On the issue of Cat5 in the rack, I would suspect that the NEC might consider a Sensor rack a device, where low and high voltage current HAS to exist side-by-side, just like the guts of a old Expression.
On the issue of how many wires in the rack, some food for thought from DN, and I admit to not being totally clear on the NEC and whether 2 load wires on a lug is allowed, but the trouble I have is that if the manufacturer has no opinion as to multiple wires on a lug (what does the lug manufacturer say ?), then it leaves you open to an installer configuring the rack in a method - in this case a lot of load wires that have potential heating issues, and is something that UL didn't test for and I believe that might be a problem.
Maybe send an e-mail to Steve Terry about these posts and see what he thinks ?.
Note that it's somewhat an academic issue, but in a few years I will likely be watching and supervising the install of another dozen racks at our new building and it wouldn't hurt to have it clear in my own head that the electricians should not be landing multiple wires, which they might be doing on a house light system as example.
Steve Bailey
Brooklyn College
Steve,
As it turns out, the lug is a combination of our design (pressure plate/tang) and an off the shelf terminal. We had to achieve UL approval on those two items in concert as part of the rack design. No doubt that conductor heating in the rack, and as important, free air space for plenum cooling are almost justification enough for only one conductor per lug. We've had some installations where two three and four wires per lug were installed and needless to say that after the dimmer modules were forced into the rack there was no allowance for cooling. Definitely UL did not test for multiple wires on a lug as you say.
Wires can be split and run multiple places through blocks and splices in troughs. We have seen quite a large number of installations where a trough is mounted just above a row of racks and wire nuts or terminal strips are used to send different circuit runs in different directiosn through conduit. It's really more effecient that way if you think about it. With dimmer racks have such a narrow access panel to them (very nice when making tight wall and floor space available) it really is difficult to get all those conduits attached to the SR48. Troughs solve these problems well.
So yes I will forward this to Steve Terry as he usually have nuggets of wisdom in such areas.
David
One of the things that suprises me is to hear about multiple wires in the rack, as I have to wonder why ?.
I can see scenarios where outlets/equipment is added afterward, and rather then trace out a wire for a tap/splice downstream, which is something that is seemingly beyond the capabilities of trade electricians (even though they sell all kinds of nice trace kits at every electrical supply house), they home run to the lug.
In a new install, I would put a stop to it. The system shouldn't require it, as one would think the cheaper method would be to splice locally, not home run back to the rack. The Nat'l Code (as well as all local codes) are/is very specific about numbers of wires in boxes, allowed junctions etc... and DN is correct that raceway/troughs do make life easier, but I like to think that someone is watching the install and pointing out poor install practices.
Ah... to live in a perfect world. Anyone know of one ?
FWIW and a rant about contractors. We just replaced our stage floor, a $475,000 project. Part of which was 39 new (as replacements) orchestra pit outlets for musicians. Poor coordination had the electricians install the brass covered receptacles (all are duplex Edisons), then the floor contractor blue taped the brass covers, then applied 2 coats of stain. The stain leaked right thru the tape and into the receptacles. The contractor then cleaned the top of the ivory receptacles, of which about 5 have a pool of hardened stain in the bottom of the receptacle so as to prevent a connector from seating. I am going to tell the college's project manager that the electricians will have to replace every outlet, as all of them look like they had an attempt at being cleaned. My concern is stain on the inside of the receptacle contacts, potentially causing arching with a load. Too friggin bad for the contractor, is my opinion.
Steve B.
My insight on multiple wires under a single lug
I have seen many small installations where the #1 FOH (and sometimes the 1E) had repeating circuit numbers left and right of center. (1-10 left and than 1-10 right) In these cases there were individual wires run all the way back to the rack. The reason, as I’ve been told, was cost. Due to cost cutting the rack was not fully populated with the thinking that the 2 wires could be separated at a later date when more funds were available to purchase more dimmers.
As much as any of us might think that doing this is a bit insane as when is a small installation ever going to get back to adding 9 or 10 new dimmers with the electrical work to make the changes….it does still happen. (I have yet to see this happen in Germany)
{Shout-out to my good friend David North…Thanks for jumping on the multiple wire grenade that I tossed. After Steve’s response to my post I kept telling myself…. ‘I hope David is reading this’ as he is the one with the double E and therefore much better versed in these sorts of things.}
Mike
I have delt with many sites where a rack is replacing a wall of 6 or 12k autotransformers (I guess there just isnt too many of them left out there) that are feeding load panels with a bunch of 10A breakers to loads. When they get moved over into a bunch of 20A breakers, loads often have to get combined.
Are the Sensor lugs designed for both solid and stranded wires? I have just been assuming they are, but I do not see anything to that effect in the installation manual. I see 90 deg Cu except for Gnd. And I see Torque ratings (except for Gnd, which says "manufacturer's spec...").
The fact is, I can not recall ever having to replace a damaged lug caused by a loose wire, in any installlation that was properly turned on.