Wires rattling when elevator start

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So I have an honest question here... Rattling?

I've heard of conductors JUMPING, I hear them jump in the conduit every time I turn the lights on in our maintenance room (20+ fluorescents). BUT it's snap, thump, ping, tink, clunk, even WHAM on the big guys... ONCE, and just a few times its been up, then down so you get the previously mentioned stuff twice. Never a rattle?

Is this just one of those things I'm "missing out on"?


Thanks,

Doug S.
 
ev58 said:
It's about 150 ft away and there's not possible to pull the wires for slack, main electrical panel contains main bus bars and may damage the existing wires, also if I damage the existing wires then I will still have to run the new EMT, plus I will be short of time and put in power back to the elevator.
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Any chance of just pulling the MC through the existing conduit (if you go the replacement route)?
 
LarryFine said:
Any chance of just pulling the MC through the existing conduit (if you go the replacement route)?
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I will have to give a second bid to my customer, since I gave him one on replacing the wires and installing a new EMT, the reason I gave him a bid, was because another contractor before me, gave him an estimate five years ago, now the contractor is not doing any electrical anymore, (change trade) since I'm the one that is doing most of the work for him on his building, I end up with this nice job, I will check prices on MC wire on Monday, they maybe more expensive but is an option.
 
I had this same problem several years ago!
If I did not know better it is like going back in time, as I too had a ~200' run to an elevator though conduit, to roughly to same type of readings on the elevator. (I think at start the I speak of was hitting 1000A intitial, then 450, then the wye/delta would kick down to 175A???)

They argued about the soft starters and replaced them for well more than a year. The final solution was replacing the conductors with 'transposed' (Spiral) conductors. Which we got special ordered - they are twisted together with a binder tape on them - much the way you see inside of say MC or other cable. (I can't find out where they got it - because that supply house in now gone....) Sort of like this... (not sure if that company does cable that size?)

When the start-up of the motor happens with the conductors flat - the conductors bounce individually (rattle) - after you put in something like MC or transosed conductors they will work against each other and move like a snake. I used to get to see this often way back when I was in the service. We had some huge motors hooked up with 250mcm SO cable.

After we pulled the cable in - it still made some noise (a thump) but only in one place in an equipment room, as opposed to that 'short circuit type rattle' you are probably hearing now - which scares the death out any electrician - and freaks out tenants in the building.

Also - if you can use larger conductors to reduce VD at start-up could help.

Other options I had entertained were using 480 for the feeder length - then a transfomer next to the elevator. Or a new service on that side of the building just for it.

I wish you luck.... :rolleyes: Let us know how it turns out.
 
ev58 said:
I will have to give a second bid to my customer...
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You might want to hold off on that!

I checked on the size of 3/C 2/0 TC cable and it was too big for the conduit. I doubt MC is any smaller :rolleyes:

You'd likely have to go with "exposed" triplex or the stuff e57 described...
 
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e57 said:
Strip the jacket off or leave the jacket on '4 conductor' thhn
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The 3C 2/0 w #1 G has an OD of 1.332"
Area = (1.332/2)?*pi = 1.39 in?
Allowable Fill 1-1/2" EMT, 1 conductor/cable = 1.079 in?

As for removing the jacket, I certainly wouldn't ;)
 
Why not - supposedly it is 3 THHN or
XHHW-2 and a ground - just twisted with a binder tape? Just like I pulled.... (although mine was insulated THHN/THHW)

If you remove the tape - you have twisted conductors.... IMO still effective for the purpose needed to a degree - less buzz...

So say 3-2/0 XHHW-2 @ .219 + #1 bare @.087 = .744 < .814 (1 1/2" EMT @ 40% fill)

However, (from experiance) I would abandon the conduit and re-run it much larger as proposed in say 3/0 or 4/0... As well as bind and twist the conductors...

The only problem I see with stripping say a MC or SE is the conductor color that may be on the assembelled cable - i.e. white....
 
It is the noise of the horses from the horsepower running in the pipe. This is what my supervisor told me in 1984 when I asked the same question. I still believe him.
 
LOL quo..that was funny. :D

Here's a VIDEO of a test on open conductors, I have been told that the conductors in a conduit will behave in a similar manner.
 
e57 said:
Why not - supposedly it is 3 THHN or
XHHW-2 and a ground - just twisted with a binder tape? Just like I pulled.... (although mine was insulated THHN/THHW)

If you remove the tape - you have twisted conductors.... IMO still effective for the purpose needed to a degree - less buzz...

