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Ok, I'm trying my best not to make this too subjective and provide all the information I can and if you can help make this a better question then please suggest.

My friend an I have a small software development business. We are looking at hosting some servers for the work we do at an (as yet to be decided) office space. Mainly to reduce costs and because we need frequent access to the servers while we develop.

They can consume upwards or 2KW peak power. We may host upwards of 3 or 4 of them + other equipment, and of course our own desktop computer gear. I have 2 PC's, my friend has about 5 high end machines.

Then there would be air conditioning and other appliances like the occasional electric kettle.

What I want to know is, would an average office designed to be running some workstations be able to cope with our electricity demands or should I be considering one that has 3 phase power available to the building from the get go?

At what point does one make 3 phase power a requirement?


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closed as not constructive by John Gardeniers, womble, devicenull, Jeff Ferland, Khaled Apr 20 '12 at 5:30

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Are you referring to 3-phase power delivery for the office or for the server rack? The setup you describe does not require 3-phase. – ewwhite Apr 20 '12 at 0:17
"we need frequent access to the servers while we develop". More access then RDP/SSH provides? More then a decent IPMI client will provide? – devicenull Apr 20 '12 at 0:56
Where did you get the 2KW number from? That's a pretty hefty server for development work. Usually you would be in the couple hundred watts range. – JOTN Apr 20 '12 at 2:03
For all your electrical needs (load analysis, capacity planning, distribution equipment advice): CONSULT A QUALIFIED ELECTRICIAN. If your business really means anything to you it's not something to mess around with: Having everything go dead because you popped a breaker can wreck your development schedule. – voretaq7 Apr 20 '12 at 2:48
@voretaq7 I need to test these wires. Stick your tongue out. – Wesley Apr 20 '12 at 3:00
up vote 10 down vote accepted

I seriously recommend you consult an electrician, not sys admins, for this kind of information. Nevertheless, for what you are describing there is no reason to go with 3 phase.

Thanks, it is good advice. It's just that I expect a sparkie will want me to pay him money for 10s worth of advice. I know there are ex trades people like sparkies (I used to know one) who work in IT so I was hoping to catch one on here. – Matt Apr 20 '12 at 2:22
@Matt, I'm a sparky myself and if it was my job to spec your power I'd start by making actual measurements, rather than relying on what's written on devices. You might be surprised at how much less power most computers use compared to their power supply rating. – John Gardeniers Apr 20 '12 at 3:16
it's slightly less than 2KW measured on one server at another location. The server we'll be getting here may be a slightly different config but is very similar. – Matt Apr 20 '12 at 4:00
@Matt, it's worth remembering that although 2KW sounds like a a lot a normal AU/NZ powerpoint is rated at 10A. Without taking power factor into consideration that's 2.4KW. Even our electric jugs/kettles are typically 1.8 to 2KW. What this boils down to is that your total load is similar to what a modern kitchen would have at breakfast time (jug, toaster, maybe a microwave etc.). Yet nobody would seriously consider using 3 phase in one of our domestic kitchens. – John Gardeniers Apr 20 '12 at 8:39

My friend an I have a small software development business.

From this I gather that you're not in the infrastructure business.

They can consume upwards or 2KW peak power. We may host upwards of 3 or 4 of them

From this I gather that your power needs are beyond a small office's normal abilities.

Then there would be air conditioning and other appliances like the occasional electric kettle.

From this I gather that you are not a hosting center. =)

At what point does one make 3 phase power a requirement?

Let's cut right to the point. If you have services and software that are hosted for customers, even if it's just backend infrastructure to support your own products, you need to look into a colocation center. They have all the power and air conditioning that you can hope to have and you can then advertise a fancy datacenter to customers. "We have a state of the art datacenter monitored around the clock..." etc.

It's not too expensive to get a half or full rack. You pay a flat fee, you get awesome service. If you need more power or bandwidth, a single phone call can upgrade your provided resources. Simple!

Don't worry yourselves about nasty 3-phase issues. Let someone else do that so you can keep doing what you do best: make software.


Okay, okay... three phase is awesome. It smooths out the current and makes things generally better behaved. However, unless there's 3-phase in the building, you're going to have a hell of a shocking bill to get a hookup, run the cabling, get 3-phase PDUs, etc. and etc. If $1,000 a month is too much for a colocation, then getting an invoice for 3-phase power is probably going to cause you to slip into a coma.

Spend the money to take your single-phase 120V building power and pump it into a decent set of power conditioners and UPSs. You'll be just fine unless you start doing so much business that you're drawing tens of Kw. At that point, you might have enough cashflow to look at a high-density colocation package.

2kW is beyond a small office's normal abilities? – womble Apr 20 '12 at 0:47
@womble No, but 6kW to 8kW with the the assumed "reliable* part is. Or perhaps I just work in ghettos... – Wesley Apr 20 '12 at 0:51
Ah, I interpreted that to mean the 3-4 servers could draw 2kW total... what's he running there, blade centers? – womble Apr 20 '12 at 1:37
@womble Your interpretation could be right. I can see that now. Not to mention, you don't want to max a circuit out, so he'll need 10kW capacity or so... and on a single circuit or two 5kW circuits? What a mess. $1000 a month for a colo and call it a day. =) – Wesley Apr 20 '12 at 2:02
Ah, bitcoin mining. Gotcha. – womble Apr 20 '12 at 2:39

Three phase power is never necessary, but you will see a 3-4% drop in your electric bill should you convert over. If you skip three phase, at least get 220v service for your rack. most equipment will run on it out of the box, and again, you will see a drop in your electric bill.

+1 220v is almost trivial to find in most of the world and results in a percent or two more efficient power usage. – Chris S Apr 20 '12 at 3:25
Note that the OP is in New Zealand, which uses 230V/240V mains anyway. – Andrew Apr 20 '12 at 3:45

From my experience, if 3 phase is available for rack equipment and you have a 3 phase PDU, it allows you to put higher loads into each rack. Assuming you are using 120V, if your outlets are all on 20 amp breakers (vs 15 amp) then you should be able to handle at least one server on each breaker at your mentioned peak load.

What I typically do for multiple servers, especially since the servers have dual redundant power supplies is we wire the rack to have two single phase 20A or 30A power feeds, which is sufficient to run at least 4 of my servers nominally (yours may be differnet).

I have only personally seen 3phase used for loads such as blade servers, which need that much power within a single rack. Even smallish building air conditioners can run single phase 208V, so it really depends on your office building.

I think an average office should be able to cope with your power needs as long as you have enough circuits available. If you have open spots on the panel for more breakers (and the panel can support it), I would hire an electrician to add more outlets on separate breakers to where you want to run your servers and plug them in accordingly.


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