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grover posted:This is probably what that grocery store's generator system looked like. Big loads (lights, air conditioning, break room) would be on the main distribution panel, and emergency loads (cash register, fire alarms, emergency lights, etc) fed from generator via the emergency distribution panel. Registers each had their own individual UPS, and were not run from generator power (oddly, every scale in the deli, meat dept, etc was on generator power). The emergency lighting up front was basically the dark lights - the ones that didn't shut off at night (mostly 277V fluorescent, a few were MH). Backroom lighting was high bay MH with emergency halogen, though the halogens had been dead for at least a decade by the time I left. Adding to the fun, the UPSs on the registers were modern intelligent UPSs, along the same lines of what I have on my own PC... but they weren't ever tied into the registers as more than power (no USB cables connected) - you'd get about a minute of constant beeping from under the counter before the registers powered off without shutting down. They were running Windows XP (NCR RealPOS), so IMO there's no reason not to do a graceful shutdown. I know it was a break before make ATS (the dark lights would all give a tiny flicker when it switched back to poco, and a good chunk of the MH high bays would shut off at the same time), and it was a Kohler natural gas set on the roof. IIRC, dark lights (about 1/20 of the normal sales floor lighting), "halogen backups" in the high bay MH fixtures (again, long dead aside from the random one here and there - the last power outage I went through there showed that 4, out of about 75, high bays had working halogens; all 75 were equipped with them), scales, about half of the ceiling fans in the produce department, cash office outlets (no lights, but the fans and space heaters kept running just fine), electric doors, and exit signs were on the generator. A handful of MH high bays would eventually light up, but since they'd been shut off while hot (and the bulbs were run until they either exploded or quit lighting up), it took several minutes for them to consider a re-strike. I know none of the comms stuff was on the gen set - phones, PA, and anything requiring online authorization (credit cards, debit cards, checks) took a poo poo. CCs would be approved in offline mode after about 30-45 seconds, same with checks; food stamps and debit would be declined after about 2 minutes. Oddly, the music system fired back up as soon as the generator came on - so I guess the PA amps were on backup power, as was the satellite receiver. But the phone system (which sat about a foot away from the sat receiver and PA amps in the same closet) was not. The phone system is how they do pages on the PA...  And no, the fire alarm was not on the generator; it would be beeping nonstop about AC failure until the power came back. Though it was usually beeping due to about 50 ground faults anyway.  The panel tied to the ATS was literally the size of my breaker panel at home (house has a typical mid 90s 100 amp service). It was certainly some form of 3 phase (the lighting was all 277), but I counted over 30 panels in the store at one point. All crammed full. I haven't worked there in nearly 4 years, but I do remember it taking about 20 seconds for the sales floor dark lights (again, fluorescent) to light up after the power went out. I'd assume that was partly "wait to make sure it's definitely out" combined with "stone cold natural gas engine firing up, running up to speed, and stabilizing a bit before the ATS says 'oh hi'" It was amusing when the store's own equipment dropped a phase during an ice storm. The phase loss was caused by a 1000A breaker doing the  bit while the store was closed (power went off-on-off-on about a dozen times in under a minute, according to the overnight stockers - guessing it didn't like the inrush of about .. 40? compressors nailing it so hard). There was phase loss detection on about 1/2 of the 3 phase stuff. It was a high 6 figure insurance payout between equipment and lost product. Store was built in the early 90s, last major electrical renovation was around 2001. I worked there from 06-10. Three-Phase posted:This video demonstrates what happens when you try to parallel a generator that is out-of-phase. Several times in a row. Something something magic smoke escaping holy poo poo I'm glad I wasn't near that  Three-Phase posted:If you have a switch that breaks before makes, you can just switch from one source to another. So you are on one source, the system disconnects from power supply one, and connects to power supply two. I can definitely see a motor causing a huge dip. Especially a 20HP, which, at least to the best of my knowledge, is larger than anything I've been close to. My neighbor's 5 ton heat pump makes my lights dim noticeably, I can't even imagine what a 20 HP motor could do to its neighbors at startup. So even with a very fast transfer switch, as long as it's break before make, and assuming no massive motors, there's no real harm in the split second switch between generator and utility power? How about if there's 3 phase motors in the mix - do they just kind of go  and sync to the new frequency quickly? Or do they go up in smoke like the genset video? Assuming there's not a delay allowing them to spin down.Something that's been bugging me for a bit - awhile back, I got bored and looked up brownout/blackout videos (yeah, I'm a weird  like that). I found one that claimed to be of a Wal-Mart running on a diesel generator (closed due to weather, filmed by employees), and claimed the generator was running out of fuel. The lights started getting incredibly bright, then dim, then another section would do the same, etc etc etc until about 30 seconds later they were on only battery powered lights (said lights were also flashing on/off as the lights in that section of the building got super bright/super dim). What causes that? Was it the generator spinning down and saying "what is this 60 hz thing"?
