# Motor disconnect



## erics37 (May 7, 2009)

Don't know how the CEC is worded but the NEC says this:



> *430.103 Operation.* The disconnecting means shall open
> all ungrounded supply conductors and shall be designed
> so that no pole can be operated independently. The disconnecting
> means shall be permitted in the same enclosure
> ...


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## Jlarson (Jun 28, 2009)

MaxPower said:


> wire a disconnect in series with the hand auto switch in the control circuit.


Seems like a waste of hack effort, just turn the HOA to off. :laughing:


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## CYoung (Apr 19, 2013)

Use a disconnect that opens the three phase and also has an auxiliary that can be wired in series with the HOA. You both will be happy......


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## glen1971 (Oct 10, 2012)

MaxPower said:


> So I'm having a little disagreement with my supervisor at work and I'm hoping some of you can help me out.
> 
> In a heat exchanger building, there are two exhaust fans being installed. They are both 3 phase 480 volt motors using 24 volt controls. The original blueprints had no disconnects whatsoever but are now being added. My boss claims that we can wire a disconnect in series with the hand auto switch in the control circuit. I'm disagreeing because I believe that the disconnect should be located in the power circuit but I can't find any specific code rules in the CEC that directly state that. The reason I think this is because I have seen contacts in the power circuit fused together, so I think having a disconnect in series between the contactor and the motor would be the proper location for the disconnect.
> 
> If anyone has any information or knowledge that can help it would be greatly appreciated. Even if it proves me wrong.


Can't say I've seen a local disconnect that interrupts the motor leads on anything bigger than a 230 volt chemical pump.. Everything I've seen on the 3 phase side only has the HOA, Stop/Start, On/Off, etc for a local isolation switch.


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## ilikepez (Mar 24, 2011)

What would be the point of putting a disconnect on the HOA switch be? Easier to lock out?


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## JRaef (Mar 23, 2009)

glen1971 said:


> Can't say I've seen a local disconnect that interrupts the motor leads on anything bigger than a 230 volt chemical pump.. Everything I've seen on the 3 phase side only has the HOA, Stop/Start, On/Off, etc for a local isolation switch.


"Local" is subjective.
Every motor circuit is required to have a means of disconnecting the *power* going to it and locking the disconnect open. But that can be the motor starter disconnect or even the panelboard CB under the right circumstances.

Putting a lock-out only on the control circuit does not satisfy the NEC requirements or OSHA requirements, but in some special circumstances may be acceptable when the entire system has been evaluated and accepted by the AHJ. One such that I did was on some 800HP blower motors for a turd farm. The motors were fed by LV Metal Clad switchgear breakers that had motorized winders for the spring. The breakers fed soft starters via Kirk-key interlocks so that the starter cabinets could not be open ended unless the breakers were open. Then at the motor, where it was impractical to put in a 1600A disconnect switch, they had just an E-Stop button with a padlock as the LOTO device. If you pushed the E-Stop, it opened the UV Trip circuit of the breaker as well as the control circuit to the soft starter (although I felt that was unnecessary), plus it killed power to the breaker recharge motor. That was the only time I saw an AHJ accept that.


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## CYoung (Apr 19, 2013)

> Can't say I've seen a local disconnect that interrupts the motor leads on anything bigger than a 230 volt chemical pump.. Everything I've seen on the 3 phase side only has the HOA, Stop/Start, On/Off, etc for a local isolation switch.


We have local disconnects for just about every motor in the plant.... from 1HP conveyor motors all the way up to 150 HP water pumps. We usually also use an auxiliary contact on the local disconnect that is wired in series with the control circuit as an added safety measure.....


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## SteveBayshore (Apr 7, 2013)

JRaef said:


> "Local" is subjective.
> 
> "Local" is not subjective. 430.102(B)(1) "shall be located in sight of the motor location" with exceptions. Article 100 also limits "within sight" to 50'. We very seldom use local disconnects on the motors that we wire but I can fit them into the exceptions (with some arm twisting).


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## nolabama (Oct 3, 2007)

Hence local being subjective


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## denny3992 (Jul 12, 2010)

CYoung said:


> We have local disconnects for just about every motor in the plant.... from 1HP conveyor motors all the way up to 150 HP water pumps. We usually also use an auxiliary contact on the local disconnect that is wired in series with the control circuit as an added safety measure.....


We have 2 locations that have 6-250hp pumps on vfds with local discos and NO aux contacs in them, weve put big labels on the discos( use only in emergency) im waiting for the day they use it and ko the old vfds


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## SteveBayshore (Apr 7, 2013)

From what I remember from the VFDs that I have installed, the manufacturers instructions strictly prohibit a disconnect between the VFD and the motor, control interlock or not.


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## denny3992 (Jul 12, 2010)

SteveBayshore said:


> From what I remember from the VFDs that I have installed, the manufacturers instructions strictly prohibit a disconnect between the VFD and the motor, control interlock or not.


Installed many per engineered dwgs with aux contact in enable circuit,


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## CYoung (Apr 19, 2013)

denny3992 said:


> We have 2 locations that have 6-250hp pumps on vfds with local discos and NO aux contacs in them, weve put big labels on the discos( use only in emergency) im waiting for the day they use it and ko the old vfds


The production employees use disconnect as start/stop station for conveyors. They refuse to walk to main control panel.


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## denny3992 (Jul 12, 2010)

CYoung said:


> The production employees use disconnect as start/stop station for conveyors. They refuse to walk to main control panel.


Ugh that sux


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## Jlarson (Jun 28, 2009)

I have plants that have all the motor discos locked off (Big F'ing padlock) and have a big red stop mushroom push button on each. Even with aux contacts for the drives, operators were killing discos flipping them all god damn day long.


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## Del (Feb 10, 2011)

*Motor Disconnect*

Section 28 of the CEC
para's 600, 602, 604 In the power(ungrounded conductors), ideally with an aux, within 9m, and within sight of the motor, as the norm unless at source, unless its a/c equipment, which is 3m.


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