250v wiring for server rack w/servers

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  #1  
Old 02-28-16, 09:38 AM
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Question 250v wiring for server rack w/servers

I am about to buy an older 42U server rack. It comes with a 250V power distribution box with a 10 AWG cable and an L630P twist-lock plug. The price for this unit is great, but I know I have to re-wire my basement for it, but I needed to do it anyways I think. I know I need a L630R, that part was the easy part. What I don't know is the type of wire I should run, or the breaker, and should I install a sub-panel?

I have two Supermicro 2U servers that have two 900 WATT power supplies in each of them (4 900 WATT PSUs total). I also will have two CisCo switches attached to this. Eventually, I will add more stuff, such as UPCs, Rackmount Console, etc, and more servers.

I have plenty of room in my breaker box to add several more breakers at the bottom, but with such a load, wouldn't I be better adding a sub-panel?

What wire should I run to the L630R? I was thinking 6/30 or 4/30.

What breaker would be best to use on this, a double pole 50 AMP?

Thanks for reading!


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  #2  
Old 02-28-16, 09:45 AM
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It comes with a 250V power distribution box
Single family residential nominal voltage is 240v. Some multi family residences and commercial locations are 208v. Are you sure you need 250 volts?
 
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Old 02-28-16, 09:50 AM
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L630 is 250 volt 30 amp device. You need to run a 30 amp circuit using #10/2 with ground cable on a 30 amp two pole breaker. No sub panel need since you have plenty of spaces.

Not 100% sure, but it sounds like this distribution box will not provide 120 volt power to any components. Not sure of that is an issue.
 
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Old 02-28-16, 11:03 AM
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The seller just sent me this via email: "The plug is for 240v 30amp. This is the same voltage and power as a standard electric clothes dryer. You can actually rewire it to a dryer plug instead of the twist lock plug. The plug disassembles.

The distribution unit divides the two lines and provides 120v on each."
 
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Old 02-28-16, 11:20 AM
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The distribution unit divides the two lines and provides 120v on each."
In that case a two wire cable w/ground is not appropriate.

You should be using a 10-3 cable that carries neutral as well as ground and use a 4 wire plug and receptacle.
 
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Old 02-28-16, 04:54 PM
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Thank You

Thank you, I am going with a dbl pole 30 using 8-2.
 
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Old 02-28-16, 05:56 PM
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The seller just sent me this via email:
The seller doesn't really have a clue! I am not so sure I'd follow through with this piece of equipment.

"The plug is for 240v 30amp. This is the same voltage and power as a standard electric clothes dryer.
WRONG! The standard electric clothes dryer needs 120/240 volt service. A dryer requires a neutral conductor and a L6-30R receptacle has no neutral terminal, just 2 hots and a ground. If this server is indeed 250 volt rated and is served through a L6-30P plug, you cannot get 120 volts from it.

You should be using a 10-3 cable that carries neutral as well as ground and use a 4 wire plug and receptacle.
PJ is correct!

Thank you, I am going with a dbl pole 30 using 8-2.
That won't work, 8-2 has no neutral when connected to a 2 pole breaker. You need a neutral to get 120 volts.
 
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Old 02-28-16, 06:30 PM
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The server is NOT 250v, the distribution box is.
It takes 250v and I think it breaks it up to power three receptacles.
 
  #9  
Old 02-28-16, 07:09 PM
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That just means 250V max. It doesn't mean it requires 250V. Also, you cannot get 250V in residential house and also most commercial buildings.

Pictures you posted are simply a surge protector and power strip. Just have different outlets because they were meant for voltages higher than 120V.

C14 (male) is what is on the surge protector and power strip. C13 (female) is what goes into equipment.
Same type of outlet (C14) is used for UPS designed for 208V, 220V, 230V, and 240V.
The reason they don't use regular 220V outlet or 240V outlet is because of their size.

What voltage you can actually use will depend on the equipment. Most will handle 208V through 240V just fine with voltage selector set to 220V (or 240V in some switches).
Free voltage devices will handle pretty much any voltages just fine.

Just make sure you don't plug 120V only devices. And make sure to change voltage selector before plug in.

I think most Cisco switches are free voltage. Pretty much all monitors now days are free voltage.
Power adapters used for routers are switches are also mostly free voltage devices. However, they usually come with 120V plug only. You can use plug adapters on those.
You could modify regular 120V power strip by change plug. But if you decide to do that, make sure to clearly mark it is 240V. I have fried a power supply once because no body marked it.
It was hooked up to 208V rack mount UPS, but wasn't marked at all.
 
