Manual motor starter as disconnecting means?

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Johnnybob

Johnnybob

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Colville, WA
So I have a chain driven by a 10hp motor. It has a fused disconnect in the MCC, then a 30A disconnect at the end of chain, which in turn terminates to a VFD. Unfortunately, where most of the crashes happen is about midway down the chain. What I would like to do, is put a size 1 manual motor starter there midway. My question is, can I use that manual starter as a disconnecting means so we could stop the chains and lock them out there, without having to go to the end of chains disconnect?
 
Johnnybob said:
So I have a chain driven by a 10hp motor. It has a fused disconnect in the MCC, then a 30A disconnect at the end of chain, which in turn terminates to a VFD. Unfortunately, where most of the crashes happen is about midway down the chain. What I would like to do, is put a size 1 manual motor starter there midway. My question is, can I use that manual starter as a disconnecting means so we could stop the chains and lock them out there, without having to go to the end of chains disconnect?
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Might not be a good idea, depending on the circumstances. If you use the MMS as a disconnect device, when someone closes it again the VFD is potentially going to start running right away. Safety related disconnect devices should follow all of the rules; in sight of the motor, lockable, controlled restart procedure. If you can make it meet all those criteria, sure. But it wouldn't need to be an MMS actually, just a disconnect switch.
 
Jraef said:
Might not be a good idea, depending on the circumstances. If you use the MMS as a disconnect device, when someone closes it again the VFD is potentially going to start running right away. Safety related disconnect devices should follow all of the rules; in sight of the motor, lockable, controlled restart procedure. If you can make it meet all those criteria, sure. But it wouldn't need to be an MMS actually, just a disconnect switch.
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Right, and the VFD IS set up as a three wire start, so it would need another start signal anyway, but I would rather see them us ethe stop button on the MMS, than have them just throw the disconnect. If they don't wanna go to the end of the line to lock it out, they're not gonna go down there to shut it off, is my thinking, but I want to get some input on it. I guess I could put a disconnect and another start/stop station, it's just another pipe for control if I could do it with a manual starter, is all. Whatever I do, it has to be done while they are not running, production is king, and maintenance should be , like, magic or something!:)
Thank you for the quick response, by the way.
 
Why another pipe

Why another pipe

Can you get 2 wires for an aux sw on the disconnect down the pipe. If you can it can control a small relay 120V control power, I have not seen a small ice cube relay get interfered with by noise on VFD wires.
 
Just remember that a shutoff which is only in the control circuit and does not interrupt power usually will not qualify for maintenance access or LOTO.
 
GoldDigger said:
Just remember that a shutoff which is only in the control circuit and does not interrupt power usually will not qualify for maintenance access or LOTO.
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Right, which is why the manual motor starter toe open all three phases of the 480V
The reason for the other pipe is, I don't really wanna run control power (120V) with the 480:happysad:.
Anyway, it's a moot point, as the MMS is not labeled as "Suitable for motor disconnecting means." Thanks for the help, though, guys!
I'll just order a 30A disconnect and install a mid-chain start/stop station. I sure don't want to cut any corners on safety, just hard to get stuff done, when shut down time is scheduled on a minute to minute basis:D.
 
Why not 480V and 120V in same pipe?

Why not 480V and 120V in same pipe?

Why not put the 480V and 120V in same pipe done all the time, both AC ??????
 
petersonra said:
how would you manage to "induce" enough voltage on a 120V circuit for it to matter any?
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So as a controls engineer you would see no problems with pulling your control wiring in the same pipe with multiple motor runs? I'm fairly new to this industry (went to college in 2009, been a trainee since I graduated in 2011) and everyone I've worked with have been adamant about keeping control and power circuits separate! And if we had any DC devices, then it is 3 pipes obviously:?
 
Johnnybob said:
So as a controls engineer you would see no problems with pulling your control wiring in the same pipe with multiple motor runs? I'm fairly new to this industry (went to college in 2009, been a trainee since I graduated in 2011) and everyone I've worked with have been adamant about keeping control and power circuits separate! And if we had any DC devices, then it is 3 pipes obviously:?
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In general, I do not have an issue with mixing 120V and 480V wires in the same conduit. There are some cases where this would not be acceptable, for instance it you wanted to take class 1 control wiring for motor A and run it with motor B.

I think you will find that putting more than two sets of motor wiring into the same raceway sometimes creates issues with derating that would require you to increase the ampacity of the wires.

I don't have a problem with specifications that exceed the bare minimum NEC requirements. If an end user wants to pay to run an extra conduit just for control wires, they are free to do so. It is not generally required though by the code.

Where in the code does it require AC wiring to be in a separate conduit from DC wiring? Again, there are some cases where wiring that just happens to be DC would have to be separated from wiring that just happens to be AC, but it is not a general requirement of the NEC.
 
petersonra said:
In general, I do not have an issue with mixing 120V and 480V wires in the same conduit. There are some cases where this would not be acceptable, for instance it you wanted to take class 1 control wiring for motor A and run it with motor B.

I think you will find that putting more than two sets of motor wiring into the same raceway sometimes creates issues with derating that would require you to increase the ampacity of the wires.

I don't have a problem with specifications that exceed the bare minimum NEC requirements. If an end user wants to pay to run an extra conduit just for control wires, they are free to do so. It is not generally required though by the code.

Where in the code does it require AC wiring to be in a separate conduit from DC wiring? Again, there are some cases where wiring that just happens to be DC would have to be separated from wiring that just happens to be AC, but it is not a general requirement of the NEC.
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It doesn't, under 600 volt's, again, it's just a habit I've learned from guy's I've worked with, especially if I'm just pulling in individual conductors. Shielded Beldens may be a different story, but then, Belden sheathing is so darned sticky, it doesn't play nice with other conductors, sometimes causing a huge cluster fustage in the raceway. So it's just easier and faster to pull them in their own pipe. If I'm running new conduit, it's just as easy to run 2, 3 or more extras at the same time. There's always stuff that needs to be added later, extra pipes are just too handy to not install them. Like pulling in control, I always pull in an extra group, that way I've got 'em if i need 'em.:)
P.S. I always de-rate where needed, and never skirt the bare minimums! Anything worth doing, is worth doing right!:happyyes: As the plant electrician, I am the end user, so I'd by far rather over-build it than not! Save myself some heartaches down the road.
 
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