No water ground or any other available electrode?

[jaylectricity]

I am trying to "finish" a 400A service for a client. Most of the work was done. Underground to a meter out near the street, then underground to the house and to 2 200A fusible service disconnects. SER from each of those to two subpanels across the room.

They drove two ground rods from the meter (remember, this is MA where the rules seem to be different from elsewhere) but didn't run a GEC to the water main. I purchased 1/0 Cu to accomplish this, but when I took a closer look the water pipe coming into the floor is PEX and aside from about 25' of copper pipe in that room, all the water pipes that go out of the room are also PEX. So it's not going to be a grounding electrode at all.

I have no idea if there is rebar in the footings, this is not a new house, just an upgraded service.

Can I just drive an additional ground rod with its own GEC to the service OCPDs? Then I have a grounding electrode there, plus a supplemental electrode system out by the meter.

Also, 1/0 seemed awfully large for the water ground, I couldn't even find water pipe clamps to accommodate both that wire size and the size of the water pipe.

 

[electrofelon]

My take on it is that the NEC does not require a grounding electrode at a meter with no disconnects (even if it is called a structure). That said, I think every utility i know of requires a GE at a meter pedestal. Just two rods at the house should do it then. Maybe bond the water, but I would even say that lone 25' piece doesnt constitute a "water piping system".

 

[jaylectricity]

My take on it is that the NEC does not require a grounding electrode at a meter with no disconnects (even if it is called a structure). That said, I think every utility i know of requires a GE at a meter pedestal. Just two rods at the house should do it then. Maybe bond the water, but I would even say that lone 25' piece doesnt constitute a "water piping system".

It's not even a 25' piece. It's just if I add up all the copper pieces it's probably 25'. But it's plastic going into the earth, so there's no reason to ground it.

In MA we do ground rods outside with a GEC to the meter socket, and a water ground with a GEC going to the box with the first OCPD/main breaker.

So to me, the ground rods to the meter socket on the pedestal would be fine for a supplemental ground. Even if I wanted to consider those the grounding electrode, I don't think they'd pass by themselves.

I'm just thinking I can drive another ground rod with its own GEC to the main fuses.
'

 

[ptonsparky]

It's not even a 25' piece. It's just if I add up all the copper pieces it's probably 25'. But it's plastic going into the earth, so there's no reason to ground it.

In MA we do ground rods outside with a GEC to the meter socket, and a water ground with a GEC going to the box with the first OCPD/main breaker.

So to me, the ground rods to the meter socket on the pedestal would be fine for a supplemental ground. Even if I wanted to consider those the grounding electrode, I don't think they'd pass by themselves.

I'm just thinking I can drive another ground rod with its own GEC to the main fuses.
'

Two rods...

 

[Dennis Alwon]

I agree that 2 rods is all that is needed.

In reference to the 1/0 I have to disagree assuming you are using 4/0 aluminum or up to 3/0 copper for the 2 main panels. #2 awg is all that is needed. If you had a 400 meter/main then I would agree with 1/0

 

[mbrooke]

All you need is one rod at 25 or drive two and your set :thumbsup:

 

[jaylectricity]

So the two rods are enough. Got it.

I agree that 2 rods is all that is needed.

In reference to the 1/0 I have to disagree assuming you are using 4/0 aluminum or up to 3/0 copper for the 2 main panels. #2 awg is all that is needed. If you had a 400 meter/main then I would agree with 1/0

Now that you put it that way, I would be basing it on having two 200 amp main fuses, as opposed to a 400 amp fuse.

 

[Dennis Alwon]

So the two rods are enough. Got it.



Now that you put it that way, I would be basing it on having two 200 amp main fuses, as opposed to a 400 amp fuse.

Yep, you would use note 1 to table 250.66 which will calculate to be #2

Note 2- meter/main would calculate to 1/0

 

[kwired]

Unless increased conductor sizes are necessary for voltage drop ambient temp, ampacity adjustments...

two 3/0 copper or two 250 aluminum would be sufficient ampacity for 400 amps - both would only require a #2 copper GEC.

two 3/0 has total cross sectional area of 335600 CM.

Jay - your meter being remote from the house is a separate structure. You need a grounding electrode system at the house, if there are no existing qualifying electrodes you can install any "made" electrode you like, ground rods are typically the simplest and least cost is why they are most common. If the meter were at the house then any electrodes connected to it could be considered electrodes serving the house.

The need to bond what metal water piping you do have is something that has been debated here many times. Most will say it is not a metallic piping system and doesn't need bonded at all. Some will still say what is metallic does still need bonded.

 

[jaylectricity]

Unless increased conductor sizes are necessary for voltage drop ambient temp, ampacity adjustments...

two 3/0 copper or two 250 aluminum would be sufficient ampacity for 400 amps - both would only require a #2 copper GEC.

two 3/0 has total cross sectional area of 335600 CM.

Jay - your meter being remote from the house is a separate structure. You need a grounding electrode system at the house, if there are no existing qualifying electrodes you can install any "made" electrode you like, ground rods are typically the simplest and least cost is why they are most common. If the meter were at the house then any electrodes connected to it could be considered electrodes serving the house.

The need to bond what metal water piping you do have is something that has been debated here many times. Most will say it is not a metallic piping system and doesn't need bonded at all. Some will still say what is metallic does still need bonded.

I did feel like the rods out by the meter weren't part of the house. Makes sense.

I'll drive another two by the house and poke the wire into the basement.

Not worried about the water pipes since they are unlikely to become energized.