225kva transformer bonding/grounding
- Thread starter Hcji
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- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Are you intending to install this as an SDS (separately derived system) or not?
Not sds
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
If it is truly not an SDS, then you need to keep the neutral and EGC separate within the setup. Connect both the H0 and X0 to the incoming neutral, connect case to EGC only.
If it is an SDS, then bond the output 0 terminal, which for a step up use might be labelled H0, to frame and ground electrode, then run a bonding jumper or GEC to the rest of the building ground system (GES)
- Location
- Massachusetts
Is that even and option under the NEC?
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Can you explain your non-SDS setup?
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Good question. If you are allowed to do it with an autotransformer, there should be no prohibition on doing the same thing with an isolation transformer. But it is not clear that there are any advantages to doing it that way.
- Location
- Massachusetts
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
If the transformer itself had an X0 to H0 bond, it could not, under that definition be part of an SDS.
How would an AHJ rule on that? Would such equipment be prohibited?
A generator with a build in ground to neutral bond is a non-SDS and is legal with the right downstream wiring. Why not a transformer wired the same way?
Does that make adding such a bond externally against code?
- Location
- Massachusetts
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
To make it a non-SDS installation, of course.
- Location
- Massachusetts
I am sticking with not compliant.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
And I will stick with why is a non-SDS generator compliant while a non-SDS transformer is not, aand yet an autotransformer is.
I am content to leave it there until somebody comes up with an authoritative answer based on published code interpretation or AHJ ruling.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
This topic of puttimg a jumper from HO to XO came up a while back but I can't remember what the consensus was or if there was one. Seems like if there was nothing wrong with this then everyone would do it to avoid the gec requirement. What would you cite as a code violation?
- Location
- Massachusetts
My thoughts exactly, we ECs seem to able to ferret out the cheapest methods.
Of course I have not priced a Wye / Wye trans and the neutral you would have to run to it
The It's weird and I don't like it section of 113.76(Q).
(I am still working on it.
)
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Well that's a good point.....I think I'd rather install the GEC.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Exactly. It is an economic decision rather than a regulatory one.
- Location
- Massachusetts
I think the jury is still out on that
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