Help! Going from 480 volt 3 phase to 120/240 volt single phase

[Sparkyonline]

My utility provider has run out of single phase and 120/208 volt three phase transformers and put me on a wait list for almost a year. They have a 480 volt transformer they can provide me to complete my project. I have changed some equipment so I can directly connect it to the 480 volt power but I have about 400 amps of single phase loads that need to still be powered. So I need to install I am thinking a 100kva transformer. I am having trouble with determining the three phase feeder breaker and conductor sizing, as well as the secondary panelboard service disconnecting device and buss rating. I seem to get 416 amps of single phase when I try to calculate it which leads me to believe that I need to have a 600 amp buss rating on my panelboard. Use of the single phase is for three 100 amp rated level two EV charging stations and 100 amps of future power in a panel for convenient outlets.

 

[hillbilly1]

Do you actually need 240 volt single phase? Or can you use 208 single phase? A 240 volt delta transformer should be sufficient if you need 240 volt, while a 208 wye would be much easier to get, and more versatile if the loads can accept 208 single phase.

 

[kwired]

My utility provider has run out of single phase and 120/208 volt three phase transformers and put me on a wait list for almost a year. They have a 480 volt transformer they can provide me to complete my project. I have changed some equipment so I can directly connect it to the 480 volt power but I have about 400 amps of single phase loads that need to still be powered. So I need to install I am thinking a 100kva transformer. I am having trouble with determining the three phase feeder breaker and conductor sizing, as well as the secondary panelboard service disconnecting device and buss rating. I seem to get 416 amps of single phase when I try to calculate it which leads me to believe that I need to have a 600 amp buss rating on my panelboard. Use of the single phase is for three 100 amp rated level two EV charging stations and 100 amps of future power in a panel for convenient outlets.

Details depend on what you actually have or mean here. Is there 400 amps of 120 volt loads, and if so are they to be split up either across two sides of 120/240 single phase or three ways across 208/120 wye system?

400 amps of 120 volt loads is 48000VA. balance that on 120/240 single phase source and it is 200 amps, balance it on three phase wye and it is only about 133 amps.

If what you have is 400 amps after balancing across three phases then total VA is like 144000, which is over the100 kVA transformer you mentioned.

You didn't mention if this is total connected load and/or if there is demand factors that can apply to at least portions of the load.

 

[Hv&Lv]

My utility provider has run out of single phase and 120/208 volt three phase transformers and put me on a wait list for almost a year. They have a 480 volt transformer they can provide me to complete my project. I have changed some equipment so I can directly connect it to the 480 volt power but I have about 400 amps of single phase loads that need to still be powered. So I need to install I am thinking a 100kva transformer. I am having trouble with determining the three phase feeder breaker and conductor sizing, as well as the secondary panelboard service disconnecting device and buss rating. I seem to get 416 amps of single phase when I try to calculate it which leads me to believe that I need to have a 600 amp buss rating on my panelboard. Use of the single phase is for three 100 amp rated level two EV charging stations and 100 amps of future power in a panel for convenient outlets.

What size??
these things aren’t hard to get. Would it be cheaper to buy it yourself and have them install it?
We get transformers in about every month.
TMS in Tennessee has reconditioned guaranteed transformers for sale every day.

 

[Sparkyonline]

Do you actually need 240 volt single phase? Or can you use 208 single phase? A 240 volt delta transformer should be sufficient if you need 240 volt, while a 208 wye would be much easier to get, and more versatile if the loads can accept 208 single phase.

Details depend on what you actually have or mean here. Is there 400 amps of 120 volt loads, and if so are they to be split up either across two sides of 120/240 single phase or three ways across 208/120 wye system?

400 amps of 120 volt loads is 48000VA. balance that on 120/240 single phase source and it is 200 amps, balance it on three phase wye and it is only about 133 amps.

If what you have is 400 amps after balancing across three phases then total VA is like 144000, which is over the100 kVA transformer you mentioned.

You didn't mention if this is total connected load and/or if there is demand factors that can apply to at least portions of the load.

Details depend on what you actually have or mean here. Is there 400 amps of 120 volt loads, and if so are they to be split up either across two sides of 120/240 single phase or three ways across 208/120 wye system?

400 amps of 120 volt loads is 48000VA. balance that on 120/240 single phase source and it is 200 amps, balance it on three phase wye and it is only about 133 amps.

If what you have is 400 amps after balancing across three phases then total VA is like 144000, which is over the100 kVA transformer you mentioned.

You didn't mention if this is total connected load and/or if there is demand factors that can apply to at least portions of the load.

What size??
these things aren’t hard to get. Would it be cheaper to buy it yourself and have them install it?
We get transformers in about every month.
TMS in Tennessee has reconditioned guaranteed transformers for sale every day.

Do you actually need 240 volt single phase? Or can you use 208 single phase? A 240 volt delta transformer should be sufficient if you need 240 volt, while a 208 wye would be much easier to get, and more versatile if the loads can accept 208 single phase.

I actually have need to power one single phase panel that will have a variety of convenience receptacles and possibly some led lights.

I also have three Level two EV chargers that draw 100 amps of 240 volt single phase each. This is going to be installed in front of a restaurant so I do not assume many people will charge long enough to cause the circuits to be considered continuous duty but I was planning on accounting for continuous duty loads non the less.

I was just speaking with a representative from the Utility and he mentioned that a similar job that was done in another area by a different contractor used only two legs of the 480 to power a single phase EV car charger. Has anyone on here ever used only two legs of 480 volt before?

Also I get that used transformers are probably easy to find at any kva but I have to deal with the Utilities answers to my requests.

 

[zbang]

Has anyone on here ever used only two legs of 480 volt before?

Sure, going into a 480->240/120v single phase transformer . If the charger will take 480v single-phase, just do it.

 

[hillbilly1]

I’m betting the other contractor is installing a DC fast charger, not an AC, as I could be wrong, but I don’t think the onboard EV charger would accept 480. It would be more practical to use a 120/208 wye, instead of a 240 volt single phase transformer with that many controllers. 208 volt single phase will work with the EV’s charger.

 

[Hv&Lv]

I actually have need to power one single phase panel that will have a variety of convenience receptacles and possibly some led lights.

I also have three Level two EV chargers that draw 100 amps of 240 volt single phase each. This is going to be installed in front of a restaurant so I do not assume many people will charge long enough to cause the circuits to be considered continuous duty but I was planning on accounting for continuous duty loads non the less.

I was just speaking with a representative from the Utility and he mentioned that a similar job that was done in another area by a different contractor used only two legs of the 480 to power a single phase EV car charger. Has anyone on here ever used only two legs of 480 volt before?

Also I get that used transformers are probably easy to find at any kva but I have to deal with the Utilities answers to my requests.

All the time. We put in single XF pole mount 240/480 units for these

Reason I mentioned used XF we had a installation for a tower that wanted some wierd 500 something volt transformer. They own two of them. We hung one and the other sits in their control house just in case…

 

[kwired]

Sure, going into a 480->240/120v single phase transformer . If the charger will take 480v single-phase, just do it.

That and there is some 480 volt lighting. Also been seeing dual volt 230/460 single phase motors more often in recent years, particularly in the 10 HP range.

 

[paulengr]

Most motors, HVAC, etc., easily run on 208 and those EVs too. If you run single phase. The biggest thing about balancing loads is to maximize the transformer capacity per leg. You don’t want say 400/0/0 loads on your transformer for instance. Ideally it’s 133 all 3 legs but that’s not realistic either.

Commercial is mostly 208/120 or 240/120 high leg delta for a reason. It just works out better that way.