120/240 delta service changing to 120/208 wye

[DKE]

Looking to upgrade the service on a 23 unit all electric building with a three phase elevator. Currently we have 120/240 delta coming in. The engineer I am working with wants to switch to a 120/208 wye. He says there will be no issues with the change. Any thoughts?

 

[hillbilly1]

You didn’t say what kind of units they are, but they probably have single phase panels in each unit. Depending on how old the units are, the a/c units may be 240 volt only, and require a buck/boost transformer for each unit. One of our salesman sold a job changing the service from delta to wye. It was a beverage store, so it had a lot of compressors. Luckily they were rated for 208/240. Changed the single phase panels to three phase, but had to do a lot of tracing to keep neutrals paired correctly.

 

[LarryFine]

The engineer I am working with wants to switch to a 120/208 wye.

Why?

And welcome to the forum.

 

[ggunn]

Why?

Yes, a wye. <ducks>

 

[Birken Vogt]

Looking to upgrade the service on a 23 unit all electric building with a three phase elevator. Currently we have 120/240 delta coming in. The engineer I am working with wants to switch to a 120/208 wye. He says there will be no issues with the change. Any thoughts?

Also, all single phase units will be attached across the low corners of the delta. This will mean that all the major load on the new wye will be across 2 of the 3 legs unless somebody goes in there and rebalances everything.

 

[charlie b]

Depending on how old the units are, the a/c units may be 240 volt only, and require a buck/boost transformer for each unit.

To add to this, if you supply a motor with 208 volts when it was designed for 240 volts, the current will be about 15% high. Whether or not that will cause issues is something you (or the engineer) will have to figure out. Also, if you supply a space heater or other resistive load with 208 volts when it was designed for 240 volts, it will operate at 75% of its full load rating.

 

[LarryFine]

Also, all single phase units will be attached across the low corners of the delta. This will mean that all the major load on the new wye will be across 2 of the 3 legs unless somebody goes in there and rebalances everything.

Exactamundo.

 

[jcbabb]

Why?

And welcome to the forum.

I'm not the OP, but around here, the utilities will try to get rid of delta services any chance they get. This may be what is driving the change.