National Electrical Installation Standards

Standards as High as Your Own

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Tuesday, July 30, 2019

Question:

If our UPS (batteries integral to equipment ) rated VA is 750VA/ 1000VA and the when main power is disconnected, the back-up time is not more than five minutes, we want to know if the EPO (Emergency Power Off) device is necessary or not?

Sammi Lee
A

Answer:

Hey Sammi thanks for your question. You don't mention what type of equipment the UPS (Uninterruptible Power Supply) is in but if the equipment is in an information technology room and you use the allowances of Article 645 all the conditions of 645.4 must be complied with. This includes a disconnecting means described in 645.10 as stated by 645.4(1). That disconnecting means is often a pushbutton device referred to as an Emergency Power Off switch. If the allowances of Article 645 are not being used then the disconnecting means described in 645.10 is not required. If your UPS is integral to the equipment and is limited to 750 VA the disconnecting means is also not required as stated in 645.11.

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