480 On Panel Door / Current Transformer

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I am building panels that require 1 ammeter for each motor in the panel. The motors only draw 4.8 amps, so I purchased 0 - 10Amp Shurite meters and CT's. I found the Shurites can take the current without a CT. This brought up many questions that I can't find good answers to......

1. Code says you have to run all three conductors together. If I would run one leg through the ammeter on the door, I would think the other legs would also have to go to the door.

2. With three motors, thats 12 lines of 480 on the door, doesn't feel the safest. But if I use my 10:1 CT with 10 wraps on the primary (to get the 1:1), I would only need 6 wires on the door with 0 volts each.

3. If a wire were to break or come loose, the door would have a wire with 4,800 volts on it. That doesn't seem safer.

So, my one discovery about the ammeter being able to take the 480 current without a CT has made me unsure about the whole idea of panel door mounted ammeters. What is best / safest practice in this situation?
 
Don't confuse wiring in raceway requirements with those inside of panels.

You would not be required to run all 3 phases to the door if you only need one. If the circuit conductors had to stay next to each all of the time, we could never split them up for terminal blocks, or like in the old days to a neutral bar at the opposite end of the panelboard.

The NEC does not do a very good job of addressing "internal panel wiring". My preference is to use NFPA79 whenever possible, which recommends against bringing more than 120V to the door.
 
jim dungar said:
The NEC does not do a very good job of addressing "internal panel wiring". My preference is to use NFPA79 whenever possible, which recommends against bringing more than 120V to the door.
Click to expand...

Exactly. That is what brought me to the 'safest solution' question. NFPA frowns on 480 at the door, but would you consider the CT leads less than 480? Or would you say they have a potential of 4800 volts if disconnected? I think the CT solutions appears safer at this point.?.?.?
 
I would not consider the CT leads to be at 4800V. If I did they could not be wired in 600V insulation.

Switchgear built to ANSI standards has never allowed more than 150V to a door but has always allowed CT leads.

If you have not purchased the equipment yet, you could always use a current transducer (like those from NK Technologies) to convert AC Amps to DC Voltage.
 
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