Transformer Nameplate, Need help!

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Npstewart

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Hi everyone, I just finished designing a project that had a lot of existing electrical equipment in the building. Our plan was to basically keep what we can use, and store the rest. The building has 480-3 phase incoming, and im hitting a 150KVA Xfrmr. Someone told me there was a existing 150 KVA Xfrmr there so im calling it out as existing. Just today I finally received a picture from the job site with the name tag. I am extremely worried now because the name tag says the secondary volts is 240-120 hi leg delta. I designed this thing planning on the secondary voltage being 208-3phase with no hi-leg. Does this mean I essentially have a open delta service here with a high B leg?

Please help, I ATTACHED THE PICTURE. :) THANKS!
 
afraid so. also note that your 120v load is restricted to 5% of the transformer kva (standard for this arrangement)...
 
Ok here is a picture of the incoming service at the meter. I suppose the orange tape means high leg delta service? Remember that its 480v-3 incoming. I thought orange brown and yellow was how 480v was marked.
 
One reason our jurisdiction doesn't allow orange for 480 :grin:
I can't get enough picture contrast to read the meter data but you probably have a a 480/Y277 Wye service. It is commonplace to tag them brown-orange-yellow, but your situation points out the problem in doing so.
210.5 requires where there is more than one wiring system the phases be distinctly identified. Since 100.15 requires Orange for the 240 hi-leg, the 480 needs to be some other color.
 
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If this is the case, what the hell is that high leg transformer doing on site lol. I dont know what to do. Im supposed to be printing these today. I put in large print that the electrical contractor is required to verify the voltage with the utility company prior to bid etc. If it was Monday I would just call the utility company. I wish the utility company would tag their transformers so your wouldnt have to call!
 
The high leg transformer is common where you need 240 for 3 phase equipment with little or no 120v load and you have a 480 volt service.
A lot of the equipment I used to see in the printing industry was 240 volt with motors and especially heaters that didn't care for 208 volt so the more common 208/Y120 transformers were of little use.
We converted several printing companies from 240 to 480 services and most often we ended up with 208Y/120 transformers for lighting and 480/240 delta for the production equipment.
 
Npstewart said:
Ok here is a picture of the incoming service at the meter. I suppose the orange tape means high leg delta service? Remember that its 480v-3 incoming. I thought orange brown and yellow was how 480v was marked.
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A three phase 480 volt system with a high leg would be very very rare. I expect that you have a 480Y/277 volt service. You will have to specify the replacement of the existing 150kva transformer with a new one that has a 208Y/120 volt secondary.
 
Im familar with the delta service, ive designed many projects this way. My question is to everyone here is, if you opened the meter like I did and removed the cover to expose what I exposed in the picture, would you think this service was 480-v wye, or a high leg delta service? I will pose the photo again.
 
I agree with Don but add you need to check the actual requirements for the equipment. As noted in the earlier post, some of your equipment may not be designed for or work properly on 208. You may need to use this transformer and add another for your 120v (or 208v) loads.
Some of these plants make compliance with 210.5 and 200.6 a real challenge. I have a case with noting but voltage identification tags and phase tapes.
 
Npstewart said:
Im familar with the delta service, ive designed many projects this way. My question is to everyone here is, if you opened the meter like I did and removed the cover to expose what I exposed in the picture, would you think this service was 480-v wye, or a high leg delta service? I will pose the photo again.
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480 wye...
but I don't see how that makes any difference with your transformer.
The primary is 480..from either wye or delta (very rare) source so,as I see it, the utility supply is not your problem here, the secondary of the transformer is.
If I understood you correctly, you planned on a 480 service and that's what you have.
You did not pllan on a 240/delta transformer..but unfortunately you have that also.
 
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I think your right about it being rare now that you mention it. The delta high leg is only common in residential areas where they derive it on site from 240v single phase. Assuming it is a residential area (which it really isnt), why would they have 480 volts in a residential area any way.
 
Ok I think I have it figured out now. I was reviewing the pictures and there is only one transformer on site. In order to derive a 240-3 delta they would need two transformers correct? There is only one, anyone see an objection to that logic?
 
Npstewart said:
... Assuming it is a residential area (which it really isnt), why would they have 480 volts in a residential area any way.
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480V in residential area is simply a matter of what transformer the POCO installs. Per customer need for negating voltage drop issues, the POCO may oblige with a 480V service... but usually single phase.
 
Replying to augie,

So your basically saying, I have a standard 480 service, I just cant re-use the existing transformer I have?
 
Square 1.
You have a service, which from all appearances is 480 volt.
Unless you have a need for 277, it makes little difference if the service is delta or wye.
You have what I imagine is a customer owned transformer to connect to that service. The transformer, by nameplate, is 480 input (3 phase-wye or delta) and 240/120v hi-leg output with a 5% tap limit for 120v.
If you need 208v or more than 7.5 kva of 120v power you will need a different or additional transformer(s).
 
Npstewart said:
Ok I think I have it figured out now. I was reviewing the pictures and there is only one transformer on site. In order to derive a 240-3 delta they would need two transformers correct? There is only one, anyone see an objection to that logic?
Click to expand...
No, in a sense. What you are referring to is a transformer enclosure. What matters is how many windings are enclosed ;)

You only need one transformer [enclosure] to make a on site derived system such as 240/120 3? 4W.
 
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