Use of H0 Position for EGC connections.

[SteveO NE]

Am I wrong for still not liking this installation? Admittedly, I think it is because of how it was before that I'm overly sensitive. This was installed under 2017 NEC, it is a PV transformer, and the H windings are towards the PV, with a delta X side (not a fan of that but I didn't design it), the left of the transformer is showing the incoming delta and the EGC coming with it terminating on the H0 bus. This is an outdoor installation so the SBJ should be in the transformer.

First things first, I am fairly confident that galvanized pole is not an adequate GEC its only loosely a "building structure" its a fence post holding up greenhouse parapets so I doubt it is in contact with the ground for 10'.

Next I'm not thrilled with that exterior lug for the ground back to the GEC; to me it feels a little too easy to tamper with, nothing is happening around it per se but would you consider that subject to physical damage if it were you blessing the installation (against a building on a gravel path that I believe facility vehicles drive up and down - no bollards in front of equipment which is a separate issue)? I am not familiar with the human or vehicular traffic or equipment that goes past this pad other than seeing a truck parked up the path a ways. I believe I typically see a stranded ground going straight through the bottom of the transformer and to a GEC right next to the transformer.

And the thing here, that originally had flagged my attention was that all of the grounds were coming out of an unbonded H0, plus other flip flopping the use of ground and neutral throughout the rest of the service equipment. They bonded it after I noticed but I still don't really like that the H0 is the ground bus, I've always seen guys just put a ground bus for EGCs, now the lugs on the bottom rail of the H0 to me doesn't bother me that much but the one coming out of the top just seems like poor practice and likely to cause future issues. I couldn't find any code reference and I'm sure after what I saw before this is just an extra cautious concern here but anyone have thoughts?

There are still other things here that I know need corrected so they will still have to go out again.

Thoughts? Am I overthinking this?

 

[SteveO NE]

Oh and also missed the other main point that bugs me with that lug - maybe its semantics but is that considered continuous from the SBJ to the GEC? I suppose one could argue the SBJ goes to that lug and the conductor to the GEC starts at the outside lug and is continuous. I believe the lugs are through bolted together and not using the steel of the transformer for electrical continuity but I cannot be sure.

 

[jim dungar]

Proper terminology, per ANSI, is for the high voltage windings to be H and the low voltage windings X. You need to look at the nameplate to determine which windings are the 'normal' primary side, they are typically the ones with the taps.

 

[kwired]

Having an H0 terminal suggests the high voltage side is wye configuration. Probably should be left floating if it is the primary, otherwise should have neutral connected if it is the secondary. For PV interconnection probably should be floating if it is the utility side or have neutral connected if it is the PV side.

 

[SteveO NE]

Proper terminology, per ANSI, is for the high voltage windings to be H and the low voltage windings X. You need to look at the nameplate to determine which windings are the 'normal' primary side, they are typically the ones with the taps.

Having an H0 terminal suggests the high voltage side is wye configuration. Probably should be left floating if it is the primary, otherwise should have neutral connected if it is the secondary. For PV interconnection probably should be floating if it is the utility side or have neutral connected if it is the PV side.

I may be misrepresenting my issue, I understand the terminology, this is actually secondary on the low side (utility side) per the nameplate which is not preferred for PV because that's where your soaking current comes from so that increases inrush to an unknown amount and can (and I have seen it) cause nuisance trips. This is a self derived system and the 277/480V side needs the neutral, the utility side is a 208V delta and that's fine as well.

My question is about the EGC/GEC connections, it feels hokey to me for best practices as best but like I said it could just be because of what I found at this site before with very poor workmanship, so I might just be looking for a problem and don't want to be that way which is why I posed it to the community to see.

 

[wwhitney]

If H = high voltage side and Primary = Utility side, then H0 is the secondary neutral point. If the primary EGC also meets the rules for a GEC, then it is providing the necessary earthing for the SDS.

Cheers, Wayne

 

[kwired]

If H = high voltage side and Primary = Utility side, then H0 is the secondary neutral point. If the primary EGC also meets the rules for a GEC, then it is providing the necessary earthing for the SDS.

Cheers, Wayne

H terminals should be the higher voltage terminals, and he said the PV side is 480/277 wye and the other side is 208 delta.

