Flexible Power Distribution on a Budget (Part 2)

Now that our switchboard is in place we need to get power to where it's needed the most and for the bulk of you, that's going to be server racks.

If you're reading this, I'm going to assume that Datacentre style overhead power distribution is out of your budget. This how I accomplish the same task.

Firstly, start with a good rack. One that's  designed for the purpose. Using a server rack designed to house servers and manage cabling at the rear is probably not the best idea for a network patching rack  which will generally have cable management at the front. After having learnt this lesson the hard way, I can't help but try to impart this knowledge onto all of you.

APC AR3100 Server Rack	Panduit S6212BF Server Rack
APC AR3340 Network Rack	Panduit CQSMDC79 Network Rack

While i love both APC and Panduit racks and accessories, i do tend to favour APC. Mostly because i always seem to be able to get my hands on their server racks with relatively short notice. As always, it's up to you what rack fits your needs but just remember, there's a little more to choosing a server rack that simply looking at its dimensions.

Overhead Power Distribution On A Budget

Now that our rack is sorted, I would normally turn my attention to overhead cable management'. The APC AR8560 cable trough connects securely to the top of the APC rack though you can get away with using this setup on other racks. These cable troughs should be Connected together allowing a single rack to be removed independently of your electrical circuits running overhead.

Have the electrician mount the power outlet boxes on the rearward facing side of the cable trough and you'll no longer need to pay an electricians call out fee whenever you need to move things around.

Just remember to mark your outlets so you can tell at a glance which electrical board they're connected to. I suggest using paint pens to colour in part of the outlet box and colour part of the electrical board cover to match. I like to use red for UPS power and blue for mains power.

Earthing

The most important part of your install should be your earthing system. It's a safety system which should never be overlooked and your plan for this system should be discussed with your electrician.

Without your direction, the electrician will run a dedicated earth from the electrical board to your server rack and use a self tapping screw and appropriate washer to earth your server rack and yes, it does work but anything beyond that will generally be your problem to deal with not theirs.

If your thinking "well, I don't know anything about this stuff" I have some suggestions below.

Piggyback Style Earthing

The piggyback style is generally going to be the cheapest. Mostly because it can be wrapped into other jobs (like running a new circuit) for relatively little labour. It also requires the least amount of additional consumables.

Despite being easy on the hip pocket, you potentially introduce additional resistance into your earthing system and by piggybacking your earth, you are creating a number of potential points of failure. Severe a link in the chain and you compromise everything that was piggybacked to it.

Not good. Let's try and float another idea shall we?

Earth Your Overhead Power Distribution System

Consider having your electrician earth your overhead power distribution system. Why you ask? Your overhead power distribution system is unlikely to be moved. If your power is also terminated here then it absolutely cannot be moved without the assistance of an electrician.

Accidents happen and by being higher up means it's less likely to be damaged by an ignorant mug like me. I don't know about you, but it seems like a safe bet.

The astute among you are probably thinking that the overhead cable management still needs to be piggybacked together so there's still a flaw isn't there? You'd be correct, however it is mitigated to a certain degree.

Finally, if you disconnect a rack (for removal) there is no risk of compromising the rest of the system.

Copper Bus Bar System

Essentially this is a long square/flat bar of copper dipped in tin to inhibit corrosion. Suppliers normally sell these in different lengths but you can also ask them to cut them down to the size you need with a variety of different hole spacing (NEMA, BICSI etc). I personally try to avoid cutting them if I can as it saves time and money.

When it comes to mounting, there are a few ways to mount them. For me, the most important thing to remember is to secure it to your overhead power distribution so the racks can still be removed independently of your bus bar.

How many you choose to install is up to you, but at the very least you'll need one per row. This will ensure your devices have a clean and solid connection to mother earth.

While your at it, you should pick up some ring terminals, a crimping tool, ground wire (min 2.5mm or 13 gauge but no more than 4mm or 11 gauge) and probably a small wire brush or sandpaper  to ensure the surface is clean. You'll need to earth PDUs, UPSs, Network gear, Blade chassis etc so it's better to spend a few bucks on tools and do this part yourself.

Flexible Power Distribution on a Budget (Part 1)

One of the most common questions that's asked by literally no one is what's the best way to power my server room?

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.