I think that something like “IT SOUNDS GOOD, THOSE ARE EXCELENT UPS” could be the appropriate response to make some kind of closure to your question. On the other hand, we don’t need people to tell us what we want to hear, but to show us some other possibilities, even if we decide to discard them.
First of all let me tell you that you don’t have to know about electricity to make the right choices; all you need is to have at hand the proper information.
If you spend $500 in an electrician to install a 208V outlet, running number 10 BX wire and replacing the breaker to properly connect the UPS that will supply power to your 13 Servers and Communications Devices’ Racks, you are making a very wise decision. How much do you spend in Anti-Virus Software for your client workstations? How much money have you invested in purchasing the Racks? How much money have you invested in deploying your IT Infrastructure, $8000, $25000, $75000, or $300000? Do you really think $500 is worth taking the slightest risk in the provision of power to your infrastructure core?
But you can think the issue from the opposite point of view: Why do I have to spend $500 in changing an outlet? Well, you are not just “changing an outlet” you are supplying 40 Amps to your Servers! Do you really want to do it from 3 common $5 electrical outlets? Do you know that many of the electrical outlets commonly founded in Server Rooms are poorly grounded (through a screw attaching the BX armor to the panel, or worst if some boxes exist)? I’ve found a lot (and I mean A LOT) of Server Room installations where the breakers do not trip fast enough when making a short circuit to ground in the outlet side. Yes, LAN Administrators, many times, knows a lot about PHP NDS, AD, PERL, or how Microsoft save the world, but nothing about Infrastructure planning. Giving proper power, grounding, noise and harmonic filtering, transient shielding, air conditioning and humidity control is, also, very important when your server room starts to grow. It is OK if you don’t know, but you have to give it proper planning.
But, let’s suppose you are in a “very tight” budgeting condition (like some other million LAN Administrators). Let’s spouse you build your servers, you use Linux, and you perform mostly all administration and maintenance by yourself. Then you can feel that an extra $500 investment is something your organization should avoid. Well, if $500 is considered “too much” money, then why don’t you choose some other lower cost Off-Line UPS? You could, also, settle for less battery run-time.
I know what you are thinking right now, but do you really think the difference between the On-Line PowerWare UPS and, for example APC Off-Line models is more important to the overall power quality performance than the difference between proper and improper power-line connection? Keep in mind you are going to drain some 40 Amps., and think again!
With Off-Line UPS you will also generate less heat so you don’t have to worry about air conditioning issues.
Don’t misunderstand my words. I prefer On-Line UPS and I like to have enough room to grow. But I don’t like to compromise other aspects of the power supply chain.
Let’s face it, you are not sure how much power you really need (I keep thinking 4000 VA inside ONE Server Rack is TOO MUCH!), and maybe you are not aware of your power line condition. If your estimation is right, the server rack alone will need more than 30 Amps. from two outlets (Let’s hope these outlets to be 20 Amps, dedicated, and with the proper breaker). If your electrical installation (panel, breakers, wiring, grounding, outlets, and any middle-connection box) is not in optimum condition this is a fault waiting to happen.
But what about if your load requires far less than the 5 KVA you are going to provide? Well, in that case you have wasted resources in the wrong direction. Maybe all you really need is a 3 KVA unit. In that case, with proper planning, you can use the resources to properly design the right solution. Maybe you can include a TVSS, or an isolated ground circuit, or both.
By the way, APC tool for estimating server power requirements is not very accurate, and worst if you have many servers together.
So, to make it clear, if your budget is reduced but you still want to do the things right the first thing you have to do is to measure the load you have (yes, if you don’t know about electricity you will need to call an electrician). With this value you can properly define how much power you will need. By the way, when the electrician performs the power measure you can ask him to test the outlets when you want to plug the UPS (condition, ground, load sharing, breaker, etc.). If you do it that way chances are you are going to save money: but for sure you are going to have a more reliable power source for your core network infrastructure.
Hope this help.
Jose.-
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Pablo Mir
pm@pablomir.com
