (Dec 15, 2016)

I can't speak to the NEC, but we do it all the time in substations


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## knight1fox3 (Dec 15, 2016)

mudpuppy said:


> I can't speak to the NEC, but we do it all the time in substations


Yes but what level of DC power are we talking about?


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## mudpuppy (Dec 15, 2016)

Typically 48 or 125 VDC, services in the 400 A range.


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## Ship Wreck PE (Dec 15, 2016)

On new residential and commercial installations we are required to connect phone and cable service grounds to the main electrical building ground rods.


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## mudpuppy (Dec 15, 2016)

Thinking about it, you aren't allowed multiple ground points for your AC system, right?  If there's any chance your DC system could end up shorted to your AC system, I would think you'd want a single, common grounding point for both, for the same reason.


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## Ultrafault (Dec 15, 2016)

You have to consider that grounding and bonding are two different things. All electrical equipment consisting of conductive materials must be bonded to a common point. (2014 NFPA 70 250.6B) I belive you are talking about the grounding electrode system. All grounding electrodes must be bonded to the same grounding system. (2014 NFPA 70 250.50) these rules prohibt two independent lgrounding systems. Thos of course is true in the U.S. I do not know about parts foriegn. If you really wlant to know the anwsers to electrical codes and design you should ask at the Mike Holt forum where you will be beat to death with codes. If you do not fully understand bonding and grounding and the terms within, Soares on Grounding and Bonding is the definitative text.


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