UPS hardwired output and Over current protection

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fun ee

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Location
Texas
Please provide your understanding on is the UPS output conductor hardwired in violation of 240.21. Is the overload protection provide internal to the UPS considered code allowable overcurrent protection for the conductors hardwired on it's output? If so, what code language tells you so? The only code I have found on UPS 645.11 and doesn't speak on this matter.

Thoughts?

Thanks Again
 

Canton

Senior Member
Location
Virginia
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Electrician
Please provide your understanding on is the UPS output conductor hardwired in violation of 240.21. Is the overload protection provide internal to the UPS considered code allowable overcurrent protection for the conductors hardwired on it's output? If so, what code language tells you so? The only code I have found on UPS 645.11 and doesn't speak on this matter.

Thoughts?

Thanks Again

Not quite sure what your asking? But yes the inverter output conductors are protected either internally or there is an output breaker in/on the UPS for this, and other features.
 

GoldDigger

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Not quite sure what your asking? But yes the inverter output conductors are protected either internally or there is an output breaker in/on the UPS for this, and other features.

:thumbsup:
Is the UPS designed for hard wired output as an option, or are you modifying one listed with receptacle outlets only?


Presumably the standards would be different between a portable UPS that is designed for plug in connection of specific equipment versus a hard wired UPS that is driving hard wired loads versus a hard wired UPS that is driving receptacles through Article 300 wiring and maybe even sub panels.
For the first one, anyway, the UL listing on the UPS should insure all the output protection you need.
 

fun ee

Member
Location
Texas
Thanks for the feedback. It is a UL 1778 listed device. Yet the overcurrent protection must be internal because there is no manual lever or operating device for disconnecting or tripping. Since UL 1778 states a listed device is designed for NFPA 70 and give that you can terminate hard wires to it, it makes since that 240.21 would only be met if the UL 1778 device provides the overcurrent protection.
 

hurk27

Senior Member
Thanks for the feedback. It is a UL 1778 listed device. Yet the overcurrent protection must be internal because there is no manual lever or operating device for disconnecting or tripping. Since UL 1778 states a listed device is designed for NFPA 70 and give that you can terminate hard wires to it, it makes since that 240.21 would only be met if the UL 1778 device provides the overcurrent protection.

You shouldn't be connecting a UPS to a circuit or feeder that is of a higher amp rating then the UPS is rated for, 240.21 is about taps from a larger feeder to a smaller feeder with the requirement of OCPD to be provided before any loads are applied to the feeder within a given distance from the tap, the UPS should be after this OCPD, in most cases a fusible disconnect would be installed ahead of the UPS that protects the UPS and or the by-pass contactor or switch's, I would believe that the UPS also has internal fuses on its input as well as protection on its output, smaller units may only have electronic overload protection for the output, buy like was asked is this unit designed to be hard wired or is it the type that has receptacles on the output?, is it single conversion or dual conversion? (does the load always run off the inverter or is it switch in when power fails)???

The way you are stating your question is not one that would be commonly asked for a UPS installation? if you can provide more data on the UPS and how you are feeding it and what it is feeding maybe we can give a more clearer answer?
 

fun ee

Member
Location
Texas
You shouldn't be connecting a UPS to a circuit or feeder that is of a higher amp rating then the UPS is rated for, 240.21 is about taps from a larger feeder to a smaller feeder with the requirement of OCPD to be provided before any loads are applied to the feeder within a given distance from the tap, the UPS should be after this OCPD, in most cases a fusible disconnect would be installed ahead of the UPS that protects the UPS and or the by-pass contactor or switch's, I would believe that the UPS also has internal fuses on its input as well as protection on its output, smaller units may only have electronic overload protection for the output, buy like was asked is this unit designed to be hard wired or is it the type that has receptacles on the output?, is it single conversion or dual conversion? (does the load always run off the inverter or is it switch in when power fails)???

The way you are stating your question is not one that would be commonly asked for a UPS installation? if you can provide more data on the UPS and how you are feeding it and what it is feeding maybe we can give a more clearer answer?


Yep there is no english degree for me, and sorry for lack of clarity. It is designed for hardwired connection (it has terminals not plugs). The incoming and outgoing wiring is compliant with their user manuals guidelines. It is an Eaton 9170 which has static transfer switch which can be configured to automatically transfer to incoming line. A circuit breaker sized per their guidelines protects the incoming wiring upstream & and a circuit breaker is connected to the output feeder. It is this output feeder that the code says should be protected at it's point of supply (the UPS terminals), and I agree it is not a tap per the code's definition of a tap. I just never have read anywhere in the code that UPS's are considered to provide overload protection to the output feeder. My understanding is that it does, but the code is not explicit about it. For ASD's, a similiar inverter type technology, it appears to be explicit.
 
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