We have existing electrical enclosure that consist of a 400 A LV breaker as main incoming and 3 MCP for a 50HP each 3ph 480 motor and 3ea motor starter. Is it permitted by NEC code for this type of installation? Could you please help to share the related article/section of the code? Thank you.
Multiple Combination Motor Starter in a Single Enclosure
- Thread starter glluga
- Start date
- Status
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
Are you talking about a listed assembly or something that you are building? #1 is allowed, #2 isn't. Must be listed.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Does Indonesia use the US National Electric Code?
Which article relates to what? The use of an MCP in a non-factory built combination starter? The use of multiple starters and a main breaker in a panel? The use of a non-listed assembly in an industrial setting?
What do YOU mean by the term MMCP"? That can mean different things in different countries. Here is means a "Mag-Only" or "Instantaneous Trip - Only" molded case circuit breaker. But in IEC world, i.e. Indonesia, that might mean a Motor Circuit Protector that is a device with adjustable thermal Overload settings and a fied magnetic Trip, something we call an MPCB here.
It's actually NOT fun to play a game of "20 questions" in order to extract information from you...
Last edited:
Hi Jraef, Our company use NEC and IEEE standard for electrical equipment and its installation. We have an existing installation in which in one panel enclosure we have :
a. Main CB, 400A, 600V, Schneider NS400N series breaker.
b. Branch MCP, 150A, Scheneider series, for 3EA motor starter. (thermal magnetic and instantaneous trip adjustable setting)
c. NEMA motor starter, size 4 - 1 unit (for 100HP motor), size 3 - 2 unit (for 50HP motor each).
d. Dry Transformer 480V-120V, 5kVA.
To clarify what I actually want to ask :
1. Is it permit by NEC code that we are having multiple CB and motor starter in one enclosure?
In my understanding, individual motor starter (include its MCP and its control wiring) shall be provided in one enclosure. I have not yet seen this type of installation. If it is not meet with NEC code, please share which article of NEC that is violated.
Sorry for being not clear in my question.
a. Main CB, 400A, 600V, Schneider NS400N series breaker.
b. Branch MCP, 150A, Scheneider series, for 3EA motor starter. (thermal magnetic and instantaneous trip adjustable setting)
c. NEMA motor starter, size 4 - 1 unit (for 100HP motor), size 3 - 2 unit (for 50HP motor each).
d. Dry Transformer 480V-120V, 5kVA.
To clarify what I actually want to ask :
1. Is it permit by NEC code that we are having multiple CB and motor starter in one enclosure?
In my understanding, individual motor starter (include its MCP and its control wiring) shall be provided in one enclosure. I have not yet seen this type of installation. If it is not meet with NEC code, please share which article of NEC that is violated.
Sorry for being not clear in my question.
MattS87
Senior Member
- Location
- Yakima, WA
It is absolutely acceptable. What you are describing is a MCC (motor control center). They are very common in industry
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Welcome to the forum,
Just like to say nice job on safety in the pic. Lock and signed tag. LOTO looks good.:thumbsup:
Dale001289
Senior Member
- Location
- Georgia
Even though its not a typical MCC its still acceptable. We see vendor panels all the time with multiple combination starters installed.
Please advice which NEC article that requires clearance between each component on the enclosure? eg. CBs, motor contactor, dry transformer, terminal block, etc.
Thank you.
The NEC does not address panel construction.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
I can't tell from your description or the picture for sure, but I see nothing that jumps out at me and says there is anything wrong with this design.
I think the problem is you are using some terminology wrong. A combination starter means something specific. It is a single assembly with a disconnect, OCPD, contactor and overload protection. You have all these pieces but they are not in a single chunk. Someone has built it this way. That is OK but it is not really a combination starter.
I think the problem is you are using some terminology wrong. A combination starter means something specific. It is a single assembly with a disconnect, OCPD, contactor and overload protection. You have all these pieces but they are not in a single chunk. Someone has built it this way. That is OK but it is not really a combination starter.
But in order to use MCP doesn't it need to be a listed combination starter?
Dale001289
Senior Member
- Location
- Georgia
MCP = Motor Circuit Protector is a magnetic only CB; it guards against short circuit only. It can be used as a stand alone protective device without overload relay, contactor etc., i.e., doesn't have to be part of a combo-starter. It all depends on the application.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
It could be that the whole assembly is UL listed as a UL508a control panel.
My understanding is that you can also assemble a set of parts including a MCP as long as the UL listing includes that assemblage of parts. You can't just come up with something on your own. But if UL says you can, then you can as it is a UL assembly regardless of who actually does the labor to put it together. This is somewhat analogous to series ratings of breakers. If UL says the series rating is OK, it is OK. If they don't accept that particular assemblage of parts, it is not OK.
I was referring to 430.52(7) which says this is allowed as part of a listed combination motor controller.
OK - that makes sense. Thanks
MattS87
Senior Member
- Location
- Yakima, WA
As Retirede said NEC does not have mandates for how a panel is constructed. NEC 110.3(B), listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling. So for clearances, that would be determined by the individual components manufacturers. However, if this is a 3rd party equipment that is uL listed then you don't have to worry about anything.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
that's what's called a "duplex" control panel, usually used for pumps, compressors and such where you have one main disconnect and separate starters. Totally legitimate, in fact that's a very nicely made panel, I see nothing of concern in there.
Not a concern of the NEC. The NEC is for FIELD installation of equipment. This is an assembly built in a shop, so the only NEC rules that apply are for your incoming and outgoing cables, and Article 409, which is about listing and labeling. Typically here, we would want to see that entire assembly UL listed under UL508A, which is the standard for custom industrial control panels. but even here, that is a State by State requirement that differs depending on where you are.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
If it has THERMAL trips, adjustable or not, it is NOT an "MCP". As I said earlier, the term "MCP" over HERE means a Magnetic-Only breaker, what the NEC refers to as an "Instantaneous Trip" circuit breaker as described in 430.52.C (3). If your devices have adjustable thermal trips, as I suspect they do because I don't see Overload Relays with the contactors, then they fall into the category of "Self Protected Combination Controllers" described in 430.52.C (6), also known now as a "Motor Protection Circuit Breaker (MPCB). Totally legitimate.
- Status