Isolated Ground Rod, No Egc!

[MD84]

Wiring several machines. Robotic welding machines. Manufacturer rep wants a ground rod for each machine with no Egc.

I said no. Not compliant and very dangerous.

They said that is how they do it. There's too much noise with all the other welders running.

I offered an isolated Ground.

Please tell me I am not getting my blood boiling over this for no reason. I need to convince several others of the dangers here.

 

[luckylerado]

I agree with you. If an auxiliary grounding electrode may be provided but in needs to be tied tot he EGC. Are they not using shielded cable properly causing noise issues on the controls. Are welding machines highly susceptible to power quality issues? How about isolation transformers for the equipment?

 

[Fitzdrew516]

You are 100% correct. I'd walk off the job before I'd kill someone because an equipment manufacturer doesn't understand grounding.

 

[Fitzdrew516]

Oh, also... Not only is no EGC a completely idiotic idea, but a ground rod at equipment risks frying the electronics in said equipment. If there is a lightening strike close enough it can travel up through the ground rod and wreck the equipment. You should force this manufacturer to watch Mike Holt's video on grounding myths.

 

[MD84]

I agree with you. If an auxiliary grounding electrode may be provided but in needs to be tied tot he EGC. Are they not using shielded cable properly causing noise issues on the controls. Are welding machines highly susceptible to power quality issues? How about isolation transformers for the equipment?

Thank you for the suggestions. I will check with the rep to see if they are using any methods to decrease noise.

You are 100% correct. I'd walk off the job before I'd kill someone because an equipment manufacturer doesn't understand grounding.

Thanks. I don't think they realize the danger.

 

[Smart $]

... I don't think they realize the danger.

I would dare to say they definitely do not realize the implications. They need to take a Grounding 101 course, for starters.

 

[tom baker]

There was a study on this by the Electric Power Reliability Institute a few years ago, I got the study, sent it to Mike Holt, and he made a great graphic. I can post the graphic later today.
What the study said was sometimes it made no difference, sometimes it made it better and most often it made the noise worse.
Having the isolated ground creates a path into the machine for lightning.
Best solution is a single point ground.

 

[MD84]

I would really appreciate that information. Pictures are worth a thousand words. I would really like to put a stop to this. If I was not there to say no it would probably have been installed with no Egc.

 

[jaggedben]

FWIW...

https://www.youtube.com/watch?v=WlnFNTay-9Q

I love how Mike Holt gets worked up about this stuff.

 

[Smart $]

...
Best solution is a single point ground.

As required per NEC.

 

[ggunn]

FWIW...

https://www.youtube.com/watch?v=WlnFNTay-9Q

I love how Mike Holt gets worked up about this stuff.

If they ever make a movie about his life, Kevin Spacey should play him.

 

[GoldDigger]

As required per NEC.

Nor entirely. The NEC requires a single ground to neutral bond point, but allows as complex a network of EGC to earth ground electrode connections as you can dream up. (Lots of bonding jumpers as well as GECs, and multiple paths such as building steel.)
Mike Holt briefly describes how to configure a single point ground in one of his Grounding videos.

 

[Smart $]

Nor entirely. The NEC requires a single ground to neutral bond point, but allows as complex a network of EGC to earth ground electrode connections as you can dream up. (Lots of bonding jumpers as well as GECs, and multiple paths such as building steel.)
Mike Holt briefly describes how to configure a single point ground in one of his Grounding videos.

Ha. My post was intended to be a question but I typo'd the question mark. So thanks.

Please describe succinctly how to achieve single point grounding and be NEC compliant...

 

[GoldDigger]

Ha. My post was intended to be a question but I typo'd the question mark. So thanks.

Please describe succinctly how to achieve single point grounding and be NEC compliant...

Divide the system into two distinct parts:
1. The EGC network, which consists of all raceway and wire EGCs but is isolated from building steel and other "incidental" earth grounds.
2. The GEC system, consisting of all electrodes, water pipes, etc which are required to be bonded. All GECs and bonding jumpers run to a single common point.
That point is where 1. and 2. are connected. Only there.
Not necessarily easy, but minimizes differential noise and keeps earth gradient currents from flowing on EGCs.

