Single Phase Transformer Secondary Grounding

[Kilowatt76]

Hi,

I have a singles phase 1.5Kva transformer, 480VAC 1ph primary to 120VAC 1ph secondary. H1 and H4 are my primary lines, H2 to H3 connected together. X1 to X3, X2 to X4 and secondary lines to X1, X4 for 1ph 120VAC. My question is, does any of the secondary need to be connected to ground? I know have seen some secondary 120VAC, 1ph be 180 - 190VAC. :?

Thanks,
Kilowatt

 

[infinity]

Yes you need to install a system bonding jumper and a GEC.

 

[Kilowatt76]

Yes you need to install a system bonding jumper and a GEC.

So, I need to connect a ground wire to X2 and X4?

 

[petersonra]

So, I need to connect a ground wire to X2 and X4?

You need to bond X2/X4 to the EGC and run a GEC to the nearest qualifying GE connected to X2/X4. often there is a stud on the transformer case for this.

 

[augie47]

It's a separately derived system that falls under 250.21. You can elect either secondary conductor to be the grounded conductor and, as infinity states, bond that conductor and connect it to a grounding electrode as specified in 250.30

 

[Kilowatt76]

Got it, thank you guys!

 

[kwired]

You need to bond X2/X4 to the EGC and run a GEC to the nearest qualifying GE connected to X2/X4. often there is a stud on the transformer case for this.

Unless there are specific instructions that state to do so on x2/x4, NEC is fine with grounding either secondary conductor.

If one were using 120/240 volts on this secondary then NEC requires grounding the "neutral" which is going to be X2/X3 connection.

 

[petersonra]

Unless there are specific instructions that state to do so on x2/x4, NEC is fine with grounding either secondary conductor.

If one were using 120/240 volts on this secondary then NEC requires grounding the "neutral" which is going to be X2/X3 connection.

The OP indicated X2 and X4 were connected together. that would make sense for a 120V secondary, as opposed to a 240/120 V secondary.

 

[kwired]

The OP indicated X2 and X4 were connected together. that would make sense for a 120V secondary, as opposed to a 240/120 V secondary.

Yes, NEC doesn't care if you ground X1/X3, or X2/X4. Neither one when used in that configuration is "neutral".

 

[LarryFine]

It's funny how often it seems "scary" to ground a conductor that doesn't enter the building already so grounded.