Industrial Control Panel motor circuit

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jb64

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Warwick, RI
We have a vendor supplied briquetter with a 20 HP, 48 FLA motor. The vendor tapped the motor contactor directly from the load side of the main disconnect for the panel. I have never done this, nor seen it done. Is this allowed by the NEC?
 

augie47

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What the NEC allows may not be relevant. Does the control panel have a UL or other NRTL label ?
 

don_resqcapt19

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And even if the installation is covered by the NEC, it may be code complaint. What is the rating of the supply side OCPD?
 

augie47

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The short answer is that with the controller being UL listed it only needs to meet UL requirements and not necessarily the NEC. Often those are similar but certainly not identical.

That said, I obviously can't see the install, but why the concern ? What would the options be ?
It would seem that if everything is sized properly the conductors could come from the load side of the disconnect on an NEC install and a 100 amp breaker for GF/SC protection would be acceptable for that size motor.
 

jb64

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Warwick, RI
The short answer is that with the controller being UL listed it only needs to meet UL requirements and not necessarily the NEC. Often those are similar but certainly not identical.

That said, I obviously can't see the install, but why the concern ? What would the options be ?
It would seem that if everything is sized properly the conductors could come from the load side of the disconnect on an NEC install.

Does that mean a panel that is UL listed is not necessarily concerned with NEC compliance? If that is the case, does UL 50, 508, 508A have a standard for designing and building industrial control panels? what about the AHJ? Do they normally opt for UL over NEC?
 

augie47

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Does that mean a panel that is UL listed is not necessarily concerned with NEC compliance?
Pretty much. I can't say the standards ignore NEC but they are their own 'set of rules'.
If that is the case, does UL 50, 508, 508A have a standard for designing and building industrial control panels?
Yes
what about the AHJ? Do they normally opt for UL over NEC?

Take a look at NEC 90.4 and 90.7
The AHJ has the responsibility of approving the materials/products/equipment/install. In almost every case, if the equipment is UL (NRTL) listed the AHJ will only look for alterations or damage as noted in 90.7
 

jb64

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Warwick, RI
Pretty much. I can't say the standards ignore NEC but they are their own 'set of rules'.

Yes


Take a look at NEC 90.4 and 90.7
The AHJ has the responsibility of approving the materials/products/equipment/install. In almost every case, if the equipment is UL (NRTL) listed the AHJ will only look for alterations or damage as noted in 90.7

Thanks, you have been very helpful.
 

Jraef

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... If that is the case, does UL 50, 508, 508A have a standard for designing and building industrial control panels? ...
To address just this point (because augie47 already covered the rest);

UL50 is JUST for the enclosure itself, it has nothing to do with what goes inside of it.

UL508 is the over-arching standard for Industrial Controls, which covers not only all of the components USED in a control system that are NOT covered in other UL standards (such as UL50 for example) but is also further broken up into sub-sections relevant to what those are and how they are used.

UL508A is the sub-section of UL508 that pertains to customized control panel ASSEMBLIES, meaning what a "panel builder" would make for a specific job or an OEM, using components listed under UL508 and any other relevant standards (again, such as UL50). UL508A can only be applied by a registered entity that has been trained and evaluated by UL to follow and adhere to their standards, and are regularly inspected to maintain compliance. This is why, as augie47 said, MOST of the AHJs out there will look for a UL508A label and accept it.

UL508B is an oddball section rarely used by most of us because it covers specialized relays used in IT equipment

UL508C is what covers Power Conversion Equipment, such as drives and power supplies.
 

don_resqcapt19

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Does that mean a panel that is UL listed is not necessarily concerned with NEC compliance? If that is the case, does UL 50, 508, 508A have a standard for designing and building industrial control panels? what about the AHJ? Do they normally opt for UL over NEC?
Assuming that the motor is a 3 phase, 230 volt motor, the NEC would permit the thermal magnetic breaker on the line side of the motor starter to be rated at 150 amps. I don't see an issue with the stater being fed from a 100 amp rated OCPD.
The code would permit the wire between the OCPD and the starter to be #4, even if the maximum permitted breaker rated at 150 amps was used.
 

Aleman

Senior Member
Location
Southern Ca, USA
I wouldn't see any problem with your load coming right off the disconnect unless there are multiple feeds and the lugs aren't rated for
multiple conductors.
 
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