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Rahim84

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How would you wire this ?


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jumper said:
I am not sure I understand what you mean.

BTW: Did you notice that in your first pic the start button was incorrect? It was NC instead of NO.
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The normally open contact is usually how I see it in my second pic, but on the first pic it's located further away. So if I drew it how I'm used to.( like the second pic) It would just look odd to me.


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Rahim84 said:
The normally open contact is usually how I see it in my second pic, but on the first pic it's located further away. So if I drew it how I'm used to.( like the second pic) It would just look odd to me.


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Not the NO contact for the start button. The one for the m coil is what I'm referring to


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Rahim84 said:
The normally open contact is usually how I see it in my second pic, but on the first pic it's located further away. So if I drew it how I'm used to.( like the second pic) It would just look odd to me.


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Click to expand...

Gotcha. The pieces were probably just plopped down when the pic was made. The m coil it self is in a strange position also if you draw it out using the first pic placements.
 
Besoeker said:
I'd have put the OLs upstream of the stop button.
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but physically, our NEMA starters are not wired that way, they are wired per our conventions, which is for the OL contacts to be on the right side of the coil, all by themselves.

The OL contacts are shown incorrectly in that original picture too, they should be depicted as NC, not NO (assuming standard functionality). Whomever made that first picture was sloppy at best, possibly incompetent.
 
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Jraef said:
but physically, our NEMA starters are not wired that way, they are wired per our conventions, which is for the OL contacts to be on the right side of the coil, all by themselves.
Click to expand...
That's fair enough.
Most of our control circuits were a bit more complex so having all the relay coils with a common neutral made life simpler.
 
Tony S said:
I wouldn’t be happy with the O/L on the return leg. What would happen if there is a earth/ground fault on the return leg?
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Nothing. If you'll notice, the return is already grounded at the transformer secondary.


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jtinge said:
Nothing. If you'll notice, the return is already grounded at the transformer secondary.


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I suspect he meant what would happen if a ground fault occurred in the conductor between the overload contact and the M coil. It's a common enough observation when someone analyses the circuit that the overload contact will be shorted and there would be loss of overload protection. However, a physical observation of a common NEMA starter would indicate that the particular conductor in question is extremely short and a ground fault occurring on it is extremely unlikely. It is somewhat hinted at in Section 430.74 where a ground fault remote from the controller​ must not bypass safety shutdowns.
 
Tony S said:
I wouldn’t be happy with the O/L on the return leg. What would happen if there is a earth/ground fault on the return leg?
Click to expand...

Typically, on a NEMA starter, the overload relay is mounted directly to the contactor assembly so the 'return leg' is usually not much more than a few inches in length, making the possibility of a fault extremely small.
 
Tony S said:
I wouldn’t be happy with the O/L on the return leg. What would happen if there is a earth/ground fault on the return leg?
Click to expand...
If you mean the right hand leg of the ladder diagram, it is shown as earthed at the transformer.
 
I don't recall ever seeing a small motor MCC with the O/L's on the "left" side of the M coil. They usually wire a motor overtemp contact or interlock there, but not the O/L's.

We built a majority of our own motor starter/control systems, and if we used a separately mounted (thermal or solid state) O/L block we always put the O/L contacts on the return (grounded) side of the 120V starter coil. Mainly because that's the way the factory wired ones were and we wanted to avoid confusion. Control wise, obviously, it makes no difference. I've never really thought much about why. Is it just an industry/NEMA standard?
 
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meternerd said:
I don't recall ever seeing a small motor MCC with the O/L's on the "left" side of the M coil. They usually wire a motor overtemp contact or interlock there, but not the O/L's.

We built a majority of our own motor starter/control systems, and if we used a separately mounted (thermal or solid state) O/L block we always put the O/L contacts on the return (grounded) side of the 120V starter coil. Mainly because that's the way the factory wired ones were and we wanted to avoid confusion. Control wise, obviously, it makes no difference. I've never really thought much about why. Is it just an industry/NEMA standard?
Click to expand...

This is what I'm used to seeing as a starter configuration. From my Ugly's book.
 

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Jraef said:
but physically, our NEMA starters are not wired that way, they are wired per our conventions, which is for the OL contacts to be on the right side of the coil, all by themselves.

The OL contacts are shown incorrectly in that original picture too, they should be depicted as NC, not NC (assuming standard functionality). Whomever made that first picture was sloppy at best, possibly incompetent.
Click to expand...

depicted as NC, not NO

Just teasing...we all know what you meant...jst a tpoy:D
 
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