ECN Forum Forums General Topics of the Trade General Discussion Area Ok theorists, help me out

Paul— About the term “network service,’ in the US, ANSI C84.1 60Hz-voltage ratings states in the footer notes: {Referring to 208Y/120-volt 3ø 4w} “A modification of this three-phase four-wire system is available as a 120/208Y-volt service for single phase, three-wire, open-wye applications.” I suppose it’s somewhat of a slang term by utilty meterguys and line crews, because it’s derived from a (potentially quite large) 4-wire network.

From one US electric utility’s electric rule book: “In locations where PG&E maintains a {4-wire} 120/208 volt secondary system, 3-wire single-phase service normally shall be limited to that which can be supplied by a main switch or service entrance rating of 200 amperes.” From: pge.com/customer_services/business/tariffs/doc/ER2.doc

An example might be a metropolitan area surrounded by multi-story office buildings, with a little old cigar store and its small electric service; i.e., 60 amperes, with only lighting loads so 208 V (versus 240) is not of concern.


[This message has been edited by Bjarney (edited 05-23-2002).]

There is at least one utility in Wisconsin that still offers 120/240V 3phase 4wire new services. We also can get 240V 3phase 3wire delta, if we want to.

Paul, you asked about other drawbacks on these wild-leg systems.

1) Utilities always have the high (orange) leg as phase C, while the NEC requires the facility to have the high leg as phase B. This means that the wiring is different on the load and line side of the service connection point.

2) Most of our 2 pole breakers are listed for a maximum voltage to ground of 120V, and so can fail violently if connected to the high leg. Non-standard 240V to ground breakers have to be used.

3) Load balancing can be a concern. Most (but not all) transformer banks are not sized to provide single phase (240V) connection with one connection being the high leg.

Thanks for all the info. I've just been trying to get an idea of how widely these "unusual" systems have been used and for what types of buildings.

I think somebody mentioned the high-leg phase B/C conflict before. Are we just talking about a matter of terminology, or is it more practical than that? For example, three panel lugs in a row, does the NEC actually require the high-leg to be on the middle lug?

Somewhat related question: How common is a corner-grounded delta system?


[This message has been edited by pauluk (edited 05-24-2002).]

JBD,
It is correct that the utility metering equipment requires that the high phase be landed on the "C" phase position at the meter, but it still is "B" phase as far as the rotation sequence.

Phase rotation from the utility is meaningless, except for parallel systems. The exact phase identification at the service entrance is unique to each service. Of course once the phase rotation has been established for a service it need to be maintained throughout the facility

Utilities alway identify the C phase as the high phase and the NEC requires the middle conductor (B phase)to be the high leg and colored orange (99NEC 384-3e & f)

[This message has been edited by JBD (edited 05-24-2002).]

Utilities in this area always maintain the ABC phase rotation on the service. The high leg is B pahse in the rotation and landed on the C phase position in the meter.
Also the code in 408.3(E) and 430.97(B)require that the phase rotation be ABC top to bottom or left to right.
Don(resqcapt19)

Hey Paul,

Thanks for the reply!

Not too sure who made that post, but it's a good idea. I did a similar thing by placing Orange tape across the "B" position filler plates and / or K.O.'s on the dead front. Also tagged or "Highlighted" the "B" position[s] circuit spots Orange when printing out Panel Schedules and Panel Directories.

<Quote>
It could be worse I suppose. Just imagine a (non-technical) U.S./Canadian tourist coming over here, buying a simple plig
adapter and hooking up to our 240V. Even more smoke than on 208...
<Quote>

LOL!!! That's called "Crash Course In European Electrical Systems 101"

EZ-Install, huh? That's an Oxy-Moron <joke>

To me, all Software Hacked [Engineered] since 1996 is EZ-Install! Remember when everything had to be done in DOS [or X Tree Gold if you were a real Computer Geek!], and the normal situation was MD [or MKDIR], then XCOPY the Floppy[s] from A: to C:
[Syntax example: XCOPY A:\*.* C:\DOOM\ /s /a /e ].

Bjarney,

When I was younger [we'll not go there just yet ] I had seen an older area of Long Beach / San Pedro where one customer still had 2 phase 4 wire service.
The setup was from a 3 Phase Delta to 2 Phase 4 wire configuration.
Very old Pots!!! This was the last one in the area, and I personally haven't seen anymore since then.

Those 120/208 1 Phase 3 wire services are quite abundant in the San Diego area!
When I first ran across one, I thought someone messed up pulling subfeeders! There was 208 VAC between the Ungrounded Lines [with 120 VAC to Ground], but only 3 wires at the Subpanel! Was expecting 240 VAC L-L, so went out to the Utility pole to investigate. Saw a typical 4 wire Wye configuration with only 3 wires dropped to the Building's service [this was a Commercial Location].
Looked at the Main Gear [Service / Meter Section] and it was clearly labeled and tagged "120/208 1 phase 3 wire, 400 Amps Max"

My first visit with that type of system!

I guess it could be figured as an Open Wye since that describes it well, but [to me] looking at a Pictorial of an Open Wye just looks like an Open Delta which has been turned around!

Now for some trivial pursute stuff

I have drawn the Scott T setups, plus the Delta / 2 Phase setups and posted in the Tech Reference section, along with a few DC 3 and 5 wire setups. For anyone interested in these, feel free to check them out Be sure to view ALL Posts, otherwise you will never find them!

Scott S.E.T.

P.S. In Regards to the Utility Co. landing Line C as the High Leg, I was thinking that this was done in the Meter section just to keep it "Away" from the "Usable" Lines, which run through the KWH Meter.

If you notice the KWH Meter used on the 4 wire Delta, it is a Single Stator Meter - typical of the common 1 Phase 3 Wire setups used in Residential Metering for 200 Amps and lower, or the ones driven by CT's in applications of 400 amps and higher.

Just my thoughts - not necessarily the method to the madness!

Scott S.E.T.

[If anyone can find out the real reason this is done, please post your findings here!]

Well, we've gone quite a way off the original topic of this thread, but thanks for the background info.

Scott,
I still use 20-year-old software on an old XT for accounts, word-processing etc. I don't like "EZ-Install" modern stuff that doesn't let you make your own installation choices. But then I grew up using an ASR33 teletype linked to a PDP-11!

"Bø or Cø Meter Stinger/Red/Orange/Purple/Power/Wild/Bastard/High Leg?" is a new thread now.


[This message has been edited by Bjarney (edited 05-25-2002).]