2/12/2007- QOD - Electrical

[Michael Larson]

Originally Posted by pabernathy

BUT.......Brian STEPPED up the plate with some GOOD info.....now the 83% of the people who KNOW exactly the intent of the Ground Rod....come forward please...

Here's my head chop away-

It serves as the equipotential point of referance for the building.
All electircal circuits, water lines, gas lines(in some jursidictions), and exposed metal that are bonded to this point should be at the same potential with referance to "earth" assuming good connections and adequate conductor sizes and that the ground rods are in moist soil.

[Paul W. Abernathy]

I wont CHOP.........good theory but not exactly correct.....BUT this what I want and NO ONE should feel they can't guess either....this is education people.....lets Educate....

[Paul W. Abernathy]

WE have to understand that WE LEARN MOST by people like Brian and Micheal taking STABS at it.........look it is NOT a ego thing....education and ego's should be left at the door........lets learn people.......

Both of you....THANK YOU........someone else please add to this....HI's please

[Doug Edwards, CMI]

It (the grounding rod/electrode) provides the path that limits the voltage potential from outside forces; lightning, cross-overs, surges, etc.

[Paul W. Abernathy]

remove the "voltage potential" portion and it would be a true statement.

[Doug Edwards, CMI]

Obi-Wan,
Explain for us...take us on the path of enlightenment

[Paul W. Abernathy]

lol......me not Obi-Wan...lol

ground rods to play a part in a Equipo. when it deals directly with making something a EQUAL potential for touch and serves a great purpose in the agriculture industry......but in the efforts of a ground rod on a house.

It really only serves (3) purposes.......

1.) To direct lightning ( high frequency ) to the earth to which it is trying to get ( lets not confuse Lightning with AC Current...Lightning is DC for the most part in this understanding )

2.) It serves as an additional fault current path for the POCO as they share it with their own in terms of aiding in clearing a HIGH VOLATGE/ HIGH AMPERAGE fault...but really it is in case their is a HIGH VOLTAGE line that comes in contact with the service drop...so to speak.....and...

3.) A sudden IN rush of voltage from the high power lines itself in a surge....

The Ground Rod on the house serves those functions..........

Now will a Ground Rod or to be frank ANY of the grounding electodes protect your inside equipment or devices in your house in a lightning strike....or surge to the high power lines....NOPE........a Surge Device or TVSS is the best line of defense on that part.

THIS is why it is so critical to have that Grounded conductor in place and a proper BOND....to allow the " stray " which are really simply electrons trying to get back to the SOURCE of their creation.....

Faults Currents and so on as it pertains to the GES are not trying to get to EARTH....they are trying to get to the source....while they can travel within earth.....creating a POOR parallel path back to the source......EARTH plays no real part in the dwellings electrical system.

[Richard L. Bennett]

Paul

Ground rods are to establish a path for current flow if one looses the neutral refference for safety. People are not a good path to ground.

The better the ground the less voltage a person will be exposed to if one were to lose the neutral refference


And that is what I think


rlb

[Paul W. Abernathy]

Another myth........lightning does not strike metal because it is metal......notice how it strikes TREE's all the time.

Lightning is LAZY..it strikes the closest object and it can originate from the ground or the sky.....all depends on the + and - configuration of the elements.

[Paul W. Abernathy]

Originally Posted by rbennett

Paul

Ground rods are to establish a path for current flow if one looses the neutral refference for safety. People are not a good path to ground.

The better the ground the less voltage a person will be exposed to if one were to lose the neutral refference


And that is what I think


rlb

WRONG..........that is simply NOT the case...........the EARTH will never conduct a good enough path to the source to cause a OCPD to trip......on standard 120/240 volt systems.

IN doing EQO planes this may be the case...it is NOT the case in ground rods for a dwelling.........

[Paul W. Abernathy]

YOU simply DO NOT drive a ground rod to reduce touch potential.....in regards to a grounding system for a dwelling unit.

It only takes 5MA to kill you........so basically lets do the math....( Fixed my own CRAPPY MATH )

I grab onto a ground rod and grab onto a HOT wire with the other hand...are you saying the potential will protect me?

Assuming the ground rod has a resistance of 25 OHMS..........120V dividided by 25 OHMS gives us 4.8A.....will this clear a 15 A Breaker in time before it kills you...?

This is a wild misconception with regards to ground rods for a house.......the ground rods at the transformer pole serves two functions...

1.) Voltage Stabilization so that when we test we accuratly get a reading

2.) TO allow high surges on the line or lightning to FAULT and trip the OCPD on the pole...which is very low.....how can this happen...

Usually at the pole you have 7,500 volts for example......do the same math on a 25 OHM rod....7,500 divided into 25 OHMS equals...300A....normally the fuse on the pole can be between 5A and 50A....depending on the area...so will a 300 A blow a 5 or 50A fuse....YEP.....

Dwelling grounding is a different beast

[Paul W. Abernathy]

I think the most important thing a HI takes from this is the following-

The Ground Rod is not going to protect a house from Lighning Damaging the components inside. The function of the Ground Rod is to SHUNT the lightning which is a high frequency current to the earth which was IT's original intent.

The Ground Rod of a dwelling is not designed to offer any fault protection....the EGC's and Bonding Jumpers are CRITICAL in this function as they provide a EFFECTIVE and ASSURED path for these currents to get back to where it was intended to go in the first place.....the source which is back at the transformer.

Earth can NEVER be used as an effective path for anything...while it may PLAY a path because we know that the old saying voltage takes the path of least resistance....fact is it takes ALL paths and the Ground MIGHT be one of them but it is not an effective one and is not the intent of the Ground Rod.

The intent was to NOT explain the potential POSSIBLE currents that COULD travel on the ground rod and earth...but most certainly a loss of the Grounded Conductor to the transformer would not aid in clearing any faults in the panel because of the ground rod, the earth is simply too poor of a conductor for that.

Hope this was helpful....those that do not agree thats is fine.....grounding and bonding is something that is a VERY tough topic.

P.S. It is also important to note that IF it was a potential thing....the Transformer ALWAYS has it's own connection to the earth to solve the potential issue....but again thats not it's focus at the pole either...I explained that earlier as well.

[Richard L. Bennett]

Paul

Math on an open neutral (not the hot wire)--- 120 volts 25 ohms = 30 volts thus not a people killer --- Hard to get the .005 amp through the higher resistance of the body


This protection is only on an open neutral and a person in contact with the neutral and earth ground -- ie water pipe etc.

Just thoughts

Never heard about voltage stabilization

[Richard L. Bennett]

Paul


Good question

Keep them comming

rlb

[Paul W. Abernathy]

Incorrect statement Richard.......VOLTS don't kill.......AMPS kill so 30 volts could very well kill someone.

But......the NEUTRAL on a OPEN service neutral richard would still be voltage at the end of that neutral wire......so it would still be 120V...provided you became the PATH....and doing that math..if you became the PATH you are still looking at 4.8A....

Now you are saying the body would aid in that...well the body is known to be roughtly 1000 OHMS of resistance......so lets do that math....

.12 AMPS..........is that not HIGHER than 5 MA lets say that a GFCI protects a person......and WHY does a GFCI protect at 5 MA....thats .005 A because above that could KILL you.

The ground rod...or the body's resistance is simply not going to protect a LIFE...the ground rod's primary function is to protect the dwelling from lightning......but even in THAT.....it is a reaching HIGH

The problem is the BODY goes into Ventricular Fib at VERY low levels and ironically the 60 HTZ we use daily is about the same FREQ as the hearts beat rythum........while the AMPS may not kill you...the FLUTTER of the heart will in a short time.