Engineering Construction procedures - 480V MCC replacement and addition

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Dale001289

Senior Member
Location
Georgia
I have a couple scenarios and not sure how to proceed from a construction standpoint - in one substation, we're installing a new MCC in the same location as the existing MCC; in another substation we're installing a new MCC immediately next to an existing MCC, since space is available.

thoughts ???
 

ron

Senior Member
I have a couple scenarios and not sure how to proceed from a construction standpoint - in one substation, we're installing a new MCC in the same location as the existing MCC; in another substation we're installing a new MCC immediately next to an existing MCC, since space is available.

thoughts ???
Sounds good
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
i don't know what your question is. personally, if I were the owner, I would want the old junk removed in both cases.

To Bob's point, often times the old MCCs are going to be such that replacement parts or add-on buckets will only be available in the grey market, either as used/refurbished or from vendors who custom build them as aftermarket retrofit units using their brand of parts inside (Cutler Hammer does this) so you end up with a mash-up of different parts in the same lineup. All that can make any future replacement parts or buckets even more expensive than usual.

Also, the older MCC may be rated for a fault current determined BEFORE the new loads were added, which may have necessitated an increase in the service size and therefor the available fault current will be higher. Make sure you check all of the data on the old ones.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
i don't know what your question is. personally, if I were the owner, I would want the old junk removed in both cases.

I'm guessing that in Scenario A that the MCC is still in use. How do you keep functionality during replacement? What about adjacent live equipment? I'm not sure what the issue is in Scenario B, but possibly you need to interrupt service from time to time or are encroaching on the 30" limit for adjacent equipment, etc.
 
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