Service Cable to sub panel theory question.

[MdGNev]

Going to be running a sub panel underground 100+- ft to new steel building will be running a 2-2-2-2 Aluminum SER Cable. (Planning n 100amp svc even thought I doubt I will EVER need it.)

If the #2 SER Cable is
2 (+)
1 (-)
1(g)

Why am I running a ground all the way back to the panel?

Seems to me since I will need a rod at the building to ground from the sub panel, Couldn't I run a 2-2-2 Aluminum SER Cable 2+ and 1-

And meet the grounding needs for the sub panel with the local rod?

 

[Deleted member 26818]

Which country is this in?

 

[westward10]

USA.

 

[MdGNev]

USA.

 

[westward10]

This is a UK based forum and whilst some members are based in the States I am not sure you are going to get the correct advice, if any.

 

[MdGNev]

Thank you, the sign on note indicated US as well.

It is a theoretical question not advice or code.

 

[Pete999]

Going to be running a sub panel underground 100+- ft to new steel building will be running a 2-2-2-2 Aluminum SER Cable. (Planning n 100amp svc even thought I doubt I will EVER need it.)

If the #2 SER Cable is
2 (+)
1 (-)
1(g)

Why am I running a ground all the way back to the panel?

Seems to me since I will need a rod at the building to ground from the sub panel, Couldn't I run a 2-2-2 Aluminum SER Cable 2+ and 1-

And meet the grounding needs for the sub panel with the local rod?

Is it DC only asking because you state 2 positives 2 negatives and 1 ground Ah I see you' re in the US

 

[static zap]

(sorry no idea of your USA codes )
..But interesting to hear some of your terminology !

 

[westward10]

Just been looking at these cables how are the cores generally configured.

 

[Charlie_]

I don’t know but I’m very interested in finding out more.

 

[Wilko]

Hi - as per Pete, AC or DC?
Assuming AC, then perhaps you’re planning two phases, a neutral and an earth. In the UK the cable would need to have a circuit protective conductor travelling with the lives irrespective of the next building’s earthing design. The size of that protective conductor may increase if it also provided bonding in the new building (which it does, by the sounds).

 

[westward10]

One option is to use one core as a cpc, this is basically a four core cable with the others as two lines (+) and a neutral (-).

 

[Deleted member 26818]

Hi - as per Pete, AC or DC?
Assuming AC, then perhaps you’re planning two phases, a neutral and an earth. In the UK the cable would need to have a circuit protective conductor travelling with the lives irrespective of the next building’s earthing design. The size of that protective conductor may increase if it also provided bonding in the new building (which it does, by the sounds).

That is not the case at all.
BS7671 requires (if there is a CPC) that it should be run with the other circuit conductors, and further that the CPC should be contained within the same ferrous-magnetic enclosures (if used).
A great many installations in the UK have one circuit which does not have a CPC run with the lives, and in TT installations, that circuit doesn’t even have a CPC.
A protective conductor would not be required.
However in many cases there will already be a protective conductor incorporated in the cable, in the form of an armour to provide protection for the cable being pierced or severed.

As for running a secondary protective conductor to provide the grounding for the subsystem, a lot will depend on the grounding method used at the primary installation, the purpose the secondary installation is intended for, how low a resistance to the general mass of the earth can be achieved at the secondary installation and of course cost.

 

[Wilko]

Thanks.
I do think that your opening sentence is off course mate. How can my post not be true “at all” when your 2nd sentence repeats what I have said? adding your own spin, naturally. Just my opinion.

 

[Lucien Nunes]

It is a theoretical question not advice or code.

In fact it is specifically about codes. In theory electricity only needs a circuit to flow around. Grounding is an extra safety measure introduced for practical reasons, and the way it is done depends on the local code. Codes differ in their requirements for protective conductors although they often achieve the same objective; a configuration that is compliant in the UK might be a code violation under the NEC, and vice versa. For historic reasons and differences in population density and preferred cable routing, public electrical networks differ in how and where their neutrals are grounded, which puts different demands on the grounding configuration within a property.

It's interesting to note just how different the details are. We would not normally use aluminium cable, do not recognise 'SER' or 2-2-2-2 (we don't use AWG so #2 means nothing to many UK electricians, we would call it 4x35mm²). We don't use two hots (a few old installations exist that do, but those are 240/480V not 120/240) so it would be either one line and a neutral or three lines and a neutral, not two. We use the term 'earthing' instead of grounding and we have bonding too, but with subtly different meanings; some connections you would define as bonding, we call earthing, while some that you would call grounding, we call bonding.

Interesting, but lots of room for misunderstanding in transatlantic discussions.