Grounding and bonding

This is a qood question,...I think. If you can rephrase the question using simpler terms, or terms civilian not military. We don't need anybody getting shocked in the shower.

One thing to keep in mind is in some places just driving a ground rod in the earth is not enough. Sometimes you have to excavate a hole, fill it with carbon or some conductor stuff to make a proper ground. Dry sand has to be a terrible conductor. Consider running a separate ground right back to the generator, don't count on dry sand to do the job.

I agree with Mike. I am having a problem understanding the military verbage. But I want you to understand one thing. A ground rod does not provide a safe fault path. Any fault that occurs will not trip a breaker if the fault flows through the ground rod.

When you say "we use 5 wire system for all CHU's" does that mean 3 phase conductors, neutral and a grounding conductor(maybe another name).

Are the CHU's metal?

Quote "Each CHU has a ground rod 10 feet long and 3/4 of an inch thick, the ground rod is connected to the frame of the CHU with a 10mm ground. The CDP (consumer distribution panel) has an equipotential bond of 10mm cable from the ground bar to the frame of the CHU."

The proper way would to connect a conductor from the ground rod to the neutral position in the CDP. Then if you need bond the neutral to the frame of the CHU. You are using the frame as a conductor to make a connection from the neutral to the ground rod.

Quote "Today while I was testing a shower unit, all of the efli readings were virtually the same , around 1.6 to 1.9 ohms with 190 ish amps, they were all type c rcbo's protecting the circuits, with a 63a 100ma main 4 pole rcd, the readings are all just over the limit for the type c breakers so I investigated further, I removed the connection for the ground rod and retested - 64 ohm's 4 amps :), there was no main cpc coming into the abb unit, I traced the cpc and found it was disconnected in the abb unit socket (all feeds to chu's are on mk commando plugs with sockets on the outsides of the units)."

I want to help but I do not understand any of this. What are you measuring to get the 1.6 to 1.9 ohms? 190 ish amps? where?

Quote "I reconnected the ground rod and i realised the toilet abb unit had a ground rod 18 inches from the shower abb unit, so the fault path was down the shower abb unit ground rod through the ground 18 inches and up the toilet abb unit ground rod back to the SDB using the toilet cpc."

Is this shower physicall seperated from the CHU? Two ground rods are dangerous unless they are bonded together. The fault path should be back to the CDP thru a conductor. The NEC trem is an EGC(equipment grounding conductor) and not thru a ground rod.

Quote "Now everything is on generator power with the generators bonded at the centre tap to ground." Do you mean bonded to a ground rod a the generator?

Quote "My question is if I take a Zdb reading at the panel using the fluke 1653B as it has the high current option so I only need to use the red and green lead, can I take the live + ground efli reading and reference it to a live + neutral efli reading to prove if the CHU's have a main cpc connected rather than having to disconnect the ground rod to check? I realise over length the R1 + R2 reading will slightly differ from the R1 + R1 reading, I also realise that I will have to make sure the main breaker is off at the CDP so I don't get any readings through equipment. But realistically the ground and neutral have exactly the same potential back at the transformer so unless i am missing something the readings should be vertually identical unless the main cpc is missing?

I am not familar with what you mean. Maybe someone else is.

I spent 16 years in the Navy, the last four of it doing electrical and electronic work, and it's all Greek to me! One more time, in English, please.

All I am getting from this is that (I think) they are using the metal frames of their housing units as a ground path, and then connecting said metal frame to a ten foot long, 3/4" rod driven into the ground.

However, as has already been pointed out, to get an adequate ground in dry sand with a simple metal rod you'd darn near have to drive it down to bedrock.

As for the rest of it? I think the Army uses different terminology, or maybe even completely different electrical systems from what we used shipboard.

Let me try and explain a little better,

5 wire means 3 phase + neutral and ground

All grounds are run separately because the American electricians here did not know how to make armored cables off properly and they have used mostly plastic glands.

The ablution unit/shower is a separate unit it has a 3 phase DB because of the 3 phase water heaters installed inside.

While testing this I noticed high readings conducting an earth fault loop impedance test 1.6 to 1.9 ohm's with a fault path of around 190 Amps

After investigation I found the main cpc running with the main armored cable had become disconnected.

All ablution units are steel structures along with all housing units and toilet blocks

They are all situated in rows around 24 inches apart

It has been raining over the last month so the ground is soaked and conducting between ground rods

Each unit has 1 DB each DB has a ground bond from the ground bar inside the DB to the metal frame of the unit

Each unit has a 10mm ground cable from the metal frame to the ground rod

Please don't ask or mention why they added ground rods when the system in 5 wire because it was just done and it has already caused allot of arguments and it isn't going to be changed.

My question is if I use a fluke 1653 B test meter set to high current earth fault loop impedance can I test between Live and Neutral and use this as a reference for the test between live and ground?? as on the fluke 1653 B the high current test allows you to only use the red and green leads instead of a normal low current test which is 3 leads red green and blue ?

Bearing in mind the whole system is 5 wire and the neutral ground bond is at the source inside the generator.

The grounding rods may also be for lightning strike protection, emp, and as a backup for the grounding wire going back to the generator. You're not in friendly country there, I would be very suspicious of any thing you find undone. Somebody who knows anything about electricity knows what ground wires are for.

Keep up the good work, we are here for you 100%. Pass it on.

How many units are fed from each generator?How far apart are the ground rods?What is the voltage supplied?What is the size of the feeders and ground wires?

Remember, the key to safety is to keep all objects at the same potential, and give fault currents only ONE place to go.Multiple grounds must all be bonded to achieve the same potential ie: Ground rods should be bonded together to form a single ground point, and all metal building components should also be bonded to the ground rods and neutral, which should be continous all the way back to the generator.

Subfed panels should not have neutral and ground bonded, only the main panel should be bonded (neutral to equipment ground).

Buildings as close as 24 inches should be bonded together also, as the potential exists for contact between two buildings.