Motor wiring using rigged metal conduit
Motor wiring using rigged metal conduit
(OP)
We have a 40 HP coolant pump motor attached to its base with a vibration dampening system (rubber mounts). The motor wiring is run to the motor enclosure with RMC. Is there an NEC or NFPA code that would prohibit this?
Is this type of wiring just fundamentally wrong? My boss would like some documentation stating that it is an incorrect method of wiring before changing the conduit to a flexible conduit.
Anyone have any suggestions?
Is this type of wiring just fundamentally wrong? My boss would like some documentation stating that it is an incorrect method of wiring before changing the conduit to a flexible conduit.
Anyone have any suggestions?





RE: Motor wiring using rigged metal conduit
What aspect are you questioning?
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RE: Motor wiring using rigged metal conduit
David Castor
www.cvoes.com
RE: Motor wiring using rigged metal conduit
I am proposing that there should be a short lenth of flexible conduit and I am trying to find some supporting documentation.
RE: Motor wiring using rigged metal conduit
David Castor
www.cvoes.com
RE: Motor wiring using rigged metal conduit
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RE: Motor wiring using rigged metal conduit
http://www.cp.berkeley.edu/cds_ucb/Div-16-2.html
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RE: Motor wiring using rigged metal conduit
A quick review of NEC section 400 confirms dpc is right it is not a code requirement.
Even though not a code requirement seems prudent to prevent vibration of conductors can be a concern for chafing wires (even when protected by bosses at entrance to boxes) and other vibration-related problems.
Personally I would think it would be more important for equipment on isolators than typical rigid-mounted equipment... because equipment on isolators tends to shake more. Most of our fans have 0.1 - 0.2 ips bearing housing vibration. We have some fans on isolators that get up to 0.6 ips.
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RE: Motor wiring using rigged metal conduit
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RE: Motor wiring using rigged metal conduit
1> Gasoline dispensing pumps where everything must be explosion proof and even there we often used explosion proof flexible sections. With the advent of premade mineral insulated gas pump connection whips, no one can aford the labour cost of fitting rigid conduit.
2> The other was an interesting individual. He called for a machine to be connected by rigid stainless steel conduit rising vertically through the ceiling without bend or offset.
No description of the machine, no size, no conduit or cable size, no location drawing to locate the conduit entry and the pressure was on the electricians to pre-install the conduit.
The designer showed up and introduced himself by denigrating the local work force,
"We build these plants all over the place with no trouble, what seems to be the problem here."
The electrical foreman showed him the print in question and asked for some further information.
"Wait, now I remember. You know, I remember when I was drawing this, wondering just what the hell that was!"
Then he left the site.
My boss knew my short tolerance for idiots and moved my to another project the next day.
But, back to the issue at hand. There may be something in the mechanical codes that says something like;
"The resilience of the resilient mounts shall not be compromised by bridging them with rigid members such as conduit."
Bill
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"Why not the best?"
Jimmy Carter
RE: Motor wiring using rigged metal conduit
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Eng-tips forums: The best place on the web for engineering discussions.
RE: Motor wiring using rigged metal conduit
They don't care if the machinery functions, now or ever, or if it produces or transmits noise or vibration.
You probably should....
Mike Halloran
Pembroke Pines, FL, USA
RE: Motor wiring using rigged metal conduit
Whippee2
RE: Motor wiring using rigged metal conduit
Bill
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"Why not the best?"
Jimmy Carter