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Old 02-28-16, 07:43 PM
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It would appear that your surge protector DOES NOT supply 120v to equipment. What ever you connect it at is what it provides.

Therefore, a two wire cable with ground will suffice as the cable is not supplying 120/240v service to your surge protector.

Lambition brought up a point that must be kept in mind..... don't connect any equipment to that SP that is not labeled for 240v supply power. Each item you connect should be explicitly identified with its power supply requirement.
 
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Old 02-28-16, 08:13 PM
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One more thing.

If rewiring in 240V is too much of hassle, you don't have to run 240V. Just replace PDU with 120V type. You don't have to buy special PDU made for a rack. You can just use 120V surge protector/power strip. Unless you buy managed PDU that you can control and monitor over IP, it basically is same as a regular power strip.

That might be cheaper than pulling 240V depending on how hard it is to pull new wire.

I still recommend using 240V over 120V to keep current lower and it usually is more efficient. But if you decide to get UPS later on, 240V UPS' are generally more expensive as well.

When you buy UPS, make sure it matches your voltage. In residential house, it usually will be 240V.
If you buy 208V model (usually for commercial buildings), UPS will detect over voltage and switch over to battery. If you buy 240V model, and hook it up to 208V, UPS will detect under voltage and switch over to battery.
With some UPS, you can select voltage. I think most high end UPS have configurable voltage.
Some UPS even have dual voltage output. (Meaning it has built in step down transformer.)
 
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Old 02-28-16, 09:15 PM
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Can I run 8/3 with on an L630R?
I was wrong about my PSUs as well, they are 1200W Switching. I have enclosed a picture for reference. My switches say "Rating 100v-240v" as well. I would really like to keep these on the 240v system as I was told it would save on electric costs. For any non-240v hardware, I have my 120 already next to the where the Rack will be, I am running my servers on it now. There are no switches to switch on the servers or Cisco switches, so I am thinking they auto switch.

My switches are Cisco 3750-48 and 3560v2-48.

BTW, I truly & gratefully appreciate all the help you all are giving me.

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Old 02-28-16, 10:38 PM
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8-3 is over kill.
L630R is 30A 240V. All you need is 10-2. You don't need neutral.

Both switches and the server is free voltage. All computer power supplies are switching power supply. And most, if not all power supplies with active PFC are free voltage.

You plug them to straight 208 or 240V.
 
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Old 02-29-16, 09:06 AM
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Sounds great! The words thank you doesn't express my gratitude enough. It seems running a 10/2 from a double pole 30 AMP fuse is all I need and I can do that myself.
 
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Old 02-29-16, 09:14 AM
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The seller of this rack has offered 26 feet of 10/3 wire for $26.00. Should I get it, or stay with 10/2?
 
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Old 02-29-16, 09:31 AM
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If the 10-3 is flexible cord the third conductor is the ground. In building cables the ground is not counted.
 
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Old 02-29-16, 09:34 AM
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I would not buy used cable. It is very unlikely they could have installed it and removed it without damage. Head down to your local home depot or similar and get 10-2/g NM-B "Romex" for the run from your breaker panel to the L630 receptacle. You'll of course need box connectors, staples, a junction box, perhaps a short length of conduit and various other assundries. You will need to color the white wire in the cable red or black to indicate its use as a hot in a 240V circuit.
 
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Old 02-29-16, 10:43 AM
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I would really like to keep these on the 240v system as I was told it would save on electric costs.
It saves on wiring costs but not on actual usage. You pay for power by the watt whether it's 120v or 240v.
 
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Old 02-29-16, 08:08 PM
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You pay for power by the watt whether it's 120v or 240v.
True, but the thing is switching power supplies in computers and other electronics tends to be a little more efficient at higher input voltage. It is not a huge difference, but for something that runs 24 hours a days, it could make difference.

http://www.apcdistributors.com/white...0Equipment.pdf

240V will not save electricity at all for simple devices like a heater if it is same wattage, but with switching power supply, wattage is lower at higher input voltage.
 
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Old 03-01-16, 08:32 AM
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The savings is all due to decreased voltage drop with higher voltage circuits. In a typical residential setting it's going to be well down into single digit percentages -- 1-2% difference would be the most I would expect. In a commercial building were circuits are hundreds of feet long the difference in efficiency and installation cost is more profound -- in residential I can't imagine it would even be measurable.
 
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