Isolated Ground

[Pat Weldon]

Is an isolated ground really neccesary for desk top computers?

 

[480sparky]

No .

 

[BryanMD]

No .

But it makes the IT guys FEEL so good

 

[iwire]

But it makes the IT guys FEEL so good

LMAO

Thats about all it's good for.

 

[weressl]

Is an isolated ground really neccesary for desk top computers?

In a power plant or production facilities with heavy electrical uses, switching surges and lightning discharges often cause undesirable current flow and potential differences in the integrated grounding system.

While this is part of their normal functioning, electronic equipment can experience misoperation or even damage as the result.

If desk top computers are used as part of the manufacturing system, either as data processing entry points ofr MEP or direct MMI fro the control system good design often take into consideration appropriate protection of continous and proper operation of these units.

Providing clean power is the first step, providing uninterruptible power is the second. Either of these preventive measures are useless with a 'dirty' ground. It is akin to wearing a full class 3 PPE suit without a faceshield.

 

[iwire]

Laszlo, IGs are dinosaurs.

As long as separate electronic equipment is not interconnected with a method that also carries the grounding conductor (RS232, coax etc) an IG is unneeded.

It is most often a waste of time and materials, it is also often compromised before the paint is dry on the job.

 

[weressl]

Laszlo, IGs are dinosaurs.

As long as separate electronic equipment is not interconnected with a method that also carries the grounding conductor (RS232, coax etc) an IG is unneeded.

It is most often a waste of time and materials, it is also often compromised before the paint is dry on the job.

Bob,

You of course are just plainly wrong.

Thankfully it is not for you to decide whether one is needed or not.

Incidentally you may want to champion to remove the IG provisions from the NEC.

 

[iwire]

Bob,

You of course are just plainly wrong.

That is one mans opinion.

I happen to listen to another mans opinion, a man that has spent a life time designing and building both data centers and and Telco plants.

Thankfully it is not for you to decide whether one is needed or not.

Right back at ya :wink:

Incidentally you may want to champion to remove the IG provisions from the NEC.

No need, they are not mandatory, they are voluntary.

 

[weressl]

That is one mans opinion.

I happen to listen to another mans opinion, a man that has spent a life time designing and building both data centers and and Telco plants.

Same here. Yet it is no proof that either of us knows anything about it.

Both of those places are without technical experts to challenge the EE's action. I know exactly the type of design/installer you are talking about. However where I work my actions are professionally reviewed by my peers.

Right back at ya:wink: .

It is my job to do so.

No need, they are not mandatory, they are voluntary.

But if it is useless and 'dinosaur' don't an upstanding member of the electrical community like you would be obligated to remedy that error?

The NEC BTW clearly indicates the purpose of employing IG. I would like you to refute the validity of those purposes.

 

[iwire]

Both of those places are without technical experts to challenge the EE's action. I know exactly the type of design/installer you are talking about.

Your unbelievable. :grin:

It is imposable for you to know that, you can certainly think it but you can not know it.

Lets also not lose site of the fact the OP was tackling about a desktop PC.

 

[dereckbc]

Lazlo and Bob please allow me to stick my nose in this contest. You both have some points, but it doesn?t appear to me you guys are talking about the same things.

Bob you are correct IG?s are antiquated for the most part, but as Lazlo pointed out there are still some applications where they might and I do say might help. As Lazlo pointed out if a PC is used in some sort of process control, IG?s might be required if the user failed Step 1 of providing clean power from something like a UPS or isolation transformer.

Now where Lazlo has a point is if the PC is using a signal protocol that uses ground as a reference point or part of the signal path like RS-232 or token ring. Personally I would just use an optical isolation modem for such applications and screw the IG.

Lazlo where I take exception with your statement is using a dirty ground in the same sentence with a UPS. Now before you go ballistic hear me out. If the system is critical to an operation I have to assume a centralized UPS will be used and possible a PDU in conjunction. If not that at least an isolation transformer would be used. If that is the case then it does not matter what the integrated ground plane voltage is because each of these system is SDS and a new ground reference point is created, and fed out as a single point ground free of noise or voltage potential differences?

Now with that said in Bob?s favor I think this is a office environment and the PC?s are networked using Ethernet which is not a ground referenced communication protocol, and therefore potential differences in the integrated ground plane are of no importance. In the PC the EGC is just for safety and operating OCPD, the PC uses a switch mode power supply or another form of SDS, and the internal ground signal buss is not connected to the EGC.

