Fused Disconnect Switch

[funseebee]

Is a fused disconnect switch or disconnect switch required by Code adjacent to a motor with circuit breaker protection already at the panel? Please help.

 

[Some Dude In Dallas]

430.102(B)(1) - disconnecting means for the motor shall be located in sight of the motor

 

[Npstewart]

In short, you dont need a FUSED disconnect, just a disconnect.

The fuses act as overcurrent protection which is already provided at the panel. Unless the motor manufacturer requires it then you just need to breaker in the panel and a non-fused disconnect.

 

[petersonra]

Is a fused disconnect switch or disconnect switch required by Code adjacent to a motor with circuit breaker protection already at the panel? Please help.

it is never generally required.

a disconnecting means of some sort is required that is required to be "within sight", with an exception for industrial sites as long as it is lockable. the disconnecting means never has to be fused.

there might be cases where fusing it is a good idea, or has some benefit.

 

[don_resqcapt19]

If the motor is large and the available fault current at the disconnect exceeds 10,000 amps, you will need a fused disconnect. As far as I know none of the non-fused disconnects are listed for use where the fault current exceeds 10,000 amps.

 

[GoldDigger]

If the motor is large and the available fault current at the disconnect exceeds 10,000 amps, you will need a fused disconnect. As far as I know none of the non-fused disconnects are listed for use where the fault current exceeds 10,000 amps.

And if for some reason you would like to have the added flexibility of being able to open and close the disconnect under load, you will be better off with a circuit breaker instead of a switch and fuses.

 

[petersonra]

If the motor is large and the available fault current at the disconnect exceeds 10,000 amps, you will need a fused disconnect. As far as I know none of the non-fused disconnects are listed for use where the fault current exceeds 10,000 amps.

but the fuses are not required to be part of the switch. they could be upstream.

 

[petersonra]

And if for some reason you would like to have the added flexibility of being able to open and close the disconnect under load, you will be better off with a circuit breaker instead of a switch and fuses.

or you could add an early break interlock aux wired into the motor starter circuit.

 

[don_resqcapt19]

but the fuses are not required to be part of the switch. they could be upstream.

I don't think so. It is my understanding that you only get the higher fault current ratings with a fusible disconnect.

 

[smoothops10]

or you could add an early break interlock aux wired into the motor starter circuit.

Interesting, is this standard ie a squared interlock switch accessory for the ds opens before the disconnect contacts standard or is this a special feature?

 

[petersonra]

I don't think so. It is my understanding that you only get the higher fault current ratings with a fusible disconnect.

The ab web site shows the nonfused disconnect PN with 200kA rating with fuses. Since the part by definition can't have the fuses built into it, they must be upstream. might be different with other switches.

 

[jim dungar]

I don't think so. It is my understanding that you only get the higher fault current ratings with a fusible disconnect.

Protection upstream is acceptable, they are basically series ratings.
Some manufacturers also have series ratings with their own line of switches and breakers (e.g. Square D with Square D and Eaton with Eaton).