120/240 Delta - A Phase Black - B Phase Orange - C Phase ????

[Tom Jones]

My apologies for something that has been hashed over before but I can find no good answer to this one.

I realize there is no stipulation in the code either.

But it really matters in this case because in hooking a standby generator to an existing 120/240 delta system, both the phase rotation and orientation must be preserved.

My main question is: A/B/C or R/S/T or L1/L2/L3: the first one presumably will be black, the middle one being the wild leg will always be orange, and the third will be red? or will it be blue?

Even though the code does not stipulate, is there some sort of de facto color code for this configuration always used by discerning electricians?

 

[ActionDave]

Around here the convention is to use Black Orange Blue.

 

[qcroanoke]

Around here the convention is to use Black Orange Blue.

Agreed

 

[livewire99]

Agreed

Black, Orange, Blue is what I have seen.

 

[kwired]

How about using whatever coding is already at the premises, no need to reinvent the wheel in an existing installation, and if the existing should happen to not meet code but is consistent otherwise, this is probably still the best thing to do, unless you want to or have an inspector that wants you to make everything right.

Keep in mind that if there is only one voltage system present at the facility, NEC doesn't require any identification of the ungrounded conductors other than which one is the high leg.

 

[Tom Jones]

How about using whatever coding is already at the premises, no need to reinvent the wheel in an existing installation, and if the existing should happen to not meet code but is consistent otherwise, this is probably still the best thing to do, unless you want to or have an inspector that wants you to make everything right. Keep in mind that if there is only one voltage system present at the facility, NEC doesn't require any identification of the ungrounded conductors other than which one is the high leg.

Yep, should have not even worried about it. It was set up black-red-blue, with blue as high leg in the C position and rotation CCW. We just continued the color code that way and called it a day. I think I saw a date of 1979 somewhere. Was this an OK setup back then?

 

[ActionDave]

Yep, should have not even worried about it. It was set up black-red-blue, with blue as high leg in the C position and rotation CCW. We just continued the color code that way and called it a day. I think I saw a date of 1979 somewhere. Was this an OK setup back then?

It was legal at one time. I think it was '75 or 76 when the rule was changed to require high leg on B phase. I wasn't pulling wire then. I was busy either trying to get smootchie with girls or trying to keep my car running.

 

[kwired]

It was legal at one time. I think it was '75 or 76 when the rule was changed to require high leg on B phase. I wasn't pulling wire then. I was busy either trying to get smootchie with girls or trying to keep my car running.

Most older installs I run into have the high leg marked with red, and is usually C phase but have run into some from 70's and 80's where it is B phase but is still red. Inspections wouldn't have been happening at that time on most of those installations either though.

 

[ggunn]

Most older installs I run into have the high leg marked with red, and is usually C phase but have run into some from 70's and 80's where it is B phase but is still red. Inspections wouldn't have been happening at that time on most of those installations either though.

Is there any such thing as absolute phase? Couldn't you just call the high leg anything you want and let rotation dictate what the other two are?

 

[meternerd]

Is there any such thing as absolute phase? Couldn't you just call the high leg anything you want and let rotation dictate what the other two are?

Here's another mind bender.....the Kwh meter for 3PH 4W Delta requires the high leg to be C phase , so the utility connection has the right hand connection marked as Power Leg. Can lead to confusion if you're a newbie. B and C phase wires are usually swapped from the socket lower jaws to the main breaker.

 

[ActionDave]

Is there any such thing as absolute phase? Couldn't you just call the high leg anything you want and let rotation dictate what the other two are?

In an absolute sense there is no absolute anything, although it's nice to have a few coventions that folks hold to. Makes things easier to work on or finish up another crew members work.

 

[ggunn]

In an absolute sense there is no absolute anything, although it's nice to have a few conventions that folks hold to. Makes things easier to work on or finish up another crew members work.

That's not really my point. If you have three unmarked black wires coming out of a transformer, how do you know which is the A phase and does it make any difference? Once you choose an A phase, rotation determines B and C.

 

[GoldDigger]

Is there any such thing as absolute phase? Couldn't you just call the high leg anything you want and let rotation dictate what the other two are?

Yes, but there is a convention for the designation of the three leads at disconnects and panels, so if everybody follows the same convention it makes life easier.
The one with the high voltage to ground is the one which has to be identified regardless of what primary phase it corresponds to.
There is also the convention that the normal phase rotation is A B C.
That can be determined unambiguously since it only involves relative phase.
Now ABC describes the same rotation as BCA and CAB, so you still have some freedom there. But once you identify the high leg as B, the other two are nailed down.


Tapatalk...

 

[ggunn]

Yes, but there is a convention for the designation of the three leads at disconnects and panels, so if everybody follows the same convention it makes life easier.
The one with the high voltage to ground is the one which has to be identified regardless of what primary phase it corresponds to.
There is also the convention that the normal phase rotation is A B C.
That can be determined unambiguously since it only involves relative phase.
Now ABC describes the same rotation as BCA and CAB, so you still have some freedom there. But once you identify the high leg as B, the other two are nailed down.


Tapatalk...

Actually, that was what I was getting at. If you get to one of these services where the high leg is A rather than B, couldn't you fix it by simply redesignating the conductors A=>B, B=>C, and C=>A?

 

[GoldDigger]

Absolutely, while occasionally cursing the guy who wired it in the first place.
However the meter base will also have designations for A, B and C which leads to some confusion.
If you just make one interchange to move high leg from C to B you will reverse the existing rotation.


Tapatalk...

 

[ggunn]

If you just make one interchange to move high leg from C to B you will reverse the existing rotation.

Well, duh.

 

[kwired]

Is there any such thing as absolute phase? Couldn't you just call the high leg anything you want and let rotation dictate what the other two are?

That's not really my point. If you have three unmarked black wires coming out of a transformer, how do you know which is the A phase and does it make any difference? Once you choose an A phase, rotation determines B and C.

Thats always been my style. I generally don't care what rotation is on new services, existing needs to match that of existing loads no matter what it was to start with. Now a high leg will be on B phase but unless I am trying to match an existing rotation - I don't care what it is on a new service or feeder.

 

[Tom Jones]

Do you mean to say that you don't mind if your new panel winds up with CCW rotation left to right?

 

[kwired]

Do you mean to say that you don't mind if your new panel winds up with CCW rotation left to right?

All that matters is the motors run the direction they need to.

POCO's (around here anyway) do not give you same rotation on all services so you can't assume anything based on the rotation at their equipment, they may place labels indicating rotation on some of their equipment but this is for their convenience should they need to replace equipment so it is easier to restore the rotation that was there originally. A new service they won't care unless you do give them a specification, but for most smaller rural services - you show up and power is already there - that usually be anything with a 320 amp or less self contained metering.

 

[L8TRG8TR]

All that matters is the motors run the direction they need to.

POCO's (around here anyway) do not give you same rotation on all services so you can't assume anything based on the rotation at their equipment, they may place labels indicating rotation on some of their equipment but this is for their convenience should they need to replace equipment so it is easier to restore the rotation that was there originally. A new service they won't care unless you do give them a specification, but for most smaller rural services - you show up and power is already there - that usually be anything with a 320 amp or less self contained metering.

you can" specify",They told me flip a coin