randomidiot fucked around with this message at 12:05 on Feb 7, 2014 |
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Feb 7, 2014 11:55
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So I got to gently caress around with a fire alarm system for the first time yesterday. Working for a new shop that does mostly residential work but they do some work for condos and apartment complexes as well. Got to install some strobes and pull stations and watched my journeyman program and flash the fire panel. He said if I decide to stick with this shop they will send me to fire alarm school. I also learned that if you touch the pos and neg wires together the firetrucks come.
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Feb 7, 2014 13:56
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I've messed around with residential alarm panels as a DIY (both Honeywell/Ademco and DSC). Haven't ever touched a fire panel, though the DSC panel I have supports smokes, heat detectors, pull stations, etc. Can't do strobes or any addressing with it though, since it's a home/small commercial burglar system (with fire support added as an afterthought). For that matter, it only has 1 siren output (though it does the 3 pulse bit if fire has been tripped). Alarms in general can be a pain in the rear end to program if you're working from a keypad, not so bad with a laptop.
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Feb 9, 2014 08:41
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https://www.youtube.com/watch?v=ow84TU3g9bk
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Mar 3, 2014 03:22
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ENDUT! HOCH HECH! Seriously though, that was pretty awesome/scary.
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Mar 4, 2014 00:29
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Working in a restaurant with wimpy 3 phase (120/208/277, no 480 available as it sits) We have three 208 volt ovens (gas, but 208 for everything else). This is the first place I've worked in where the ovens are not somehow tied into the vent hood. I've walked in more than a few times and found myself immediately dizzy, thanks to 3 gas pizza ovens running full bore with the vent/fresh air fans not running for a few hours. The exhaust and fresh makeup fans are 120V. What would it take to somehow set it up so that the ovens can't be turned on without the fans running? Previous places had either 120V versions of the ovens, or 208/277 fans that were tied into a DPST switch that also cut power to the ovens. I know this isn't wired to code at all (the building is only a few years old), but I'd like to present code-compliant options that would minimize cost to the owner.
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Mar 11, 2014 07:12
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some texas redneck posted:Working in a restaurant with wimpy 3 phase (120/208/277, no 480 available as it sits) What controls the gas flow to the ovens? You could wire a normally-open relay to the oven supply such that it only gets power if the fan is energized. However, if the gas flow is some manual valve, you've gone from having the ovens on to flooding the place with gas. Welcome to explosion-town.
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Mar 11, 2014 19:15
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The ovens are electronically controlled - if they lose power, the gas valve closes immediately. Internally, they're much like any gas furnaces from the past 20+ years - they have an ignitor (no pilot), an electrically controlled gas valve tied into a thermocouple, blower motors, and overtemp sensors that shut off the gas if poo poo gets too hot. Except they heat to 500 degrees (with an adjustable temp display on the front), have a conveyor, and everything is a lot bigger than what you'd see in a household furnace (and runs off of 208V/277V instead of 120V). If it goes into overtemp, the gas portion shuts down, and the blowers will run until they're shut off (only if the oven drops below 200F - we had this happen a few weeks ago on one oven, the display was flickering between 32F and 650F; there was a bad crimp between the controller and main temp sensor, from what I was told - it went into overtemp after burning the poo poo out of several orders). Tiny picture, but this is what we have (ours are reversed to run right to left, which puts the controls at the other end - but it's otherwise identical).  3 switches - blower, heat, conveyor. Heat won't run without the blower running; if you shut off all 3 switches, the blower continues to run until the oven drops below 200F. If you really want info on them, it's the PS570-3 with leg extensions. Most places I've worked in had an electric valve tied into the main oven gas feed to all of the gas appliances - if the fire alarm was triggered, or someone pulled the Ansul "oh poo poo" trigger, the gas would be shut off automatically to everything in the store. Also, every place I've worked had the exhaust/make up fans tied into the oven power in such a way that the oven had no power whatsoever unless the fans were running. I haven't worked in any restaurant built since the 80s that didn't have some form of automated gas shutoff tied into the fire alarm before this place (built in 08). I'm thinking the easiest way to fix this clusterfuck is #1, add CO sensors (because who the gently caress packs 7 gas appliances into a building without them?), and #2, maybe add some contactors that would prevent the ovens from powering on without the fans running? The ovens each have individual plugs (some sort of 4 prong twist 208/240/277 NEMA plug), with a 120V switch nearby for the vent hood. Said switch powers exhaust + make up fans, plus the lights in the hood, plus a pilot light in the switch). Each oven has its own 3 phase breaker, while the vent hood (lights, fresh air, and exhaust) has its own 20A 120V breaker. It won't be cheap by any means, but a bit of digging revealed that we never even got a certificate of occupancy (we have a temporary one from when the place was built.. in 2008.. city public records show the place never got a final inspection and was never issued a final CO). This may turn into a  clusterfuck.
