Delta / Delta transformer.

[cowboyjwc]

Straight 3 phase delta / delta transformer for x-ray equipment and A/C units. 208/480

1) Does it require a ground detctor as per 250.21 or is that only if it meets one of the conditions lised.
or
2) Do you have to corner ground the system?
3) If you corner ground the system, do you need to reidentify the equipment grounding conductor as a grounded conductor?
4) Can the grounded phase be fuse protected?

 

[raider1]

1) Does it require a ground detctor as per 250.21 or is that only if it meets one of the conditions lised.

Ungrounded systems are required to have a ground detector in accordance with 250.21(B)

2) Do you have to corner ground the system?

If you want a grounded system then that is most likely what you are going to have to do.

3) If you corner ground the system, do you need to reidentify the equipment grounding conductor as a grounded conductor?

No, the EGC's will still be identified green. The grounded conductor will have to be identified in accordance with 200.6

4) Can the grounded phase be fuse protected?

Take a look at 240.22.

Chris

 

[cowboyjwc]

Thanks Chris.

Just one of those things that I've never installed or looked at and it's brought up several questions.

Like we say, something new all the time.

 

[raider1]

Your welcome.

Chris

 

[Pierre C Belarge]

You may also need to use Circuit breakers that are not slash rated, but straight rated.
See 240.85

 

[scott thompson]

My 2? per the Delta / Delta

My 2? per the Delta / Delta

1) If Ungrounded, requires some type of Fault Detection / Indicator.

2) You _MAY_ Corner Ground the System, or the System could be Center Tap Grounded.
Only seen a few 480V 3? 3W Center Tap Grounded Systems.
The Voltage to Ground is nominal 240V, and max. is 416V.

Advantage for this is no Grounded System Conductor to deal with!

3) No, EGC's will still be Green - and used with either Ungrounded or Grounded Systems.
The Grounded Conductor is identified White (or Gray), typical of any other System's Grounded Conductor.

4) No Fuses in line with the Grounded Conductor. Use "Solid Inserts" at Fusible Disconnects, or use 2 Pole Disconnects, with an Isolated (from the Bonded Enclosure) Termination for the Grounded Conductor.

Grounded Conductor may run through 3 Pole Breakers, provided the device is common trip (opens all lines at the same time).
AIR of devices shall not be slash rated.
(exeption... center tap grounded system _might_ allow slash rated devices, dependent on available SCA)

Refer to the following drawings for additional information:

ECN Corner Grounded Delta

http://www.electrical-contractor.ne...737/Corner_Grounded_3A_3_Wire_Delt#Post148737

*** Note ***

This is a good example of why a Grounded Conductor is _NOT_ always a "Neutral".

Scott

 

[e57]

Hey ya Scott - not seen you in this forum before. That said I haven't been over to ECN in a while either....

 

[scott thompson]

Hey Bud! (E57)

I hang out here at MHE occasionally.

Posts are infrequent, as the topics are normally covered in great detail by others.

If not for this Forum (MHE), I would have never been invited to ECN.
Back in the "Old Days" - when the MHE Forum was young, I was asked by Bill to discuss "What Defines A Neutral" at ECN.
ECN was a young Forum at that time, too.

If I remember correctly, that must have been circa 2000 / 2001.
MHE was a basic Text-Only Forum at the time - similar to USENET Newsgroups (such as "alt.electrical.engineering").

Talk with you later!

Scott

p.s. how did things go on that Project, which you were going to compile an Electrical Plan Set for?

 

[cowboyjwc]

Pierre: Yes, I found that out.

Scott: Look at 430.36 about the fuses.

 

[e57]

Hey Bud! (E57)

I hang out here at MHE occasionally.

Posts are infrequent, as the topics are normally covered in great detail by others.

~~
Talk with you later!

Scott

p.s. how did things go on that Project, which you were going to compile an Electrical Plan Set for?

I too still stop over at ECN here and there - mostly to rob some of your graphics collection, as many others here and elsewhere do... :roll: (If you get web-stats for ECN - you can probably track them to a dozen or so sites regularly...)

And I believe the job you're talking about is my "5 miles of architectual conduit job" Which since - I have made a standard practice of one-lines, and line diagrams for every job since a standard practice. (lay-out, progress, and final.) I am now a full-blown site documentation junkie...