MCC Bucket Changeout Question
MCC Bucket Changeout Question
(OP)
I have to replace a size 1 with a size 2 starter. It's the same 12" space requirement. I've done an Arc Flash calc showing it's just Category 0. Are there any other issues with removing and replacing the bucket without shutting the rest of the MCC down.





RE: MCC Bucket Changeout Question
2. Make sure that you control the conductors you may have to disconnect to remove the bucket.
3. Make sure you know the locations of ALL the screws and locking devices that hold the bucket in place.
4. Have a competent standby person(s)outside the blast area. This person should know the location of the best communications device AND the switch/breaker that turns off the MCC you're working on.
5. Before work commences, have a meeting to discuss safety, the process of the task, and emergency measures.
6. When you start the process, if at any time things don't seem to go right, i.e., too much force is required, things stick, etc. STOP and investigate.
old field guy
RE: MCC Bucket Changeout Question
RE: MCC Bucket Changeout Question
Keith Cress
kcress - http://www.flaminsystems.com
RE: MCC Bucket Changeout Question
RE: MCC Bucket Changeout Question
Star for Keith - ain't it the truth. I was once told 'we have old electricians and we have bold electricians - we don't have any old bold electricians.'
"An 'expert' is someone who has made every possible mistake in a very narrow field of study." -- Edward Teller
RE: MCC Bucket Changeout Question
Looking at a Siemens MCC instruction manual I have, it makes no mention of having to kill power to the bus first.
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: MCC Bucket Changeout Question
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: MCC Bucket Changeout Question
I'm glad I said a SMALL wager
But I just checked a GE instruction book and don't find anything specific in there either. So I stand corrected.
Cheers,
Dave
"An 'expert' is someone who has made every possible mistake in a very narrow field of study." -- Edward Teller
RE: MCC Bucket Changeout Question
You're absolutley correct, but that was back in a time where rules were somewhat more relaxed. I swapped out dozens in my time, from live MCC's.
There were a lot of tasks we USED to do differently than today: manually racking out circuit breakers, rolling out PT drawers, etc. but in today's safety environment it's a different story.
old field guy
RE: MCC Bucket Changeout Question
Regarding the "projectile" comment from ScottyUK: Keep in mind that NEMA MCC design requirements are likely different from IEC MCC requirements. I was involved in a redesign of an MCC structure years ago at a better-left-unmentioned manufacturer because the base design came from Europe and we were to "NEMA-nize" it. A big issue was that NEMA required that there is a detente or stop point at which the bucket cannot be "jerked" off of the bus without taking another active effort to continue after it has come free. Some mfrs do it with a simple catch point and tab in the frame, requiring that the bucket be lifted off of the tab and designed so that this can only take place after the bucket has traveled far enough to clear the bus. Others do it by having a second mechanical device such as a quarter turn screw that must be turned. We had to create one from whole cloth because the IEC design had no provisions as such.
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: MCC Bucket Changeout Question
Did you do your arc-flash calculations based on the available current on the MCC bus? Unless this MCC has a very weak supply, Category 0 doesn't sound right to me.
RE: MCC Bucket Changeout Question
"The perfect is the enemy of the good." -- Voltaire
RE: MCC Bucket Changeout Question
Even though it is Category 0, we are still going to have the electricians wear gloves and face shields.
RE: MCC Bucket Changeout Question
A main with an INST function.