vw55
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- California
For 110-26 (a), does a dry transformer disconnect (either primary or secondary) qualify as equipment "likely to require examination, adjustment, servicing, or maintenance while energized..."?
Working Space Requirements
- Thread starter vw55
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- Location
- Lockport, IL
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- Semi-Retired Electrical Engineer
Re: Working Space Requirements
Yes. Almost anything can be worked on live. As bad a general practice as that might be, it will happen. From the perspective of the designer, I want to leave the space available for a future electrician to work on the equipment, no matter what the owner may say today about, "Oh, we'll always make the electrician turn it off first."
Yes. Almost anything can be worked on live. As bad a general practice as that might be, it will happen. From the perspective of the designer, I want to leave the space available for a future electrician to work on the equipment, no matter what the owner may say today about, "Oh, we'll always make the electrician turn it off first."
Re: Working Space Requirements
But Charlie, it says anything likely to " require examination, adjustment, servicing...." An electrician may work on the disconnect while hot, but that doesn't mean its required. Its his/her option to shut off the power.
I think this one can go either way, depending on the exact use of the transformer.
What if the transformer just feeds a single piece of equipment? I find it hard to believe that someone would have to work on a disconnect while hot, when the only purpose for the disconnect is to allow one to shut off the transfromer.
And what if the transformer (and disconnect) are mounted above the ceiling?? A "step-back" distance doesn't make much sense when you have to stand on a ladder.
Steve
But Charlie, it says anything likely to " require examination, adjustment, servicing...." An electrician may work on the disconnect while hot, but that doesn't mean its required. Its his/her option to shut off the power.
I think this one can go either way, depending on the exact use of the transformer.
What if the transformer just feeds a single piece of equipment? I find it hard to believe that someone would have to work on a disconnect while hot, when the only purpose for the disconnect is to allow one to shut off the transfromer.
And what if the transformer (and disconnect) are mounted above the ceiling?? A "step-back" distance doesn't make much sense when you have to stand on a ladder.
Steve
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Working Space Requirements
I think the word ?require? should be interpreted in a different sense. You are using the sense of, ?I?m the boss, and I?m telling you to do it live.? But there are some maintenance tasks (particularly in the troubleshooting line) that cannot be done without power. If the component is likely to ever require a troubleshooting or inspection task that can only be done live, then the NEC paragraph on working clearances applies. It does not matter that a person might chose to do a task today with all power off. The clearance is there for the person who may someday do another task that can only be done with the power on.
I think the word ?require? should be interpreted in a different sense. You are using the sense of, ?I?m the boss, and I?m telling you to do it live.? But there are some maintenance tasks (particularly in the troubleshooting line) that cannot be done without power. If the component is likely to ever require a troubleshooting or inspection task that can only be done live, then the NEC paragraph on working clearances applies. It does not matter that a person might chose to do a task today with all power off. The clearance is there for the person who may someday do another task that can only be done with the power on.
- Location
- Bremerton, Washington
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- Master Electrician
Re: Working Space Requirements
You could argue that every piece of electrical gear can be de-energized, hence no working space is ever required. But in court of law you would lose that argument.
My supporting documentation is:
Have you ever worked a piece of gear hot?
Why?
By the way some work has to be done hot, such as amperage or voltage readings.
[ April 18, 2005, 03:10 PM: Message edited by: tom baker ]
You could argue that every piece of electrical gear can be de-energized, hence no working space is ever required. But in court of law you would lose that argument.
My supporting documentation is:
Have you ever worked a piece of gear hot?
Why?
By the way some work has to be done hot, such as amperage or voltage readings.
[ April 18, 2005, 03:10 PM: Message edited by: tom baker ]
Re: Working Space Requirements
Also what I used to say: Everything is considered hot until you check it dead with your meter. Even if you are going into a simple fused disconnect to check fuses. It's hot until you check it dead. So you are working on something hot no matter what.
Also what I used to say: Everything is considered hot until you check it dead with your meter. Even if you are going into a simple fused disconnect to check fuses. It's hot until you check it dead. So you are working on something hot no matter what.
Re: Working Space Requirements
However, when a fusible switch is off, the line terminals are still hot.
Also, there is still a minimum working space requirement for parts with a voltage less than 42 volts or whatever. You still also need working space even if everything is deenergized.
Also, Alcoa's crane repair contractor told me that I am not fat enough read not a fat ethnic to work for Alcoa or any of their other customers. Took me a year to figure out that he was trying to help me by telling me how pursue a race discrimination laawsuit. Evidentally, the definition of heavy industrial is that a man has to weigh at least 250 pounds to work there.
However, when a fusible switch is off, the line terminals are still hot.
