Locking a disconnect in the closed position?

Better check with your safety person. I have seen this done with what is called an shop lock. Every electrician had an key to the shop lock, and they were an different color. Where I used these, we were required to put an tag explaining what was the issue when something was locked.

I would think in your situation as long as everyone who would be an emergency responder had a key it would be ok.

It is common to lock service disconnects in the on position. You can often see this at McDonald's or Burger King restaurants. However, most local authorities require that person(s) responsible and the local fire department have the key. Perhaps, this rule can be applied at your facility. I know of no rule in the NEC or OSHA that this practice violates.

| Here's a good question that came up at work. We have many 480v outdoor motor | disconnects at water plants. | | The bosses are worried that kids could come in and turn pumps off at night. | They want to lock the disconnects in the closed/on position. | | I can't find anything in the code saying you can't do that. Only it has to | be lockable in the open/off position. | | Anyone know of such a rule in the NEC, OSHA, etc? | | To me, it wouldn't make sense in case of an emergency. | | Thank you, Texas Master

Maybe you should have a barbed wire fence around the facility to keep them out. If that doesn't work ... well you do have 480 volts available :-)

When I was in high school, I was frequently given the task of switching on the lights for the football field. They had 2 outdoor disconnects and used

480 volts. The boxes had places to put the padlocks in closed or open. So we locked them in the closed position, too, presumably to prevent people turning the lights off during the game or other activities.

| It is common to lock service disconnects in the on position. You can often | see this at McDonald's or Burger King restaurants. However, most local | authorities require that person(s) responsible and the local fire department | have the key. Perhaps, this rule can be applied at your facility. I know | of no rule in the NEC or OSHA that this practice violates.

I have one of those "keys". It is about 4 feet long, weighs about 15 pounds, and has 2 big handles. Works on most padlocks, chain link fences, etc.

I was just thinking the same thing. I doubt the local fire department is going to take the time to mess around with a key-ring full of dozens of business's disconnect 'keys'. They too probably just use a 'master key' and cut the lock off!!!

daestrom

The disconnect is not there in case of emergency. It is there to reliably remove power from the device so it can be worked on. Most dosconnect switches are not even rated for load breaks.

You might want to consider I taller fence with bobbed wire. :)

it depends on the system used. One local town each commercial bulding has a small outside lock box with the master key and/or individual unit keys. The fire department has one master key that will open the all the lock boxes. This way the fire department is only dealing with the key(s) for the specific building they are at.

Yes, you get a point. The disconnect could even be inside the building, as long as it can be locked in the open position. The disconnect is NOT intended as an e-stop.

And you lost a point. In general, switches in a motor circuit, which is what the OP is questioning, must be horsepower rated, which means they are able to break the current of the motor in any condition of load or overload. The only common exception is that AC motors over 100hp (and DC motors over 40 hp) may use non-horsepower rated switches, but in that case the switches must be labelled "Do not open under load." In practice, this is rarely seen except in the case of double throw switches, which are hard to find over about 15 - 25 hp.

So, in a nutshell, if it doesn't have a "Do not open under load" label, it is designed to break (and make) the circuit under load.

Fire departments just pull the meter.

| And you lost a point. In general, switches in a motor circuit, which is what | the OP is questioning, must be horsepower rated, which means they are able | to break the current of the motor in any condition of load or overload. The | only common exception is that AC motors over 100hp (and DC motors over 40 | hp) may use non-horsepower rated switches, but in that case the switches | must be labelled "Do not open under load." In practice, this is rarely seen | except in the case of double throw switches, which are hard to find over | about 15 - 25 hp. | | So, in a nutshell, if it doesn't have a "Do not open under load" label, it | is designed to break (and make) the circuit under load.

I would not jump to the conclusion that it is installed correctly in the first place. Maybe it was correct at the time it was installed.

So why would a safety disconnect intended not for stopping the motor, but only for making sure no one starts it while someone is working on it, need to be anything more than isolation rated? Could it be horsepower rated only in the closed state?

No. A horsepower rated switch is also suitable for use as a motor controller, and is designed to start and stop an appropriate motor regardless of the motor load. Use of the horsepower rated switch as the motor disconnecting means gives you added flexibility and protection against the problems which could arise if an isolating switch were inadvertently opened under load.

"Steve Alexanderson"

2) Puller is exposed to arc flash and molten

I'm confused. Why would this occur with a "CT meter," as you call it?

Just curious.