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Reuse existing MCC bucket to feed panel

Merry Christmas
B

bcm

Member
Location
Atlanta, Georgia
Occupation
Engineer
Happy Thursday, my sparky friends!

I have been asked to reuse a spare bucket in a 600A, 480V, 3 ph MCC to feed a 200A, 120/240V, 1 ph panelboard. I've never seen an MCC used for anything but serving motors in the past, but I haven't found anything in the NEC that prohibits serving a panelboard. It feels like a gray area code-wise.

As far as the design, the MCC is 600A, 480V 3 ph fed by 2 sets of (3) 350 MCM & 1#2 ground. The bucket is a spare from a removed 15 HP AC motor. Can I replace the "guts" (HOA, transformer, etc.) from the bucket with a 100A, 480V fuse or CB? I would then put a step-down transformer downstream which would bring voltage to 120/240 for the loadcenter, and wouldn't it also provide the required neutral?

Thanks so much for your input!
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
It is not a gray area. It is not prohibited and is actually very common.

The issue is with primarily the overcurrent protection being rated for branch circuits. If you have fuses you are good to go. If you have a circuit breaker it will probably need to be replaced.
 
D

David Castor

Senior Member
Location
Washington, USA
Occupation
Electrical Engineer
It's commonly done. No NEC issues as long as you have the proper overcurrent device. Just keep in mind that the Motor Circuit Protectors (MCP) commonly used in combination motor starters cannot be used to protect a feeder. MCPs do not have any overload (thermal) element, just a magnetic trip. You have to install a standard thermal-magnetic MCCB.
 
petersonra

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Its a common practice to feed all kinds of external branch circuits from an MCC bucket.

In fact, most MCC manufacturers have standard options for feeder breakers or fused disconnects and most also have a standard option for panelboard and transformer.

If the bucket is adequately sized for the transformer I would not be at all concerned about using it. Just take out what you don't need.

Another poster mentioned being aware that there is some chance that a motor circuit protector was used instead of a MCCB. If so, you should be able to get a MCCB of the same frame size to replace the MCP that would use the same handle.
 
B

bcm

Member
Location
Atlanta, Georgia
Occupation
Engineer
jim dungar said:
It is not a gray area. It is not prohibited and is actually very common.

The issue is with primarily the overcurrent protection being rated for branch circuits. If you have fuses you are good to go. If you have a circuit breaker it will probably need to be replaced.
Click to expand...
Thanks for your help! It's probably best in this case to replace it since my field guy didn't get me a lot of detail about the buckets in the MCC.
 
B

bcm

Member
Location
Atlanta, Georgia
Occupation
Engineer
petersonra said:
Its a common practice to feed all kinds of external branch circuits from an MCC bucket.

In fact, most MCC manufacturers have standard options for feeder breakers or fused disconnects and most also have a standard option for panelboard and transformer.

If the bucket is adequately sized for the transformer I would not be at all concerned about using it. Just take out what you don't need.

Another poster mentioned being aware that there is some chance that a motor circuit protector was used instead of a MCCB. If so, you should be able to get a MCCB of the same frame size to replace the MCP that would use the same handle.
Click to expand...
Great point! Thanks for bringing that up!
 
E

Eddie702

Licensed Electrician
Location
Western Massachusetts
Occupation
Electrician
Agree that it can be used and that the breaker if if not thermal magnetic needs to be changed.

I had a big argument with an in house electrician. They used an old bucket that used to feed a motor with a MCP and they used it for a feeder to feed multiple VFDs mounted on a wall. Told him he had to change the breaker. Eventually he saw it my way.

With an MCC the motor starter and the MCp work in conjunction with one another and have to be looked at as a complete package.

I have no issues using a mCC bucket for other uses although there may be a listing issue I have no problem doing it.
 
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
If you try to roll your own, you can get bogged down in trying to get older operating handle mechanisms and linkages to work with newer circuit breakers etc., then plugging unused holes in the door and after all that the assembly will not be UL listed.

Find the nameplate of the MCC and if it’s made by a manufacturer who is still in business, call up their distributor to give them the serial number and tell them you want a new bucket with a 100A FCB (Feeder Circuit Breaker). Every mfr offers FCB buckets.

If the manufacturer is defunct, you can probably get aftermarket listed buckets from Eaton, using their components but listed for the old MCCs.
 
ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
Jerzeysfinest said:
If I have a 200 amp breaker at the disconnect outside and the new mobile home has a 100 amp panel I can run the service with 4/0 aluminum wiring if the 100 amp panel accepts that wire correct ???? Seeing as the main panel won’t allow more then 100 amps anyway
Click to expand...
Nice try, but your other thread was closed. Your electrician should be able to help you.
 
Knightryder12

Knightryder12

Senior Member
Location
Clearwater, FL - USA
Occupation
Sr. Electrical Designer/Project Manager
bcm said:
Happy Thursday, my sparky friends!

I have been asked to reuse a spare bucket in a 600A, 480V, 3 ph MCC to feed a 200A, 120/240V, 1 ph panelboard. I've never seen an MCC used for anything but serving motors in the past, but I haven't found anything in the NEC that prohibits serving a panelboard. It feels like a gray area code-wise.

As far as the design, the MCC is 600A, 480V 3 ph fed by 2 sets of (3) 350 MCM & 1#2 ground. The bucket is a spare from a removed 15 HP AC motor. Can I replace the "guts" (HOA, transformer, etc.) from the bucket with a 100A, 480V fuse or CB? I would then put a step-down transformer downstream which would bring voltage to 120/240 for the loadcenter, and wouldn't it also provide the required neutral?

Thanks so much for your input!
Click to expand...
This is done all the time. Most MCC buckets can be replaced with a breaker or fusible bucket with no controls. I am doing a project right now that I have to feed new VFD controlled pumps out of an MCC. Nothing against code. An MCC is just a switchboard with controls built in to the bucket.
 
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