Which side one might choose to call primary possibly subjective though most setups I would guess would normally be the utility side since you usually need to sense power from utility before PV equipment will allow sending power to the utility.

 

[jaggedben]

I don't see an issue with using the bar connected to H0 as a ground bar. Ground is ground, having a separate bar on the enclosure doesn't really make any electrical difference I can see. As I see it, it is the same as landing GEC and EGCs on the neutral bar of a service panel, no big deal.

I do believe that the GEC needs to be continuous and terminated directly to the H0 bar, not the enclosure and not to the SBJ. The way they did it is not an irreversible splice. Also it's supposed to be bonded to the conduit; I see plastic bushings instead.

Without understanding more about the structure containing the pipe being used as an electrode, the following is hard to say for sure. But if that is the structure supporting the PV, and if it connects to a network of structural steel with multiple piers in the ground, I would think that's far more effective than a couple ground rods and wouldn't make a big deal out of it.

The attachment of the lug to the pipe being used as an electrode would get as much scrutiny from me as anything else mentioned. I'd use a direct burial rated pipe clamp (bronze screws) if I were doing that. Unclear from the pic if it's not just attached with a self tapping screw that will break as the lug corrodes galvanically.

 

[jaggedben]

If H = high voltage side and Primary = Utility side, then H0 is the secondary neutral point. If the primary EGC also meets the rules for a GEC, then it is providing the necessary earthing for the SDS.

Cheers, Wayne

Yes but if the transformer and array are separate structures from wherever is supplying the 208/120V feeder, then there needs to be a GES at the transformer and/or array and the GEC must be run to there. Unclear from the info given.

 

[SteveO NE]

H terminals should be the higher voltage terminals, and he said the PV side is 480/277 wye and the other side is 208 delta.

Which side one might choose to call primary possibly subjective though most setups I would guess would normally be the utility side since you usually need to sense power from utility before PV equipment will allow sending power to the utility.

Sorry for the really slow response on this, just noticed, but its not actually subjective if we are talking about what the manufacturer calls the primary side, it has nothing to do with the direction of power flow or the relative voltage, nor the NEC's reference to us considering both sides primary and secondary within our designs, it has to do with which winding is closer to the core and tested as the primary side to meet the maximum inrush requirements. That was my reference to primary/secondary and that is why the primary winding should usually be facing the excitation current source.

Yes but if the transformer and array are separate structures from wherever is supplying the 208/120V feeder, then there needs to be a GES at the transformer and/or array and the GEC must be run to there. Unclear from the info given.

Again, this is an old post, but for internet completeness if someone searches this, the array, the transformer, and the 208v feeder supply are all separate structures and yes it has a GES for each.

As for below, just in case you really were curious:

I don't see an issue with using the bar connected to H0 as a ground bar. Ground is ground, having a separate bar on the enclosure doesn't really make any electrical difference I can see. As I see it, it is the same as landing GEC and EGCs on the neutral bar of a service panel, no big deal.

I do believe that the GEC needs to be continuous and terminated directly to the H0 bar, not the enclosure and not to the SBJ. The way they did it is not an irreversible splice. Also it's supposed to be bonded to the conduit; I see plastic bushings instead.

This is pretty much how I left it with them. I believe I was getting picky in my head with that because was originally flagged my attention is that the EGC was flip/flopping throughout the system - they confused themselves in each panel and essentially the grounds and neutrals were mixed throughout - in other words they interchangeably used the ground/neutral and in some cases just bonded it again in a down-stream panel. It was a total mess.

Without understanding more about the structure containing the pipe being used as an electrode, the following is hard to say for sure. But if that is the structure supporting the PV, and if it connects to a network of structural steel with multiple piers in the ground, I would think that's far more effective than a couple ground rods and wouldn't make a big deal out of it.

That pipe has nothing to do with anything, the it is a pole that holds up fabric in the summer and corrugated fiberglass in the winter that is affixed from pole to pole. There is not "building structure" per se as its a green house...lots of gravel and fences. The PV array is a ground mount located 100' away.

The attachment of the lug to the pipe being used as an electrode would get as much scrutiny from me as anything else mentioned. I'd use a direct burial rated pipe clamp (bronze screws) if I were doing that. Unclear from the pic if it's not just attached with a self tapping screw that will break as the lug corrodes galvanically.

The pipe was hokey as hell made them run a GEC with proper clamps.