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#175136 - 02/23/08 09:16 AM
Rooftop Equipment
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highground
Member
Registered: 11/14/04
Posts: 49
Loc: Chama, NM
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Hello,
I have a rooftop vent fan (3HP 480V) that the customer wants to control with a frequency drive. The panel is within sight (in the shop below). Is a disco required on the roof and prior to the drive to provide lockout capability, or does one on the roof suffice?
Also, do you guys provide additional motor protection in addition to the drive? (assuming it provides overcurrent protection)
Thanks in advance,
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#175145 - 02/23/08 11:22 AM
Re: Rooftop Equipment
[Re: sparkyinak]
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Yoopersup
Member
Registered: 03/04/03
Posts: 444
Loc: Michigan
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2005 N.E.C. 430.102 B States: Must be within sight of the MOTOR Unless meets Exceptions 430.102 (B) Exception (a)or(b).
Thats the way I read it anyway.
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#175159 - 02/23/08 02:23 PM
Re: Rooftop Equipment
[Re: sparkyinak]
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Yoopersup
Member
Registered: 03/04/03
Posts: 444
Loc: Michigan
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I agree that why I noted must be within sign . Kinda hard to see thru the roof!
BUT what if they had a skylight?
:))
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#177478 - 05/04/08 10:18 AM
Re: Rooftop Equipment
[Re: Yoopersup]
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mikethebull
Junior Member
Registered: 03/18/07
Posts: 17
Loc: Rhode Island
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I also agree although it is in 440.14. Also was a service receptacle within 25 feet or on the roof with the equipment this is 210.63.
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#177481 - 05/04/08 12:11 PM
Re: Rooftop Equipment
[Re: highground]
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renosteinke
Moderator
Registered: 01/22/05
Posts: 3052
Loc: Reno Nv USA
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From a practical standpoint, such a motor need two different types of protection; overcurrent as well as overload.
Overcurrent protection is what you get from fuses and breakers. Overload protection is what you get from the heaters in the starter. It's quite possible for a VFD to provide this secondary protection.
As for the disconnect ... I wish folks would forget the fine print of the code, and look at the application from a servicing standpoint. Do you want to shut it off before you work on it - or not? If so, doesn't it make sense to have some disconnecting means at the site of the motor? Why make / expect the guy to run up and down ladders multiple times, hope his LOTO is adequate, worry about automatic controls, etc?
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