[AusNOG] Power audit

[Tony de Francesco]

Alastair,

It depends a bit on the method of power reticulation and the type of power
cables feeding your equipment.

My guess is that you have one or two rack mounted power rails that are fed
from a local power socket. There are products on the market that can clamp
around a single phase cable and give you an approximate current draw
reading, although these generally rely on the user knowing the spec. of the
wires in the cable to achieve a more accurate reading, which makes this
method somewhat cumbersome and inaccurate.

The most accurate method is to clamp a Current Transformer (CT) around each
individual wire in the cable, although assuming the power cable to the
power rail is covered with black rubber sheathing then this probably isn't
an option. Placing CTs over each individual wire could be done back at the
distribution switchboard although this would require an electrician.

It should be noted that all of the methods listed above will only provide a
current (amps) reading and not the actual power (kW) or energy (kWh) as
power and energy can only be determined by wiring into the system to
measure voltage, which can only be done by taking down the power to your
rack.

There are inline power meters that can be quickly plugged into the power
rail incoming feed, however these rely on taking the power down for about a
minute.

Hope this helps and happy to explain more on or off list if you like.

Kind Regards

Tony de Francesco
Technical Director
P.U.E. Pty Ltd
Mob: +61 (0) 457 701 179
Email: tonyd at pue.com.au

On Jun 4, 2013 7:15 PM, "Alastair Waddell" <awaddell at legion.com.au> wrote:
>
> Hi All,
>
> Warning: much ignorance about all things power related.
> I'm wondering if I can commission a power audit of a rack-load of gear.
> Who might provide such a service?
> Can it be done without powering down?
> ie Power person attaches something around each AC cord and reports amps
drawn. The sum should approximate what my provider bills which would
address concern #1 and the individual results should let me identify any
miscreant device which would address concern #2
>
> Regards,
> --
> Alastair Waddell
> Legion Internet
> Australia
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