There is no code requirement that keeps you from locking a dicsonnect in the closed position is there? We've got equipment that is being turned off and causing problems. Our maintenance personel are hestitant to lock the switch closed but this would solve the problem. We would use a lock that all our maintenance people have a key to......... thanks. I thought I saw this recently discussed somewhere but could not locate the source.....
locking switch
- Thread starter cleveland
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- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: locking switch
Locking a disconnect in the ON position will not prevent any overload device from performing its safety function. If there is an overload or a short circuit, then the fuse will still blow, or an upstream breaker will still trip, or some other OCPD will operate. So there is not safety concern from this perspective. Bennie is right, in that there might be a safety concern if a person opened a disconnect switch under load, particularly if it is a large motor load. I have seen photographs of disconnects that have exploded, and killed the operator, when the operator opened the switch under load. So there may be a safety advantage to locking certain disconnects in the ON position.
The only downside I can imagine would be this: If there were a need to de-energize the equipment (i.e., not just stop the motor, but turn off all power) in an emergency (perhaps a life-threatening emergency), then what would you do? Is this the concern your maintenance people have?
Locking a disconnect in the ON position will not prevent any overload device from performing its safety function. If there is an overload or a short circuit, then the fuse will still blow, or an upstream breaker will still trip, or some other OCPD will operate. So there is not safety concern from this perspective. Bennie is right, in that there might be a safety concern if a person opened a disconnect switch under load, particularly if it is a large motor load. I have seen photographs of disconnects that have exploded, and killed the operator, when the operator opened the switch under load. So there may be a safety advantage to locking certain disconnects in the ON position.
The only downside I can imagine would be this: If there were a need to de-energize the equipment (i.e., not just stop the motor, but turn off all power) in an emergency (perhaps a life-threatening emergency), then what would you do? Is this the concern your maintenance people have?
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: locking switch
I forgot to answer your specific question. No there isn't such a code requirement.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: locking switch
This is not much different than a hotel where the OC devices are locked, under a provision the NEC allows when continuous building managment is provided.
In many cases the disconnect has to be locked on, an example is a wastewater liftstation with an exterior disconnect.
This is not much different than a hotel where the OC devices are locked, under a provision the NEC allows when continuous building managment is provided.
In many cases the disconnect has to be locked on, an example is a wastewater liftstation with an exterior disconnect.
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