Would it be legal or against code to lock a fused Disconnect "ON" with a maintenance lock. This Disconnect feeds Parking Lot Lights at the plant I work at. The supervisor wants to lock it on because of security reasons.If for some reason there was a problem the nearest disconnect would be inside our plant.(It would probably take about 7 to 10 minutes to cut off feed to this outside disconnect.)This is a 277 volt feed with (4) 1000 watt lamps.
Locking a Disconnect on
- Thread starter ibdacat
- Start date
- Status
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: Locking a Disconnect on
For HID lighting there is no requirement for disconnect to be within sight or readily accessbile. The disconnect inside the building would serve as a disconnect and would meet safety requirements for lock out tag out. I don't know what the purpose of the disconnect is you are asking about, there may be some other issues.
For HID lighting there is no requirement for disconnect to be within sight or readily accessbile. The disconnect inside the building would serve as a disconnect and would meet safety requirements for lock out tag out. I don't know what the purpose of the disconnect is you are asking about, there may be some other issues.
B
bthielen
Guest
Re: Locking a Disconnect on
This raises a question for me. What is the intended purpose of a disconnect switch? Emergency shutoff, safety lockout, or both? I have always thought them to serve both purposes but, maybe I'm mistaken. If they are to serve as a means for emergency shutoff then I would have to think that it would not be acceptable to lock it in an "on" state. If it is for safety lockout only then I could see where it would be okay.
Bob
This raises a question for me. What is the intended purpose of a disconnect switch? Emergency shutoff, safety lockout, or both? I have always thought them to serve both purposes but, maybe I'm mistaken. If they are to serve as a means for emergency shutoff then I would have to think that it would not be acceptable to lock it in an "on" state. If it is for safety lockout only then I could see where it would be okay.
Bob
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Locking a Disconnect on
If some type of action is needed, in order to terminate an ?emergency? situation or to restore a facility to a safe condition, then under no circumstances should the restoration of safe conditions rely upon human intervention.
I am not saying that a disconnect should not be used to turn something off, when that something appears to be in need of being turned off very quickly. What I am saying is that the design should not rely upon their being a human in the vicinity, when the situation arises, and further rely upon that human to (1) Know what action needs to be taken, (2) Be willing and physically able to take that action without undue risk to his or her own safety, and (3) Successfully take the necessary action in time to prevent an injury or a catastrophic failure.
If there is a need to protect equipment from electrical-related failures, then let us rely upon breakers, fuses, thermal overloads, GFCIs, AFCIs, relays, and the host of other tools that we have at our disposal. Let the disconnect switch give us a method of safely turning off the equipment while we perform maintenance. The disconnect should have no other duties.
This question came up at work recently. A motor?s disconnect had been installed behind a run of pipes. There was sufficient working clearance in front of the disconnect, but in order to get to it (for example, to attempt an emergency shutoff of the motor), you would have to crawl over the pipe. My answer was, and is, that the function of a disconnect is for safety lockout, and absolutely not for emergency shutoff. Here is the basis of my perspective:
If some type of action is needed, in order to terminate an ?emergency? situation or to restore a facility to a safe condition, then under no circumstances should the restoration of safe conditions rely upon human intervention.
I am not saying that a disconnect should not be used to turn something off, when that something appears to be in need of being turned off very quickly. What I am saying is that the design should not rely upon their being a human in the vicinity, when the situation arises, and further rely upon that human to (1) Know what action needs to be taken, (2) Be willing and physically able to take that action without undue risk to his or her own safety, and (3) Successfully take the necessary action in time to prevent an injury or a catastrophic failure.
If there is a need to protect equipment from electrical-related failures, then let us rely upon breakers, fuses, thermal overloads, GFCIs, AFCIs, relays, and the host of other tools that we have at our disposal. Let the disconnect switch give us a method of safely turning off the equipment while we perform maintenance. The disconnect should have no other duties.
roger deas
Member
- Location
- North_Carolina
Re: Locking a Disconnect on
Charlie B, I agree that disconnects are not intended for Emergency Stop opperations.
If "E Stops" are required, (as you know and would design for) there are specific componets that would be necessary for this function ie: mushroom buttons, and / or shunt trip breakers, and / or FA interfacing, and / or limit switches ETC...
Disconnects and the reason for their locations are for safety consideration, but not for shutting down equipment.
Although as you said, using a "Safety Switch" as a switch is what it is designed for.
Roger
Charlie B, I agree that disconnects are not intended for Emergency Stop opperations.
If "E Stops" are required, (as you know and would design for) there are specific componets that would be necessary for this function ie: mushroom buttons, and / or shunt trip breakers, and / or FA interfacing, and / or limit switches ETC...
