Little-Miss Posted August 22, 2012 Posted August 22, 2012 After the fire we had a few modifications made to the school. I have moved myself and the servers to another area of the school. This area didnt have any sort of power supply until now. The electricians have put a small box with a single RCD (?) in purely for this area. Im starting to think its not strong enough as since I've moved the servers up there it keep flicked off a couple of times. I know nothing about this sort of thing, am I on the right lines? Is it something that can be fixed or do I have to maybe reduce the amount of servers up with me? So frustrating, they are on a UPS but they don't come back up and it's hard when I'm at home!
Oaktech Posted August 22, 2012 Posted August 22, 2012 What numbers are on the RCD, how many servers and what make/model? What else is in with you - workstations, kettle, toaster anything like that? They might need to add some more. Or upgrade the one they've put in depending on what type of cable they have already used.
twin--turbo Posted August 22, 2012 Posted August 22, 2012 Yeah it realy does depend, but we have a DB with 130A incommer and about 5 circuits of that from memory. It feed nothing else and goes back to the localised sub board before going back to the main switch room. Rob
Little-Miss Posted August 22, 2012 Author Posted August 22, 2012 *sigh* it's such a long story and a bit political The servers are in a better position then they were before - believe me. I think something is gonna need upgrading, but the council aren't gonna pay for it - boy I'm gonna be popular when I tell them this. :/ I haven't found the point of overload. What's interesting is it's the holidays, my colleague is in but doubt she'd have gone round switching loads of things on. It's happened three times now, once when my UPS brought all the servers up at one (there's 4 varying makes and models), another time when no one was around and the office manager rang to tell me she couldn't log in and sometime this afternoon.
Oaktech Posted August 22, 2012 Posted August 22, 2012 *sigh* it's such a long story and a bit political It always is. I haven't found the point of overload. What's interesting is it's the holidays, my colleague is in but doubt she'd have gone round switching loads of things on. It's happened three times now, once when my UPS brought all the servers up at one (there's 4 varying makes and models), another time when no one was around and the office manager rang to tell me she couldn't log in and sometime this afternoon Does the ups complain at all? it could be that you have something like a leak-to-ground fault, rather than an actual overload, as that will randomly bring stuff down. Especially if the line to new location is long, or tacked onto an old installation. You need to bring it up with whoever installed the line in the first place, or your building services people, before its not the holidays any more and the situation gets worse and more critical!
twin--turbo Posted August 22, 2012 Posted August 22, 2012 Our "professionaly" installed UPS/Server solution had one load-site loaded to the extent that if there was a marginal extra draw on that load then the output circuit breaker tripped. That in turn caused the supply circuit breaker to trip. We resolved that one, only took a moments thought. Our other "professional" install .. we asked them to put in a second UPS and said it would need a new feed as there were none spare. 32A please.... a few weeks passed and I got a call from my colleauge Colleauge := "They say there is a spare 16A feed in the roofspace already!" Me:= "Laughs... No it needs a 32A , it's an 8KVA UPS." Co:= "They say it's fine" Me:= "on what assumption?" Co:= "The other UPS is already on a 16A feed" Me:= -Spits Coffee across office- "£$%£$^, 16A $%£$%£$ 32A !$$!£!"£$" "Hold on...." Me:= "Ask them to check the incommer rating plate on the back of the ups" Co:= "They are ordering 2x 32A now." Me:= "Oh good" 2 days later the 16A supply to UPS1 tripped, and 2 weeks later. Rob 1
glennda Posted August 22, 2012 Posted August 22, 2012 This is when your electrician is rather good and also very friendly ( but he is a 6ft 2 giant!). And when you say I want x here he puts X there unless its not safe etc He wired my 2nd 32amp 3ph connector for the Borri B500 10KVA live!
