1 KVA transformer

[richlattof]

Bonding question? I have a 1 KVA transformer. It is 480 delta single phase to a 120 volt secondary. It is mounted in a roof top unit to provide power to a convenience GFI outlet. The inspector called me out on not bonding it to building steel due to a transformer being a separately derived system. I know larger transformers are always bonded to building steel but this seems a little ridiculous. I have searched the code with not much luck to prove him wrong. Any help would be much appreciated. Thank you.

 

[iwire]

The size does not change the need for a grounding electrode and bonding the neutral to ground.

 

[augie47]

The only exception that would come close to being applicable would be Exception 250.30(A)(5) and that would be for a Class 1 2 or 3 circuit and frankly I don't know if this application could be so classified. Perhaps some others will know.

 

[iwire]

IMO this circuit cannot be a class 1 circuit due to the limitations of 725.41(A).


Far too much power for a class 2 circuit.

 

[richlattof]

Sounds like I will be drilling through the roof for a ground to building steel even know we are grounded through the main feeder feeding the roof top unit. The worst part about it is there is one right next to it that came from the factory with the transformer and outlet and because it is factory installed it does not need to grab steel.

 

[rlundsrud]

I assume this transformer is not part of the unit. Why not just pull a 120 volt circuit up and not use the transformer?

 

[GoldDigger]

So that one disconnect will remove all power from the unit?

 

[Jraef]

So that one disconnect will remove all power from the unit?

So, run the 120V through an aux contact on the disconnect.

 

[GoldDigger]

So, run the 120V through an aux contact on the disconnect.

But I am using the branch breaker as the disconnect.
("There's a hole in my bucket Dear Liza, Dear Liza...")

:angel:

 

[iwire]

So that one disconnect will remove all power from the unit?

That would be a violation.

210.63 Heating, Air-Conditioning, and Refrigeration Equipment Outlet. A 125-volt, single-phase, 15- or 20-ampere-rated receptacle outlet shall be installed at an ac-cessible location for the servicing of heating, air-conditioning, and refrigeration equipment. The receptacle shall be located on the same level and within 7.5 m (25 ft) of the heating, air-conditioning, and refrigeration equip-ment. The receptacle outlet shall not be connected to the load side of the equipment disconnecting means.

 

[GoldDigger]

That would be a violation.

Thanks for the reference. That means that the factory wired outlet derived by transformer from the machine feed cannot be the required maintenance outlet, and the two branch circuit approach is the only one that can work if the breaker is also the machine disconnect.

 

[iwire]

Thanks for the reference. That means that the factory wired outlet derived by transformer from the machine feed cannot be the required maintenance outlet, and the two branch circuit approach is the only one that can work if the breaker is also the machine disconnect.

Disagree with both points there.

Typically the factory wired outlet is tapped ahead of the factory wired disconnect and in the case of a 480 unit so is the the transformer for the outlets.

As far as using a second branch circuit for the service outlet we do that very often, there is no requirement for a disconnecting means for the outlet.

Kind of funny, it 2:30 AM here, at 3:00 I am picking up a coworker, heading to a BJs store to swap out two RTUs at 4:30AM. The old units have the two circuit method, the new ones will have (or are supposed to have) the factory service plug and disconnects already in place.