[Bldg-sim] ASHRAE Appendix G EER Calculation

[Maria Karpman]

Karen, 

 

Since minimum cooling efficiencies in ASHRAE Section 6 are given for ARI
rating conditions, we need to use fan power at ARI rating conditions to
calculate the baseline EIR. You can get fan power at rating conditions for
different types of systems from AHRI website, or simply trust the attached
document that is included in eQUEST documentation. After calculate EIR for
the baseline, I use G3.1.2.9 to determine the fan power.   

 

Maria 

 

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 5:55 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

 

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

 

 

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