[Equest-users] Modeling Typical IT Rooms AC Units

[Nick Caton]

I should be quick to emphasize:  I'm only relating some personal experience here for others' benefit and to constructively add to the discussion.  I appreciate James's perspective and accept there are probably a few good reasons for the way things are in the world of DX data center cooling, considering the environment and physical limitations.  It seems obvious to me that 90.1 was not built to consider minimum efficiencies for this sort of equipment/environment, but that won't stop others from trying to enforce the standard in spite of my opinions.  The section 2.3  reference is starting to make a lot of sense from this angle...

 

That said, I don't think it's entirely unreasonable to expect some progress from the commercial industry either.  For smallish IT closets these days, perhaps a residential split with a high EER/SEER is really the way to go.  For larger cases requiring high-static distribution or heavier capacities, I'm only advising that it never hurts to take stock of who/what's out there and what might fit the budget/performance/efficiency requirements for the situation at hand.  If nothing truly "fits the bill," at least we can rest easy knowing that's the case and not wonder whether we missed a better option.

 

An extra bit for Will and others considering HVAC systems as "process loads:"  this isn't always so tricky as it might seem =)!  Rather than construe a custom fractional schedule to approximate the system's energy consumption (like a plug load), there's another approach:  submeter these systems and report separately on the LEED template...  Report PS-B will show the monthly consumptions/demands for the submeters after setting it all up.  Following are some quick/rough screengrabs illustrating the concept/setup:

 

 

 

 

 

~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 Andy Phelps
Sent: Tuesday, June 28, 2011 10:56 AM
To: Will Mak; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Modeling Typical IT Rooms AC Units

 

Will:

 

I couldn't agree more with you on Section 2.3.  However, what matters is not what I think, but the LEED/USGBC review team.  

 

In my experience, I've modeled data rooms in offices as a System 3/4 for the baseline and as scheduled for the design case.  I've modeled small rooms with a mini-split DX unit, and also for larger rooms with CRAC style units (Liebert, DataAire, etc).  I haven't had any issues with this in the review process.  In addition, from some internet research, it appears that architects/engineers are getting large-scale data centers certified, so they must be wanting us to split data center HVAC usage from server/process usage.  

 

Sorry that I do not have any more insight than this, but I do understand your frustration with data rooms/centers and applicability to 90.1.  

 

I would also point you to some addenda for 90.1 that does mention data centers and outlines some requirements (addenda BU).  It looks like these Liebert units would meet the requirements for efficiency in this addenda.  For the purposes of LEED certification, I would caution to read all addenda, since LEED doesn't let you pick and choose addenda, there may be some addenda out there that might hurt your energy savings percentage.  

 

Andy

 

 

From: James Hansen [mailto:JHANSEN at ghtltd.com] 
Sent: Tuesday, June 28, 2011 10:36 AM
To: Will Mak; Nick Caton
Cc: equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Modeling Typical IT Rooms AC Units

 

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 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.

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20110628/1f840fdf/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/jpeg
Size: 1459 bytes
Desc: image001.jpg
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20110628/1f840fdf/attachment.jpeg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 17098 bytes
Desc: image002.png
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20110628/1f840fdf/attachment.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 23721 bytes
Desc: image003.png
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20110628/1f840fdf/attachment-0001.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 27596 bytes
Desc: image004.png
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20110628/1f840fdf/attachment-0002.png>