Separately derived system transformer

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VanmBuilders

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California
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Contractor
Hello, have a main utility service cabinet That has 600 amp breaker feeding two 200amp breakers and one 125amp breaker inside the same cabinet. 125 amp breaker feeds directly to a primary 75 kva 480volt delta/secondary 208 volt y transformer. A neutral wire was ran with the three hot legs inside conduit from125amp breaker but neutral wasn’t attached to XO lug. The neutral is terminated by means of a knuckle. There is also no green wire in that conduit raceway coming from the 125amp breaker. At one time this 125amp raceway was attached to a panel near a utility room. However now diverted to a transformer. So I’m assuming this is a separately derived system. And transformer creates a new system bond via XO with its own ground rod and neutral bond for 208 service cabinet with a separate ground and separate neutral at the new 208v panel.
 
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VanmBuilders said:
. A neutral wire was ran with the three hot legs inside conduit from125amp breaker but neutral wasn’t attached to XO lug.
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The neutral should not be connected, what is a knuckle?


VanmBuilders said:
There is also no green wire in that conduit raceway coming from the 125amp breaker.
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What type of raceway? A metal raceway that is permitted as an EGC can serve as the SSBJ.
 
Since that neutral originates from a main panel, you could use it as the EGC/GEC if it is sized appropriately.
 
VanmBuilders said:
Hello, have a main utility service cabinet That has 600 amp breaker feeding two 200amp breakers and one 125amp breaker inside the same cabinet. 125 amp breaker feeds directly to a primary 75 kva 480volt delta/secondary 208 volt y transformer. A neutral wire was ran with the three hot legs inside conduit from125amp breaker but neutral wasn’t attached to XO lug. The neutral is terminated by means of a knuckle. There is also no green wire in that conduit raceway coming from the 125amp breaker. At one time this 125amp raceway was attached to a panel near a utility room. However now diverted to a transformer. So I’m assuming this is a separately derived system.
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Sounds like you have a white wire run where there should have been a green wire (EGC). If it is connected to the transformer enclosure then that white wire would be serving the same purpose. It's unclear from your description where it is terminated; the burndy connector you linked to is a splice. In any case you are evidently talking about the primary side of the transformer, which you said was delta, so being connected to XO is not necessary. The 208V side is a separately derived system, yes. The 125A primary feeder where you are asking about the neutral is not the SDS, it is the same system as the service.

Technically the EGC is supposed to be green not white, but if I didn't have an inspector asking me to change it, and the white wire is doing everything an EGC is supposed to do, then I'd probably just wrap the ends of the white wire in green tape.

VanmBuilders said:
And transformer creates a new system bond via XO with its own ground rod and neutral bond for 208 service cabinet with a separate ground and separate neutral at the new 208v panel.
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Technically the XO for the secondary should be connected to the same grounding electrode system (rods or whatever) as the service. Grounding electrodes aren't what make a system an SDS.
 
jaggedben said:
Sounds like you have a white wire run where there should have been a green wire (EGC). If it is connected to the transformer enclosure then that white wire would be serving the same purpose. It's unclear from your description where it is terminated; the burndy connector you linked to is a splice. In any case you are evidently talking about the primary side of the transformer, which you said was delta, so being connected to XO is not necessary. The 208V side is a separately derived system, yes. The 125A primary feeder where you are asking about the neutral is not the SDS, it is the same system as the service.

Technically the EGC is supposed to be green not white, but if I didn't have an inspector asking me to change it, and the white wire is doing everything an EGC is supposed to do, then I'd probably just wrap the ends of the white wire in green tape.



