How to get 120/240V Single Phase

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goodoboy

Senior Member
Location
Houston
Then your choices are a 480V to 240V single phase transformer or feed your panel from one of your 208V panels and buck/boost for the a/c.

Is this some kind of special a/c unit?

Thank you ActionDave,

What does "feed your panel from one of your 208V panels and buck/boost for the a/c. " ?

Thanks
 

goodoboy

Senior Member
Location
Houston
If the A/C unit is only rated for 240 and this is new and was specified by the A/C contractor then he needs to haul the unit back and get the correct one. The plant should not have to jump through hoops and install special things because the A/C contractor did not do his homework.

That is IMHO

Thanks Sierrasparky,

Its my fault because I approved the vendor panel for 120/240V, so I approved the 240V A/C unit for the building I need to power up.

Thanks
 

Smart $

Esteemed Member
Location
Ohio
Thanks Sierrasparky,

Its my fault because I approved the vendor panel for 120/240V, so I approved the 240V A/C unit for the building I need to power up.

Thanks
Though it could, in the end it may not matter...

Also, is the A/C equipment 1Ø or 3Ø?

The first question when adding to an existing system is always whether it is capable. Until you answer that question with certainty and amount, all other preparations are moot. For example, your 208/120 system may not be capable while your 480V system is.... and you are left converting anyway. The main difference is going to be how the system is balanced now and how it will be balanced after the addition.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Thanks Sierrasparky,

Its my fault because I approved the vendor panel for 120/240V, so I approved the 240V A/C unit for the building I need to power up.

Thanks

Where is that "UNDO" button? If construction has not started yet can't you fall back and regroup?
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
Thank you ActionDave,

What does "feed your panel from one of your 208V panels and buck/boost for the a/c. " ?

Thanks
If you are able to feed your new panel from an existing 208V panel you can install a buck/boost transformer on the circuit to the A/C to get your 240V instead of buying a 480V to 240V transformer. I wouldn't but it is an option.

I still think the A/C will work on 208V.
 

goodoboy

Senior Member
Location
Houston
Though it could, in the end it may not matter...

Also, is the A/C equipment 1Ø or 3Ø?

The first question when adding to an existing system is always whether it is capable. Until you answer that question with certainty and amount, all other preparations are moot. For example, your 208/120 system may not be capable while your 480V system is.... and you are left converting anyway. The main difference is going to be how the system is balanced now and how it will be balanced after the addition.


Thank you for response.

The A/C unit is 1 phase.

How do I confirm if existing system is capable?

Thanks,
 

goodoboy

Senior Member
Location
Houston
If you are able to feed your new panel from an existing 208V panel you can install a buck/boost transformer on the circuit to the A/C to get your 240V instead of buying a 480V to 240V transformer. I wouldn't but it is an option.

I still think the A/C will work on 208V.

Thank you,

Is there somewhere in the NEC where 208V is allowed when the load requires 240V?

Thank you
 

Smart $

Esteemed Member
Location
Ohio
How do I confirm if existing system is capable?
Well there is no easy way to do what is required, which is an Article 220 load calculation for the service and any subpanel feeders in the path. Once you know the calculated load, you can verify wire ampacities and ocpd ratings are good for both existing and existing plus anticipated. See especially 220.87.

Considerations for any intermediate transformers' capacity will also be required. Should be good if service and feeders are okay but if you go to this degree, you may as well verify transformers in the process.
 
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goodoboy

Senior Member
Location
Houston
Thank you so much to all that has helped me.

I was approved to purchase transformer. I will start new thread on proper way to size it.

Thank you kindly.
 
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