NEC 230.7 & 230.91

[Technodude]

Hi

I recently moved from Hawaii to Minnesota after being gone for a long time. I'm used to installing a combination meter socket + main breaker in same enclosure with the ground directly below. If the distance is over say a hundred feet installing a second ground rod and the tie to the water pipe near the panel.

I just found out that Minnesota doesn't require a disconnect from the service entrance (meter) for three horizontal feet and basically unlimited vertical runs. For instance from the meter into an attic down a wall into a basement and then landed into a main breaker panelboard. The ground rod is sometimes attached to the pole or pad mount transformer, and the ground to the water pipe is brought to breaker panel.

This seems to me to have any number of issues. Unprotected wire running from the meter through the residence, no unified ground, etc.

Question is.... how can this meet NEC 70? Is this common practice in other jurisdictions.

Bewildered

Technodude

 

[George Stolz]

Welcome to the forum!

Hi

I recently moved from Hawaii to Minnesota after being gone for a long time. I'm used to installing a combination meter socket + main breaker in same enclosure with the ground directly below. If the distance is over say a hundred feet installing a second ground rod and the tie to the water pipe near the panel.

A ground rod is always required to be supplemented by one more rod, unless the AHJ can determine that the first ground rod is 25 Ohm's to earth or less. These days, rods are less common because of the common use of concrete encased electrodes.

Edit to add: 250.50 requires all electrodes at a structure be used, so there isn't a scenario where you can leave out a metal water pipe electrode, as you seem to have indicated.

I just found out that Minnesota doesn't require a disconnect from the service entrance (meter) for three horizontal feet and basically unlimited vertical runs. For instance from the meter into an attic down a wall into a basement and then landed into a main breaker panelboard. The ground rod is sometimes attached to the pole or pad mount transformer, and the ground to the water pipe is brought to breaker panel.

It is their call how they would like to interpret "inside nearest the entry of service conductors." Three feet doesn't seem that long. Around here it's often seen as the distance a meter socket would be directly nippled to the service disconnect enclosure back-to-back, around 4" of raceway.

This seems to me to have any number of issues. Unprotected wire running from the meter through the residence, no unified ground, etc.

I would be interested to hear what you mean by "unified ground" - I've never heard that term before.

 

[kwired]

Hi

I recently moved from Hawaii to Minnesota after being gone for a long time. I'm used to installing a combination meter socket + main breaker in same enclosure with the ground directly below. If the distance is over say a hundred feet installing a second ground rod and the tie to the water pipe near the panel.

I just found out that Minnesota doesn't require a disconnect from the service entrance (meter) for three horizontal feet and basically unlimited vertical runs. For instance from the meter into an attic down a wall into a basement and then landed into a main breaker panelboard. The ground rod is sometimes attached to the pole or pad mount transformer, and the ground to the water pipe is brought to breaker panel.

This seems to me to have any number of issues. Unprotected wire running from the meter through the residence, no unified ground, etc.

Question is.... how can this meet NEC 70? Is this common practice in other jurisdictions.

Bewildered

Technodude

First I don't see that the NEC sections mentioned in the thread title have to do with anything you have asked about.

Second a meter doesn't designate a service entrance location - NEC could care less if there even is a meter, but does permit one to be located in the service conductors - it has been said here before and I don't know who to credit for saying it first but a meter is just a wide point in the conductors/wiring method.

230.70(A)(1) says "The service disconnecting means shall be installed at a readily accessible location either outside of a building or structure or inside nearest the point of entrance of the service conductors."

It does not give us any dimensions, this leaves that determination up to AHJ. Some jurisdictions are very strict and allow very little service conductor into a building - others are fairly relaxed and may allow a surprisingly long distance in some instances. I think most typically are in the three to five feet range of service conductor allowed inside a building. Some may put less emphasis on this if it is vertical - though that sort of doesn't make too much sense IMO.

Some AHJ's may have preferences on where you connect grounding elecrode(s), but the general rules in NEC are that they must connect to the service disconnecting means or any point on the same structure that is ahead of the service disconnecting means is also acceptable. All elecrtodes present must be connected, driven rods connected to equipment beyond the service equipment are optional - but that equipment must still be supplied with an equipment grounding conductor.