Inquiry about 277/480v(Delta-wye) wiring

[Rory Choicllroy]

The voltage of the new transformer at the new site I am in charge of is 277/480V (DELTA-WYE).



Connected from the transformer to the Manual Transfer Switch and from the Manual Transfer Switch to the main switchboard.



Typically a 3 pole main breaker is installed inside the main switchboard and the neutral wire is connected to an integrated neutral busbar.



However, due to field conditions, a situation arose where electricity had to be used using a temporary electric panel, and the temporary electric panel was manufactured by connecting a 4-pole main breaker and a 4-pole sub-breaker with a bus bar. (Use of R, S, T, N phase integrated circuit breaker)



There is no separate integrated neutral busbar.



In the original design, the main switchboard was a 3-phase 4-wire configuration with a voltage of 277/480v.



However, due to site conditions, temporary electrical panels must be used for several months.

I would like to inquire as to whether there may be any problems other than electrical regulations when the system is configured like this.



The current site is in an Asian country, and local engineers believe there are no problems.



I'd like to hear an expert's opinion.

 

[electrofelon]

Where is the service disconnect?

 

[Rory Choicllroy]

Where is the service disconnect?

The Manual Transfer Switch outside the electrical room is the Service Entrance.

 

[electrofelon]

The Manual Transfer Switch outside the electrical room is the Service Entrance.

Does it have overcurrent protection?

 

[Rory Choicllroy]

Does it have overcurrent protection?

There is no overcurrent protection device in MTS, but there is an overcurrent protection device in the temporary electrical panel.

 

[ptonsparky]

There is no overcurrent protection device in MTS, but there is an overcurrent protection device in the temporary electrical panel.

Is the MTS marked 'Suitable for Use as Service Equipment'?

 

[ggunn]

Is the MTS marked 'Suitable for Use as Service Equipment'?

Wouldn't it have to have OCP to qualify?

 

[ptonsparky]

Wouldn't it have to have OCP to qualify?

That was the point.

 

[kwired]

Wouldn't it have to have OCP to qualify?

He said in an Asian country, such details may not matter, I think he was more concerned about performance issues with the somewhat unusualness of having a four pole breaker and feeding the neutral through it.

IMO it shouldn't really be a problem as long as you have a bond on supply side and never bond the neutral again.

 

[ptonsparky]

He said in an Asian country, such details may not matter, I think he was more concerned about performance issues with the somewhat unusualness of having a four pole breaker and feeding the neutral through it.

IMO it shouldn't really be a problem as long as you have a bond on supply side and never bond the neutral again.

That would be where ...other than electrical regulations...plays into the answer.

 

[electrofelon]

Wouldn't it have to have OCP to qualify?

It could be just the service disconnect, and the OCP is separate. The two things would need to be "immediately adjacent" to each other.

 

[ggunn]

It could be just the service disconnect, and the OCP is separate. The two things would need to be "immediately adjacent" to each other.

With OCP on the line side of the TS, right? But then the TS wouldn't be service equipment, so moot point.

 

[electrofelon]

With OCP on the line side of the TS, right? But then the TS wouldn't be service equipment, so moot point.

There is no requirement that the overcurrent protection be on the line side of the service disconnect, in fact if fuses are used as the overcurrent protection, then the service disconnect is required to be on the supply side of the fuses.

 

[ggunn]

There is no requirement that the overcurrent protection be on the line side of the service disconnect, in fact if fuses are used as the overcurrent protection, then the service disconnect is required to be on the supply side of the fuses.

Point. I wouldn't want to change the fuses on the line side of a service disconnect.

 

[electrofelon]

Point. I wouldn't want to change the fuses on the line side of a service disconnect.

.....OF course it is mostly academic to have fuses that are not in a disconnect switch. I guess you can just put a fuse holder in a cabinet but i doubt people are doing that.

 

[kwired]

.....OF course it is mostly academic to have fuses that are not in a disconnect switch. I guess you can just put a fuse holder in a cabinet but i doubt people are doing that.

I think the rule is mostly carry over from some (much) older equipment where the switch and fuse holders were not always a single assembly.