Electrical Design Assistance for Australia

[DCI]

Hello forum users.
I am building an industrial control panel (in Australia) for use in Nth Dakota.
Due to the huge variations in electrical code requirements between Oz & the US I need some assistance -for which I am happy to pay for.
Most answers are black & white however there are a few that may involve "workarounds" to satisfy the US NEC & our methods of construction. An example of the type of question is as below.
Q1. We have a Motor Control Centre with a total motor loading of 180A. Due to the machine operation & diversity factor, these machines typically draw 60-80A when running. Note: there are not any interlocks that prevent the operating current going higher, other than the motors never reach FLC together and that the process would not be operating correctly with all motors running simultaneously. We normally supply the machine with 125A C curve miniature CB. (In Australia we only need rate the supply cables at 125A, as the maximum demand is current limited to 125A). How does this scenario fit in with NEC?

Many thanks,

Gavin Schofield

gavin@dcie.com.au

 

[bob]

Gavin
I think that you will need to have a name plate on your panel that
states the Voltage and Full load amps of the device. In your example that would be 125 amps. You would need to specify if it is single phase or three phase. The std voltages are 120, 240, 120/208 3P, 277/480 3P, and 600 3P
all at 60 HZ. This info would allow the designer to spec the conductor size
and breaker size. The NEC would require that the conductor carry the
FLA x 1.25 if the load is continuous (3 hrs or more). If you have a copy of the NEC,
section 430.7 provides additional information.
Maybe someone else can add to this info.

 

[dbeasley488]

Gavin
I think that you will need to have a name plate on your panel that
states the Voltage and Full load amps of the device. In your example that would be 125 amps. You would need to specify if it is single phase or three phase. The std voltages are 120, 240, 120/208 3P, 277/480 3P, and 600 3P
all at 60 HZ. This info would allow the designer to spec the conductor size
and breaker size. The NEC would require that the conductor carry the
FLA x 1.25 if the load is continuous (3 hrs or more). If you have a copy of the NEC,
section 430.7 provides additional information.
Maybe someone else can add to this info.

What about UL listing? UL testing may probably require this info. If UL testing was not in the works, a licensed engineer in N Dakota may be able to inspect the ICC for a fee and provide a letter stating all the requirements of the NEC, OSHA, and any other local regulations are acceptable.

 

[dingokangaroo]

Gavin
I think that you will need to have a name plate on your panel that
states the Voltage and Full load amps of the device. In your example that would be 125 amps. You would need to specify if it is single phase or three phase. The std voltages are 120, 240, 120/208 3P, 277/480 3P, and 600 3P
all at 60 HZ. This info would allow the designer to spec the conductor size
and breaker size. The NEC would require that the conductor carry the
FLA x 1.25 if the load is continuous (3 hrs or more). If you have a copy of the NEC,
section 430.7 provides additional information.
Maybe someone else can add to this info.

he is correct on this mate. am suprised you do not have a spec. and hello from a crow eater state side

 

[DCI]

Electrical Code Assistance for Australia

Electrical Code Assistance for Australia

Thanks for your comments guys.

I have had some discussions with the UL bloke that is going to inspect it....plus cramming in study on NEC 2005 / Article 409 and UL508A supplement SB.

Hopefully all will end up OK!

 

[ramsy]

building an industrial control panel (in Australia) for use in Nth Dakota. ..We normally supply the machine with 125A C curve miniature CB. (In Australia ..maximum demand is current limited to 125A). How does this scenario fit in with NEC?

Is current limited related to Austrailia's Single wire earth return (SWER); with 5-10 ohm returns to local earth, thru 6m (20ft) ground rods, resulting in equally safe, more reliable, and less cost than conventional power lines?

If the North Dakota control panel is not supplied by an impedence-grounded system, similar to SWER's 5-10 ohm service return, than those short-circuit current ratings (SCCR) for CB's / equipment, or any reclosers may not be appropriate for excessive fault-current levels found in low-impedance systems, as required by NEC 110.9 & 110.10

While local engineering consultants should be familiar with equipment selection based on available-short-circuit current (ASCC), and all listing authorities including UL, if you can match equip. to ASCC listings yourself, and the supply, transformer / grounding impedences are known, the most impressive calculator I've seen for doing ASCC calcs was available as a free trial, but the only OCPD reference tables included were from "Little Fuse".