Shielded cable run with VFD output wiring

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sii

sii

Senior Member
Location
Nebraska
We just purchased a new industrial machine and I received a preliminary copy of the wiring schematic today. It shows many conduits run to remote pull boxes and from there split out to devices, mostly solenoids and limit switches. The conduits all contain both motor and control wiring. The devices are all to be wired using Belden 8770 shielded cable home-run all the way back to the MCP. Control is 24VDC, motor wiring is a mix of 240 and 480 VAC, some run via inverters, some via motor starter.

The number of control cables greatly outnumbers the number of motors on this machine. A little quick math tells me that it would have been far less expensive to run the motor leads in shielded cables and use MTW for the control wiring. Is there a reason to do it the way they did? The manufacturer didn't really give me an answer when I asked.
 
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
sii said:
...
The number of control cables greatly outnumbers the number of motors on this machine. A little quick math tells me that it would have been far less expensive to run the motor leads in shielded cables and use MTW for the control wiring. Is there a reason to do it the way they did? The manufacturer didn't really give me an answer when I asked.
Click to expand...
Top 10 answers they would likely have given if they weren't afraid of pissing you off:

10) "Because, well, just because." (basically the answer they ended up giving you).
9) "Because we don't like you and don't care."
8) "Because we like to make things as complicated as possible so that you have to hire our technicians to fix anything."
7) "Because my brother in law sells conduit and junction boxes, not cable."
6) "Because we don't really know what we are doing."
5) "Because we wanted to make it look like there was a good reason why we charged you so much for this machine by adding superfluous conduits and cables that make it look more complicated than it really is."
4) "Because up until this moment, we didn't know that shielded motor cable existed until you asked us why we hadn't used it."
3) "Because we are always trying hard to stay one step behind modern technology and methods, just in case there is something wrong with it that we hadn't thought of and we just started putting VFDs on our machines last year, so give us a break, OK? Sheesh..."
2) "Because we are idiots."

1) "Because we've always done it that way"
 
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