VFD with integrated fuses and disconnect

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PeterOven

PeterOven

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NEC 2017, New Hampshire.

I have a pair of 10 HP pumps that I want to power from a single breaker on a 480Y/277 V panel. They will each use a VFD, and the VFDs will be mounted next to the motors. The 480 V panel will be more than 50' from the VFDs and pumps.

I have the option to buy from Danfoss a VFD with a line side disconnect and line side fuses all integrated into the NEMA 12 drive housing. Since they are provided by the manufacturer, I would assume that these fuses would meet the manufacturer's requirements for branch circuit protection 430.130(A)(2), and that the disconnecting means would meet 430.128 by having a rating not less than 115% of the rated input current.

Therefore, would it be accepted that the line side of these drives are a feeder, and not a branch circuit? This drive option seems nice if it can avoid the need for a separate fusible switch before each VFD to provide short circuit protection and LOTO.
 
petersonra said:
I suggest that you look in the code for the definition of feeder.
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Yes, my question boils down to whether the line side fuses in the VFD package are considered a branch circuit OCPD. I would say that they are such, since they meet the requirements of the VFD manufacturer. What I'm not sure is whether this is accepted in practice.
 
PeterOven said:
Yes, my question boils down to whether the line side fuses in the VFD package are considered a branch circuit OCPD. I would say that they are such, since they meet the requirements of the VFD manufacturer. What I'm not sure is whether this is accepted in practice.
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Whether it is accepted or not is irrelevant. If the code says they are the branch circuit overcurrent protection device they are which would make anything on the line side of it a feeder.

By the way most ul 508a panel shops can make you a similar box with all the pieces for a lot less than what you will pay from one of the drive manufacturers.
 
paulengr said:
The last OCPD before the load is the line between a feeder and branch circuit.
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Unless you can argue that it is a "supplemental" OCPD only. I believe that OCPD which is integrated into the load equipment often meets this provision. The demarcation between feeder and branch must, by definition, be within the building wiring system.
 
GoldDigger said:
Unless you can argue that it is a "supplemental" OCPD only. I believe that OCPD which is integrated into the load equipment often meets this provision. The demarcation between feeder and branch must, by definition, be within the building wiring system.
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That would suggest that MCPs (magnetic only breakers) in MCCs are not legal disconnects and the bus is branch, not feeder. So the main breaker for the whole MCC becomes the dividing line. NEC doesn’t differentiate UL 489 vs 508 vs 1077.


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In relation to the specific case, I have obtained from the VFD manufacturer the details on this drive:
Fuses are Type GG, they are user replaceable, but do not incorporate a rejection feature.

It appears that type gG is an IEC fuse type, and the fuses would be certified to IEC 60269. However they are not UL listed, and thus I will not be considering them to be the branch circuit OCPD. So in this case the line side of this VFD/disconnect/fuse combo device would be a branch circuit.
 
PeterOven said:
In relation to the specific case, I have obtained from the VFD manufacturer the details on this drive:
Fuses are Type GG, they are user replaceable, but do not incorporate a rejection feature.

It appears that type gG is an IEC fuse type, and the fuses would be certified to IEC 60269. However they are not UL listed, and thus I will not be considering them to be the branch circuit OCPD. So in this case the line side of this VFD/disconnect/fuse combo device would be a branch circuit.
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I think these are basically to protect the semiconductors and are not BC protection.
 
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