[Equest-users] Modeling Typical IT Rooms AC Units

[James Hansen]

Liebert is no less efficient than any of the other computer grade self-contained units out there.  The problem is that the units have to fit the niche that has been created for them.  They need to be no more than 3' deep to work with typical server room design, they have to generally have high static fans to pressurize under floor systems, and they have to be fully serviced from the front of the unit.  All of these have implications on the evaporator / condenser coil layout, and thus efficiency.  

 

There are certainly things that you can do to improve computer grade AC unit design (like using the ECM motors that have been popping up for a lot of manufacturers, and playing around with higher space temperatures), but ultimately, you're never going to have a Liebert (or Stulz, etc) unit with an EER of 18. 

 

Also, in almost all cases, the efficiencies you are getting from the manufacturer or manufacturer's rep are probably based on the abnormal operating conditions of a server room (68, 70, 72 degrees) - make sure you are properly accounting for this in eQuest, as these are not ARI conditions.  

 

GHT Limited
James Hansen, PE, LEED AP

Senior Associate

1010 N. Glebe Rd, Suite 200

Arlington, VA  22201-4749

703-338-5754 (Cell)

703-243-1200 (Office)

703-276-1376 (Fax)

www.ghtltd.com <http://www.ghtltd.com/> 

 

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Will Mak
Sent: Tuesday, June 28, 2011 11:27 AM
To: Nick Caton
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Modeling Typical IT Rooms AC Units

 

Ironically, I'm in almost the same case. The Liebert units on this job have efficiencies that are below the ones listed in ASHRAE 90.1-2007.

 

The approach to model these systems as process loads is great in theory but you and I know it's a pain in eQuest, especially since you are now trying to mimic the same energy consumptions, when other factors like lighting are different...

 

William Mak, LEED AP BD+C
Mechanical Design Engineer

EPSTEIN
Architecture
Interiors
Engineering
Construction

Sustainability

600 West Fulton Street
Chicago, Illinois 60661-1259

D: (312) 429-8116
F: (312) 429-8800

E: wmak at epsteinglobal.com
W: www.epsteinglobal.com <http://www.epsteinglobal.com/> 

þ Epstein is a firm believer in sustainability. We ask that you please consider the environment before printing this e-mail.

 

From: Nick Caton [mailto:ncaton at smithboucher.com] 
Sent: Tuesday, June 28, 2011 10:20 AM
To: Will Mak; equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Modeling Typical IT Rooms AC Units

 

Hi Will!

 

We were almost burned hard specifying and approving Liebert for a LEED project under similar circumstances.  Despite their large presence for a niche market, their efficiencies aren't entirely up to snuff with today's commercial energy codes.   

 

We ultimately avoided having to send the equipment back (and foot the bill) in that case, but only because we were able to reason with both the local 90.1-compliance, LEED reviewers and other parties in play that  this was a reality of the industry we had to live with.  We did not attempt to "dodge" the code per the advice you were given below, but I do feel we were lucky.  It takes no stretch of the imagination to picture an uncooperative AHJ/reviewer striking this down.  The building altogether was an impressive performer, to be sure, but these isolated data room units left a sour taste.  I will personally think hard about compliant alternatives before falling back to designing around Liebert for future LEED work.

 

That said, the approach given below is a new one to me.  I also tend to model the proposed systems as they are, and apply a baseline system to the corresponding baseline zones.  I haven't tried calling data room systems process loads before, but I suppose it could work if you're consistent in applying/documenting it that way.  You might still find headaches trying to simultaneously document prescriptive compliance.  

 

I'd be interested to hear others share any related experience =)!

 

~Nick

 

 

 

NICK CATON, P.E.

SENIOR ENGINEER

 

Smith & Boucher Engineers

25501 west valley parkway, suite 200

olathe, ks 66061

direct 913.344.0036

fax 913.345.0617

www.smithboucher.com 

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Will Mak
Sent: Tuesday, June 28, 2011 8:47 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Modeling Typical IT Rooms AC Units

 

Hey all,

 

I'm working on a LEED energy model for an office building that has a couple standard sized data rooms for server storage. They will be served by a couple air cooled Liebert units. I started inputting information about the units in the proposed design model and requested EER information from our vendor. The EER value was provided but also pointed me towards ASHRAE 90.1-2007 Section 2.3 as the reason why EER values aren't typically provided for these types of units (he claims the cooling of the server rooms would be considered process cooling):

 

ASHRAE 90.1-2007 Section 2.3 - The provisions of this standard do not apply to:

a.       Single-family houses, multi-family structures of three stories or fewer above grade, manufactured houses (mobile homes), and manufactured houses (modular)

b.      Buildings that do not use either electricity or fossil fuel, or

c.       Equipment and portions of building systems that use energy primarily to provide for industrial, manufacturing, or commercial processes.

 

I've typically model the scheduled units on the proposed design model and System Type 3 or 4 on baseline model. However, if the above Section 2.3 applies, should we be modeling the systems that serve IT rooms in an office building as "process energy" and be equal?

 

William Mak, LEED AP BD+C
Mechanical Design Engineer

EPSTEIN
Architecture
Interiors
Engineering
Construction

Sustainability

600 West Fulton Street
Chicago, Illinois 60661-1259

D: (312) 429-8116
F: (312) 429-8800

E: wmak at epsteinglobal.com
W: www.epsteinglobal.com <http://www.epsteinglobal.com/> 

þ Epstein is a firm believer in sustainability. We ask that you please consider the environment before printing this e-mail.

 

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