control transformer

[njhvac]

5kva single phase dry transformer 480v primary with 120v secondary for control panel installation.
Shouldn't X2 be bonded to the metal cabinet?

 

[petersonra]

5kva single phase dry transformer 480v primary with 120v secondary for control panel installation.
Shouldn't X2 be bonded to the metal cabinet?

if you want to have grounded control power.

 

[kc8dxx]

250.21 covers some situations where a transformer secondary may not need to be grounded, and it includes control circuits under certain conditions. I typically have them grounded.

 

[tom baker]

1. If its not grounded and there is a line to case fault, the fault current can't get back to its source.
2. On a non grounded CPT, when you check voltages, if you go to ground as a normal system, you get odd readings.
3. I have not seen a nongrounded CPT, they may be used in locations where you can't tolerate a system shut down.

 

[njhvac]

Shouldnt the 480V primary require the secondary bonding?