Medium Voltage (2400VAC)- Disconnect Requirement

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tenee

Member
Location
Illinois
My question concerns the requirement for a local (within site of) disconnect for a 2400vac to 120/240vac 25KVA transformer. Here's the installation: a wellhouse is to be fed from a main control/power distribution building. Three wells exist already- they are located on the riverbank approximately 1500' to 2000' from the main control/power distribution building. Each are their own discreet building. A fourth is proposed in the same general area. The building is to be off the ground by approximately 15' or so. The building itself is to be 16'x 16'x 12'. The building will contain a 350HP vertical turbine well pump, a 25kva transformer, a Lighting receptacle panel and all of the required accessories (lights, ventilation fan, electric heater etc.). The transformer will feed the lighting receptacle panel and will be grounded as required. According to Article 430.102 the disconnect for the motor can be located 2000' away in the control/power distribution building, fed from a starter with a fusible disconnect (lockable in the open position). My question is regarding the transformer. My first assumption is that it too falls under Article 430.102 (as it is a controller by definition supplied in Article 100- Controller- A device or group of devices that serves to govern, in some predetermined manner, the electric power delivered to the apparatus to which it is connected.). Am I required by the NEC to provide a disconnecting means for the transformer? Article 110.58 would tend to infer that a local disconnect is required but is this general requirement superceded by specific requirements of Article 430.102?
 

tenee

Member
Location
Illinois
Re: Medium Voltage (2400VAC)- Disconnect Requirement

I neglected to mention that the 25KVA transformer is going to have a fused disconnect switch at the main control/distribution building.

Thanks in advance,

TENEE
 

wanderer20001us

Senior Member
Re: Medium Voltage (2400VAC)- Disconnect Requirement

110.58 only applies to Tunnel Installations Over 600V. If the transformer is protected on it's own feeder from the distribution building, IMO it does not need a disconnect at the pump building.

If I were designing this installation, though, I would put a disconnect at the pump building as a best practice measure.

Sam
 

steve66

Senior Member
Re: Medium Voltage (2400VAC)- Disconnect Requirement

You should probably read Article 225 parts II and III. It looks like there may be several requirement your installation needs to meet with regards to disconnects. And I also agree with Sam, if I were designing this, I would provide a disconnect. Maintenance can be a real pain if you have to walk or drive a half mile to turn a disconnect on or off.

Steve
 

steve66

Senior Member
Re: Medium Voltage (2400VAC)- Disconnect Requirement

See 225.30. I am not sure you can have separate feeders running to the transformer and to the pump. Maybe 225.30(D) would allow it, but I'm not sure.

I am wondering if a local disconnect may be required because of the separate building.

Steve

Edit: You can't call your transformer a "motor controller" and apply article 430 when it is feeding other loads instead of motors :)
(I'm not saying a disconnect is required, just that 430 doesn't apply to the transformer).

[ April 20, 2004, 04:32 PM: Message edited by: steve66 ]
 

iwire

Moderator
Staff member
Location
Massachusetts
Re: Medium Voltage (2400VAC)- Disconnect Requirement

I got you Steve, I think that 225.30(D) would allow the separate motor feeder.

However being in a separate building it seems both the motor feeder and the transformer feeder will need disconnects at the building.

I have never bought a 2400 volt disconnect but I think I would think seriously about placing the transformer outside the building so I could use a standard 250 volt disconnect the general purpose loads.
 

steve66

Senior Member
Re: Medium Voltage (2400VAC)- Disconnect Requirement

Good idea, Iwire. At 25KVA, a standard disconnect wouldn't be too expensive. I bet the disconnect for the motor still causes some long faces though. I wonder what voltage you need to feed a 350HP motor from across "the back 40".

Steve
 
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