[tech] antarctica, vs Additional/upgraded air conditioner

[Nick Bannon]

On Fri, Dec 13, 2013 at 09:06:26PM +0800, Andrew Adamson wrote:
[...]
> 1. We've added several machines to the machine room since the aircon was 
> specced and installed
> 2. The aircon we have isn't being used to its full potential due to the 
> airflow in the room
3. We already have all the air conditioning we can cope with.

We're (still!) not paying for power, but we can't suck unlimited
amounts. [BOB] organised getting antarctica, the $1100? Kelvinator,
around 2010-04-09 - it's proven itself as a pretty good buy, heading
into its fourth summer now. 5.3KW of cooling, about 10A/2400W consumption.

Previously we had one, then two, small aircons instead of one large
one: simpson/gobi/gibson/atacama/judean. In case of a single failure,
two small ones does buy us a few extra minutes before temperatures hit
critical, if that helps. An aircon is a consumable for us, gibson made it
through one summer, started icing up and being unreliable in its second
year (causing machine room outages) and died. [DAA] got it fixed under
warranty after much chasing, but it didn't last to another summer.

On a 42 degree day, 5.3KW of cooling (in as-new condition, with good
airflow) means that we can have about 5.3KW of servers running. If the
aircon fails or its power circuit trips, temperatures will go critical
in a few minutes, probably before anyone is around to react usefully.
If antarctica starts icing up or failing, we're not going to do much
planning/fiddling/approving at that point, we'll replace it. Chances are
that it'll happen this time of year-ish; and chances are that the aircon
will still be in warranty, but hard to prove that it's irreparably broken.
If/when it is fixed, it just means we have a spare.

[...]
> On a side note, we have the option on the aircon of taking uncooled air 
> from either inside or outside. At the moment the source of air is 
> selected manually using a lever on the front of the aircon. Would it be 
> worth making something that can automate this action in order to be 
> cooling the air that is already the coolest at any one time?

Handy in an emergency... but on a warm day, we expect the machine room to
be below ambient temperature. If it's not, we've got too much turned on.

Nick.

-- 
   Nick Bannon   | "I made this letter longer than usual because
nick-sig at rcpt.to | I lack the time to make it shorter." - Pascal