2005 nec 430.108(a)(6)

[erickench]

After reading the above NEC section I noticed a contradiction. The first sentence begins:

Listed manual motor controllers additionally marked "Suitable as Motor Disconnect" shall be permitted as a disconnecting means where installed between the final motor branch-circuit short-circuit protective device and the motor.

The second sentence then reads:

Listed manual motor controllers additionally marked "Suitable as Motor Disconnect" shall be permitted as disconnecting means on the line side of the fuses permitted in 430.52(C)(5).

But the next sentence reads:

In this case, the fuses permitted in 430.52(C)(5) shall be considered supplementary fuses, and suitable branch-circuit short circuit and ground-fault protective devices shall be installed on the line side of the manual motor controller additionally marked "Suitable as Motor Disconnect".

Now the fuses in 430.52(C) were meant for branch circuits. Now why we do have a branch-circuit protective device connected on each side of the controller? The first sentence says that the controller is connected from the FINAL motor branch-circuit short-circuit protective device. Now how could this be if the controller is connected between two protective devices? I think there is something wrong with the second sentence because it states that protective devices are to be connected downstream from the controller.

 

[tom baker]

I read it and it makes sense as written but I see your point.
It seems as if the manual motor disconnect must be protected by fuses, no matter where it is located.
Its odd, thought that the NEC calls out fuses and does not allow any OCPD.
This may have to do with the manual motor controller.
The answer lies in the UL listing (hint: go to ul website and download a copy of the UL white book)

MOTOR CONTROLLERS, MANUAL (NLRV)
Motor Controllers, ManualNLRVGENERAL
This category covers the following manually-operated devices intended for across-the-line starting of motors:
Across-the-line starters
Autotransformer starters
Reactance-type starters
Resistance-type starters
Speed regulators
Combined starters and speed regulators
Motor disconnect switch ? Manual motor controllers that have been additionally investigated for use as a motor disconnect switch are marked "Suitable as Motor Disconnect." These devices are intended to be installed on the load side of motor branch-circuit protection in accordance with Section 430.109(A)(6) of ANSI/NFPA 70, "National Electrical Code" (NEC).
Tap conductor protection ? Manual motor controllers that have been additionally investigated for use as tap conductor protection within a motor group are marked "Suitable as Tap Conductor Protection in Group Installations." These devices are intended to be installed on the load side of motor branch-circuit protection for a motor group in accordance with Section 430.53(D)(3) of the NEC.

 

[erickench]

Tom, I am using the 2007 New York City Electrical Code which is based on the 2005 NEC. You see a few years ago the two codes were integrated. The city just takes the NEC and makes amendments to it. Then it publishes the code two years after the NEC. Are you by any chance looking at the 2008 NEC? Did they change the wording in section 430.108(a)(6)?

 

[erickench]

Correction. I meant 430.109 (A) (6). But the wording in the code is still improper. Protection devices should never be on the load side of motor controllers.