[Bldg-sim] ASHRAE Appendix G EER Calculation

[Nick Caton]

Hi Karen,

 

Apologies if I haven't been following closely enough, but I think you
may be unnecessarily complicating the issue for yourself... if in doubt,
turn to the 90.1 glossary (section 3) regarding whether the efficiency
metrics are/aren't inclusive.  

 

EER is a simple ratio of total input power to net cooling capacity.  It
includes fan power.  SEER is the same idea, only it's weighted over a
"normal" annual period.  Again it includes fan energy.

 

While pulling the (calculated) baseline fan energy out of the prescribed
EER/SEER values may result in "unrealistic looking" efficiencies, that's
normal because fans are a big part of energy used by packaged equipment!


 

Put simply and correcting your last statement:  All Appendix G baseline
model system types require fan energy calcs.  These energies can be
subtracted from the "fan-inclusive" EER/SEER efficiencies prescribed in
Section 6 to determine cooling EIR figures.  

 

Hope that helps! 

 

~Nick

 

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

Smith & Boucher Engineers

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

www.smithboucher.com 

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Karen
Walkerman
Sent: Monday, January 31, 2011 4:55 PM
To: Sam Mason; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] ASHRAE Appendix G EER Calculation

 

Hi Sam,

 

I guess my question is the definition of "packaged" for the baseline
system case.  Systems 1 and 2 are very clearly packaged systems, with
relatively low fan power.  The fan power calculation reflects this, with
much lower fan powers for these systems.  However, systems 5 and 6 are
called "packaged" systems, but these systems typically serve a large
portion of a building with more extensive ductwork and higher fan powers
(reflected in the fan power calculation), subtracting out fan powers
from these systems and manipulating the EER of these systems results in
very high EERs (upwards of 18???).  

 

It is unclear to me which air conditioners listed in section 6.8 have a
rating which includes fan power and which do not.  I am assuming that
where different "single package" and "split system" EERs are given, that
the first includes fan energy while the second does not.

 

Anyway, it seems that to model baseline systems, the simplest approach
is to choose the split system EER (if listed) in section 6.8, and
calculate the fan power according to the G3.1.2.9 guidelines.
Therefore, the only time you would have to do the calculation mentioned
by Sam is for a proposed design system where the fan energy is included
in the EER.

 

--

Karen

 

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Nick Caton
Sent: Monday, January 31, 2011 4:58 PM
To: Arpan Bakshi; Sam Mason
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] ASHRAE Appendix G EER Calculation

 

Mr. Sam is referencing/providing:

 

User's Manual for ANSI/ASHRAE/IESNA Standard 90.1-2007

Example 11-C  "Calculating COP for Compressor and Condenser"

 

(Found on page 11-18)

 

~Nick



 

NICK CATON, E.I.T.

PROJECT ENGINEER

Smith & Boucher Engineers

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

www.smithboucher.com 

 

 

On Mon, Jan 31, 2011 at 5:30 PM, Sam Mason <sam.mason at atelierten.com>
wrote:

Karen,

>From the user's guide, the fan power should be removed from the standard
EER rating of packaged cooling systems. Excerpt below but let me know if
you have any further questions.

 

A 15-ton packaged rooftop single-zone system having an EER of 8.6 (COP
of 2.5) is

specified for a building. The following table gives the design
specifications. How should

this be modeled?

Equipment parameter                               Value

Net Cooling Capacity (Btu/h)                   174,000

Total Packaged Unit Input Power (W)        20,128

EER                                                         8.64

Gross Cooling Cap (ARI conditions)         182,000

A

The supply fan power is the difference between the gross and the net
cooling capacity.

Supply Fan Power  = (182,000 - 174,000 Btu / h) / 3.413 Btu /W h =  2343
W

 

>From the equation for cooling system COP, the cooling provided by the
compressor and

the condenser into the airstream in Btu/h per Btu/h of electrical power
input is:

COP  = (182,000 Btu / h) / {(20,128 - 2343 W)* 3.413 Btu / W h } = 3.0

Some simulation programs use an energy input ratio (EIR), which is
1/COP. In this case,

the EIR for this piece of equipment would be 1/3 or 0.333.

 

--

Sam Mason

Atelier Ten

 

T  +1 212 254 4500 x221

 

From: bldg-sim-bounces at lists.onebuilding.org [mailto:
bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Karen Walkerman
Sent: Monday, January 31, 2011 3:53 PM
To: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] ASHRAE Appendix G EER Calculation

 

A clarification:

 

My question pertains to baseline models, with baseline systems.

 

--

Karen

 

On Mon, Jan 31, 2011 at 12:09 PM, Karen Walkerman <kwalkerman at gmail.com>
wrote:

Hi All,

 

G3.1.2.1 in ASHRAE 90.1 says that "Where efficiency ratings, such as EER
and COP, include fan energy, the descriptor shall be broken down into
its components so that supply fan energy can be modeled separately."

 

However, I am a little unclear as to which baseline systems this applies
to.  It seems that it would apply to systems 1 - 2, and not to systems 3
- 8?

 

Thanks,

 

--

Karen

 

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20110131/893b7da9/attachment-0002.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/bldg-sim-onebuilding.org/attachments/20110131/893b7da9/attachment-0002.jpeg>