right and wrong colored conductors for 480volts

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Cow said:
Are you sure?

The one and only time I've seen something different was on an old farm. I installed 3 new services on various places around the farm and two of them had one leg that measured 405 volts to neutral if I remember correctly. 480 between phases.:-?
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I would have to say there were transformer issues, ie wrong tap, if you had that sort of voltage.
 
tryinghard said:
480 does not have a high leg.
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It can have two of them with a corner grounded delta, when measured from ground. :D

I don't think I've ever seen a mid-tap on a 480 volt delta system, though and I'm not sure why you would want one. For that matter, I don't see why one would want a mid-tap 240 delta system when you can have a wye setup.
 
paul said:
For that matter, I don't see why one would want a mid-tap 240 delta system when you can have a wye setup.
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It's like saying why haven't there always been stop-lights at busy intersections. Not every existing service installation was done recently, or with the benefit of today's knowledge. They have evolved.

It's easy to think that there were always McDonald's, too.

The open-Delta system began as a modification to existing 120/240v 1ph services. Look at one minus the second transformer and high leg conductor; it's identical to a residential 1ph service.

Why would an open Delta service be installed today?

The only reason I can think of is to take advantage of an existing POCO installation, or re-use an existing service drop. Otherwise, you get a wye system. Who would want one for any other reason?

Now, if we're talking an industrial service with a 480D versus a 480/277Y, that's a different, but similar story. A majority of motor loads would probably get 480D (but not open), but a large lighting load might get 480/277Y.
 
paul said:
It can have two of them with a corner grounded delta, when measured from ground. :D

I don't think I've ever seen a mid-tap on a 480 volt delta system, though and I'm not sure why you would want one. For that matter, I don't see why one would want a mid-tap 240 delta system when you can have a wye setup.
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240 delta is really common around here, industrial voltage.
 
paul said:
It can have two of them with a corner grounded delta, when measured from ground. :D

I don't think I've ever seen a mid-tap on a 480 volt delta system, though and I'm not sure why you would want one. For that matter, I don't see why one would want a mid-tap 240 delta system when you can have a wye setup.
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around here (Nebraska) there are lots of field irrigation machines supplied by mid tap 480 volt open delta systems. These machines are relatively small load and is more cost effective in some areas for power suppliers to provide only two primary phases and install open delta transformer banks. Have also seen many services where all three phases are there and they still install the open delta transformers. This is also common on 240 volt system where three phase load is somewhat minimal or if it is more economiocal for power supplier to only supply two phase conductors but there may be a lot of 120/240 single phase load. Many times the transformer for the third (high) leg will be smaller than the other transformer.
 
LarryFine said:
Why would an open Delta service be installed today?

The only reason I can think of is to take advantage of an existing POCO installation, or re-use an existing service drop...
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Two transformers rather than three, and they don't ballance well.
 
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