VFD wire entry

[Flex]

I was wiring up a small ABB VFD today and had to move around the control guys 300v rated wire so that I could get to the terminals for my 600v rated THHN. I got to thinking is this code compliant considering the only way to enter the drive is in the bottom?

 

[tryinghard]

Cheezy at best! I've often thought the same, even thought these are listed!

 

[Flex]

I figure I must be missing something cause surely they couldnt pass inspection at the countless jobs Ive seen them on.

 

[Cow]

The cheesiest drives I've dealt with lately are the Cutler Hammer MX? line. Stubbing a bunch of 1" conduits into the bottom of several 15-20 HP drives and the locknuts barely fit in the wiring compartment. So little room in fact it angles the connector because the locknut won't hardly sit flush.:roll: And they come factory with an oversized 1" knockout!!

On top of that the wiring compartment is 2"x2" so there is no room to maneuver your wires. I can't even believe someone designed something like this.

Third, what's up the split-bolt-like grounding stud in these things?? They couldn't use a terminal entry like the line/load conductors use?

All done now, I feel better.:grin:

 

[Doug S.]

All done now, I feel better.:grin:

I found this to be true on many drives in the 10 - 25hp range, when using a conduit adapter "plate" they all seem to come with. I'm pretty sure there is no way to meet be wire bending radius spec's even when using MTW.

I found (occasionally) screaming at the drive helps. It doesn't get hurt feelings, and doesn't mind if you use "naughty" words. :grin:

 

[tom baker]

I suspect a lot of these drives are intended for the international market. In Europe they don't use pipe and wire as we do, and the products are are smaller and designed with no extra space.

 

[Besoeker]

I suspect a lot of these drives are intended for the international market. In Europe they don't use pipe and wire as we do, and the products are are smaller and designed with no extra space.

Yes, it isn't very common to use conduit (here in UK) for installations. Mostlt it is steel wire armoured.
That said, for the sectors we serve, the drives are fitted inside a cabinet along with a means of isolation (fuse-switch as a rule) a contactor, and all the other control gear required for the system. So the problem of terminating inside the drive is eased to some extent.

 

[Flex]

But isnt this design a code violation?

 

[jim dungar]

But isnt this design a code violation?

It is almost impossible for equipment construction to be a code violation. It is very easy for the installation of equipment to violate codes.

Manufacturers can build what they want, you however need to install what is correct.

 

[Flex]

so the control guy needs to ues 600v rated wire?

 

[Doug S.]

so the control guy needs to ues 600v rated wire?

If wiring area of a drive is an "enclosure", and there is no barrier, yep ( 300.3(C)(1) '05 NEC ), but I'll stick with calling it a device.

"The control guy" = HVAC installer? I would think you could separate things quite nicely if you think ahead. If it's simple discrete I/O I would think "he" would be using 600v MTW already? If it's hack work tell 'm... ... ... It's your license. ( At least that's how it works in MI. )

 

[petersonra]

so the control guy needs to ues 600v rated wire?

Mostly that is what we would do, although sometimes we use a 300V shielded cable.

There is no requirement to seperate them inside the device, even though it is a good idea.

Think about it - often the 480V terminals are within a fraction of an inch of the 24VDC stuff.

We almost always put these inside another cabinet, but I have seen some big ones installed just as you mentioned. Sometimes the installers end up putting some kind of jbox under the VFD to make it easier on themselves.

 

[jdsmith]

...We almost always put these inside another cabinet, but I have seen some big ones installed just as you mentioned. Sometimes the installers end up putting some kind of jbox under the VFD to make it easier on themselves.

I just bought a 20HP AB 755 drive and a big junction box at the bottom is a factory option. I'll take some pictures of what it looks like with and without the "NEMA 1 kit" as they call the optional junction box.