Disconnects and the reason for their locations are for safety consideration, but not for shutting down equipment.
Although as you said, using a "Safety Switch" as a switch is what it is designed for.
Roger
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: Locking a Disconnect on
We need to make sure we don't confuse the motor disconnect rules with the disconnect for the HID lighting, its not the same requirement.
A motor & controller may require 2 disconnects, one for the motor and one for the controller. One of those has to be readily accessible and the othe only accessible. See 430.102. If there is one disconect it has to be readily accessible.
We need to make sure we don't confuse the motor disconnect rules with the disconnect for the HID lighting, its not the same requirement.
A motor & controller may require 2 disconnects, one for the motor and one for the controller. One of those has to be readily accessible and the othe only accessible. See 430.102. If there is one disconect it has to be readily accessible.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Locking a Disconnect on
I see the distinction, but it does not alter my views. The NEC defines ?Readily Accessible? as, ?Capable of being reached quickly for operation, renewal, or inspections without requiring those to whom ready access is requisite to climb over or remove obstacles or to resort to portable ladders, and so forth.? I think that requiring certain disconnects to be readily accessible is for operational convenience, not for operational safety. The phrase, ?quickly for operation? is not the same as ?quickly for emergency shutdown.?
I see the distinction, but it does not alter my views. The NEC defines ?Readily Accessible? as, ?Capable of being reached quickly for operation, renewal, or inspections without requiring those to whom ready access is requisite to climb over or remove obstacles or to resort to portable ladders, and so forth.? I think that requiring certain disconnects to be readily accessible is for operational convenience, not for operational safety. The phrase, ?quickly for operation? is not the same as ?quickly for emergency shutdown.?
bonding jumper
Senior Member
Re: Locking a Disconnect on
What about a situation where there is a partial short circuit to ground. Not large enough to blow the fuse in the disconnect switch, but large enough to kill a person? I think that having a disconnect locked in the on position negates the fact that it is a disconnect switch and the device now must be viewed as a locked, fused subpanel. There are multiple saftey features in a disconnect switch. One is the overcurrent protection, one is the lock-out feature and one is the ability for human interaction to manually disconnect. By locking the switch in the on position, you are limiting the human aspect, therefore limiting the saftey of the overall system. But I don't know any code issues that involve this, perhaps if there was a motor/refridgeration/hvac load being served and the po co had a brown out and burned up all the motors, I don't know, maybe I have to think about it a little more. If you locked a DS in the on position would you require 24 hour on site supervision to operarate? Perhaps you would be allowed to lock the DS in question, but maybe you would be required to have a means of disconnecting elsewhere, ie feeder breaker? But I like Charlies idea because in the event of an emergency, you don't wanna find the correct disconnect and go on an easter egg hunt to find the next disc. means to operatie.
[ December 26, 2003, 04:29 PM: Message edited by: bonding jumper ]
What about a situation where there is a partial short circuit to ground. Not large enough to blow the fuse in the disconnect switch, but large enough to kill a person? I think that having a disconnect locked in the on position negates the fact that it is a disconnect switch and the device now must be viewed as a locked, fused subpanel. There are multiple saftey features in a disconnect switch. One is the overcurrent protection, one is the lock-out feature and one is the ability for human interaction to manually disconnect. By locking the switch in the on position, you are limiting the human aspect, therefore limiting the saftey of the overall system. But I don't know any code issues that involve this, perhaps if there was a motor/refridgeration/hvac load being served and the po co had a brown out and burned up all the motors, I don't know, maybe I have to think about it a little more. If you locked a DS in the on position would you require 24 hour on site supervision to operarate? Perhaps you would be allowed to lock the DS in question, but maybe you would be required to have a means of disconnecting elsewhere, ie feeder breaker? But I like Charlies idea because in the event of an emergency, you don't wanna find the correct disconnect and go on an easter egg hunt to find the next disc. means to operatie.
[ December 26, 2003, 04:29 PM: Message edited by: bonding jumper ]
- Location
- Massachusetts
Re: Locking a Disconnect on
Can anyone point to a code article that prohibits locking a disconnect on?
Often disconnects are behind locked doors anyway.
I just finished a 400 amp service for a small store in a bad neighborhood, you can be sure the service disconnect located outside has a padlock on it.
I have not seen a padlock slow a fireman down, the have the means to open the switch.
I agree with Charlie having someone with the knowledge of what to do near the switch at the precise time a fault is occurring sounds pretty remote.
Can anyone point to a code article that prohibits locking a disconnect on?
Often disconnects are behind locked doors anyway.
I just finished a 400 amp service for a small store in a bad neighborhood, you can be sure the service disconnect located outside has a padlock on it.
I have not seen a padlock slow a fireman down, the have the means to open the switch.
