ART 645

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pgordon

pgordon

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Location
Maine
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Electrician
Art 645.10 talks about disconnecting means for CRAC units .
Do I need shunt trip breakers to remove power to the units via: EPO system or can the EPO system
simply shut off the CRAC unit with its oun integral contacts with power still at the unit but shut down ?
Please advise .
 
The disconnecting means will be remotely activated via buttons near the prinicpal exit doors. You typically do it with relays and the CRACs typically have an EPO input to shut down the equipment at low voltage.

FWIW - remember that 645 is an optional code article and should be used with caution. I haven't done a new data center with an EPO in a long while.
 
ron said:
It is covered in 645. NFPA 75 covers it too but it is a standard often not adopted by jurisdictions.
Click to expand...

Where in 645, just 645.10? That doesn't say much about the use of EPO's or using a control activated shutdown vs. a shunt trip.
 
infinity said:
Where in 645, just 645.10? That doesn't say much about the use of EPO's or using a control activated shutdown vs. a shunt trip.
Click to expand...
645.10 refers to removing power from the equipment, not just turning the equipment off. That leads me to believe that using the integral shutdown contacts in the equipment itself (especially if that control is located within the zone) is not sufficient.
 
645-11 talks about the UPS. I understand it as , If the ups's are in the data center then you need shunt trip breakers to remove the input and output feeders . If the UPS 's are remote with PDU's in the data center then the remote EPO (can be manual buttons) will meet the code requirements .

645-10 talks about the CRAC units , is this the same requirement ? I am a bit confused on 645-10
 
GoldDigger said:
645.10 refers to removing power from the equipment, not just turning the equipment off. That leads me to believe that using the integral shutdown contacts in the equipment itself (especially if that control is located within the zone) is not sufficient.
Click to expand...

That is my take also and is the way the AHJ on our last 3 data center installs viewed it.
The integrated EPO shutdown on the CRACs and UPSes was not compliant according to the AHJ.
We installed a red mushroom switch that operated shut trip breakers on all of the equipment in the room, CRAC units, PDUs, UPSes, racked equipment, etc... to keep the AHJ happy.
The same circuit is also triggered by an alarm condition in the fire/smoke alarm systems.
 
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