Hi,
I have received following comment:
Supporting documentation provided includes Proposed System (VRV)
specification sheets. Additionally, the narrative reports modeling
efficiency for System Type 6 as per Table 6.8.1A. Further, narrative
document ?Energy simulation report? reports Baseline system with 2.78 COP.
However, as per section G3.1.2.1, Baseline Case System cooling efficiency
has not been appropriately broken out from fan power. Further, for Baseline
system, there appears to be no narrative confirming cooling efficiency has
been appropriately broken out from fan power. Please note, for Baseline
System, as per section G3.1.2.1 ?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.? Since the
efficiency ratings are calculated at ARI?rated conditions, the fans should
also be broken out at ARI?rated conditions.
Can someone guide me on how to break down supply fan power? In that case,
what would be my baseline system COP?
Rakesh Desai
Dear Rakesh,
You are correct in the section G 3.1.2.1 it is specified as that Base
case system efficiencies are inclusive of the indoor fan power.
But as per the G3.1.2.4 the supply and return fans shall operate
continuously whenever spaces are occupied and shall be cycled to meet
heating and cooling loads during un-occupied hours . if the supply fan is
modelled as cycling and fan energy is included in the energy ? efficiency
rating of the equipment, fan energy shall not be modelled explicitly.
If the above case is not true then you can follow the method specified in
Alternative calculation manual(Ref attached image) to segregate the Fan
power from the total EER if you know the combined EER at a particular dry
bulb and wet bulb temperature(may be even at AHRI condition) having said
that the fan power for all the fans has to be calculated as per the
Table-G3.1.2.9
Hope this helps
*Vignesh Kumar*
Dear Vignesh,
My supply fan shall operate only when building is working. Can it be
considered as cycling fan as per G 3.1.2.4?
If yes, then if my supply fan energy is included in the EER rating of the
equipment, then is that I do not have to consider supply fan energy as per
Table G 3.1.2.9 additionally and in my model supply fan energy to be set to
zero for all zones?
With best regards,
Rakesh Desai
Rakesh,
My understanding is your fan can not be considered as cycling fans
since it's not running during unoccupied hours / Night. In your case,
supply fan power shall be calcualted during only building working
hours and fan power can be calculated per G.3.1.2.9. So your fan power
will be included in EER.
Also make sure outside air ratio is zero during unoccupied hours in
your equipment hourly results.
Hope this helps.
GK
Gopi,
Thank you.
It means I have to model my supply fan power separately and it need to be
deducted from EER of the equipment and equipment EER to be modified as per
attached formula.
Please confirm.
With best regards,
Rakesh Desai
Dear Vignesh,
Thanks. It is of great help.
With best regards,
Rakesh Desai
Rakesh,
I haven't tried with the formula you attached.
In general,my understanding is EER in ASHRAE 90.1 includes
compressor,supply fan and condenser fan power. You can calculate
supply fan power based on G.3.1.2.9 and you can broken out from
equipment (compressor/condensor) EER.
Hope it make sense.
Thanks
Gopi