Will turning on my rack trip the Circuit Breakers?

warlockedyou

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Sep 4, 2016
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Hi all,
This is my first time putting together a rack and I was wondering how to calculate how much power it will need?

This rack is setup in a room where two out of three outlets are 2 pins, so I am left with plugging in the UPS directly to the wall to the single outlet.

Here is the setup I have in mind. I have about 4-5 servers. So:
Server 1 + Server 2 + (Space for 1 more) --> Power Strip (PDU) --> UPS
Server 3 + Server 4 + (Space for 1 more) --> Power Strip (PDU) --> UPS
I also have a 10G LB6M that needs power, but I'll try to plug that in somewhere since I dont think it would need a lot of power.

How do I make sure that I don't trip the circuit breaker when I power on this rack? I don't even know what else will turn off if this breaker is tripped. I live in a rental place and I can't be disturbing others if I trip the switch.

Any advise would be appreciated.
Thanks!
 

sullivan

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Mar 27, 2016
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I am not sure where you live, but if you are in the US, you probably have 15A outlets which can provide roughly 1800W. So, the outlet is probably wired to a 15A breaker. But you are using a UPS and two power strips. The power strips likely have 15A fast-blow fuses. These would probably blow before the breaker. However the main limiting factor is your UPS, which is probably capable of delivering 1000-1500W. The UPS will probably shut down first in most situations.

If you are turning the servers on one at a time, the UPS will usually "warn" you in some way as you get close to its limit. It may start beeping loudly, but it may also have a loud fan that kicks on. You'll just have to try it, but you probably won't trip the breaker. If your UPS has an LCD power display you can use that as a guide. As a general rule of thumb I try not to run my home rack over 1000W on a regular outlet.
 
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pyro_

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mainly you will need to figure out how much power each server is using. Figure on 100-150W for the lb6m and you have about 15A on the circuit in most places in north america
 
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warlockedyou

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Sep 4, 2016
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I am not sure where you live, but if you are in the US, you probably have 15A outlets which can provide roughly 1800W. So, the outlet is probably wired to a 15A breaker. But you are using a UPS and two power strips. The power strips likely have 15A fast-blow fuses. These would probably blow before the breaker. However the main limiting factor is your UPS, which is probably capable of delivering 1000-1500W. The UPS will probably shut down first in most situations.

If you are turning the servers on one at a time, the UPS will usually "warn" you in some way as you get close to its limit. It may start beeping loudly, but it may also have a loud fan that kicks on. You'll just have to try it, but you probably won't trip the breaker. If your UPS has an LCD power display you can use that as a guide. As a general rule of thumb I try not to run my home rack over 1000W on a regular outlet.
Yep, North America.
If the outlet allows, I was thinking of changing my original plan to the following new one:
Server 1 + Server 2 + (Space for 1 more) --> Power Strip (PDU) 1 --> UPS 1
Server 3 + Server 4 + (Space for 1 more) --> Power Strip (PDU) 2--> UPS 2

So, two different Power strips with two different UPS. This is to avoid overloading the UPS. But I'm not sure if the two UPS plugged into one outlet will be a problem or not.
I can start by measuring at least the servers I am planning on using immediately while others can stay in rack Powered Off.
 

warlockedyou

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Sep 4, 2016
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mainly you will need to figure out how much power each server is using. Figure on 100-150W for the lb6m and you have about 15A on the circuit in most places in north america
Thanks! Yea, I will measure the power each servers is using. Also, thanks for the usage on LB6M.
 

polar101

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Mar 19, 2016
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Also, most rooms do not run on separate circuit breakers. All electrical plugs from all rooms run to only one circuit breaker.
 

JeffroMart

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Jun 27, 2014
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Please also keep in mind that there is a 80% NEC electrical code that says if the equipment is in use for more than a 3 hours of continuous usage you can only use 80% of the branch circuit rating.

For example, if the circuit you are using is 15A you should only load it to 12A, if it is a 20A circuit do not load it to more than 16A.
 
