Re: History of the EPO (Emergency Power Off)
> Many years ago when we were much, much smaller, the EPO was wired to a special EPO circuit breaker on the main panel which fed the subpanel for the datacenter room. A short on that breaker was like pressing the "test" switch on a GFCI breaker. Do most people who do have functional (as opposed to decorative) EPO buttons have them connected to the building/suite mains disconnect? or to the output of your UPS units? to a special EPO panel which trips the EPO cutoffs on other units? I'd guess what you are describing is what is known as a "SHUNT TRIP" coil in the large breaker you need to trip. This is a readily available option even on relatively small breakers - just feed it power and it trips the breaker. However it does need seperate power run through the EPO button and fed from a small dedicated 15 or 20AMP normal branch circuit breaker. Once the inspector has permanently departed, that little breaker can be "accidentally" left tripped and then the EPO function does not work - no "wiring/unwiring" skills needed. Ususal issues of liability, so decide if/how to inform other staff.
Re: History of the EPO (Emergency Power Off)
When I was designing a sizeable machine room at BU I remember getting into a bit of a debate with someone from buildings because they wanted (I think the numbers are right) 140F sprinklers and I wanted 175F sprinklers, images of an accidental sprinkler discharge dancing in my head (we had halon and all that, but 140F at the ceiling didn't seem all that high w/ all those big racks.) Me: *I've* got over $2M in computers in that room! Him: *I've* got over $20M building around that room! Me: You win! -- -Barry Shein The World | [EMAIL PROTECTED] | http://www.TheWorld.com Purveyors to the Trade | Voice: 800-THE-WRLD| Login: Nationwide Software Tool & Die| Public Access Internet | SINCE 1989 *oo*
Re: History of the EPO (Emergency Power Off)
From: "Sean Donelan" <[EMAIL PROTECTED]> Subject: History of the EPO (Emergency Power Off) The interesting thing about the EPO and data centers is it wasn't orginally for life-safety, but came out of a recommendation by IBM to the NFPA for property protection.<< Fwiw, the EPO on IBM's mainframes back in those days, had to be -pulled- and had a mechanical 'latch' that kept it from being pushed back in. Took both hands to reset it. --Michael
Re: History of the EPO (Emergency Power Off)
At 08:10 PM 7/25/2007, Sean Donelan wrote: Sometimes you need to revisit the rules. For example, for folks thought having automatic water sprinklers in data centers was a bad thing. Slowly folks have started to rethink it, and now automatic sprinklers are found in more data centers. I don't have hard data, but my experience is there have been fewer outages from accidental sprinkler discharges than from accidental EPO activations. There was an interesting study conducted by the US Air Force about fires and other failure modes in computing facilities protected with Halon/FM200/FE227 vs. dry pipe preaction. I know I saved the PDF, but I can't seem to find it at the moment. If my memory is correct, it boiled down to the fact that there had only been two fire incidents at all US Air Force installations and both were due to (surprise, surprise) human factors. One was a stray incendiary munition which breached the datacenter and other was due to a Jet A fuel spill and fire - which is odd because it is hard to ignite kero, diesel, jet A without atomization. The point of the study was that there was zero damage over a 30 year period from water based fire protection systems and I suspect it was pretty handy to have sprinklers when both datacenter fires happened. The munition breach of the physical structure would have rendered any gas based fire suppression system ineffective. In theory, I'm not a big fan of EPOs due to the "Is this the button to exit/open the door?" problem. One of our redundant 150KVA UPS units caught fire a couple years ago, the input breaker became the EPO since the on-board front panel EPO was completely ineffective (and it still would have been ineffective had it been connected to an external EPO button.) That incident prompted a design change in all of our new datacenter power systems since and all existing systems were also updated. Now all UPS units have separate input and bypass breakers and feeds. Previously we used a single feed, but you can't isolate a burning UPS without dropping your attached load when they share a single breaker and are tied together inside the unit where the fire is happening. Having discrete A & B power systems is also a very good thing! Many years ago when we were much, much smaller, the EPO was wired to a special EPO circuit breaker on the main panel which fed the subpanel for the datacenter room. A short on that breaker was like pressing the "test" switch on a GFCI breaker. Do most people who do have functional (as opposed to decorative) EPO buttons have them connected to the building/suite mains disconnect? or to the output of your UPS units? to a special EPO panel which trips the EPO cutoffs on other units? -Robert Tellurian Networks - Global Hosting Solutions Since 1995 http://www.tellurian.com | 888-TELLURIAN | 973-300-9211 "Well done is better than well said." - Benjamin Franklin
History of the EPO (Emergency Power Off)
The interesting thing about the EPO and data centers is it wasn't orginally for life-safety, but came out of a recommendation by IBM to the NFPA for property protection. But like many things, the original reasoning been lost to history, and the codes grew in different ways. http://www.datacenterknowledge.com/archives/2007/May/07/averting_disaster_with_the_epo_button.html The history of the emergency power off switch dates back to 1959, when a fire in the Air Force's statistical division in the Pentagon caused $6.9 million in property damage and destroyed three IBM mainframe computers. "Nothing gets the government.s attention like something that happens to government," said Sawyer. The National Fire Protection Agency (NFPA) was tasked to develop rules to address fire risks in IT environments. Sometimes you need to revisit the rules. For example, for folks thought having automatic water sprinklers in data centers was a bad thing. Slowly folks have started to rethink it, and now automatic sprinklers are found in more data centers. I don't have hard data, but my experience is there have been fewer outages from accidental sprinkler discharges than from accidental EPO activations.