 

[gar]

160411-1708 EDT

From an NEC and safety viewpoint it is wrong to disconnect exposed conductive parts of a machine or device from the EGC. Under normal and typical conditions this EGC connection reduces the likelyhood of a person getting shocked by touching the conductive surface and some other grounded item, and provides a fault clearing path.

Disconnecting from the EGC and using a local ground rod is probably not a very good solution to a noise problem, if it is a solution at all.

What is the noise problem that needs to be solved? The nature of the problem will determine how it should be solved. More information on how noise affects this welding system is needed, and what part of the welder is affected.

.

 

[cuba_pete]

There was a study on this by the Electric Power Reliability Institute a few years ago, I got the study, sent it to Mike Holt, and he made a great graphic. I can post the graphic later today.
What the study said was sometimes it made no difference, sometimes it made it better and most often it made the noise worse.
Having the isolated ground creates a path into the machine for lightning.
Best solution is a single point ground.

Great response.

I get EE's and electricians who get grounding schemes confused when we refer to receptacles as isolated ground. It's hard to convince them that there is no legal definition or use for "isolated grounds", but IG receptacles as part of a single-point grounding system is what they unknowingly really need/desire.

I break out the NEC, Green, and Emerald books to no avail.

The EPRI study is on my shelf, too.

 

[cuba_pete]

Ha. My post was intended to be a question but I typo'd the question mark. So thanks.

Please describe succinctly how to achieve single point grounding and be NEC compliant...

You may want to start with the 640 section:
Technical Power System. An electrical distribution system with grounding in accordance with 250.146(D), where the equipment grounding conductor is isolated from the premises grounded conductor except at a single grounded termination point within a branch-circuit panelboard, at the originating (main breaker) branch-circuit panelboard, or at the premises grounding electrode.

250.96
250.146(D)
408.40 exception

etc.,

It doesn't have its own dedicated section in the NEC, but it is an allowed configuration of the grounding system which makes great use of Kirchoff's law.

If you cannot figure out how to make it compliant, then get with a sparky who does it for a living and have them go through it with you. It's a lot easier to understand if you can see it in action (testing and measurements).

 

[don_resqcapt19]

You may want to start with the 640 section:
Technical Power System. An electrical distribution system with grounding in accordance with 250.146(D), where the equipment grounding conductor is isolated from the premises grounded conductor except at a single grounded termination point within a branch-circuit panelboard, at the originating (main breaker) branch-circuit panelboard, or at the premises grounding electrode.

250.96
250.146(D)
408.40 exception

etc.,

It doesn't have its own dedicated section in the NEC, but it is an allowed configuration of the grounding system which makes great use of Kirchoff's law.

If you cannot figure out how to make it compliant, then get with a sparky who does it for a living and have them go through it with you. It's a lot easier to understand if you can see it in action (testing and measurements).

The only code permitted use of a technical power system, under the rules of the NEC, is for applications covered by Article 640.

 

[Smart $]

Divide the system into two distinct parts:
1. The EGC network, which consists of all raceway and wire EGCs but is isolated from building steel and other "incidental" earth grounds.
2. The GEC system, consisting of all electrodes, water pipes, etc which are required to be bonded. All GECs and bonding jumpers run to a single common point.
That point is where 1. and 2. are connected. Only there.
Not necessarily easy, but minimizes differential noise and keeps earth gradient currents from flowing on EGCs.

While that all sounds good, I am familiar with the concept of isolated grounding, even taking it to extremes. It all still has to be NEC compliant. Most IG implementations only isolate the wire-type EGC. Isolating raceways and armors can be most difficult in structure with steel framework. In some scenarios non-metallic raceways help, but in general, that is comparable to running shielded vs. unshielded cable.

 

[Smart $]

...
If you cannot figure out how to make it compliant, then get with a sparky who does it for a living and have them go through it with you. It's a lot easier to understand if you can see it in action (testing and measurements).

I see that as a rather condescending remark on your part.