Acceptable Methods of Motor Lockout - Branch circuit fuse holder inside an industrial control panel?

[JustAGuyInMN]

Obviously I have opinions about what I explain here, but I'm looking for others' opinions and ideally code reference to show whether this motor lockout practice meets code / the intent of the code and any other factors anyone might like to mention.

I have experience in a facility where their standard practice is to use the 430.102(B)(2) Exception 2, to not have local disconnects in line of sight of motors. I am trying to get to the bottom of the state and level of detail of their "written safety procedures" so see if I'm satisfied that that framework is in place to even claim that exception, but let's assume that it is for the sake of this post.

The real topic I want to talk about is the location/style of the "disconnects" they are using that aren't in line of sight of the motors, and their practices for using them. Effectively they have 480V UL508A industrial control panels for many motors, which they enter when energized (with appropriate PPE) and open and lock out individual fuses/fuse holders that feed the branch circuit to the motor they want to lock out.

I think most people would agree there are better ways than this, but is there any specific reference that would forbid this from being their practice? There's commentary text in the NEC under the 430.102(B) section that says that breakers inside locked rooms or locked panelboards wouldn't be acceptable but that's not what we have here. If anything these fuses are only "behind" the defeat-device of the industrial control panel disconnect. Also that's just commentary text anyway, so it's not a direct code statement.

I appreciate your input. Thanks.

 

[David Castor]

There has to be a disconnecting means within sight of the controller. Do they consider the fuses a disconnecting means? How do they lock out a fuse holder?

 

[JustAGuyInMN]

Yes "they" (the facility) are considering the fuses the disconnecting means.
I don't have the part number of the fuse holder on hand but it looks to be that when you open the fuse holder which opens the circuit, there is a lock hole that if you put a lock through that hole it prevents the fuse holder from being closed.

Interestingly they have a JOA/HOA switch local to the motor (hence not local to the disconnecting means since the disconnecting means is inside the feeding panel which is remote from the motor/JOA. That JOA is wired back to the panel also, typically hardwired to a starter or VFD input.

 

[don_resqcapt19]

I am not seeing the fuses as a permitted motor disconnect device per 430.109.

Even if it was, it would require an electrically qualified person to do the lockout, even when the reason for the lockout is for mechanical work. We have often installed rotary disconnects on the doors of the control panels for the purposes of motor lockout.

 

[JustAGuyInMN]

This is a great point about 430.109! This is the most concrete thing yet. I did some more reading and indeed it's very established that UL512 fuse holders are not listed in 430.109 and cannot be used as a disconnect.

I also did some more reading yesterday and realized that 430.107 says at least one disconnect needs to be readily accessible. NEC defining readily accessible, including that it can't need tools (except keys) to access it. This fuse holder being the only disconnect location and being inside an industrial control panel means that it's behind the main door disconnect defeat device requiring a screwdriver to open when energized.

Thank you for the help in putting together something concrete showing it doesn't meet code and not just "this is a bad idea for these reasons" (which there are plenty of as well).

 

[petersonra]

The fuse holder is not a disconnecting means per the nec.

That does not mean it cannot be used as a means of locking out a circuit.

The circuit clearly has a nec legal disconnecting means in the form of the main disconnect to the control panel so the nec disconnect requirement is met.

It seems kind of cumbersome to do it this way but I do not see there is any rule violated.

As for written procedures for disconnecting the motor. I would argue a label near the motor stating where the power is fed from is adequate.

 

[JustAGuyInMN]

I agree with that statement, except procedurally they aren’t using the main disconnect on the panel. They are entering the energized panel and using the fuse holder for the individual motor as the disconnecting means. So with how they are using the components there I would think they are violating NEC?

 

[don_resqcapt19]

The fuse holder is not a disconnecting means per the nec.

That does not mean it cannot be used as a means of locking out a circuit.

The circuit clearly has a nec legal disconnecting means in the form of the main disconnect to the control panel so the nec disconnect requirement is met.

It seems kind of cumbersome to do it this way but I do not see there is any rule violated.

As for written procedures for disconnecting the motor. I would argue a label near the motor stating where the power is fed from is adequate.

Only the types of devices in 430.109 are permitted to be used as a motor disconnect. Other upstream disconnects cannot serve as the required motor controller disconnect.

 

[petersonra]

Only the types of devices in 430.109 are permitted to be used as a motor disconnect. Other upstream disconnects cannot serve as the required motor controller disconnect.

The main circuit breaker on the control panel is the disconnecting means.

 

[petersonra]

 

[jim dungar]

View attachment 2571391

These are 'block' offs not 'lock' offs. They are used with tag out procedures. They are not appropriate for lock out procedures.

 

[don_resqcapt19]

View attachment 2571391

Not permitted for applications where the NEC requires a lockable disconnect.

 

[petersonra]

Not permitted for applications where the NEC requires a lockable disconnect.

There are similar devices you can get for locking

 

[don_resqcapt19]

There are similar devices you can get for locking

If the lockout is required by the NEC, the provisions for the lock to be applied must always be in place. Nothing similar to the item in your post would be compliant for anything where the NEC required provisions for lockout.

 

[petersonra]

If the lockout is required by the NEC, the provisions for the lock to be applied must always be in place. Nothing similar to the item in your post would be compliant for anything where the NEC required provisions for lockout.

The nec does not anywhere require a lockout. That is an OSHA thing. The nec does require lockable disconnects. They are not the same function although often a lockable disconnect is used to electrically lockout a device.

 

[don_resqcapt19]

The nec does not anywhere require a lockout. That is an OSHA thing. The nec does require lockable disconnects. They are not the same function although often a lockable disconnect is used to electrically lockout a device.

They are the same function and the only reason lockable disconnects are required is to provide a permanently installed method of lockout.

 

[petersonra]

They are the same function and the only reason lockable disconnects are required is to provide a permanently installed method of lockout.

They are not the same thing. They are similar. There is a huge difference.

 

[kwired]

They are the same function and the only reason lockable disconnects are required is to provide a permanently installed method of lockout.

I look at is as NEC can at times require a lockout method to be installed but doesn't require anyone to use a lockout method, that is per safe work practices rules to determine when it should be used.

NEC requires disconnecting means within sight of equipment in many instances - pretty much none of them are required to be lockable. Where NEC permits the disconnecting means to not be within sight - often it may require the disconnect to have a locking means - but doesn't have any rules on the use of the locking means.

 

[don_resqcapt19]

I look at is as NEC can at times require a lockout method to be installed but doesn't require anyone to use a lockout method, that is per safe work practices rules to determine when it should be used.

NEC requires disconnecting means within sight of equipment in many instances - pretty much none of them are required to be lockable. Where NEC permits the disconnecting means to not be within sight - often it may require the disconnect to have a locking means - but doesn't have any rules on the use of the locking means.

And it shouldn't...the lockable rule is just facilitate the use of a lock when required by other documents.

 

[garbo]

A lot of companies do not want to go to the expense of purchasing a safety switch with a normally closed micro switch on motors controlled by drives. Wish the NEC would make it mandatory that at bare minimum when motor is not on the same floor as the drive then the motor must have a local lockable disconnect within 50' & visible from the motor. Would be ok to have disconnects say on water towers to be on the outside. We had 4 water towers with 60 HP motors where they only installed a 30 amp non fixed safety switch to LOTTO motors. I always walked hundreds of feet then climbed thru two door ways to install LOTTO on the drive disconnect.