ECN Forum Forums General Topics of the Trade General Discussion Area Triplexed feeders (re-post)

Just another thought, and don't know if it would work:

Could you install a transformer on both sides of the feeders and reduce the voltage drop and current flowing through the feeders from the disconnect to the softstarter?

208X480 and then 480X208 on the other side?

The 2 1/2" conduit runs through conditioned office spaces. And back to backing two tranformers was a thought, but no place to put them on either side.

Shortcircuit - The wire size is just under as the motor is 206 FLA, but I totally agree, a big mess up was done on planning the design for that voltage, distance, wire size. And I too am weary of 350, being too low as well. Although the use is intermitant, it is frequent, so LRA constitutes 50% of actual run time. I had given some thought to buss duct for major portions of it, but a little cost prohibitive. More than to replace with larger conduit to accomodate 500MCM w/ ground.

Now Steve, I know of no UL listed product for that purpose. We are also talking about a huge amount of cubic inches of conduit.

Sad news for me to read, but unfortunately it is very true - the Theory area is the least active / posted to.
Hopefully your question(s) will be answered in this area.

Per the loud and noisy bouncing Conductors at Locked Rotor, I have only a suggestion - which may or maynot be effective:

Noise Is Enhanced By External Issues - Locate And Nullify The Culprite

In the past, found a few noisy feeders where the noise was greatly Amplified from several ambient / external conditions - each scenario adding to each other:

<OL TYPE=A>

[*] Conduits loose in strapping means (not completely fastened),


[*] Loose Fittings - Setscrews not tight, or Compression "Nuts" loose,


[*] Conduits not completely set into Couplings - with the securing methods loose (as listed above),


[*] Excessive spacing between strapping means - like 15 feet or more between straps, where there should have been straps at 10 foot intervals,


[*] Loose Conduits + examples above, run on light gauge steel studs - with the framing being very loose fitting, or with loosly attached materials inside wall cavities,


[*] Same types of walls with abilities to create "Standing Waves", and/or resonate easilly from the vibrations of the feeders,


[*] Loose Flex against easilly resonated walls,


[*] Loose Flex against T-Bar Ceiling grids and supports for long distances.
</OL>

Found these scenarios from either an excessive starting surge (LRA), or fault condition.
Securing Conduits on one, along with applying some "External Damping Techniques", greatly reduced the noise of Locked Rotor situation - but did not eliminate it 100%

Wish I had conclusive examples and advise, but your condition may be like the ones covered above... who knows!

Scott35

Hey Scott, I did not mean to bag on the Therory area... Lots of nice things happen down there at the bottom of the page.

Anyway, this is all exposed in open cieling office space, and seeing that the sound can be heard 2 floors above, I doubt closing it would help. It's fairly well supported, and I hit most of the fittings with an impact wrench already.

e57...although a most difficult installation, has MC cable been considered as a replacement for the conduit?

shortcircuit

shortcircuit
THAT is a darn good idea!

Not sure if I can use it, but a darn good idea. You'd have to strap it down almost the whole length, as it will move on start-up.... Hmmmm...

I'm confused. What would force the MC cable to move upon start-up? The forces would try to push the conductors apart, not whip the cable about.

e57...you will let us know what you will do to fix the rattle and hum of that pesky feeder to that mamouth electron devouring elevator motor,won't you?

shortcircuit

I was due to replace it with 350mcm (Not my choice...) in the existing conduit, but all hell broke loose when I told them I had to shut down the house side of the main, that contains 2 other elevators, 4 house lighting, and some massive air handlers on the roof. Other-wise, I'd have to get inside the 1600A busses to pull it in. That and one tenant will have to vacate for 2 days during the pull. (1 day out, the next in. If it comes out at all!) So right now its on hold.


But I am there tomorrow to trouble shoot poss harmonic +/or neutral problem in one of the tenant areas that I didn't do...... Go figure! So might get some PQM then.... Apparently the lower floor has turned into a discotech. Lights and computers flickering on occasion. Maybe this service call will lead me into the main. I'm dying to open it up.

Maybe I'll take the camera, I have some pipe work you guys and gals might find interesting.

Hey e57...

you been letting Randy (lostAZhell) sub for you or something?

This sounds like the type of deals he usually gets!

[This message has been edited by DougW (edited 04-06-2005).]