Transformer Secondary Overcurrent....

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emahler

Senior Member
What is the consensus on this potential installation....

225A 480V 3 wire feed of 4/0 THHN CUto a 150kVa Delta-Delta transformer...

the 150kVa transformer steps the voltage down to 240V at 400A.

we are looking to install two (2) 225A MLO panels on the secondary side. Each panel fed with 4/0 THHN CU

will 240.21(C) allow this installation without overcurrent protection on the secondary side?
 

raider1

Senior Member
Staff member
Location
Logan, Utah
408.36(B) requires that panelboards supplied from a transformer have the panelboard overcurrent protection provided on the secondary side of the transformer.

Chris
 

emahler

Senior Member
If you want to use the exception the panels would have to be rated at 450 amps. They are only rated at 225 so you have to protect them at 225 amps or less.

that was what I thought...by the way, this install is under the 2005 code...but I don't see that it makes a difference regarding this installation.
 

emahler

Senior Member
next part of this question...the branch circuits are feeding receptacles/power for 14 refrigerated trucks to be plugged in overnight.

and yes, i am asking purely out of laziness...

is there a requirement for the cords that feed power to the trucks to be plug/cord or can we install disconnects and feed the cords directly out of the disconnects?

i am under the impression there was a change in this requirement in the 2008 code, but at this point, it's purely conjecture...
 

raider1

Senior Member
Staff member
Location
Logan, Utah
next part of this question...the branch circuits are feeding receptacles/power for 14 refrigerated trucks to be plugged in overnight.

and yes, i am asking purely out of laziness...

is there a requirement for the cords that feed power to the trucks to be plug/cord or can we install disconnects and feed the cords directly out of the disconnects?

i am under the impression there was a change in this requirement in the 2008 code, but at this point, it's purely conjecture...

A new Article 626 was added to the 2008 NEC that contains the requirements for electrified truck parking spaces.

Chris
 

emahler

Senior Member
A new Article 626 was added to the 2008 NEC that contains the requirements for electrified truck parking spaces.

Chris

yeah chris, you're not being helpful here:D

626 has a bunch of requirements...Hubbell/Leviton make some nice mechanical interlock devices that meet the NEC requirements...for about $1000/ea:D

we are doing this project under the 2005...so, we don't have to meet 626 requirements...

and we're installing 2 75kVa delta-wye transformers, so we need secondary protection...

so, all's well that ends well...

and milehi, you didn't know that the back my truck was filled with beer and food...you're loss
 
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