Also, there is still a minimum working space requirement for parts with a voltage less than 42 volts or whatever. You still also need working space even if everything is deenergized.
Also, Alcoa's crane repair contractor told me that I am not fat enough read not a fat ethnic to work for Alcoa or any of their other customers. Took me a year to figure out that he was trying to help me by telling me how pursue a race discrimination laawsuit. Evidentally, the definition of heavy industrial is that a man has to weigh at least 250 pounds to work there.
Re: Working Space Requirements
I still say in some cases the working clearance wouldn't apply. Voltage and current readings could just as easily be taken at the transformer. These disconnects are often fed from a panel breaker - shut off that breaker and the whole disconnect is off.
What could possibly go wrong with a disconnect that would require live troubleshooting? And how "likely" is that to occur? After all, the code doesn't say "may" or "possibly" - it says likely. To me, that means there is a certain probability of live work required.
I think working space for disconnects in general should be determined on a case by case basis by the AHJ.
Steve
I still say in some cases the working clearance wouldn't apply. Voltage and current readings could just as easily be taken at the transformer. These disconnects are often fed from a panel breaker - shut off that breaker and the whole disconnect is off.
What could possibly go wrong with a disconnect that would require live troubleshooting? And how "likely" is that to occur? After all, the code doesn't say "may" or "possibly" - it says likely. To me, that means there is a certain probability of live work required.
I think working space for disconnects in general should be determined on a case by case basis by the AHJ.
Steve
Re: Working Space Requirements
Steve, are you saying just because you went over and opened the breaker that the disconnect is de energized? How do you verify that the disconnect is de energized? You must take a voltage reading. That is the only way to tell if it is de energized. I have seen to many people misread even a properly labeled panel breaker. Luckily they were smart enough to check before they grabbed the fuse. Because since they had opened the breaker they figured they didn't have to open the disconnect switch, (don't ask me why they would bother to take out a tool to override the latch so they could open it with out opening the switch, instead of just opening the switch to open the panel, just things I have observed from electricians that have worked for me).
But, back to subject, you could of opened the wrong breaker, breaker poles may not of opened (been welded closed and breaker still seemed to operate). Everything is always energized until you read it with a meter, and do it the right way. Live source, checked equipment, live source, I am still even leery when I stick my hands on something even after checking it.
Steve, are you saying just because you went over and opened the breaker that the disconnect is de energized? How do you verify that the disconnect is de energized? You must take a voltage reading. That is the only way to tell if it is de energized. I have seen to many people misread even a properly labeled panel breaker. Luckily they were smart enough to check before they grabbed the fuse. Because since they had opened the breaker they figured they didn't have to open the disconnect switch, (don't ask me why they would bother to take out a tool to override the latch so they could open it with out opening the switch, instead of just opening the switch to open the panel, just things I have observed from electricians that have worked for me).
But, back to subject, you could of opened the wrong breaker, breaker poles may not of opened (been welded closed and breaker still seemed to operate). Everything is always energized until you read it with a meter, and do it the right way. Live source, checked equipment, live source, I am still even leery when I stick my hands on something even after checking it.
Re: Working Space Requirements
Boss:
I see what you are saying, but you can check for voltage just by waving a probe by the disconnect. I don't think that meets the intent of "likely to require examination....".
Your same arguement could be applied to everything from a receptacle to a stop switch. If the intent was that all electrical equipment needs working space, then why doesn't the rule just say "all electrical equipment"?
Just my opinion:
Steve
Boss:
I see what you are saying, but you can check for voltage just by waving a probe by the disconnect. I don't think that meets the intent of "likely to require examination....".
Your same arguement could be applied to everything from a receptacle to a stop switch. If the intent was that all electrical equipment needs working space, then why doesn't the rule just say "all electrical equipment"?
Just my opinion:
Steve
Re: Working Space Requirements
Troubleshooting tasks is where this comes into play the most. You need to room to work on this equipment (especially now that you have to wear some of the stuff that 70E calls for). The thing though is it is almost all electrical equipment.
One other note, I never trust and really don't even like my guys carrying the little magic wands that tell you if there is voltage present. If it does indicate voltage, fine but what level and if it doesn't indicate voltage did you really get it in the right spot. To easy to get complacent with them.
Just my opinion.
Troubleshooting tasks is where this comes into play the most. You need to room to work on this equipment (especially now that you have to wear some of the stuff that 70E calls for). The thing though is it is almost all electrical equipment.
One other note, I never trust and really don't even like my guys carrying the little magic wands that tell you if there is voltage present. If it does indicate voltage, fine but what level and if it doesn't indicate voltage did you really get it in the right spot. To easy to get complacent with them.
Just my opinion.
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