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General Chat Thread, Question about electrical supply in General; After the fire we had a few modifications made to the school. I have moved myself and the servers to ...
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    Little-Miss's Avatar
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    Question about electrical supply

    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!

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    Oaktech's Avatar
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    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.

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    twin--turbo's Avatar
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    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

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    Little-Miss's Avatar
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    *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.

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    twin--turbo's Avatar
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    What's the RCD and what's on it?

    Rob

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    Oaktech's Avatar
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    Quote Originally Posted by Little-Miss View Post
    *sigh* it's such a long story and a bit political
    It always is.


    Quote Originally Posted by Little-Miss View Post
    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!

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    twin--turbo's Avatar
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    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

  8. Thanks to twin--turbo from:

    Oaktech (22nd August 2012)

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    glennda's Avatar
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    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!

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    twin--turbo's Avatar
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    Our Sparks used to do that, but he retired when his hands got to shakey..

    Rob

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    Oaktech (22nd August 2012)

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    Oaktech's Avatar
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    Quote Originally Posted by twin--turbo View Post
    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)

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    Little-Miss's Avatar
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    Is there any numpty guides to stuff like this? You guys lost me a few posts ago and I don't like that lol!

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    glennda's Avatar
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    Quote Originally Posted by Little-Miss View Post
    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.

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    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.
    Last edited by Oaktech; 22nd August 2012 at 04:57 PM.

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    Little-Miss (23rd August 2012)

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    plexer's Avatar
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    My office has a 125a main but then it feeds 7 rings and a network cab spur.

    Ben

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    twin--turbo's Avatar
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    Quote Originally Posted by Oaktech View Post
    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

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