Now with that said if the engineer specifies IG in an office environment, install it and laugh all the way to the bank. Personally I would recommend SG with a quality dual conversion UPS installed on critical PC like the boss and let the other kick rocks if there is a brown/black out or interruption.

 

[jim dungar]

Not that i don't like a good arguement.

But, Bob did say that IG's are not needed unless there is an interconnecting ground path.

As long as separate electronic equipment is not interconnected with a method that also carries the grounding conductor (RS232, coax etc) an IG is unneeded.

 

[brian john]

I have spent 25 years working on and around IG systems, testing and solving issues associated with these systems. In my expierence a properly installed electrical distribution with no IG works adequately and saves copper.

I have worked in Data centers, schools, telco installs, server rooms, TV stations, recording studios, satellite up-links........and all have the following issues, no matter who the engineer, inspector or installer is.

1. Most IG systems are not installed properly.
2. The very few that are properly installed are at sometime in the future compromised.
3. Then there is the WHO DO VOO DOO, magic stick that suck electrons into a massive sump located in the center of the earth.

 

[weressl]

Lazlo and Bob please allow me to stick my nose in this contest. You both have some points, but it doesn?t appear to me you guys are talking about the same things.

Bob you are correct IG?s are antiquated for the most part, but as Lazlo pointed out there are still some applications where they might and I do say might help. As Lazlo pointed out if a PC is used in some sort of process control, IG?s might be required if the user failed Step 1 of providing clean power from something like a UPS or isolation transformer.

Now where Lazlo has a point is if the PC is using a signal protocol that uses ground as a reference point or part of the signal path like RS-232 or token ring. Personally I would just use an optical isolation modem for such applications and screw the IG.

Lazlo where I take exception with your statement is using a dirty ground in the same sentence with a UPS. Now before you go ballistic hear me out. If the system is critical to an operation I have to assume a centralized UPS will be used and possible a PDU in conjunction. If not that at least an isolation transformer would be used. If that is the case then it does not matter what the integrated ground plane voltage is because each of these system is SDS and a new ground reference point is created, and fed out as a single point ground free of noise or voltage potential differences?

Now with that said in Bob?s favor I think this is a office environment and the PC?s are networked using Ethernet which is not a ground referenced communication protocol, and therefore potential differences in the integrated ground plane are of no importance. In the PC the EGC is just for safety and operating OCPD, the PC uses a switch mode power supply or another form of SDS, and the internal ground signal buss is not connected to the EGC.

Now with that said if the engineer specifies IG in an office environment, install it and laugh all the way to the bank. Personally I would recommend SG with a quality dual conversion UPS installed on critical PC like the boss and let the other kick rocks if there is a brown/black out or interruption.

Thank you for your comments.

In my experience if the SDS ground is not isolated, but it is allowed to intermingle and make incidental connections to ground via the utilization of bare ground conductors, there is a potential that switching and lighting surges CAN produce ground current flow through the system that can adversely effect the system.

As far as Ethernet goes, even though it is not a ground referenced system, it is still subject to induced and coupled noise. In industrial environment shielding is used. The Ethernet data protocol has extensive error checking and validation process that ignores corrupted date and then resends it until it is validated. High error rate results in reduced throughput.

Ethernet is not necessarily the only communication protocol involved. There are number of other interfaces that desktop PC uses for industrial communications and connections.

I agree with other comments that IG is difficult to obtain and maintain its integrity. It does get compromised and become useless. I am not certain I agree that it is a ?lot of extra copper?.

I think that monitoring the signal, current flow between the IG and plant ground could reveal its usefulness if the bond between the two systems is of sufficient impedance to limit the ?undesired current flow? to a harmless limit.

 

[weressl]

I have spent 25 years working on and around IG systems, testing and solving issues associated with these systems. In my expierence a properly installed electrical distribution with no IG works adequately and saves copper.

I have worked in Data centers, schools, telco installs, server rooms, TV stations, recording studios, satellite up-links........and all have the following issues, no matter who the engineer, inspector or installer is.

1. Most IG systems are not installed properly.
2. The very few that are properly installed are at sometime in the future compromised.
3. Then there is the WHO DO VOO DOO, magic stick that suck electrons into a massive sump located in the center of the earth.

OK, I can chalk up 35 years with industrial environment. Industrial environment and the benign places you mentioned can not be compared when it comes to ground current issues. The magnitude of the energy involved is just not comparable.

