MCC Rules

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Tim Ganz

Member
Location
Dallas, Texas
We are installing more roof fans in my building and we are using SMC-3 soft starts to run them. Where there are several fans close by in a group we were thingking of pwering them from a local MCC that has lots of free buckets.

One of the guys here has a large bucket that has a nema reversing starter in it and he wants to remove the reversing starter and put 4 soft starts in it with start stop pushbuttons on the front of the bucket and have a 480 x 120 trans former in it for control voltage.

This will all fit and work but is it correct and legal? I don't think so but he says it is and has been it much longer than I have. Just want to know what is correct?

I thought it was only supposed to be one motor control per bucket. In this case he is planning to use the bucket as a small control panel?
 
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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
We are installing more roof fans in my building and we are using SMC-3 soft starts to run them. Where there are several fans close by in a group we were thingking of pwering them from a local MCC that has lots of free buckets.

One of the guys here has a large bucket that has a nema reversing starter in it and he wants to remove the reversing starter and put 4 soft starts in it with start stop pushbuttons on the front of the bucket and have a 480 x 120 trans former in it for control voltage.

This will all fit and work but is it correct and legal? I don't think so but he says it is and has been it much longer than I have. Just want to know what is correct?

I thought it was only supposed to be one motor control per bucket. In this case he is planning to use the bucket as a small control panel?
I don't think I have a big problem with this. Presumably there will be individual OCPD for each motor. You have essentially created a group motor installation. You may want to look at the disconnecting means requirements for such an installation and make sure you are covered. If you have a local disconnect at the motor, it won't matter any. If you are trying to use the disconnect at the MCC, you could run into some issues.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
The bucket disconnect rating will likely be too large to provide the required protection of the soft starts. If you have room you may be able to install fuses and fuse blocks to provide the line side soft start protection.
 

dicklaxt

Senior Member
Do you have enough in your budget and physical MCC room to buy 4 new doors,buckets/starters and demo out the large bucket,and do a new install .

dick
 

Tim Ganz

Member
Location
Dallas, Texas
So a Bucket with a 60 amp breaker will service all the motors and I plan to mount soft starts with load side protection built in and line side fusing before the soft starts. There will be a non fused disconnect at each fan motor so within site and within 3 feet of the motor.

Does this plan sound ok? Meet code?
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
So a Bucket with a 60 amp breaker will service all the motors and I plan to mount soft starts with load side protection built in and line side fusing before the soft starts. There will be a non fused disconnect at each fan motor so within site and within 3 feet of the motor.

Does this plan sound ok? Meet code?
I see nothing inherently wrong with this plan.
 
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