Motor Disconnects Within Sight

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infinity

infinity

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As a general rule is it ever permissible to have a motor disconnect (10 hp, 480V, 3 phase) not within sight of the motor? I have some VFD's that are mounted on the outside of a few large fan units. The motors are on the inside of the fan unit with a metal door to enter the unit. The VFD's were installed from the manufacturer on the outside of the unit but not within sight of the motors. Wouldn't this require a disconnect inside of the unit within sight of the motor? I'm being told that this is compliant since the VFD is capable of being locked in the open position.
 
Rob,
Unless you can meet the requirements of one of the exceptions to 430.102(B)(2), you need a disconnect within sight of the motor. Maybe part (a) of the exception would apply..not sure.
 
infinity said:
As a general rule is it ever permissible to have a motor disconnect (10 hp, 480V, 3 phase) not within sight of the motor? I have some VFD's that are mounted on the outside of a few large fan units. The motors are on the inside of the fan unit with a metal door to enter the unit. The VFD's were installed from the manufacturer on the outside of the unit but not within sight of the motors. Wouldn't this require a disconnect inside of the unit within sight of the motor? I'm being told that this is compliant since the VFD is capable of being locked in the open position.
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see 2005 NEC 430.102 exceptions
 
don_resqcapt19 said:
Rob,
Unless you can meet the requirements of one of the exceptions to 430.102(B)(2), you need a disconnect within sight of the motor. Maybe part (a) of the exception would apply..not sure.
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Thanks Don (and Brother), I was perusing that section and felt that although it's not a great place to install a disconnect (inside of the unit), it would not be impractical to put one adjacent to the motor. I kind of came to the conclusion, that based on the wording of the exception, a separate disconnect within sight of the motor would be required. I'm just trying to foresee all of the arguments against requiring one before I go and open my mouth.:rolleyes:
 
Don of course is correct, and Brother as well, but read the exceptions carefully.

Part (a) of the exception to 430.102(B)(1) and 430.102(B)(2) uses the word impracticable the exception does not use the word impractical

The two words at first glance look similar but have very different meanings.

Basically impracticable means imposable.

im?prac?ti?ca?ble (ĭm-prăk'tĭ-kə-bəl)
adj.

1. Impossible to do or carry out: Refloating the sunken ship intact proved impracticable because of its fragility.

2. Unfit for passage: roads impracticable in winter.

3. Archaic. Unmanageable; intractable.
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USAGE NOTE The adjective impracticable applies to a course of action that is impossible to carry out or put into practice; impractical, though it can be used in this way, also can be weaker in sense, suggesting that the course of action would yield an insufficient return or would have little practical value. A plan for a new stadium may be rejected as impracticable if the site is too marshy to permit safe construction, but if the objection is that the site is too remote for patrons to attend games easily, the plan is better described as impractical. See Usage Notes at practicable.
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As an example, it is impracticable to have a disconnect within sight of the motor when the motor is a submersible well pump located at the bottom of a 100' well. It can't be done because it is imposable or impracticable.
 
Good catch Bob. :cool: I read that 5 times and never really read the word impracticable. Although these units had the VFD's factory installed they were wired by another contractor who installed the VFD feeder and conduit into the unit to feed the motor. IMO they require another disconnect since it would not be impracticable to install one.
 
I do not think VFD's are considered disconnects, as all VFD's must have disconnecting means.
VFD's on outside and disco on inside would seem correct?
 
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