Bill 12
Member
- Location
- Vallejo, ca
Wondering if it's OK to connect a 208 3ph 230-240Y 112kva transformer to a 3phase subpanel the input current is 100amps
208 3ph to 230-240 Y transformer
- Thread starter Bill 12
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mbrooke
Batteries Included
- Location
- United States
- Occupation
- Technician
oldsparky52
Senior Member
- Location
- Wilmington, NC USA
I'm curious, why that large of a transformer for a 100-amp circuit?
If you have the proper OCP in place, I don't believe the NEC has a problem in under using a transformer's rating. I have heard that transformers might waste more energy when lightly loaded.
If you have the proper OCP in place, I don't believe the NEC has a problem in under using a transformer's rating. I have heard that transformers might waste more energy when lightly loaded.
Bill 12
Member
- Location
- Vallejo, ca
It will feed a 3ph sub panel that is powering a bunch of 240 3ph equipment one is a 100amp welder.
https://www.larsonelectronics.com/p...EVKNXefRoEe8lD45ow9L7KSo5C-rJOZBoCQuwQAvD_BwE
This is the transformer they want me to get. Sorry it a 75kva not 112 that was wrong
https://www.larsonelectronics.com/p...EVKNXefRoEe8lD45ow9L7KSo5C-rJOZBoCQuwQAvD_BwE
This is the transformer they want me to get. Sorry it a 75kva not 112 that was wrong
- Location
- Connecticut
- Occupation
- Engineer
That transformer is single phase. You won't be able to power 240 3ph equipment with it.
Maybe the wrong link?
- Location
- New Jersey
- Occupation
- Journeyman Electrician
So I'm guessing that this will be a 3Ø, 3wire, 240 volt system without a neutral? If you need to supply any 120 volt loads then a 3Ø,4W Delta secondary might be better. A 240 volt Wye system has a phase to neutral voltage of 139 volts.
Last edited:
Bill 12
Member
- Location
- Vallejo, ca
Larson gave me 2 quotes here is the other one
https://www.larsonelectronics.com/p-147482-.aspx
https://www.larsonelectronics.com/p-147482-.aspx
Bill 12
Member
- Location
- Vallejo, ca
So we are trying to keep from running a new service which would entail changing a main panel to a 400amp and doing a hot tap and 200ft of new wire
mbrooke
Batteries Included
- Location
- United States
- Occupation
- Technician
112.5kva is the correct one.
Yes it can be done- make sure your sub panel has straight rated breakers only and no 120 volt loads.
Bill 12
Member
- Location
- Vallejo, ca
OK cool. So if they wanted 120 also could I get a transformer that would do that also?
mbrooke
Batteries Included
- Location
- United States
- Occupation
- Technician
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Look at post #6.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Very confusing thread; let's try to clarify:
So you HAVE a 208V 3 phase system, right?
They WANT you to supply their equipment with 240V 3 phase, is that right?
If so, on that 240V system, do they need you to have 120V single phase as well?
So you HAVE a 208V 3 phase system, right?
They WANT you to supply their equipment with 240V 3 phase, is that right?
If so, on that 240V system, do they need you to have 120V single phase as well?
oldsparky52
Senior Member
- Location
- Wilmington, NC USA
Have you done a load calculation for the new equipment? Is there room in the existing service load calculation to accept the new loads?
And that 112 kVA transformer is overkill for a 100-amp sub panel.
Bill 12
Member
- Location
- Vallejo, ca
Yes there was. Well they ended up not using the transformer they ended up doing a new 400amp panel, disconnects 200ft of wire and $24,000
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