twin--turbo Posted August 22, 2012 Posted August 22, 2012 Our Sparks used to do that, but he retired when his hands got to shakey.. Rob 1
Oaktech Posted August 22, 2012 Posted August 22, 2012 Our "professionaly" installed UPS/Server solution had one load-site loaded to the extent that if there was a marginal extra draw on that load then the output circuit breaker tripped. That in turn caused the supply circuit breaker to trip. We resolved that one, only took a moments thought. Our other "professional" install .. we asked them to put in a second UPS and said it would need a new feed as there were none spare. 32A please.... a few weeks passed and I got a call from my colleauge Colleauge := "They say there is a spare 16A feed in the roofspace already!" Me:= "Laughs... No it needs a 32A , it's an 8KVA UPS." Co:= "They say it's fine" Me:= "on what assumption?" Co:= "The other UPS is already on a 16A feed" Me:= -Spits Coffee across office- "£$%£$^, 16A $%£$%£$ 32A !$$!£!"£$" "Hold on...." Me:= "Ask them to check the incommer rating plate on the back of the ups" Co:= "They are ordering 2x 32A now." Me:= "Oh good" 2 days later the 16A supply to UPS1 tripped, and 2 weeks later. Rob Oh, this is familiar... Back when I used to do BIG sound systems for nightclubs I had a job where we had specified 20x 16a feeds on C forms on the wall in the amp room, and the apropriate cabling, and incomers to support that, and then 10 assorted feeds terminating in fused spurs rated at between 5 and 13 amps around and about for other kit all to the same clean earth and all on the same phase., and we specified that everything should be capable of being run at full tilt at the same time. Well, you can guess what happened. The electrician saw the spec, thought we were taking the pi55 as he ran a mobile disco and therefore knew best, and wired everything back to a single 100a feed, which popped as we turned the rack on for the first time. Yup, that electrician got paid for materials only and was escorted off site and a new one arrived who re did everything to our spec (we breathed down his neck untill it was right)
Little-Miss Posted August 22, 2012 Author Posted August 22, 2012 Is there any numpty guides to stuff like this? You guys lost me a few posts ago and I don't like that lol!
glennda Posted August 22, 2012 Posted August 22, 2012 Is there any numpty guides to stuff like this? You guys lost me a few posts ago and I don't like that lol! Lol - Find out what is connected and there fuse ratings and also check the ampage of the RCD.
Oaktech Posted August 22, 2012 Posted August 22, 2012 (edited) Sorry. Basically, if you add up the amps or watts of everything that is connected to that feed, and it totals more than the amps specified on the RCD. it will go wrong in the way you have described. add up in watts and then employ the following as rough guide to convert into amps, which is what the RCD will be rated in. P divided by V where P is the watts you've added up, and V is mains 230v. so, a server marked as consuming 800w, if you do the maths, is consuming about 3.4 amps. this is not 100% correct as AC is a bit more complicated complicated but it's a guide. for example, our office, has a 32amp supply to it. we have the following... kettle 2000watts, 4x workstations - 375 watts each - 1500 4x monitors - 0.8amps (maths bit... P=IxV [i is amps] 0.8x230 = 184 watts x4 = 736watts speakers x2 10watts each - 20watts etc... so 2000 + 1500 + 736 + 20 = 4256watts 4256watts/230volts = 18.5amps so all is well, but we couldn't run it all off a 13amp, or even 16amp supply! As I say, this is not 100% accurate as the actual equation for AC power involves phase angles and other stuff you don't need or want to know about (this is why UPS are quoted in VA as VA is the unit of apparent power in AC circuits) but this method is accurate enough to show up any kind of glaring overload. Edited August 22, 2012 by Oaktech 1
plexer Posted August 22, 2012 Posted August 22, 2012 My office has a 125a main but then it feeds 7 rings and a network cab spur. Ben
