Convert 240/120 volt delta service to 120/208 volt wye

[hbendillo]

We have similar thread with discussing this topic but although I posted there about my situation thought better of hijacking that one for my situation.

I got a call from an electrician and building owner who had already started work to convert an existing 240/120 volt, three-phase delta service to 120/208-volt wye. The power company wanted to get rid of the old transformers and service and provide a new pad mounted transformer for the building. Existing service uses three, pole mount type transformers mounted on timbers at ground level within a concrete block enclosure next to the building. The main panel for the building is mounted on the outside wall next to the enclosure. 1000 amp main breaker and sub breakers feeding panels within. Service runs along wall from main panel through the wall of the enclosure, terminates with weather heads and ties to secondary of existing transformer. They want to eliminate that service and run a new one underground to a pad mounted transformer, 120/208 volt three phase.

Now I am left with considering any implications for making the conversion. The only time I have ever made a conversion like this is when the entire building is being renovated and distribution system redone for the most part with new electrical and mechanical system. What are the implications that I have to consider?

 

[Jraef]

We have similar thread with discussing this topic but although I posted there about my situation thought better of hijacking that one for my situation.

I got a call from an electrician and building owner who had already started work to convert an existing 240/120 volt, three-phase delta service to 120/208-volt wye. The power company wanted to get rid of the old transformers and service and provide a new pad mounted transformer for the building. Existing service uses three, pole mount type transformers mounted on timbers at ground level within a concrete block enclosure next to the building. The main panel for the building is mounted on the outside wall next to the enclosure. 1000 amp main breaker and sub breakers feeding panels within. Service runs along wall from main panel through the wall of the enclosure, terminates with weather heads and ties to secondary of existing transformer. They want to eliminate that service and run a new one underground to a pad mounted transformer, 120/208 volt three phase.

Now I am left with considering any implications for making the conversion. The only time I have ever made a conversion like this is when the entire building is being renovated and distribution system redone for the most part with new electrical and mechanical system. What are the implications that I have to consider?

Considerations are something your electrician should be helping you with. He will have to investigate all of the the loads you have and the mix of 3 phase and single phase loading, then look at the 3 phase motors and any 230V single phase loads to see if they will be fine at 208V vs 230V (they usually are, but it needs looking at). If he is suggesting the changeout, he has likely already done this and maybe just not communicated it to you well.

It might be that you actually do not have a choice, and they are just being gentle with you in allowing you to think you do. On a 120/240 3 phase 4 wire srevice, you are only allowed a certain percentage of single phase 120V loads, because they represent an unbalance to the 3 phase service. If you are expanding and you are exceeding your limit, they are not going to allow you to continue having that service drop.