MCC powering transformer aux 3

[Sanchez01]

I know MCCs are commonly used for providing power to a motor circuit, such as pump or even motor etc. They have the OL/OC protection and starter cicuitry.
Question I have is, can I use one of the bucket from a generic 480V MCC cubicle to provide power for Transformer auxilliaries which do not have motor (such as cabinet heaters etc). I have some pumps and fans which need power from MCC, but I now also need to power my cabinet components (for say 10kA, 120V) so I was thinking of bringing in the 480V-3 phase power from the MCC to a small cabinet and stepping it down to 120V to power the cabinet components.
Anybody sees any problem with it? Hopefully I am not being too vague.

 

[jraef]

Assuming you are in North America and referring to UL Listed MCCs...

The MCC is the structure, the devices you put into it are up to you. So yes, you can certainly get what is called a "feeder bucket" that is just a circuit breaker in a cubicle that taps power from the MCC bus bars to send to any kind of load you like. Not at all a problem.

If you want to be able to turn it on and off remotely, order a "Contactor Feeder" bucket. it will have a standard thermal-magnetic circuit breaker and a contactor that you can control remotely. it will not have "overload heaters" as you would find on a motor starter.

But if you have an existing motor starter in an MCC, you cannot use that to feed any other load besides a motor. They are not listed (or intended) to be used that way. Likewise you cannot just remove the OL heaters and use it that way, the circuit breaker used in an MCC starter bucket is different and can ONLY be used as part of a motor starter assembly.

"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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[DANSES]

You can.
At least you still use breaker at feeder outgoing to protect your load and cable.

 

[waross]

Many MCC starters don't have a breaker, they have a Motor Circuit Protector. A motor circuit protector does not have thermal overloads and can not be used as a circuit breker.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

Sorry. I meant to say thermal trips, not thermal overloads.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ASimmons23]

Absolutely, as the other posters have said. The MCC is the structure for feeding local loads.

I have always fed lighting transformers, battery chargers, UPS bypass transformers etc. from 480V MCC's. Just put in a correctly sized molded case circuit breaker, size the cable properly and you're set.

 

[jraef]

On several occasions I used MCCs that had nothing but feeder breakers, not one motor starter. The way I saw it was as a poor man's draw-out low voltage switchgear!

"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

 

[Sanchez01]

What I collect from all your responses is that MCC can be used to supply power to my intended loads as long as the bucket has a breaker (molded case) NOT a MCC starter/protector. I guess that confirms my question, now only thing I need is an empty bucket in my MCC where I can install a ckt breaker.

Thanks to Jraef, Danses, Waross, ASimmons23. You guys made this post more than worthwhile.

 

[jraef]

Just a hint if you are running out of room. Some mfrs offer what are called "high density" starter buckets for small starters, or "twin" starter buckets that are only 1/2 as large as one. So for example if you have 4 Size 0 starters, each in it's own 12" bucket, you can replace them with 2 twin starter buckets that are 18" each and end up with an extra 12" space for your new feeder.

Elicit the help of your nearby supplier of that brand of MCC. If it's really old and no longer supported, there are numerous after-market MCC retrofit suppliers out there that will do whatever you need done. This is one that I use quite often:

http://www.pcsep.com/eMerchantPro/pc/viewCategories.asp?idCategory=17

"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