twin--turbo Posted August 22, 2012 Posted August 22, 2012 Sorry. Basically, if you add up the amps or watts of everything that is connected to that feed, and it totals more than the amps specified on the RCD. it will go wrong in the way you have described. add up in watts and then employ the following as rough guide to convert into amps, which is what the RCD will be rated in. P divided by V where P is the watts you've added up, and V is mains 230v. so, a server marked as consuming 800w, if you do the maths, is consuming about 3.4 amps. this is not 100% correct as AC is a bit more complicated complicated but it's a guide. for example, our office, has a 32amp supply to it. we have the following... kettle 2000watts, 4x workstations - 375 watts each - 1500 4x monitors - 0.8amps (maths bit... P=IxV [i is amps] 0.8x230 = 184 watts x4 = 736watts speakers x2 10watts each - 20watts etc... so 2000 + 1500 + 736 + 20 = 4256watts 4256watts/230volts = 18.5amps so all is well, but we couldn't run it all off a 13amp, or even 16amp supply! As I say, this is not 100% accurate as the actual equation for AC power involves phase angles and other stuff you don't need or want to know about (this is why UPS are quoted in VA as VA is the unit of apparent power in AC circuits) but this method is accurate enough to show up any kind of glaring overload. You do have to remember though, that the max rated Wattage on the device is not what is consumed ( except in a device like a kettle ).. To further my frustration with out installers, on another occasion. I had to argue with them that a pair of supplies in a server active/redundant do not take twice the power of one. even if they were active/active the power consumption would be spread ( with an overhead for the losses in the PSU itself.) Rob
sjatkn Posted August 22, 2012 Posted August 22, 2012 An RCD effectively measures the current in the live and neutral of the supply and if they differ by more than the rating of the RCD then it trips. RCD's ratings are in milli Amps (mA) rather than Amps. I've seen several causes to the trips being a little keen: The trip is aging and is tripping at a lower level than the rating. The devices plugged are heavily filtering the mains. The mains is 'dirty' and the filters in the supplies are just doing their job to keep the devices safe. The cure is to get the electricians back in to test the RCD is at its specification and all the devices plugged in do not have leaky PSU's. If these show up as good then it is possible to get a monitor installed to check to see what condition the mains is in, does the supply voltage vary, does it have any spikes, etc. If all else fails it may be necessary to replace the RCD with one with a slightly higher rating simply because you have too many devices filtering just a little too much when combined together. 1
SimpleSi Posted August 22, 2012 Posted August 22, 2012 When I was liitle, you only needed RCDs to feed electricty to certain areas (like outside or anywhere where water was present) Have things changed? If not, get the RCD dumped and just put in straight forward MCB (minature circuit breaker) as that will be very cost effective The other problem can be that lets say your kit takes 30 amps and breaker is 32amps so your on the edge but get away with it until some little event occurs (mains dip followed by 40A surge for instance) Simon 1
twin--turbo Posted August 22, 2012 Posted August 22, 2012 When I was liitle, you only needed RCDs to feed electricty to certain areas (like outside or anywhere where water was present) Have things changed? If not, get the RCD dumped and just put in straight forward MCB (minature circuit breaker) as that will be very cost effective The other problem can be that lets say your kit takes 30 amps and breaker is 32amps so your on the edge but get away with it until some little event occurs (mains dip followed by 40A surge for instance) Simon We are just on MCB's for the server room to avoid issues with RCD losses. In our old building we had a room on RCD's that tripped every morning until we had the RCD's replaced with less sensetive ones. Rob
Little-Miss Posted August 23, 2012 Author Posted August 23, 2012 (edited) Ok here's a daft one. The little box which houses the RCD for the room is next to the bigger box with different areas of the school. I'm guessing there was no more physical space in the big box, hence having its own. But new cables would've been run as like I said this area didn't have electricity before. Sound about right? So run from old box, new cabling. Another thing that's just dawned on me is my mahussive new sparkling master cab, which is also up with me has its own separate power supply which is connected to the main fuse board (I suck at the terminology) . Lol would it be bad practice to run my ups/servers from that..... Edited August 23, 2012 by Little-Miss
twin--turbo Posted August 23, 2012 Posted August 23, 2012 You realy need to know what the circuits are and where else they feed. If someone trips the mains in a room halfway down the corridor you don't want it to be the same circuit that your cab is on. Rob
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