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Posted by on July 7, 2006, 9:21 pm
Fat Eddy wrote:
> aboschmann@hydro.mb.ca wrote:
> > Hi I'm just a layman and a newbie at HVAC. I am looking for second or
> > third opinions on the advice that we're getting from a local HVAC
> > engineer.
> >
> > We have a computer room that needs more cooling capacity. Currently
> > there are 2 cooling units, about 5 tons each. This has been adequate,
> > until one of them fails. Also we are adding a lot of computer and
> > network equipment and expect to add a lot more. We expect to need 25 -
> > 30 tons at the end of 5 years from now.
> >
> > The computer room has a raised floor with only cabling underneath and
> > no room for anything else. There is a drop ceiling, which contains the
> > supply and return ducts. The air cooling is done in a room in the
> > floor above. Apparently there is no more room above the drop ceiling
> > for more ducting. The approach we've been using so far is the cold
> > aisle/hot aisle method, where you dump cold air in the aisle between
> > two rows of computer racks, suck the cold air through the computer
> > equipment and dump the warm air in the aisles behind the racks, where
> > the return ducting sucks up the warm air. Seems to work fine.
> >
> > We've hired a local HVAC consulting engineer but I'm not sure he's had
> > much computer room experience. We don't want to put additional cooling
> > units inside the computer room itself. His advice was to add a
> > mechanical room to our building right next to the computer room (ground
> > level), put the cooling units in the mechanical room, and punch holes
> > through the computer room's outside concrete wall for the ducting.
> > There would be 2 Lieberts of 25 tons each. The supply ducting would be
> > two semi-circular rings that run just under the drop ceiling and right
> > against the walls. There would be no return ducting, just two big
> > return vents built right into the outside wall back to the cooling
> > units.
> >
> > So it looks to me like he's just going to let the new cooling units
> > cool the room air as a whole, instead of dumping the cold air in the
> > cold aisles. He seems to know what he's doing but I don't know if this
> > approach is OK. I guess he's depending on the air to just mix around
> > but is that good enough? I know he's really overloaded with work so
> > I'm just a little nervous that he may not be putting enough thought
> > into this, but I don't know enough to question his approach.
> >
> > Any thoughts or advice?
> >
> > Thanks.
> > Armin
>
> Well Armin, it sounds as though he is not given much opportunity due to
> the limited space constraints that he has to work with, if I were
> suspect of the design I would ask him to show me another setup like the
> one that you describe, I can tell you from my experience that there are
> a lot data centers out there that have air patterns similar to what he
> is describing.
>
> Fat Eddy
> www.hvactalkforum.com
Thanks! OK, that's useful information "there are a lot of data centers
out there that have air patterns similar...". I still don't know why
he wouldn't run the supply ducting right over the cold aisles. Maybe
he's thinking it's to our advantage to keep the ducting to the sides,
for when racks are moved or power distribution unit expansions are
installed. I think there's enough room but maybe I need to have a
closer look.
Thanks again! It's a load off just to know it's "within normal".
Armin
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