1. Agree
2. Agree
3. Since electrical theory is STILL just a theory, even seemingly kooky ideas may prove to have some explanation.

On both 1 and 2, you are suggesting that we accept failure instead of trying to solve it so that it does not happen, so as the result you are 'throwing the baby out with the bathwater'.

4. Some grounding issues can be detected, found and eliminated. However, the most problematic issues are NEVER there when you investigating them since they are the results of switching surges and lighting and even just the movement of charged clouds without discharge.

 

[iwire]

On both 1 and 2, you are suggesting that we accept failure instead of trying to solve it so that it does not happen, so as the result you are 'throwing the baby out with the bathwater'.

Outside of a highly controlled building / plant / campus you will never stand a chance of preventing #2.

When the plans call for IGs of course I install them and keep it exactly as specified. That is my job.

But no mater what I do, I can not prevent the compromising of that IG system. Once compromised it will never be fixed so all the customer money spent on the IG system could have been better spent in another direction.

 

[dereckbc]

Thank you for your comments.

In my experience if the SDS ground is not isolated, but it is allowed to intermingle and make incidental connections to ground via the utilization of bare ground conductors, there is a potential that switching and lighting surges CAN produce ground current flow through the system that can adversely effect the system.

As far as Ethernet goes, even though it is not a ground referenced system, it is still subject to induced and coupled noise. In industrial environment shielding is used. The Ethernet data protocol has extensive error checking and validation process that ignores corrupted date and then resends it until it is validated. High error rate results in reduced throughput.

Ethernet is not necessarily the only communication protocol involved. There are number of other interfaces that desktop PC uses for industrial communications and connections.

I agree with other comments that IG is difficult to obtain and maintain its integrity. It does get compromised and become useless. I am not certain I agree that it is a ‘lot of extra copper’.

I think that monitoring the signal, current flow between the IG and plant ground could reveal its usefulness if the bond between the two systems is of sufficient impedance to limit the ‘undesired current flow’ to a harmless limit.

Lazlo, I don't have any problem with your comments, please allow me to make a couple.

In my experience if the SDS ground is not isolated, but it is allowed to intermingle and make incidental connections to ground via the utilization of bare ground conductors, there is a potential that switching and lighting surges CAN produce ground current flow through the system that can adversely effect the system.

I think I am the guy Iwire referred too who does the data centers and Telco's. Anyway back in the 70's through 90's we use to use IGR, no more. Today we use a large scale UPS and feed it to PDU's. I think you know what I mean but just in case the UPS feeds a special isolation transformer (PDU) via 480 delta. The PDU's are strategically located in the equipment line-ups, and have built in distribution, monitoring, bells, and whistles. From the PDU each equipment rack has a two dedicated branch circuits with insulated EGC.s. Each equipment rack is bolted/bonded together to for a line-up. Each equipment rack is bonded to the raised floor Signal Reference Grid, and overhead frame ground if DC power is supplied. What I am getting at here is everything is bonded together to form an Integrated Ground Plane or one massive equipotential ground plane. In some case like the new routers they are installed on sheet metal.

In the event there is a fault from switching, L-G faults, lightning, ect, the extremely low impedance nature of the Integrated Ground Plane keeps the potential difference low or below operating thresholds. In this case since all communication is either Ethernet or optical IG adds no value. Since the data centers and telcos are Point of Presence involving many customers who we cannot control, IG is compromised regardless of the effort we make to monitor and control them. So we just took it away and went the other direction. It works and works great.

Ethernet is not necessarily the only communication protocol involved. There are number of other interfaces that desktop PC uses for industrial communications and connections.

I agree 100%, my background is Telco oriented and we occasionaly have problems mostly with RS-232 entering what we call an Isolated Ground Plane Zone to some operations personnel PC monitoring the system. Fix is easy, an optical isolation modem.

I think that monitoring the signal, current flow between the IG and plant ground could reveal its usefulness if the bond between the two systems is of sufficient impedance to limit the ‘undesired current flow’ to a harmless limit.

I agree 1000%. We have ground fault monitors in all our facilities with loud bells and whistle alarms. 99% of the time when they go off it is a result of installation activites from equipment installers and electricians improper wiring. It makes them jump and stop with their hands in the cookie jar.

My final comment is what you and I do is very specialized and outside the scope of the NEC and what most of these folks do here. Most are commercial and residential and do not need the specialized techniques you and I use. In the most part I agree with most IG is antiquted and problems are best hadled with other means. But there are times it has niche applications such as you have brought to my attention..