randomidiot fucked around with this message at 08:06 on Mar 12, 2014 |
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Mar 12, 2014 07:59
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In general what I would do is have a manual wall switch and temperature sensor(s) connected in parallel that act as the control signal into a contactor panel with a normally-open relay, and run your fan power through the relay. This way you can turn the fans on manually or they will turn on automatically when the temperature hits a certain point. Fair warning, I did not read your entire posts. That's just the general approach I've used in restaurant kitchens. E: You may want to have a fire alarm input upstream of the wall switch and temperature sensor to shut the fan down in case of fire (connected to a fire alarm control module). Papercut fucked around with this message at 00:34 on Mar 13, 2014 |
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Mar 13, 2014 00:15
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some texas redneck posted:I've walked in more than a few times and found myself immediately dizzy, thanks to 3 gas pizza ovens running full bore with the vent/fresh air fans not running for a few hours. some texas redneck posted:…a bit of digging revealed that we never even got a certificate of occupancy… Call 1-800-321-OSHA. Your employer needs to have a licensed and bonded electrician make your workplace safe.
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Mar 13, 2014 00:25
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Cocoa Crispies posted:Call 1-800-321-OSHA. Your employer needs to have a licensed and bonded electrician make your workplace safe. Yes, this. You keep mentioning 208/240/277 volts but say you don't have 480 available. While it would be possible to have 208 & 240 simultaneously available, how can you have 277 but no 480? (Doesn't help your problem I know, just curious?)
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Mar 13, 2014 11:30
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some texas redneck posted:Lets talk about what it takes to avoid rolling blackouts.
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Mar 13, 2014 18:52
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^ Related, in the new California energy code, all buildings over 10k sf will be required to be equipped to accept a demand response signal from the utility that drops load. I'm not sure how much has to be dropped from the HVAC side, but on the lighting side you have to be equipped to drop to 85% max output based on the demand response signal. All of the lighting designers in my office think this is the end of the world, but I personally don't think someone is going to notice the lights dimming by 15% at 3pm on a hot summer day.
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Mar 13, 2014 19:24
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Papercut posted:^ Related, in the new California energy code, all buildings over 10k sf will be required to be equipped to accept a demand response signal from the utility that drops load. I'm not sure how much has to be dropped from the HVAC side, but on the lighting side you have to be equipped to drop to 85% max output based on the demand response signal. All of the lighting designers in my office think this is the end of the world, but I personally don't think someone is going to notice the lights dimming by 15% at 3pm on a hot summer day. I personally find most office spaces to be garishly over-lit, anyway.
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Mar 13, 2014 20:31
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ncumbered_by_idgits posted:You keep mentioning 208/240/277 volts but say you don't have 480 available. While it would be possible to have 208 & 240 simultaneously available, how can you have 277 but no 480? (Doesn't help your problem I know, just curious?) Going by the panel labels - they're all labeled as "120/208/277", and list the colors of each phase. Why they're labeled like this, I don't know, but it's a plastic engraved plate attached to each panel (4 panels total, all side by side). So true 480 is likely available somehow. Cocoa Crispies posted:Call 1-800-321-OSHA. Your employer needs to have a licensed and bonded electrician make your workplace safe. This
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Mar 19, 2014 08:10
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Call the local fire department / fire marshal / building inspector and have them do an inspection. They will have their own CO meters. They also probably have better access to the local permits, and if they really don't have an occupancy permit, will know immediately.
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Mar 19, 2014 11:37
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We have 120/208 V breaker panel at work. My understanding is that you can pop in a two-pole breaker to pull a 208V single phase circuit. Is this correct? If so, my question is what kind of receptical do you put on the other end? The only 208V NEMA connectors I've seen are a five conductor, L-L-L-N-G configuration. Do you run it to a L6-20 and just write 208V in sharpie on the wall plate? By the way, I'm not planning on doing the work myself. I just don't want to sound like an idiot when I try to tell the electrician what I want.
