Computer room E-Stop

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shockin

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I have a client who would like to replace his existing e-stop in the computer room. The e-stop shuts down the UPS. Instead of a standard "mushroom" style, he would like a selector switch with a tamper proof cover over it. My question is; is there a code that requires an e-stop for a UPS, and would this set-up meet the intent of the code. IMO it seems too cumbersome.
 
Look at Article 645. A lot of people think E-stops are required in data centers. They're not. But Article 645 says if you're going to have one as well as some other items then this is how it should be done.

I don't like them because it creates a single point of failure. But that's just me.
 
My question with 645 would be the sentence "Where a pushbutton is used as a means to disconnect power, pushing the button in shall disconnect power." This seams to be very gray. It seems that a selector switch would be allowed???
 
the first sentance of 645.10 'a means shall be provided' in the '05

the first sentance of 645.10 'an approved means' in the '08

also, in regard to LOTO, you cannot use a contol circuit for a disconnect, you must remove power. i would use a device that is listed as a disco.
i.e. a hubble 3pst. is listed. JMSO
 
According to 645.10 "an approved means shall be provided to disconnect power..."

Approved means, approved by the AHJ.

NFPA 75 10.4.8 also has the same language as 645.10.

Also refer to NEC Article 685, Intergrated Electrical Systems.

Looks like you would need the blessing of the AHJ to make the changes that you want.

Why cant you just add the stopper cover over the button and be done with it?
 
some local jurisdictions require an EPO in datacenters. San Francisco is notorious for this. Some disgruntled employee hit one (i think it was in the cal-iso datacenter that controls the state's electric grid).
 
billsnuff said:
also, in regard to LOTO, you cannot use a contol circuit for a disconnect, you must remove power. i would use a device that is listed as a disco.
i.e. a hubble 3pst. is listed. JMSO
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While this sounds like it could be true, could you site a code reference. I have always used a "control circuit" to shut down the UPS. The UPS makes provisions for this. But maybe it's not code compliant.
 
29CFR1910.147(b)

29CFR1910.147(b)

Energy isolating device. A mechanical device that physically prevents the transmission or release of energy, including but not limited to the following: A manually operated electrical circuit breaker; a disconnect switch; a manually operated switch by which the conductors of a circuit can be disconnected from all ungrounded supply conductors, and, in addition, no pole can be operated independently; a line valve; a block; and any similar device used to block or isolate energy. Push buttons, selector switches and other control circuit type devices are not energy isolating devices.
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http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_id=9804&p_table=STANDARDS
 
I don't believe the requirement for the disconnect in 645 is for LOTO.
 
i only mentioned it because of the possibility it could be used and the language change in the '08 (which may or may not apply, in this case) which says approved means, approved meaning acceptable to the AHJ, which to me could mean listed..........JMSO
 
It's semantics.

For a UPS, you want to kill output power in the vent of a fire, because remember, the fireman killing the building's main circuit breaker is NOT going to kill the output of the UPS! An E-Stop operating an air gap contactor is considered viable for that purpose. What they do in the Semiconductor Manufacturing industry is label the button EMO for EMergency Off (probably since there are usually no moving parts to "Stop"). This requirement is set up in what is called SEMI S-2, a set of industry standards for the Semiconductor industry similar to NEMA. Most device manufacturers have these now as standard products for the High Tech industry and as a result, the concept has spilled over into the Data Center industry as well. You can get shields and guards for them, some of which can accept padlocks. I don't believe that a Selector Switch would qualify however because there is an element of "panic operation" involved.
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But they do NOT qualify for LOTO rules with regards to disconnecting power to service the equipment, because you cannot guarantee that the contactor dropped out. Hence the term EMERGENCY. You still need a lockable isolating manually operated disconnecting device at the equipment to meet LOTO rules such as NFPA 79. Most likely that is built-in to the UPS or the UPS load center has LOTO capability, but just not easily accessible in an EMERGENCY.
 
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The emergency power off buttons we have just installed have a bit more "active" interface. It is placed in an enclosure that you have to open which sets off an alarm to make sure you know what you are doing. Inside is a selector switch that must be turned instead of pressed, then the UPSs shut down.

Overkill, maybe, but it put the datacenter folks at ease since the guy hauling boxes around couldn't accidentally shut the place down.
 
MIEngineer said:
The emergency power off buttons we have just installed have a bit more "active" interface. It is placed in an enclosure that you have to open which sets off an alarm to make sure you know what you are doing. Inside is a selector switch that must be turned instead of pressed, then the UPSs shut down.

Overkill, maybe, but it put the datacenter folks at ease since the guy hauling boxes around couldn't accidentally shut the place down.
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I don't think the cover with the alarm is overkill at all. I think it is becoming a standard install.

Steve
 
I thought the computer room power disconnect requirement came from an NFPA document on computer room fire protection. I could not find it in a quick search.

The cover idea with an alarm is a great idea.

If you are using a contactor, make sure the contorl circuit is from the UPS. I know of a major Ma Bell telephone system blackout because the computer room EPO contactor got its control circuit from the nearest house power outlet. It was wired by the fire alarm contractor. (Two utility services, two generators, redundant switchgear, eight ATS, four UPS systems and all critical power still went out.)
 
rcwilson said:
I thought the computer room power disconnect requirement came from an NFPA document on computer room fire protection. I could not find it in a quick search.

The cover idea with an alarm is a great idea.

If you are using a contactor, make sure the contorl circuit is from the UPS. I know of a major Ma Bell telephone system blackout because the computer room EPO contactor got its control circuit from the nearest house power outlet. It was wired by the fire alarm contractor. (Two utility services, two generators, redundant switchgear, eight ATS, four UPS systems and all critical power still went out.)
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There isn't anything that requires a "fail safe" EPO circuit. IMO, when it's pressed, the EPO switch should make contact, which applies power to a shunt trip to shut off the computer room. The exact opposite of how you would normally wire an Estop.
 
I agree with Steve.
If the 20A branch breakers feeding the EPO control panels are turned off, nothing happens except the control panel power indicator light goes off, and the BMS is notified of a trouble condition via a contact closure from within the control panel.
 
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