[Bldg-sim] ASHRAE Appendix G EER Calculation

Karen Walkerman kwalkerman at gmail.com
Tue Feb 1 07:41:07 PST 2011


Hi Maria,

Thanks for your response.  Can you provide a direct link to the AHRI page
that has the fan power rating conditions?

Hi Nick,

Thanks for your response.

I haven't found anything in the glossary that helps me.  Are there any
specific references you can point me to?

Thanks

--
Karen



On Mon, Jan 31, 2011 at 6:44 PM, Nick Caton <ncaton at smithboucher.com> wrote:

>  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
>
>
>
> [image: cid:489575314 at 22072009-0ABB]
>
> * *
>
> *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
>
> [image: cid:489575314 at 22072009-0ABB]
>
> * *
>
> *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
>
>
>
>
>
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