What's wrong with this picture?

[MD84]

I'm not sure if there is an ongoing thread for this type of discussion. If so mods please merge. Otherwise feel free to post similar topics.

This panel is fed from a 480:120/240 transformer. Primary is tapped from 100A feeder. #6 wire for primary and secondary. Primary and secondary conductors <10'

 

[K8MHZ]

Black wire connected to ground/neutral bar. They could have at least put some tape on it.

 

[MD84]

I saw that and thought and thought something was off. I Checked L1 to nuetral bar and got 207v, L2 to nuetral bar 31v, L1 to L2 239v.
Opened up the transformer and found black wire connected to case. No SBJ.

 

[jap]

I saw that and thought and thought something was off. I Checked L1 to nuetral bar and got 207v, L2 to nuetral bar 31v, L1 to L2 239v.
Opened up the transformer and found black wire connected to case. No SBJ.

That sneaky black wire is probably the same culprit that stole your missing 1 volt.


JAP>

 

[MD84]

That sneaky black wire is probably the same culprit that stole your missing 1 volt.

:lol: maybe if I put a bucket under there I could catch the volt drop.

The way it stands I am going to have to provide a ground reference to the otherwise floating secondary coil. I think I will land the black wire on the secondary nuetral point and pull a ssbj. Heck I may as well pull a white nuetral and use the black as my ssbj.

Less than #4 needs to be ALL white or grey anyway.

 

[kwired]

I'm not sure if there is an ongoing thread for this type of discussion. If so mods please merge. Otherwise feel free to post similar topics.

This panel is fed from a 480:120/240 transformer. Primary is tapped from 100A feeder. #6 wire for primary and secondary. Primary and secondary conductors <10'

If primary is 100 amps @ 480 volts then 6AWG is ok for the primary side.

primary to secondary ratio is 1:2. so secondary conductors need to have ampacity of 1/3 of 200 amps which is which is 66.6 A - 6 AWG is just a little under so 4 AWG is needed.

Secondary also needs to land in a single overcurrent device.

I get this from 240.21 (C)(5) "Secondary Conductors from a Feeder Tapped Transformer" which tells you it needs to comply with overcurrent protection in 240.21(B)(3)

If there is no neutral load being supplied there doesn't have to be a white conductor.

Where does the green conductor in the supply conduit go to?

 

[MD84]

If primary is 100 amps @ 480 volts then 6AWG is ok for the primary side.

primary to secondary ratio is 1:2. so secondary conductors need to have ampacity of 1/3 of 200 amps which is which is 66.6 A - 6 AWG is just a little under so 4 AWG is needed.

Good call. Since no nuetral is needed (both loads are 240v) and this would be a single voltage two wire secondary could I get away with #6? I am thinking of 1/10th but not sure.

Secondary also needs to land in a single overcurrent device.

I thought that would be the case but was not sure of the code section. Would this be the case for a single voltage transformer?

I get this from 240.21 (C)(5) "Secondary Conductors from a Feeder Tapped Transformer" which tells you it needs to comply with overcurrent protection in 240.21(B)(3)

If there is no neutral load being supplied there doesn't have to be a white conductor.

I was originally thinking I would tap onto the nuetral point of the secondary and bring that to the panel. This would allow me to perform my bonding and grounding at the panel. This will give me a dual voltage system. In this case the nuetral would need to be identified as a grounded conductor. If I would like to leave it as a single voltage system I could ground one leg. I suppose in this case even though there would be no nuetral I would still need to ground one conductor and therefore I would need to identify it as a grounded conductor.

Where does the green conductor in the supply conduit go to?

It also goes to the transformer case.... I have no idea..... It seems the black wire was to be used as nuetral but perhaps the nuetral point could not be found. Just a guess...

See response in italics

 

[kwired]

You touched on it some - if the secondary is grounded at midpoint - you have a multi-wire system even if there is no neutral load.

For it to be a two wire system you would have to leave the mid point float and ground one of the ends. It would then be a "grounded conductor" and need to be identified with white or gray. The other complication to doing that is your breakers would need to be rated 240 volts not the typical 120/240 variety that are relatively inexpensive - which will not be cheap or easy to find. 277/480 breakers may be easier to find but would work.

 

[banion23]

No bushings on the pipes. Neutral identification. Neutral exceeds bend radius of conductor size. It's just...not pretty. Needs glitter.

Sent from my SM-N920V using Tapatalk

 

[MD84]

No bushings required for wire size <#4. No code on bend radius of those conductors. Please correct me if I am wrong.

I think I will put a SBJ in the transformer. Pull out the green wire. Leave the black wire as a SSBJ.

Still not sure about the multiple Ocpd. Will neef to check on the code reference kwired referenced.

No bushings on the pipes. Neutral identification. Neutral exceeds bend radius of conductor size. It's just...not pretty. Needs glitter.

Sent from my SM-N920V using Tapatalk

 

[MD84]

Good call kwired. I checked 240.21(B)(3). Secondary conductors need to terminate in a single OCPD. Secondary conductors need an ampacity of 66.6A so #4 is required.