On Wed, Sep 15, 2021 at 12:23 PM Daniel Seagraves < dseagrav@humancapitaldev.com> wrote:
On Sep 15, 2021, at 10:58 AM, Adam Thompson <athompson@merlin.mb.ca> wrote:
Now I'm curious... in all of the DCs and COs I've worked in - to the best of my knowledge, I haven't personally tested this! - the EPO button does *not* switch to emergency power. It turns off ALL equipment power in the space - no lights, no klaxons, nothing. In simpler setups, the EPO is connected to the UPS so anything plugged in to the UPS does dark instantly. In one DC I'm familiar with, the EPO switch kills all the UPS output *and* uses several relays to kill commercial power at the same time. In some, the room lights were not covered by the EPO switch, in some they were. Emergency exit lamps will continue to be lit, as they have internal batteries, and are required by building/fire code.
It was always my understanding EPO was to be used for “We have an electrical fire and need to remove the source RFN”, not “we need to be on the redundant power instead of city power and don’t want to wait for the automatic transfer”.
Well, there is the EPO button, which generally does that, and the (variously labeled) HALON/FM-200/GAS FIRE SUPPRESSION/GAS DISCHARGE button, which does the flashy lights and klangly bell and similar. This is fairly much always required by code, to give people time to evacuate before the gas dumps and they suffocate. People often refer to both of these as EPOs (or "the buttons that must not be pressed unless you have a REALLY good reason."). When I grew up (in South Africa), Halon/BCF was still in active use. When there was a fire (or you pressed and held the big red HALON button) a siren would sound and lights would flash for a few seconds to allow everyone time to evacuate the machine room. I'm assuming that things are now less stupid, but at the local University, the BCF was stored in large gas bottles, with a pyrotechnic valve to release it. The pyrotechnic charge was initiated with LA/LS (Lead Azide/Lead Styphnate) hot-wire initiators, which were supposed to be replaced every 2 years as part of some maintenance schedule - when LA/LS ages, especially in the presence of humidity, it apparently can form a much more sensitive crystal structure, which is very shock sensitive. The system was installed in the 1960s, and the initiators were replaced once or twice. Eventually, however, with sanctions, especially on things that can be made to go boom, it became hard to get replacements, and so they stopped replacing them... and eventually forgot about them ...... right up until sometime in the early 1990s, when someone accidentally knocked into the bottles with a loaded equipment cart. By this time the initiators had become sufficiently old and ornery that they decided that they'd had enough, and set off the pyro charges, which dumped all of the Halon into the room. Luckily everyone survived, but IIRC, two people passed out before making it to the door, and someone had to rush in and pull them to fresh air. The added gas pressure also cracked the big glass window (what's the point in having a big mainframe with flashy lights and spinning tapes if you cannot show it off?), and also caused a few head-crashes. W -- The computing scientist’s main challenge is not to get confused by the complexities of his own making. -- E. W. Dijkstra