Pole Building -- Electrical Question

[dcyrilc]

Yes, things change but the way things were wired using 3 wires and a grounding rod is safe and grandfathered in so I would not lose any sleep over it.

Chris

Another reason for the code change has to do with too many electricians and inspectors who do not properly understand grounding. Many systems were built and approved even though not properly (safely) constructed because of improper bonding of 3 wire and 4 wire systems. By eliminating the option, it now must be built to a single standard and no mixup should be possible.

Another misnomer has to do with ground rods. Ground rods DO NOT provide short circuit or overload protection! Gound rods provide protection from transient voltages within an electrical system. You can hook a #12 wire with a 20 amp breaker directly to a ground rod without tripping! Ohms law on a 25 ohm ground rod (code requirement) is under 20 amp of curent flow, no short circuit! This is why the ground and neutral must be bonded on three wire systems. Note, the feed from the power company is a three wire system. Bond neutral and ground for short circuit/overload protection.

 

[dcyrilc]

Jim, if you have an existing 3 wire feed to a separate building, yes bond the neutral to the cabinet and make sure there is a ground rod installed. It's the best you can do at this point.
The NEC was changed because the old arrangement was causing current to be carried on the neutral conductor in a fault to ground situation. The ground rod does not make a "ground". It is just a method of bleeding off transient voltage, such as lightning. The earth is a poor conductor for a fault to ground to return to it's supply and will not be a low impedance path back to to the supply. The neutral conductor then must try to be that low impedance path.

My hat is off to you sir. As a 30 year liscensed electrician, I have been amazed over the years at how many inspectors (and electricians) did not understand the principles grounding and bonding. The people in your area are lucky to have someone who understands this element of safety.

 

[dcyrilc]

ATTENTION EVERYONE: I Got it!!!!!!!!!! Cyril, When you come down from your high horse just understand that not everyone knows everything. This is why people on this forum ask questions. The way I understand it, the code prohibiting a 3 wire system was only changed in 2008. So lets not pretend that this has never been an accepted method. Hopefully this will put the issue of 3 and 4 wire subpanels to rest. I appreciate your knowledge but lets not belittle someone for not being as in the know as you might be in the electrical field. Love and Kisses, Jim

Jim,
If you felt belittled by me, then I appoligize for that was not my intent. My intent was to try to clarify the difference between three wire and four wire systems and help to explain the necessity for how each is wired so that it would be a safe system. It was was not intended as critism of anyone.

As for the 2008 code change, I for one have been disapointed by this change, as I prefer the three wire system and have six outbuildings across my 17 acres wired as three wire subpanels.

The three wire system is better for longer runs in my opinion. Four wire systems are great for short runs, but can create issues for providing short circuit protection on long runs due to line loss and inherent resistance in the wire.

Anyway, again I appoligize if you felt that I had critisized you. I applaude anyone who desires to learn and know more about the things they are involved in with their lives. I complimented Inspector507 on this, since the principles of bonding and grounding are not well understood within the electrical industry and from reading his posts believe that he works within this industry.

I hope that this softens any hurt feelings between us. I have the utmost of admiration for you Sir.

 

[LD1]

All this confusion about three wire and 4 wire and ground rods has got me wondering wether my set-up is "ok". Those of you in the electrical field please confirm if it is "up to code" or not.

I have 3-wire direct burry triplex 200A to the house. Neutral is bonded and the ground rod is connected with a 8 ga copper wire.

From the house I installed a 100A breaker and ran 60ft of direct burry triplex to the 100A main breaker of the pannel in the garage. Neutral is bonded there to but no ground rod.

Should there be a ground rod at the garage?? Bonded neutral of not??

This is how I have seen many buildings wired, including 3 @ my parents and have never had any problems.

 

[dcyrilc]

All this confusion about three wire and 4 wire and ground rods has got me wondering wether my set-up is "ok". Those of you in the electrical field please confirm if it is "up to code" or not.

I have 3-wire direct burry triplex 200A to the house. Neutral is bonded and the ground rod is connected with a 8 ga copper wire.

From the house I installed a 100A breaker and ran 60ft of direct burry triplex to the 100A main breaker of the pannel in the garage. Neutral is bonded there to but no ground rod.

Should there be a ground rod at the garage?? Bonded neutral of not??

This is how I have seen many buildings wired, including 3 @ my parents and have never had any problems.

With the 3 wire system, the sub-panel is treated as a main panel. This means bond the neutral and ground at the sub-panel and install a ground rod. The ground rod is not as critical as the bonding, but is still a good idea. Bonding the neutral and ground at the panel is critical for short circuit protection or more accurately, ground fault protection.

In short, yes the neutral and ground should be bonded, and yes there should be a ground rod.

 

[Inspector507]

I've been going through my NEC book (1993 edition) and I can't seem to find the answer. Thanks in advance, Jim

Jim here's your answer. The 1993 NEC also required a 3 wire system to have a ground rod installed.

 

[Inspector507]

My hat is off to you sir. As a 30 year liscensed electrician, I have been amazed over the years at how many inspectors (and electricians) did not understand the principles grounding and bonding. The people in your area are lucky to have someone who understands this element of safety.

Learning and understanding that element and everything else in the NEC is what allows me to eat. It's been my living for more than 20 years as an inspector.

 

[firefighter jim]

Jim,
If you felt belittled by me, then I appoligize for that was not my intent. My intent was to try to clarify the difference between three wire and four wire systems and help to explain the necessity for how each is wired so that it would be a safe system. It was was not intended as critism of anyone.

As for the 2008 code change, I for one have been disapointed by this change, as I prefer the three wire system and have six outbuildings across my 17 acres wired as three wire subpanels.

The three wire system is better for longer runs in my opinion. Four wire systems are great for short runs, but can create issues for providing short circuit protection on long runs due to line loss and inherent resistance in the wire.

Anyway, again I appoligize if you felt that I had critisized you. I applaude anyone who desires to learn and know more about the things they are involved in with their lives. I complimented Inspector507 on this, since the principles of bonding and grounding are not well understood within the electrical industry and from reading his posts believe that he works within this industry.

I hope that this softens any hurt feelings between us. I have the utmost of admiration for you Sir.

Apologies on my behalf also Cyril. No hard feelings. Jim

 

[buckeyefarmer]

Paul and any other person in the know, I did NOT bond the neutral in the subpanel of my outbuilding that I fed with the 3 wire system a couple years ago. Should I leave it that way? I'm hearing conflicting stories (to bond or not to bond subpanels with 3 wire supplies). I've been going through my NEC book (1993 edition) and I can't seem to find the answer. Thanks in advance, Jim

In the 1996 code it is 250-24, can't find my 93 code book at the moment but should be in that area. Exception 2 says you don't bond if you pull the 4th wire (Equipment Ground).

A 3 wire to another building was as if you were coming off a transformer (but you weren't). This works ok if there are no other paths for grounds to connect back to the source panel, but once you run a phone line or cable tv or cat 5, etc.., you have put in a path and that makes the 3 wire setup unsafe.

 

[dcyrilc]

In the 1996 code it is 250-24, can't find my 93 code book at the moment but should be in that area. Exception 2 says you don't bond if you pull the 4th wire (Equipment Ground).

A 3 wire to another building was as if you were coming off a transformer (but you weren't). This works ok if there are no other paths for grounds to connect back to the source panel, but once you run a phone line or cable tv or cat 5, etc.., you have put in a path and that makes the 3 wire setup unsafe.

I cheated on the communication and video between my out buildings... I used fiber optics. Nonconductive.