Motor Starter

[Guardiano]

Hi forum members,

A conventional motor starter usuallly consists of a motor circuit breaker, a contactor and an overload device which is quite often combined in the motor breaker.The above three components are mounted in the same enclosure but I'm confronted with a problem because the motor breaker supplied is not provided with facilty to externally isolate the power source for maintenance purposes. The enclosure door has to be opened to physically isolate the circuit breaker before any repairs or maintenance is effected on this source.I am looking for the possibility to install a disconnector or isolator, with lockout and tag out facilities, to physically isolate the power source before any intervention is effected on this starter.This isolator is available at hand and my intention is to install it just before the circuit breaker.
I have seen many designs with a disconnector switch , used for isolation purposes, installed just before circuit breakers or switch fuses? Am I in the right direction?

Thanks.

Guardiano

 

[dpc]

Per NEC, the motor controller (starter) must have a disconnecting means within sight of the controller. It should be capable of being locked out to comply with upcoming NFPA 70E revisions.

The NEC contains definition of "within sight of".

If this is not in NEC-land, I basically have no idea.

David Castor

http://www.cvoes.com

 

[ScottyUK]

What kind of breaker? Most MCCBs can take a motorised actuator which would allow you to open it prior to opening the enclosure door. Once the breaker is open you could then secure the isolation.

A photo would help - if there was one attached the link has gone bad.


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If we learn from our mistakes I'm getting a great education!

 

[waross]

Many years ago it was common practice to install a fused safetu switch ahead of a magnetic motor starter. A magnetic motor starter was just that, a contactor with overload protection added.
These installations were replaced with combination starters (a fused safety switch or circuit breaker in one enclosure) and Motor Control Centers which also have lockable disconnecting means.
As far as I know, a safety switch with lockable operating mechanism and lockable cover is still acceptable to comply with the disconnecting provisions of the electrical code and safety codes.

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

 

[dpc]

FWIW - US Terminology:

Starter = On-Off device PLUS overload protection. Can be manual or magnetic.

Combination Starter - Magnetic Starter PLUS dedicated short-circuit protection, generally a MCCB or Fused Disconnect that also serves as Disconnecting Means for the Starter.

Basic NEC rules also require another disconnecting means within sight of the motor, but there are some exceptions to this.



David Castor

http://www.cvoes.com

 

[jraef]

If you are not in North America the references to the NEC (or CEC) would be pointless. But the issue is still valid, the direction you take is going to be dictated by the local codes wherever this installation is regardless of what we say or suggest. You should not be taking responsibility for this without being thoroughly up to speed on your local codes, that is where the answer lies.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
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[waross]

Well said Jeff.

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

 

[Guardiano]

Thanks all for your kind replies. I am not in the NEC world and where I am, basically, there is no local code. I usually use as a guide NEC codes to design my installation. I wanted to know that by using a disconnector switch ahead of the motor MCCB, I am not in violation of the code.

Guardiano