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Apr 10, 2014 16:59
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Yes, you can just do a two-pole breaker and go L-L. The receptacle type is also going to depend on what you're plugging into it (namely: does it need a neutral?) but at the datacenter I work at, any 208V single-phase circuit gets a NEMA L6 outlet (L6-20R, L6-30R, etc).
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Apr 10, 2014 17:06
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IOwnCalculus posted:Yes, you can just do a two-pole breaker and go L-L. It needs a ground but no neutral. Thanks.
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Apr 10, 2014 17:17
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Taking some code classes - the requirements for AFCIs in homes are getting even more strict.
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Apr 13, 2014 15:09
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Jesus christ, how so? More circuits required to be protected by them, or better AFCIs? Glad I'm using almost all AFCIs as it is...
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Apr 13, 2014 15:36
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I had a relative just remodel a house and apparently they are mandatory for all residential circuits in his jurisdiction with a few exceptions.
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Apr 14, 2014 01:28
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Plus the thing is that a GFCI outlet is very simple compared to an AFCI which needs to analyze the waveform to detect arcing.
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May 2, 2014 00:05
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Holy poo poo, this thread exists  I was a fan of Three-Phase's science posts in the Bitcoin thread, and I had a dumb question for a sci-fi thing I'm helping with, and here I am with sixty pages of this to read.  Actual question: Is it possible to melt a power transformer? The usual failure mode is to boil the oil in the can, right? Maybe I'm an idiot and you need to break down failure modes of power transformers to me. Please do.
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Jul 18, 2014 04:56
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Hey I was just about to find this thread to post a couple pictures from work, and here it is at the top. Anyway to your question, I suppose if all protection failed then a transformer could melt in some specific situation. I've only dealt with oil submerged pots that exploded. Usually the top blows off as a designed failure point. Something I found, I came here on a scheduled service appointment to take this bank out of service per request so they could work on the electric panels, and found the crew that added another span of wire off the back side of this (previously) dead-end pole had forgotten something very important.. 
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Jul 18, 2014 05:20
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Fill the poor marine engineer in? I'm too tired to figure out what I'm looking at.
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Jul 18, 2014 11:27
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There's a bit of loose ground wire bungling about.
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Jul 18, 2014 11:38
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When the new neutral wire was pulled up, the excess wire never got cut off. You can see it there winding down, laid against the non-grounded x2 wye tie on the primary side, then continuing down through the transformers and laid against one of the tanks near a secondary bushing. The bank was re energized that way. =/ Here's what can happen when re energizing a faulted transformer. 
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Jul 18, 2014 18:05
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LordSaturn posted:Actual question: Is it possible to melt a power transformer? The usual failure mode is to boil the oil in the can, right? Like Angry said, there are a lot of different things that would prevent a transformer from getting to that point. For a big transformer you'd have stuff like:
Otherwise the oil would ultimately boil and blow out a relief valve. There are videos of transformers on Youtube that have caught on fire with pretty spectacular results. If you had a very, very serious short circuit, one other effect would be severe mechanical damage. When you have 50,000 amps going through a piece of metal that should be carrying 100A, you'll generate tremendous magnetic fields. One story I heard (but cannot confirm) was part of a transformer's iron core being "ejected" during a serious short circuit. When we buy big MCCs (motor control centers) the bus has a short circuit rating, with options to brace it for higher currents (like 20,000A, 65,000A, etceteras). What that says is the equipment won't catastrophically fail if exposed to that much current. (In some offerings for the higher current withstand, there is extra mechanical bracing installed for the conductors.
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Jul 23, 2014 22:56
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If the protection engineers did their job, none of those catastrophic events should happen. The fault should be isolated but, I can't speak for every situation.
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Jul 24, 2014 07:44
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Yeah, assuming there isn't also a mechanical failure in the protection scheme. I worked with our substation engineer a couple years ago testing and adjusting mechanical relays. One of the first tests involves bypassing the main substation breaker, and tripping a relay to test the circuit all the way to the breaker opening. The breaker itself was a oil submersed, spring loaded device 3 phase, 69kv. Anyway, it didn't open. The spring loaded bits were gummed up. If there had been an actual problem inside the protection zone, it world have been a really bad day.
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Jul 24, 2014 17:33
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Speaking of bad engineering: So right now I'm doing some testing at a new 115/230 kV switchyard for an hydroelectric dam generating facility. Today we were doing some functional testing and discovered that the Local/Remote switch at each HV breaker completely bypasses all protection schemes associated with the breaker (including both the breaker and bus 86 lockouts) when it is in Local. This is by design.
