Over the years I've probably powered server rooms every which way you can think of and there definitely isn't a one size fits all solution to the problem.
Today, I'm going to walk you through a couple of different solutions which will hopefully make this decision just that little bit easier.
The Pay As You Grow Model
In most small scale installations an electrician is brought in, installs a circuit breaker at one end, an outlet at the other and runs some cable (generally single phase) between the two. Once he's finished, he hands you a very large bill and calls it a day.
... 250 million metres of cable? 1 bazillion hours of labour? You can scarcely believe your eyes! Surely this can't be real... But you pay it despite lamenting over the fact that you'll have to pay it again when you add another rack.
When you eventually start adding extra servers, racks, electrical circuits, switching, SAN and a blade center, you end up in one or more of the following situations:
- You cannot effectively manage your energy usage efficiency ratio's
- You run out of space in your electrical board for new circuits
- You run out of capacity (amperage) in your electrical board
- You destroy your budget due to additional, unaccounted for electrical works.
Planning Starts From The Beginning
Let's rewind the clock to when your office/server room fit out is first taking place. Actually, let's rewind the clock even further to when we're planning the electrical for the floor. It's at this time where you should be considering how the server room should be powered because in many cases, you'll only get one shot.
Ensure you share your plans with the electrician or electrical engineer at every step of the way. If not, you could end up with a bunch of standard 10 amp single phase circuits.
Going too small will not only limit your options in the future, but you also risk overloading the circuit. Conversely, going too large may limit your equipment choices down the road and put a larger dent into your pocket than you expected.
Using A Dedicated Electrical Board
If you're installing an electrical board for the entire floor, chances are they need to run a new circuit up to your floor from the meter room. If they're going to all that trouble, now might be a good time to run an additional line straight into your server room and connect it to a new electrical board.
If Joe bloe decides to switch the power off to a circuit and gets the wrong one, at least you know he's not going to be messing with your server room. Yes, I've seen this happen, by an electrician funnily enough. We can laugh about it now though.
Also, by obtaining our own dedicated feed, we can cater for much larger amount of growth than we would have been able to otherwise.
Secondary Electrical Board
The above option may not always be available to you. If that is indeed the case, I normally opt for running ONE massive three phase circuit (the bigger the better) from your existing electrical board to a shiny new electrical panel inside your server room.
You can of course mount the panel outside if you want but subsequent new runs will require more labour, more materials and will probably look ugly. Mind you, it'll probably still look ugly inside the server room but fewer people will notice.
Don't Forget The UPS!
If you have a bare wire UPS output, don't forget that a separate electrical board can also be used to distribute UPS power to your racks! Connect your UPS to the electrical board (to where mains power would normally be connected).
Just remember to use an appropriately sized electrical board. Using the same size as your mains electrical board may be overkill although I will admit, it would look perfectly symmetrical.
*ahem* Just remember, your UPS will always power less than your mains electrical board. Don't believe me? In part 2, we'll discuss overhead power distribution from the switchboard to the equipment.
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