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01-27-2013, 09:13 PM   #1
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## 120/208panel

Will the I'd tag show if delta or wye

01-27-2013, 10:14 PM   #2
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No it won't. The only way to know for sure is to take voltage readings.

One dead giveaway though is if one of the phases has no single pole breakers on it. Then it's most likely a delta.

Another way is to measure voltage on a known device that uses two phases. If it's close to 208, it's a wye. If it's more like 240, it's a delta.

 01-27-2013, 10:21 PM #3 Member   Join Date: Nov 2007 Location: Nashua, NH, USA Posts: 7,971 Rewards Points: 1,548 Not unless someone put the label on it. Measure the voltage between hot and neutral, or between two hots, as needed if you are encountering this panel for the first time. A 120/208 volt 3 phase system will have 120 volts from any hot leg to neutral (and 208 volts between any two hots). A wye 3 phase system has hot to neutral voltage the same for all three phases. __________________ The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit. Last edited by AllanJ; 01-27-2013 at 10:28 PM.

 01-28-2013, 12:08 AM #4 Semi-Pro Electro-Geek   Join Date: Jul 2009 Location: Arizona, USA Posts: 3,045 Rewards Points: 2,990 If it's 120/208, then it's a wye system by definition. If there's no neutral present then it can only be used for delta-connected loads - but it's still a wye system. The square root of three (1.73) ratio of voltages indicates that the grounded conductor is at the "midpoint" of the three hot legs on a phase diagram, which is achieved by connecting the transformer secondaries in a wye configuration. __________________ I am a lawyer, but not your lawyer. And who cares anyways? We're here to talk construction. This is DIY advice, not legal advice.
 01-28-2013, 07:03 AM #5 Member   Join Date: Nov 2008 Location: Northern Virginia Posts: 751 Rewards Points: 764 Not always. Ever hear of a stinger? Mark
01-28-2013, 07:04 AM   #6
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Quote:
 Originally Posted by mpoulton If it's 120/208, then it's a wye system by definition. If there's no neutral present then it can only be used for delta-connected loads - but it's still a wye system. The square root of three (1.73) ratio of voltages indicates that the grounded conductor is at the "midpoint" of the three hot legs on a phase diagram, which is achieved by connecting the transformer secondaries in a wye configuration.
Not always.

Mark

 01-28-2013, 08:33 AM #7 Electrical Contractor     Join Date: Jun 2004 Location: Newnan GA Posts: 7,030 Rewards Points: 656 I personally have never seen a 120/208 as anything but a wye. Of course i have only seen 1 delta before also. __________________ "The problem isn't that Hillary Clinton lies. We all know she lies. The problem is that her supporters don't seem to care"
01-28-2013, 08:36 AM   #8
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Quote:
 Originally Posted by busman Not always. Ever hear of a stinger? Mark
Stinger or Hot leg IS evidence of the 120/240 Delta winding. two legs of 120 and a third leg or 208, or 240 across any two legs.

 01-28-2013, 09:46 AM #9 Member   Join Date: Nov 2007 Location: Nashua, NH, USA Posts: 7,971 Rewards Points: 1,548 There is no raison d'etre for (and no socially redeeming value of, and no easy way of producing) a 120/208 volt system that is not from a symmetric wye configuration. The reason 208 volts became accepted as a standard is because it is the natural result of configuring a return conductor to have 120 volts potential from each of the 3 legs of a 3 phase system. It combines the advantages of 3 phases with the advantages of 240 volts over 120 volts (fewer or thinner conductors needed), although some appliances come in slightly different versions for 208 versus 240 volts. Also the high leg, or stinger, is the natural result of configuring a return conductor having 120 volts potential from each of two legs of a 240 volt 3 phase system so as to provide a 120/240 volt feed (or subfeed). __________________ The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit. Last edited by AllanJ; 01-28-2013 at 09:57 AM.
 The Following User Says Thank You to AllanJ For This Useful Post: mpoulton (01-28-2013)
01-28-2013, 10:48 AM   #10
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Quote:
 Originally Posted by busman Not always. Mark
What's an example of "not always"? To produce a 208V delta without wye-connected secondaries would require transformers with 208V secondaries - and that's very odd. To produce a 208V delta with 120V from each hot to ground and not use a wye configuration would be... darn near impossible. I can't think of an easy way to do it.

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