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Jul 25, 2014 04:40
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I had a design issue with the trip/close strings for a high voltage breaker that also involved a local/remote control selector. I can't remember the exact issue. It might have been a sneak circuit. Bypassing protection is pretty crazy - I take it they want to operate the breaker when it's isolated (for testing general operation and timing of the contacts opening and closing) and don't want it to trip free? Three-Phase fucked around with this message at 00:14 on Jul 26, 2014 |
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Jul 26, 2014 00:12
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So there was a pretty awesome thunderstorm overnight. Got to drive home in it. Tons of nearby strikes, some too close for comfort even in a car (watching the morning news now, there were several fires in the immediate area I was driving through attributed to lightning). Lightning hit a nearby line, and I saw what could best be described as a Jacob's Ladder... except it was travelling down the line until it hit the next pole. I guess it shorted to ground at that point, as there was a nice big boom and all the power for about a block went out. It was It was at least a 13.2kV line, likely higher given the industrial area.
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Jul 31, 2014 12:53
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Three-Phase posted:I had a design issue with the trip/close strings for a high voltage breaker that also involved a local/remote control selector. I can't remember the exact issue. It might have been a sneak circuit. Not really sure what their reasoning is but apparently for now they want to keep it that way.  some texas redneck posted:So there was a pretty awesome thunderstorm overnight. Got to drive home in it. Tons of nearby strikes, some too close for comfort even in a car (watching the morning news now, there were several fires in the immediate area I was driving through attributed to lightning). My best guess would be that the lightning strike produced enough of a voltage spike to cause a phase-to-phase fault between the conductors (through the air) and the arc propagated down the line until it hit the pole and faulted to ground. As a side note, I'd be mildly surprised if the line was any greater than 13.8. Almost every industrial or commercial site I've been to has been 13.2 or 13.8. About the only places where I see higher voltages than that are data centers, where 24.9 and 34.5 are pretty common (usually only see 34.5 at very large data centers). Noctone fucked around with this message at 17:04 on Jul 31, 2014 |
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Jul 31, 2014 17:01
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I found a video on YouTube that's pretty much exactly what I saw happening on the lines. https://www.youtube.com/watch?v=8bBRm-W90Rc It was loving awesome to see, though I'm sure it did a bit of damage to poco equipment. Probably some customer equipment too? It took out the power in the immediate area for a short bit. Actually, somewhat related - once I got home, the storm was still going strong. We have underground lines once you get off of the main roads. Our lights dimmed for a couple of seconds twice, but never went completely out (it was enough to piss off every electronic not on a UPS though). With underground lines within the neighborhood, I'm assuming that was either lightning hitting one of the distribution lines coming into the neighborhood, or a tree doing the same? randomidiot fucked around with this message at 08:45 on Aug 1, 2014 |
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Aug 1, 2014 08:40
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The dimming was probably the recloser that protects the circuit that feeds your home, operating because of a fault. The fault could be a local lightning strike, or wind blowing a tree limb into the energized line. On a fast curve, it can be so quick to operate (depending on capability and settings of protective device) that you could see it as a dimming of incandescent bulbs. The line was actually opened for a set amount of time or cycles, and so your digital clocks and router must reset. The reason for this operation, is that most faults are temporary, and given a few operations will clear themselves most of the time, minimizing nuisance outages. Tree limb burns off, squirrel gets blown off line, etc. To the poster that asked about a pot melting -here's one sort of melted? Direct lightning strike to this distribution transformer. 
angryrobots fucked around with this message at 22:55 on Aug 1, 2014 |
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Aug 1, 2014 18:37
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Noctone posted:As a side note, I'd be mildly surprised if the line was any greater than 13.8. Almost every industrial or commercial site I've been to has been 13.2 or 13.8. About the only places where I see higher voltages than that are data centers, where 24.9 and 34.5 are pretty common (usually only see 34.5 at very large data centers). For most light or medium industrial customers I'd agree. Very heavy industries with possible loads greater than, say, 100 megawatts have been supplied with higher voltages like 69 or 135kV. But we're talking places like steel mills, oil refineries, auto plants, sites that are almost more like small cities than just a big workplace. Places big enough to require multiple high voltage substations (outdoor and indoor) within the facility itself. Hell, I've worked around motors that were like 3 megawatts. Just one motor. Three-Phase fucked around with this message at 02:06 on Aug 5, 2014 |
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Aug 5, 2014 02:04
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14.4/24.9 distribution (the line running down the road) is common to see anywhere, even in residential areas.
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Aug 5, 2014 02:25
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SeaBass posted:If the protection engineers did their job, none of those catastrophic events should happen. The fault should be isolated but, I can't speak for every situation. I want to live in this perfect world you describe.
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Aug 5, 2014 03:31
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