Sizing disconnect switch

SELECTING SWITCHES per NEC and IEC. Article 4of the US National Electric Code includes two methods for properly sizing disconnect switches : 1. Disconnect or circuit breaker size = 8amps. Wire size = (2) 5mcm per phase.

Revised disconnect requirements for Articles 4through 450.

Select the next size down protection device, which would be an 80A breaker.

And the 80A disconnect will likely be one of those rotary IEC style that may not be rated for 50HP either, plus it would not be ULrate meaning it has to have another OCPD ahead of it anyway.

I hate to say it, but you can usually get the correct info on the disconnect switch size by reading the catalog for . Compact Circuit Protector (CCP) fused disconnect switches . Maximum distance between busbar support and switch terminal 70mm. IEC 947- utilization category B, infrequent operation. Select an enclosure suitable for the environment that controller occupies, per Table 430. There will be some supporting information on the AC side as well as DC over-current protection. Section of the Canadian Electric Code includes two methods for properly sizing disconnect switches : 1. NEC Article 4is divided into ten parts, shown in Figure 3. When sizing circuit components, it is important to address each part in order.

Doing so will help to minimize. Motor feeder short-circuit and ground-fault protection. The horsepower rating of the disconnecting means must be at least equal to. Size Fuse amp rating rather than stating Maximum Overcurrent Device amp rating, only. Use the nameplate FLA when sizing conductors, branch circuit short circuit and ground fault protection, and disconnecting switches for: Motors built to operate under 2rpm.

Motors that have high torques (and thus higher FLCs). Multispeed motors (FLC varies with speed). ULswitches can also be applied). A properly sized disconnect switch . Do not exceed conductor ampacity.

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