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warlockedyou

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Also, most rooms do not run on separate circuit breakers. All electrical plugs from all rooms run to only one circuit breaker.
Crap, now how do I check how much of the 15A I am already currently using? I already have so much stuff plugged in... :(
 

warlockedyou

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kill-o-watt meter?
I have the little device that can measure the watt usage. But the problem is I dont know which "rooms" share the same 15A circuit, so I know which devices I should be measuring.
One thing I can think off is try to find the circuit breaker switch and turn it off. See which rooms dont have electricity and figure out that way...
 

gigatexal

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if you know an electrician you might buy him or her dinner or something to walk you through your circuts and stuff -- or research how your breakers are setup to see how each room might be setup.

i just assume i can pull 12A to 15A in each room, maybe use multiple outlets in a given room that might split the amperage load
 

warlockedyou

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Sep 4, 2016
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if you know an electrician you might buy him or her dinner or something to walk you through your circuts and stuff -- or research how your breakers are setup to see how each room might be setup.

i just assume i can pull 12A to 15A in each room, maybe use multiple outlets in a given room that might split the amperage load
When I get home, I will be checking how many Amps my breaker can support and which rooms are on that breaker. I also have to calculate how much power I am already drawing from that breaker, so I know how much more I need to power on the servers.
 
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Michael Hall

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Oct 9, 2015
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Yeah, depends on how your place is wired. My friend's old 2-bedroom apartment only had 3 fuses for the whole place: a main fuse (probably 40-60A, I don't remember for sure) and 2 15A branches. The stove was only protected by the main fuse.

Current code I believe calls for 2x 15A circuits for each room; one for the lights and one for the outlets. The kitchen should have a 20A circuit for each duplex outlet, or if you're really lucky, 2x 15A circuits.
 

fractal

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I have bought circuit breaker finder tools before. Several of them.

I always fall back on plugging a table lamp into a plug, then switching off breakers with someone watching the light and yelling "OFF" when it goes off. Make sure the wife isn't watching netflix when you do this ;)

Low tech but it never fails. Those circuit tracers were always hit or miss for me.
 

warlockedyou

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Sep 4, 2016
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I have bought circuit breaker finder tools before. Several of them.

I always fall back on plugging a table lamp into a plug, then switching off breakers with someone watching the light and yelling "OFF" when it goes off. Make sure the wife isn't watching netflix when you do this ;)

Low tech but it never fails. Those circuit tracers were always hit or miss for me.
Yea, I usually do the same thing. But in this case, my server room is on first floor and the breaker is in the basement. I am too lazy to run up and down 2 flights of stairs to check :eek:
 

Blinky 42

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Assuming the load of all the equipment at normal operating is within the excess capacity of the circuit(s) in question you can swap your PDUs for managed ones that let you stagger when power is turned on for each item.

With the UPSs in the rack, they will probably be what actually trips the breaker. If your servers are drawing say 8A and you loose power for 10 min then when the power kicks back on, the UPS will be drawing up toward the full rated input load between powering the equipment and recharging the batteries at the same time.
 
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warlockedyou

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Assuming the load of all the equipment at normal operating is within the excess capacity of the circuit(s) in question you can swap your PDUs for managed ones that let you stagger when power is turned on for each item.

With the UPSs in the rack, they will probably be what actually trips the breaker. If your servers are drawing say 8A and you loose power for 10 min then when the power kicks back on, the UPS will be drawing up toward the full rated input load between powering the equipment and recharging the batteries at the same time.
Hmm this is confusing. Let me whip out Visio and draw something real quick. I like visual examples :)

BRB

Edit: Nevermind, I dont have Visio installed and I can't find the installer :(
 
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warlockedyou

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Sep 4, 2016
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Ok, so I have some quick testing numbers for my servers on boot and idle without any hard drives installed in them.

All the numbers below are in Amps on a 120V 60Hz
  • 4U Server w/no drives --> 2.11A
    • 2.11 -> 1.76 -- During bootup
    • 1.40 -> 1.50 -- Idle after boot with
  • 1U SuperMicro w/ no drives--> 2.70A
    • 2.70 peak during boot
    • 2.55 -> 2.65 --> No boot screen (No boot drive was installed, so it stayed at this screen)
  • 3U Storage Server w/ no drivess -->3.04A
    • With 1 power cable plugged in -> 3.04(startup) -> 1.98 - 2.03(Idle)
    • With both power cable plugged in -> 3.62(startup) --> 3.50(mid way) -> 2.12 - 2.30(Idle)
  • LB6M 10G Switch with nothing plugged in -->1.05A
    • 1.05(startup) --> 0.88-0.98(Idle)
I still have to measure one 1U, one 3U and 2 5U Tower Servers.
What do you guys think of this?