Technically the XO for the secondary should be connected to the same grounding electrode system (rods or whatever) as the service. Grounding electrodes aren't what make a system an SDS.
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from 125amp breaker 3hot legs 480v and one neutral-wire same size wire as feeder wires were feeding a 480volt panel in a utility room. 125amp breaker is inside cabinet out side right up against the building 600amp main breaker feeding 2- 200 amp breakers and one 125amp breaker. The panel inside utility room was being used for some equipment however they needed to step down to a 208. The burndy splice caps off the white/neutral inside that panel in utility room. The three feeder wires 480v were diverted to a new raceway to a 200amp disconnect with 125amp fuses then to a transformer primary side 480v delta. Without knowing if the white wire is doing everything as an EGC is suppose to do back at the main service entrance wouldn’t it be best to use ground rod and bond neutral to ground at XO. Then the new 208 panel would have separate neutral and ground.
 
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VanmBuilders said:
Without knowing if the white wire is doing everything as an EGC is suppose to do back at the main service entrance wouldn’t it be best to use ground rod and bond neutral to ground at XO. Then the new 208 panel would have separate neutral and ground.
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I would forget the white conductor. It's almost guaranteed to be connected to the neutral bus in the service panel and is not relevant to the feeder to the transformer primary. Also since it's a white conductor within a raceway it cannot be re-identifed as something else.

The transformer secondary neutral is bonded via a SBJ typically within the transformer. The GEC is terminated at the same location that the SBJ is installed and is run back to the building GES.
 
infinity said:
I would forget the white conductor. It's almost guaranteed to be connected to the neutral bus in the service panel and is not relevant to the feeder to the transformer primary. Also since it's a white conductor within a raceway it cannot be re-identifed as something else.

The transformer secondary neutral is bonded via a SBJ typically within the transformer. The GEC is terminated at the same location that the SBJ is installed and is run back to the building GES.
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Today, 6:38 AM
the second part “gec is terminated at same location”- ground rod at the transformer? I’m assuming it’s talking about the neutral/ground which is established inside the transformer at xo and has nothing to do with anything up stream at service cabinet since only thing coming from upstream at outside utility cabinet is three hot legs to transformer. But than ran back to building GES is that suggesting having a ground attached to building and not a ground rod. Just thought transformer created its own separate service/system and ground rod to earth is needed GEC then to XO, bond to cabinet and have neutral leave from XO to new 208 panel.
 
MTW said:
Insulated Multiple Tap Connectors, that's what their maker calls them. Different regions use different slang terms, Never heard the word knuckle used for them. In my area they are typically called a Polaris connector.


nsiindustries.com

Polaris v3

Powering Connections Inquire About Polaris Connector Solutions
nsiindustries.com nsiindustries.com
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Polaris is the name of a particular product line from NSI industries. They might have been one of the first out there of this design and kind of ended up sticking as an in the field name for all connectors of thay style.
 
VanmBuilders said:
Just thought transformer created its own separate service/system and ground rod to earth is needed GEC then to XO, bond to cabinet and have neutral leave from XO to new 208 panel.
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Is the location of this feeder and transformer in a separate structure?
 
infinity said:
Is the location of this feeder and transformer in a separate structure?
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The feeder is a 125amp breaker inside a utility cabinet on the outside of the building. Then feeds to The transformer which is outside. However the secondary will feed a 208 panel that will be inside the building about 10ft from transformer.
 
VanmBuilders said:
The feeder is a 125amp breaker inside a utility cabinet on the outside of the building. Then feeds to The transformer which is outside. However the secondary will feed a 208 panel that will be inside the building about 10ft from transformer.
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Closest building steel is about 20ft from transformer
 
VanmBuilders said:
The feeder is a 125amp breaker inside a utility cabinet on the outside of the building. Then feeds to The transformer which is outside. However the secondary will feed a 208 panel that will be inside the building about 10ft from transformer.
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So this building is separate from the utility cabinet and will be fed by a single 480 volt feeder stepped down to 208Y/120? Is there a grounding electrode system already established at the separate structure?
 
This is where the 125amp breaker is located going to disconnect before the transformer. This is where the transformer is outside the building. The job wasn’t completed so there isn’t any grounding or GEC at transformer. It’s currently not in use
 

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This is where the transformer is outside the building. The job wasn’t completed so there isn’t any grounding or GEC at transformer. It’s currently not in use.
 
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