430.102 Motor Disconnecting means exception

[Rickyghart]

I have a situation where the MCC and VFD are located in one building that serves a 75 HP motor in another building across a service driveway. There is no disconnect within site of the motor and the MCC/VFD is in a controlled access building. The motor is in an enclosure for a natural gas turbine generator and may even be deemed a classified location. Written LOTO procedure is to lock out the local motor disconnect.

I do not think exception 430.102(B)(2)(b) applies here which says if the controller to the VFD is locked a local disconnect is not required. Before I insist that this be done, I want some professional opinions on the exception.

 

[Smart $]

I have a situation where the MCC and VFD are located in one building that serves a 75 HP motor in another building across a service driveway. There is no disconnect within site of the motor and the MCC/VFD is in a controlled access building. The motor is in an enclosure for a natural gas turbine generator and may even be deemed a classified location. Written LOTO procedure is to lock out the local motor disconnect.

I do not think exception 430.102(B)(2)(b) applies here which says if the controller to the VFD is locked a local disconnect is not required. Before I insist that this be done, I want some professional opinions on the exception.

The exception applies IMO, and I've seen it done countless times in industrial installations (not necessarily with VFD's as the controller, but motors and their controllers in general).

 

[infinity]

Often we apply the exception when a VFD is involved.

430.102(B) Motor. A disconnecting means shall be provided for a
motor in accordance with (B)(1) or (B)(2).
(1) Separate Motor Disconnect. A disconnecting means
for the motor shall be located in sight from the motor loca-
tion and the driven machinery location.
(2) Controller Disconnect. The controller disconnecting
means required in accordance with 430.102(A) shall be
permitted to serve as the disconnecting means for the
motor if it is in sight from the motor location and the
driven machinery location.
Exception to (1) and (2): The disconnecting means for the
motor shall not be required under either condition (a) or
condition (b), provided the controller disconnecting
means required in accordance with 430.102(A) is indi-
vidually capable of being locked in the open position.
The provision for locking or adding a lock to the con-
troller disconnecting means shall be installed on or at
the switch or circuit breaker used as the disconnecting
means and shall remain in place with or without the lock
installed.
(a) Where such a location of the disconnecting means
for the motor is impracticable or introduces additional or
increased hazards to persons or property
(b) In industrial installations, with written safety pro-
cedures, where conditions of maintenance and supervision
ensure that only qualified persons service the equipment.

Informational Note No. 1: Some examples of increased or
additional hazards include, but are not limited to, motors
rated in excess of 100 hp, multimotor equipment, submers-
ible motors, motors associated with adjustable speed drives,
and motors located in hazardous (classified) locations.

 

[rbalex]

The exception applies IMO, and I've seen it done countless times in industrial installations (not necessarily with VFD's as the controller, but motors and their controllers in general).

I concur, but I'm biased having been on the API tech committee that proposed and continued to develop the Exception. I personally submitted about 3/5 of FPN/IN No. 2.

 

[infinity]

So is there really that much of a hazard if you had a local disconnect between the VFD and the motor? IMO from a safety standpoint it might be better to get rid of the exception and require an aux contact in the disconnect to kill the VFD and have the switch within sight of the motor.

 

[iwire]

My own belief is that the exception should be very restrictive and the well being of a VFD should not take precedence over safety equipment for workers.

Perhaps it works fine in true industrial locations but there are many motors installed in areas that are very unlike industrial locations with trained personal.

 

[Rickyghart]

This instance is for a new gas turbine start motor being operated as a CHP plant in a medical center. The drive and MCC are in another building with controlled access that would not be granted to the servicing technician. Not an industrial operation. Certainly one that lawyers would sort out.

RBAlex- the determination of what is an industrial location - or not - should be what the owner says it is, not a design engineer interested in raising thier profit in a design build project.

I suggest tightening up this requirement or eliminating the requirement for a motor disconnect. Nevermind that last part; do the first.

 

[don_resqcapt19]

There is very likely a violation of 225.30 in this installation, and if there is not that violation, then 225.31 & .32 require a disconnect at the second building unless you comply with the exception to 225.32.