I agree with Charlie having someone with the knowledge of what to do near the switch at the precise time a fault is occurring sounds pretty remote.
- Location
- Illinois
- Occupation
- retired electrician
Re: Locking a Disconnect on
Bennie,
Don
Bennie,
How? I've never seen a lock that the equipment on our rescue truck can't "unlock".
Don
- Location
- Illinois
- Occupation
- retired electrician
Re: Locking a Disconnect on
Bennie,
Every call is different. If there is danger to the firefighters caused by an "emergency system" the system will be shut down.
Don
Bennie,
Every call is different. If there is danger to the firefighters caused by an "emergency system" the system will be shut down.
Don
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Locking a Disconnect on
ibdacat Is this what your looking for?
I'm not sure if this applys to light's
230.93 Protection of Specific Circuits.
Where necessary to prevent tampering, an automatic overcurrent device that protects service conductors supplying only a specific load, such as a water heater, shall be permitted to be locked or sealed where located so as to be accessible.
I think neon is the only discharge Lighting system that has a secondary that is over 1,000 volts which would require a disconect (see 410.81), so since a disconect is not required locking the disconect closed should not matter. As the disconnect now becomes just a safty switch.
As far as certain disconnects like for fire pumps, They are required to be locked in the closed position. There is other emergency systems that require this too.
695.4 Continuity of Power.
Circuits that supply electric motor-driven fire pumps shall be supervised from inadvertent disconnection as covered in 695.4(A) or (B).
(2) Disconnecting Means. The disconnecting means shall comply with all of the following:
(1) Be identified as suitable for use as service equipment
(2) Be lockable in the closed position
(3) Be located sufficiently remote from other building or other fire pump source disconnecting means such that inadvertent contemporaneous operation would be unlikely
And when equipment is required to be Accessible (as applied to equipment). The definition states "Admitting close approach; not guarded by locked doors , elevation, or other effective means." (Pad lock's)?
And for Readily Accessible : Capable of being reached quickly for operation , renewal, or inspections without requiring those to whom ready access is requisite to climb over or remove obstacles or to resort to portable ladders, and so forth.
So if the disconnect has to be readily accessible then it has to be reached "quickly for operation" I don't think a lock would allow for that.
Then you read a artical that say's:
230.92 Locked Service Overcurrent Devices.
Where the service overcurrent devices are locked or sealed or are not readily accessible to the occupant, branch-circuit overcurrent devices shall be installed on the load side, shall be mounted in a readily accessible location, and shall be of lower ampere rating than the service overcurrent device.
so now service equipment are allowed to be locked as long as there is branch circuit breakers that the occupant can get to.
[ December 27, 2003, 02:55 AM: Message edited by: hurk27 ]
ibdacat Is this what your looking for?
I'm not sure if this applys to light's
230.93 Protection of Specific Circuits.
Where necessary to prevent tampering, an automatic overcurrent device that protects service conductors supplying only a specific load, such as a water heater, shall be permitted to be locked or sealed where located so as to be accessible.
I think neon is the only discharge Lighting system that has a secondary that is over 1,000 volts which would require a disconect (see 410.81), so since a disconect is not required locking the disconect closed should not matter. As the disconnect now becomes just a safty switch.
As far as certain disconnects like for fire pumps, They are required to be locked in the closed position. There is other emergency systems that require this too.
695.4 Continuity of Power.
Circuits that supply electric motor-driven fire pumps shall be supervised from inadvertent disconnection as covered in 695.4(A) or (B).
(2) Disconnecting Means. The disconnecting means shall comply with all of the following:
(1) Be identified as suitable for use as service equipment
(2) Be lockable in the closed position
(3) Be located sufficiently remote from other building or other fire pump source disconnecting means such that inadvertent contemporaneous operation would be unlikely
And when equipment is required to be Accessible (as applied to equipment). The definition states "Admitting close approach; not guarded by locked doors , elevation, or other effective means." (Pad lock's)?
And for Readily Accessible : Capable of being reached quickly for operation , renewal, or inspections without requiring those to whom ready access is requisite to climb over or remove obstacles or to resort to portable ladders, and so forth.
So if the disconnect has to be readily accessible then it has to be reached "quickly for operation" I don't think a lock would allow for that.
Then you read a artical that say's:
230.92 Locked Service Overcurrent Devices.
Where the service overcurrent devices are locked or sealed or are not readily accessible to the occupant, branch-circuit overcurrent devices shall be installed on the load side, shall be mounted in a readily accessible location, and shall be of lower ampere rating than the service overcurrent device.
so now service equipment are allowed to be locked as long as there is branch circuit breakers that the occupant can get to.
[ December 27, 2003, 02:55 AM: Message edited by: hurk27 ]
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