Can anyone explain a change in code "service"

[cyamaha2007]

The quick and short im wondering why the change in the code for services. It used to be 3 wire from the service disconnect to your panel and a bonded neutral/ground also a ground rod was placed near the panel. What benifits does this new rule carry? Also lets say you have a 400a meter feeding a 200a panel in your house its a old style. Now say i add another panel to be fed off the same meter in a outbuilding, can that new panel be the 4 wire setup and not interfere with the house 3 wire setup. Or does the the house need to be upgraded to the 4 wire setup?

Thanks alot Chuck.

 

[sberry]

Where is this change? A service is still a 3 wire feed, a service feed from an existing service is 4 wire and I am not sure how they would treat this from a set of lugs off of a meter base, I would suspect they would call for a disconnect and 4 wire from there and here is why,, and forget the ground rods for a moment, they really have nothing to do with this,, you want an insulated neutral between these buildings and not bonded at the second. A 3 wire feed at the second would be fine except that (especially these days) you do not want neutral currents finding their way back on any other interconnected metal pathways, metal water lines, phone lines or metal gas lines. The goal here is insulated neutral.
I am sure someone will come along with better worded explanation.

 

[cyamaha2007]

I will have to look it up in the nec i was briefed about it at work. The guy that briefed us had no idea but was just reading off a paper someone wrote for him

 

[Charles (in GA)]

Everything up to the first disconnect (where ever that may be) is 3 wire. After the first disconnect, its 4 wire.

Charles

 

[cyamaha2007]

Ive searched hi and low for a 4 wire setup for me to look at. I assume you remove the jumper in panel that bonds/creates continuity between the neutral and ground buss. Right now i have transformer on a utility pole-->400a meter base 2ft away--> 200a service disconnect thats right below the meter base--> house 200a panel 100ft. Every part of that system is 3 wire 2 hots and 1 neutral. The only place a 4 wire system is used is inside the panel.

 

[Charles (in GA)]

DEPENDING ON WHEN IT WAS INSTALLED and what code cycle you were under at the time, it should have been 4 wire from that 200 amp disconnect at the meter, but may have been three wire if that was legal at that time and place.

Charles

 

[cyamaha2007]

Ok i understand. Do feel that it would be ok to mix the two systems? I would like to comply with the code ( i dont have inspections) I am not going to dig up my service to the house. I just want to be sure that the newer system wont conflict with the older system in place. Thank you for your response.

 

[sberry]

No, run 4 wire to the new. In theory as long as the N is insulated in the new all should be well,,, but,,, I haven't had coffee yet
I want to add as I am thinking about this, since this service is on a remote pole there will not be other metal pathways between it and the existing, with new 4 wire feed you should be good.

 

[kbs2244]

If you want to know what a joke this whole thing is, go shopping for a new electric stove.
They come with “4 to 3 adaptors” so you can plug the new 4 wire code stoves into the old 3 wire outlets.

Don’t even get me started on the required “anti tip over” brackets.

 

[rwreuter]

the 4 wire (has a GEC, or a grounding electrode conductor) is a current code requirement if you are running a sub panel from the meter location.

when i built my house i ran into this. i installed a pedestal meter and the main 200 amp panel was in the house about 200' away. the nec requires ground rods at the pedestal and at the main 200 amp panel along with 4 conductor....2 hots, neutral, and a GEC.

the code prior to that didn't require it UNLESS there was a connection between the main panel and the sub panel structure. that was mostly exclusive to commercial facilities. now, it is required in all situations.

i asked, inquired, researched my head off and got to the bottom of it. the way the code writers thought process went was, something in the future might connect the two structures and so to eliminate the hazard they required ALL set up to be four wire.

now i don't fully understand the next part. i guess it has something to do with the ability of the OCP (over current protection device (or CD)) to trip if there is a fault.

ok, so why the big deal.........the cost.....triplex cost vs 4 conductor difference is large. so what did i do? i sucked it up and ran the four conductor in 3" PVC. i knew there would never be a chance in hell that the two would be connected but the NEC is the NEC and i didn't want there to be any questions when i wanted to sell my house in the future. it would be a pia in 5-10 years if i had to rip up my yard and fix that because some home inspector saw my house was built when that was a requirement.


does that help?