[Bldg-sim] ASHRAE Appendix G EER Calculation

[Karen Walkerman]

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
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20110131/460fc0f3/attachment-0001.htm>