3ph 208 not available from xfmr bank?

[ccschoch]

Hey y'all, I've got a customer who's building formerly had a 3ph 240v high leg delta service fed from 3 pole mounted transformers (Two 15kva and one 25kva). They're the only customers on this bank. At some point the building switched to a single phase 240/120 (it's complicated). Now, there's new owners renovating for a new business, and they're looking to get a 3ph service, 39kva load.

The utility won't provide a high leg delta anymore, and originally said I can't get a wye service at all. Now they're saying I can, but I might have to upgrade the transformer. I'm not all that familiar with the utility side of things, so I'm not really sure why that would be the case. Seems to me like it's a pretty simple reconfiguration, and the transformers should be sized appropriately.

The utility reps haven't seemed like they've spent a ton of time actually looking at the situation, but again, I don't really know what the utility is taking into consideration here, so maybe I'm missing something?

 

[ron]

For Wye 3phase, they typically want the (3) transformers to be the same size, although not required. High leg delta is (3) transformers with one of them often oversized due to the single phase loads. Maybe that is why they want to make "upgrades"

 

[electrofelon]

In addition to one being a different size which they may not want/like, remember that a 240 Delta would have 240 volt transformers (one with a center tap). For a 120/208 service you actually need 120 volt transformers. Some transformers are designed to be reconfigurable so you can either series or parallel two 120 volt windings, but perhaps these are not that type.

 

[augie47]

More so than in the past, utilities look at everything from a cost benefit perspective.
A 39kva load is not going to produce enough revenue for them to change configuration on an existing transformer bank so are are going to look toward the customer (or E/C) to make any changes profitable.

 

[winnie]

So there is an already existing 3 phase high leg transformer bank?

The existing service into the building was changed to single phase, using just the 'base' of the high leg.

Now a new owner wants 3 phase service, and the utility won't connect the _existing_ transformer because they don't want to provide high leg services anymore?

IMHO: identify your location more accurately than 'CA' and see if anyone else on this board has experience with your particular utility.

-Jon