SDS no direct electrical connection

[chris kennedy]

Is there a problem with this definition?

Separately Derived System. A premises wiring system whose power is derived from a source of electric energy or equipment other than a service. Such systems have no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.

I have a transformer, 480 delta primary and 208y/120 secondary. I'm reverse wiring this as a step up. My now 208y/120 primary EGC is bonded to the transformer enclosure. My B phase of the 480 now delta secondary is bonded to the transformer enclosure. Would this not be a direct electrical connection of the different systems grounded conductor?

 

[winnie]

One does seem to end up with a bit of a paradox.

The requirements for how to ground and bond a separately derived system seem to cause the system to no longer be separately derived after they've been applied.

-Jon

 

[LarryFine]

The bond seems to eliminate the SDS status, but one could say the same thing about any grounded secondary.

But, the EGC isn't technically a supply conductor, even though there is one bonded to it.

Why do you need to know? That might help answer the question in the context of your use.

 

[chris kennedy]

Why do you need to know? That might help answer the question in the context of your use.

Long story but in a nut shell two guys new to our crew overheard Al and I discussing corner ground delta and when I drew it for them I saw that I did indeed have a direct connection between the grounded conductors.

Side note: The guys I was trying to explain it to can't wrap their heads around this. Anyone know of a good resource that explains this? Maybe a better picture than the one I drew.:roll:

 

[winnie]

The key is that you need a complete circuit for electric current to flow.

If you have an SDS, then you have _no_ connection.

Once you make your bonding connection, then you do have an electrical connection...but you've gone from _no_ connections to _one_ connection; you still do not have a complete circuit.

-Jon

 

[chris kennedy]

The key is that you need a complete circuit for electric current to flow.

Of course, thanks Jon.

 

[chevyx92]

Long story but in a nut shell two guys new to our crew overheard Al and I discussing corner ground delta and when I drew it for them I saw that I did indeed have a direct connection between the grounded conductors.

Side note: The guys I was trying to explain it to can't wrap their heads around this. Anyone know of a good resource that explains this? Maybe a better picture than the one I drew.:roll:

Here's some information that explains a corner grounded delta.
http://ecatalog.squared.com/techlib/docdetail.cfm?oid=09008926800b38e9