Wires rattling when elevator start

[ev58]

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)

 

[bob]

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)

I think you meant to say "in 1 1/2" emt". Is it the wires or is it the conduit that is making the noise?

 

[ev58]

I think you meant to say "in 1 1/2" emt". Is it the wires or is it the conduit that is making the noise?

Yes that's correct, in 1 1/2" EMT, and it's the wires that is making the noise, EMT is inside the concrete from the main panel to the disconnect switch.

 

[bob]

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)

I had to leave. Sorry for the double post. When you have a change in current from zero to 460 amps, it creates a magnetic force field that is perpendicular to the conductor. It will cause the conductor to try to move and may move the conduit. I suspect that the conduit is not strapped well enough to prevent the rattling. I do not think a change of conductor would help except that the 4/0 would be stiffer and heavier. Check the conduit.

 

[ev58]

ok, I will check the conduit, only when it comes out of the concrete wall above the main electrical panel and above the disconnect switch in the elevator room, the rest is inside the concrete when they built the building.

 

[bob]

EV
I was posting at the same time as you. After reading you post I doubt that the conduit is moving. I am not sure if installing the 4/0 would stop the noise.
The force will still try to move the conductor but the 4/0 would be stiffer and heavier less room to move. Maybe someone else has a suggestion.

 

[ev58]

If I change the wires, will have to install new 2" EMT outside to meet the code for (3) 4/0000 wires + (1)#4 ground wire, and that means more room inside the conduit and the wires will rattle more?

 

[wireguru]

Am I correct in that the magnetic force pushes the conductors apart, so if the conductors were twisted in a planetary fashion, like mobile home feeder cable, that would eliminate the rattling right?

 

[charlie b]

Yes, twisting the conductors would stop the rattling. I'm not at all sure it can be done, however., nor that it would be a good solution. It might result in damage during the cable pulling effort, since the conductors will not be able to pass as smoothly through the conduit.

 

[Smart $]

Is putting a soft starter on the motor a feasible and code-compliant solution?

 

[broadgage]

Would it be possible to replace the wires in conduit, with a suitable multi core cable ?
(this would be the normal way to proceed here in the UK)

Since the wires in a cable are twisted together, and held together by the outer sheath, no movement can result and therefore no noise result.
I dont think that British type SWA (steel wire armoured) is much used in the USA, but perhaps something similar to underground feeder cable would be compliant.

As others suggest, larger conductors would still produce the same magnetic field, but would probably move less due to being heavier and stiffer, and therefore produce less noise.

 

[Smart $]

Would it be possible to replace the wires in conduit, with a suitable multi core cable?

I believe that's a highly viable solution

 

[Jraef]

I believe that's a highly viable solution

If you can pull multi-core cable through the conduit. Remember, it doesn't do corners as well as separate conductors. That is probably why charlie b mentioned that twisting the existing cables probably couldn't be done. 1-1/2" conduit is fairly tight quarters for 3 x 00 cables if they are twisted. By the way, that is called "triplexing" the cables and it is usually mentioned as a necessity in elevator installation manuals for this very reason (I deal with a few major elevator equipment mfrs.).

In answer to your other question, changing to a soft starter is also a very common solution to this problem.

 

[MarkyMarkNC]

Is putting a soft starter on the motor a feasible and code-compliant solution?

The elevator motor should have a soft starter already. I would be willing to bet there is something wrong with it which is causing this problem. I would have someone knowledgeable from the elevator company check this out before I started re-pulling wires.

I've run into rattling conductors before on large motor loads, and the problem every time has been something in the motor controls.

 

[ev58]

The elevator motor should have a soft starter already. I would be willing to bet there is something wrong with it which is causing this problem. I would have someone knowledgeable from the elevator company check this out before I started re-pulling wires.

I've run into rattling conductors before on large motor loads, and the problem every time has been something in the motor controls.

I will check with the elevator company today, to see if they have a soft starter in the motor, also the last I heard about the elevator, is that they adjust the variable speed allready and they can't do anything anymore, also this motor is been like that for the last 5-6 years that I know, (I have been going to this building off and on) no burnt out fuses, practically no problems at all, just the owner is concern about the noise, also you can hear the rattling thru the parking garage, and if could damage something else in the main panel or in the elevator equipment.

 

[ev58]

OK, I checked with the elevator company and they told me that they installed a soft starter about 2 years ago, also that they adjusted the soft stater already, and the next thing to do is, changing the wire, well I don't mind changing the wire, but I'm afraid that the noise will still be there, and that will be an expense that the customer is not going to like it, if the noise still be there, twisting the wires is an option, keeping the wires together with tape or something else every 2 ft will be another option, since I will be installing a new 2" EMT, I will be able to run the wires anyway I want.
I'm running out time due to customer and elevator company asking me when I will finish the installation. I appreciate and thank you all your help and ideas, I still will be reading all your posts until the day I start the job, which may be the end of next week.

 

[electricalperson]

i dont believe the wire moving in the conduit is an actual problem other than just annoying. can you try to pull slack out of the wires?

 

[augie47]

If you end up having to "repalce" the wire and it requires a new conduit run, how about using an MC cable instead. Seems the compacting of the conductors might eliminate the problem (plus you would not need to up-size)
just an idea... not tested.

 

[electricalperson]

If you end up having to "repalce" the wire and it requires a new conduit run, how about using an MC cable instead. Seems the compacting of the conductors might eliminate the problem (plus you would not need to up-size)
just an idea... not tested.

thats a good idea. im sure the electrical room is not that far from the elevator room

 

[ev58]

thats a good idea. im sure the electrical room is not that far from the elevator room

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.