At our facility we have been getting in many machines with main disconnects set up so that you can turn disconnect on by closing the door without having to have the door latched. Now the last time I did any checking----this was not allowed. I know the JIC used to cover this and I think ANSI does now, but I am not sure. If some one knows where this is covered I would appreciate their input.
I know that at one time this was a requirement. If it was changed, I'd like to know when? If there is a fault you can have quite an arc flash, and if the door isn't latched even when you're standing to the side the door opening with the flash will deflect somewhat off to the side. I do not think that this is a good idea.
Would a professional really close the disconnect under a load without making sure the door is shut? And what is the layman doing messing with stuff he doesn't have any business messing with? The point:You cannot build a foolproof world,because fools will always find a way to defeat you.
Re: Machinery Disconnects#94892 08/19/0511:19 AM08/19/0511:19 AM
Pick me. I will be forever greatful for the requirement that a door be closed and latched before you are able to turn the disconnect on. Toward the end of a 12 hour day after getting motor hooked up, I had to get 3 new fuses to put in a 60 Amp Combination Starter. I just wanted to check rotation. The only reason door was latched was because the disconnect couldn't be turned on without it being latched. No load on disconnect till motor starts (my thinking at the time) Motor starter and motor both checked fine with me triplet meter. Well there happened to be a carbon track across line side of starter. When I turned on the disconnect, it blew the door off of the panel. I was off to the side and only wound up with a slight burn and scrape on my arm. However, I couldn't see or hear anything for close to an hour. No permanent damage. Sure did cause a lot of excitement though. It took out fuses in the power center and kicked out 2000 amp breaker in the sub station. The people yelling at me from 3' away trying to find out if I was ok were alarmed because I didn't answer them. This was after I had managed to get out of the door of the separate building I was in. I didn't know they were there that fast. I thought it had only take me 4 or 5 seconds to get out. I was closer to a minute. You move slower when you can't see anything... When Tom Clark grabbed my arm I told him I thought I was okay but I couldn't see or hear anything. I realize available fault current was considerably higher than it is now, but I still feel it is a good idea to have to have the door latched before turning on disconnect.