People, if you don't yet subscribe to the UK's RAC magazine then
here's a good reason why you should. They publish my articles in the
associated RAC Service Engineer Magazine. Of course this argument can
be substantiated - everyone should read my articles and we all doubt
anyone would disagree.
Thoughts on better application of mini splits in server rooms. It has
only been out a few days but already I've received a hand full of
phone calls from suppliers and contractors wanting to discuss the
The link is to a low resolution scan of the most recent issue's
Let me know what you think.
Interesting idea Marc, congrats on being published. I have been having
trouble getting a couple of server rooms to
keep up with the growing loads being added to the racks (not large enclosed
racks though). I am wondering do think this
principle could be applied to an open rack sever room? Also would some
conversion give a strained system a little more
capacity? Funny thing is even though the loads have gone up the icing issues
It's trying to get people to get away from thinking that server rooms must
be kept at a constant 18 deg'c throughout the room. The idea of the chiller
strips is to stop the hot air from mixing with the room air before it
returns to the conditioner. It's best to think of the warm air out side of
the server racks as the start of the return duct and design from there.
Correctly ducted the 'air on' will be 30+deg'c and therefore will hold more
heat to help prevent coil freezing and save energy by not allowing it to mix
with air that's just been cooled. This method will also increase the
performance of the existing equipment by supplying cool air to where it's
best needed -i.e. the air intake side of the servers and not where it's not.
The big problem is converting conventional rooms to this configuration....
Personally I would have liked the r/h diag to have the return in the centre
and the cold to the outside. (as per chiller strip picture) Then draw the
chiller strips in for a better explaination of the design. However I know
that the articles are sub'ed heavily and time isn't always available..
Most of the server rooms I work on are set at 68/69*F. The couple rooms
that are having trouble (icing minisplits)
are set at 71*F.
Last week I was called out to an iced unit. 3 or 4 ceiling tiles had been
taken out and not replaced. Unit head
was 12" or from the open attic, replaced tiles, unit hasn't re-iced.
Most of the server fans I see blow out the back of the rack. My problem
will be airflow from the minisplit heads
that are wall mount, not ducted. Small server rooms, with growing heatloads. I
have the go ahead to change one out to
catch up with demand. Have to give it some thought, might be worth looking at
for an upgrade.
My idea behind drawing the cold isle in the centre was so that the hot
isles we then exposed to the outdoors or surrounds so that in winter
they are cooled by cooler walls and in summer there is less heat
transmission through the walls on account of a reduced TD across the
Don't really like minisplits protecting Electronic Equipment (incl LAN)
Rooms as the quality of the units is usually not reliable enough and if
someone's such a cheapskate that they'd use a minisplit on a 100% sensible
load then they're probably too cheap to build in any redundancy. Unless
these minisplits are high quality and high airchange rate units.
You want to stop icing, vapour seal the room. I mean Joseph - what's this
about ceiling tiles. Glue the bastards up seal all the holes (and get some
of that stuff that gives birds a hotfoot to identify and inhibit the
culprits), put double strip rubber seals on the doors and paint every
surface of the fabric with acrylic. then no ice. Anybody that wants to stuff
things up... just set the room setpoint below 20 degrees (you increase the
risk of drying out the room as the coil strips more moisture over time and
elevate humidifier running, you also increase the risk of short cycling and
increase the risk of failure).
Given all that Marc's idea does have merit for some applications (cheapskate
customers) but as for the pomy "Service Engineer" subscription, I think that
I prefer to invest my subscription money in the Chartered Instutute of
Building Services Engineers Journal (another pomy publication) and our local
Australian Institute of Heating & Refrigeration Engineers Journal, the
Institute of Plant Engineers of Australasia Journal and Climate Control
The hot isle cold isle server farm room solution is a well researched idea,
so I'm surprised you haven't heard of it.?
So actually it's not the a cheapskate option but is a much better system to
ensure correct airflow through the server cabinet. The fact that it leads to
a better utilisation of the cooling duty (and hence lower energy costs)
should be aplauded too.
P.S 'Service Engineer' is a 4 x per year free issue from the people who
produce R&A.C magazine.
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