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Re: rack power question

  • From: paul
  • Date: Tue Mar 25 13:01:57 2008

forwarded with permission.

> From: "Bob Bradlee" <[email protected]>
> To: "Paul Vixie" <[email protected]>
> Date: Tue, 25 Mar 2008 11:16:17 -0400
> X-Mailer: PMMail 2000 Professional (2.20.2717) For Windows 2000 (5.1.2600;2)
> Subject: Re: rack power question
> On 25 Mar 2008 06:17:15 +0000, Paul Vixie wrote:
> >this has been, to me, one of the most fascinating nanog threads in years.
> >at the moment my own datacenter problem is filtration.  isc lives in a
> >place where outside air is quite cool enough for server inlet seven or more
> >months out of the year.  we've also got quite high ceilings.  a 2HP roof
> >fan will ....
> Point taken, and I agree ...
> May I suggest we, make that the collective we, take all that extra floor
> space that we don't have power for anywaydue to all the new blades servers
> that need the cooling and put it to good use as a dust or (not so clean)
> clean room to lower your cooling and cleaning costs.
> I worked on a project many years ago where "they" had built a big dust
> collection room as an air scrubber for the computer room and some labs.
> Outside air and inside return air was brought in and mixed to an optimun
> temp for the season at one end of a very long, very tall, very large, not so
> clean, room sized dust collector they called the "clean room".  On the far
> wall was an array of low cost filters that fed the HVAC cold air return
> path.
> Because the room was very large with a small inlet and a huge filtered
> outlet wall.  The air in the room stayed at a low pressure and was slowly
> exhausted from the area at a very slow surface velocity.  The vast majority
> of the dust and just about all of the grit just fell out of the air onto the
> floor where it could be cleaned up with a big shopvac or a snow shovel if I
> had my way :-).
> Because most of the particulate matter hit the floor before it got to the
> filters, the filter wall lasted many months vs the previous few weeks
> between cleaning before the dust room was built. The "normal" filters in the
> HVAC system had quality HEPA filters and rarely needed to be changed because
> the air was being so well precleaned in the (not so) clean room long before
> it ever got to the HVAC system.
> I was told me that what I was looking at was the second version, about twice
> the cubic feet as the origional halway they first used. The filters now
> lasted almost twice as long and they were moving much more air.
> The dust room I saw was very tall, I think 10 or 12 foot to the roof, it was
> also very long over 30+ feet as I remember, but was limited to about 8 or 10
> feet wide (for other reasons). The filters used on the back wall were
> designed to be used in the back wall of an auto paint booth and were low
> cost and could be washed.  Now that I think about it I expect the width was
> determined by the size of the filter rack. I was told that before
> remodeling, version one started as a long wide hallway that was off sealed
> off and used as a big cold air return, using the old double doors on one end
> as the "filter rack". I worked so well that when they remodeled, the hall
> was widened and was opened up so that the cubic area of the low pressure
> area could be maximized.
> What made it work was, the fact that small inlet vs a large outlet creates
> low pressure in a large area.  A long run of slow moving air in low pressure
> will drop its dust and grit along the way, long before it gets a chance to
> plugged up the filters. Think of it as a room size shopvac or a big Dysen
> vacuum cleaner. :)
> I was told by the operator it worked better than he thought it would, and if
> he was to build it again he would have wasted more floor space and made it
> wider but could not justify the Sqfoot cost at that time. If he was
> designing from scrach at todays energy costs, it would feed the whole
> building not just the computer room and labs.
> He pointed out that while increased room height increased the cubic feet and
> reduced pressure allowing more particulate to fall per SQfoot, increasing
> the floor area was the same as increasing the effective filter area while
> also reducing the static pressure in the room, win win.
> Bottom line, the bigger the better, make a dust room big enough you might
> not need filters :-).
> Got a back room, you can seal up, or some unimproved space you can convert
> into a home built open air scrubber ?
> I have seen it work ..... and it has been working for many years .... 
> Sorry I just can't tell you where, or I would have to kill you :-)
> Bob Bradlee
> 614-xxx-xxxx
> PS. As I can not post to this list from this address, feel free to reply on
> list if you think others might like to chime in.