So say 3-2/0 XHHW-2 @ .219 + #1 bare @.087 = .744 < .814 (1 1/2" EMT @ 40% fill)

However, (from experiance) I would abandon the conduit and re-run it much larger as proposed in say 3/0 or 4/0... As well as bind and twist the conductors...

The only problem I see with stripping say a MC or SE is the conductor color that may be on the assembelled cable - i.e. white....
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I guess that can be painted or tape it an any color I want, and going back to your job, what size of wire did you use, how many and what color, also the noise stopped?
 
We got if I remember right 3-4/0 and ground - like I said we/I searched for a while and found our supply house (now out of biz) at the time (when I was with a different company) got it special order. It came BK/R/BL/G with a set of spiraling nylon ties on a huge 235' reel (I remember the length...) Took a month to get.... It was really easy to pull with a lot of soap - but there was one LB we changed to a box...

It did completly stop the rattle noise that went through the whole building which made the offices that it went through happy enough to not renegotiate their lease... :rolleyes: But it did still make a moderate thump in the equipment room.
 
Ive been looking - because there has to be some video of it out there some where - of conductors jumping around. All I can find is this and this.... Neither video demonstrates what happens when the initial starting current hit the (AC) conductors - in my case was ~1000A for a 1/2 second even with soft starts and a wye/delta motor. When laying flat and loose they bounce all over the place. When twisted clock-wise - they flex like a snake. They still move... but less. They are 1.) weighed down by each other, and 2.) when the EMF from the current hits that initial peak have a tendency to contract together. Binding them together pretty much cinches them together so they can not move - i.e. "buzz"

But for a length and amperage you are going - a high starting current is going to move the wire - to what degree it can be mitigated is up to you and your customer. What I am trying to say is - 'educate your customer' that you may not be able to "fix" this so that it goes away... But more that you can do some things to decrease how much noise it makes.

The one I had, I found out about because it would scare the death out of me. There a was doing a TI in the building and kept hearing that unmistakable 'short circuit' sound - REALLY LOUD! I would run around questioning my guys on the job - then I went tracking it down. Even though it was a feeder in a basement level - I could hear it on the 3rd floor. In the basement offices it was unbelievably loud. The feeder ran open across the ceiling from one end of an office to the other - and the people in there would physically jump when it hit. Theres an old thread about it here somewhere - one of my first here...
 
EV58,

Becarefull with using MC cable, in this area the Elevator Inspectors do not allow any type

of " flex " in the Elevator Equipment Room, except for the final connection to the control

cabinet. Your area may be different.

I'm glad the Elevator Co. recomended changing the pipe and wire and not you, it seems

like a big expense for something that a little properly placed spray foam could cure !!
 
ev58 said:
Hi, I need some help on this issue, my customer have a passenger elevator that when starts, you car hear a rattling noise coming from the wires that feeds the elevator, checked amps when motor start and shows 460 amps for one second and then settles down to 110- 108 amps, voltage 208-206, 3phase , motor shows 60 hp on name tag, main wires feeding are 2/00 on 1 1/2" emt, no ground wire coming from main disconnect, distance from main disconnect to elevator room is about 150 ft. If I increased the size of the main wires to 4/0000 for example would it stop the rattling noise? thank you in advance for you help. (This buidling was built about 20 years ago)
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Who is complaining and why? Like one building,I work in, the elevator main breaker buzzes everytime someone pushes the call button like the magnetic trip has had enough,ready to trip.(Not in 25 years.)
 
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benaround said:
a big expense for something that a little properly placed spray foam could cure !!
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How does one get spray foam into 150'+ of conduit? And have it still remain re-pullable as a conduit should be. No gripe - as I too have thought of the same - but figured if it did not work I was really screwed...
 
e57 said:
Ive been looking - because there has to be some video of it out there some where - of conductors jumping around. All I can find is this and this.... Neither video demonstrates what happens when the initial starting current hit the (AC) conductors - <snip>
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Mark, did you see the video in my post above? I feel it closely demonstrates the effect of AC cables in pipe.

Both videos you posted however are very impressive and still show the effects of magnetic fields on conductors.

I think there is video on Youtube of Locomotive jumper cables moving around...
 
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