Reuse MCC for new motors/VFDs

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greenspark1

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New England
The scenario is a facility with an older SquareD Model 5 motor control center. It currently feeds a number of motors, including a couple of ~5hp fans we are replacing. We are providing new fans and VFDs for them. I would like to reuse the feeds from the MCC and keep just the breaker in use in each bucket (remove overloads, contactors, etc). Then the breaker will feed a VFD (remote mounted), motor disconnect, then motor. Any issues reusing MCC buckets like this? The breakers will be instantaneous trip, but I think the VFD will provide all the remaining protection- mainly overload.

2nd, the fans out outside the building so I'd like to put VFDs inside, about 50' away. Any issues running VFD wiring this far? I'm reading some concerns about voltage reflections but haven't ever seen them before for VFDs. I'll put motor disconnects at each fan with early break contacts to tell the VFD to turn off.
 
greenspark1 said:
The scenario is a facility with an older SquareD Model 5 motor control center. It currently feeds a number of motors, including a couple of ~5hp fans we are replacing. We are providing new fans and VFDs for them. I would like to reuse the feeds from the MCC and keep just the breaker in use in each bucket (remove overloads, contactors, etc). Then the breaker will feed a VFD (remote mounted), motor disconnect, then motor. Any issues reusing MCC buckets like this? The breakers will be instantaneous trip, but I think the VFD will provide all the remaining protection- mainly overload.

2nd, the fans out outside the building so I'd like to put VFDs inside, about 50' away. Any issues running VFD wiring this far? I'm reading some concerns about voltage reflections but haven't ever seen them before for VFDs. I'll put motor disconnects at each fan with early break contacts to tell the VFD to turn off.
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Let others chime in but I am pretty sure you will not be able to use the existing breakers without thermals in this way.

Keep in mind the NEC requires a disconnecting means on the line side and within sight of the controller, in this case the VFD so make sure to put disconnects in sight of the remote VFDs.
 
ptonsparky said:
I think the problem is with the MCP not being listed for use with the VFD, or some such minor detail.
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That is what I vaguely remember, something about mag only breakers can only be used in listed combinations with motor starters.

Hoping one of the guys sharp on this will chime in.
 
iwire said:
Let others chime in but I am pretty sure you will not be able to use the existing breakers without thermals in this way.

Keep in mind the NEC requires a disconnecting means on the line side and within sight of the controller, in this case the VFD so make sure to put disconnects in sight of the remote VFDs.
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Thx for the responses:
You are right on. I went digging and found 430.52 (C)(3)- Only allows instant trip CBs if used as part of a listed combination motor controller (w/ OL & SC for each phase). So, looks like we have to find new panels to power these VFDs/fans from?

I don't see that disconnect requirement anywhere in 430. The VFD needs its own disconnect, which must be within sight (430.102 (A)). And the motor needs its own disconnect, which must be within sight (430.102(B)). But I don't see anything that the motor disconnect has to be within sight of the VFD.
 
greenspark1 said:
I don't see that disconnect requirement anywhere in 430. The VFD needs its own disconnect, which must be within sight (430.102 (A)). And the motor needs its own disconnect, which must be within sight (430.102(B)). But I don't see anything that the motor disconnect has to be within sight of the VFD.
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What I was trying to say is you need a disconnect within sight of the controller.

If the controller is remote from the MCC and remote from the outside motor you may have need to have a disconnect at the controller.

You may already know that, I was just pointing it out based on your description.
 
petersonra said:
some schneider vfds are listed for use with some schneider MCP.

If they are not schneider VFDs it won't be a listed combination.
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Even if the are so listed, would it not still be a code violation if the MCP and VFD are not part of a listed combination starter?
 
petersonra said:
some schneider vfds are listed for use with some schneider MCP.

If they are not schneider VFDs it won't be a listed combination.
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No longer. UL put the hammer down on listing combination drives and soft starters with MCP breakers. They must all be T-M breakers now.

If you remove the starters you cannot use the MCPs as breakers, that's correct. But what you can do is buy the exact same T-M feeder breaker as what was used as the MCP and the handle mechanism etc will be the same.
 
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