240V L-N, single phase?

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mdprice55

Member
Location
Tennessee
In an industrial setting I notice a panel that was labled 240v Single Phase. There was one black and one white wire coming off the load side of the panel disconnect, implying "hot"-black, and "neutral"-white (I assume). 240V single phase L-N? Does this seem right? My experience seems to say that it is not.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Unusual, but certainly possible if that was the voltage desired.
Possibly an example of the misunderstanding between the term "neutral" and "grounded" conductor.
Its certainly possible they could have a SDS with a grounded conductor, which by Code would be white (or gray) but that conductor might not be a "neutral" and would not be in a two wire system.
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Any chance this is on a piece of equipment manufactured for places other than North America? In a lot of other countries, the common 3 phase voltage supply is 415Y240, so phase to neutral is 240V 1 phase.
 

jeremysterling

Senior Member
Location
Austin, TX
Could there be a failure to re-identify the white conductor of a multi-conductor cable assembly? Sounds like run of the mill 240V missing an inch of black tape.
 

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
I have a couple pole lights tapped up 240v Line-Neutral on a farm. The disconnect feeding it is high leg 480v system. We wouldn't of intentionally wired them this way, as we assumed it was a 480/277 volt system when they were ordered.

If I remember right:

A-N 240v
B-N 410v
C-N 240v
 
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SG-1

Senior Member
This panel could be designed for use with a transformer secondary that is two wire. The transformer only has X1 & X2 connections. There is 240 between X1 & X2. The phase conductor connected to X2 is grounded and treated like a "neutral" afterwards. This conductor is called the grounded conductor. A corner grounded delta is treated simular to this. The grounded conductor is only allowed to be opened if the phase conductor(s) is opened at the same time.

The NEC term grounded conductor can mean neutral or it can be an intentionally grounded phase conductor. See NEC Article 100 for the definition of neutral conductor, neutral point & grounded conductor.

If you have access to the NEC 2008 Handbook there are examples shown on page 30 for the neutral point and page 203 shows a grounded phase conductor ( grounded conductor ).
 
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I am not sure what type of facility you are working in. This as a 2-wire installation sounds very unusual.
It would be cool if you could get some pictures of the installation.

It sounds to me like it is either a corner grounded delta or midspan tap delta installation.
 

mdprice55

Member
Location
Tennessee
I am actually working in a panel shop. We do not install the panels themselves, we just build them to spec. But these panels I speak of, they have a controller that runs on 240v, but the practice has been to wire the panels with a black for L1 and a White for L2. We have had customers request that we change the White wire to a black. The only justification I can get for the white wire is that it is a grounded conductor.

I wish I could share the schematics, but I am only an employee here and do not want to cross any lines. I am really asking these questions so I can bring a valid presentation to my employer if anything is askew.

Thank you all...
 

jghrist

Senior Member
But these panels I speak of, they have a controller that runs on 240v, but the practice has been to wire the panels with a black for L1 and a White for L2. We have had customers request that we change the White wire to a black.
Sounds like the customer is planning to use 240V for the controller with no neutral and he doesn't want the ungrounded wire improperly colored white. What's the problem with complying?
 
I am actually working in a panel shop. We do not install the panels themselves, we just build them to spec. But these panels I speak of, they have a controller that runs on 240v, but the practice has been to wire the panels with a black for L1 and a White for L2. We have had customers request that we change the White wire to a black. The only justification I can get for the white wire is that it is a grounded conductor.

I wish I could share the schematics, but I am only an employee here and do not want to cross any lines. I am really asking these questions so I can bring a valid presentation to my employer if anything is askew.

Thank you all...


Sounds like your company is custom building panels for a customer. The customer's panels are supplying loads that do not require a grounded/neutral conductor...which is permitted as long as the panels are not located as service equipment.
Changing the conductor identification to a color other than white/gray or green would seem to be required, as per 200.6 & 250.119.
 
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