Utility 480 volt wye system connected to a delta transformer

Status
Not open for further replies.
K

kidkill

New member
I recently was called out to replace a transformer at a machine rental shop. I wrote down the model number and got a replacement transformer (75 KVA 480 volt primary 240 volt delta/delta). After hooking it all up and turning it on everything seemed fine. I then went outside to look at a separate project. I then noticed there were 3 utility transformers on the pole and it appeared to be a wye system. The question I have is, is the new delta transformer going to burn up if it is indeed connected to a wye?
 
It really should not matter, the coil voltage is 480 from phase to phase in a 480 Delta or480 WYE, and that is where the secondary voltage is derived from, the primary voltage across the coils. As long as you have 480 between all three legs and I assume your secondary voltage is correct, you're fine.
 
I would say 99% of the transformers I have installed where Delta / Wye supplied from a Wye source. the transformer does not care at all. :)
 
Will not make a difference, Most transformers used for stepping down 480 to 120/208 are delta primary, with a wye secondary, the poco transformers feeding the building are usually wye connected hence 277/480. wye/wye transformers are not used much do to unstable voltages delta/deltas are fairly common, but not as much as the delta/wye configurations. I had an installation simular to that, Our local color code for 277/480 is brown/orange/yellow. Since code requires the high leg to be identified as orange, that causes a problem. Since it was a new service, I identified the 277/480 as yellow/brown/purple, and promptly got turned down by the inspector. He said he had never seen this color used for 480 before, and would not pass the installation. After explaining I could not use orange for the 480 volt service due to the code requirements, he still would not budge. So I did what most electricians do, and changed back to the local color code, but left the delta black/orange/blue and passed the inspection.
 
Hill, it should never be an issue with the orange being used on both voltages. On 480/277, the neutral is traditionally gray, and you're likely to see other line condcutors.

Since you're not supposed to use the high leg for line-to-neutral loads on 240/120D, there will always be another phase conductor run with an orange high leg on 240v.
 
LarryFine said:
Hill, it should never be an issue with the orange being used on both voltages. On 480/277, the neutral is traditionally gray, and you're likely to see other line condcutors.

Since you're not supposed to use the high leg for line-to-neutral loads on 240/120D, there will always be another phase conductor run with an orange high leg on 240v.
Click to expand...

But would this not violate the code requirement of distinguishing conductors of different voltages or systems? Using the same color for two different voltages, especially if it's a 480 volt single phase circuit using Brown and Orange, would look very close to the same as Black and Orange 240 volt single phase circuit in a poorly lit area. That is one of the reasons that the Yellow/Brown/Purple color code was phased out by a lot of jurisdictions, the brown and purple were hard to distinguish in low light conditions.
 
hillbilly1 said:
But would this not violate the code requirement of distinguishing conductors of different voltages or systems? Using the same color for two different voltages, especially if it's a 480 volt single phase circuit using Brown and Orange, would look very close to the same as Black and Orange 240 volt single phase circuit in a poorly lit area.
Click to expand...
If their local code requires orange on the high voltage system, and the NEC requires orange on the low-voltage system, what would you recommend? :-?
 
LarryFine said:
If their local code requires orange on the high voltage system, and the NEC requires orange on the low-voltage system, what would you recommend? :-?
Click to expand...
Why not use tagging to distinguish the two systems? Use the traditional colors and mark the phases with some kind of tag that says 240∆ on the low voltage legs and 277/480 on the high voltage legs.

210.5(C)
 
Status
Not open for further replies.
Top