Dear Jeannie,
While you are correct that fan efficiency is generally better
for larger fans, consider:
·
E+ can use whatever efficiency you define. If you want a large
fan with the same efficiency as 5 small fans, just define the fan object with
the correct efficiency for the small fans.
·
When modeling a building that has not actually been operated
(i.e., it’s in construction or brand new), it’s anyone’s
guess as to the actual fan power (It hasn’t been purchased or installed
yet), operating schedule, setpoints, etc. Your goal as the modeler is to
create a realistic model that is defensible. I think you
have latitude in which to use a realistic “average” fan efficiency.
·
The same approach is true for lighting and plug loads. Who
really knows what the actual light and plug load diversity will be?
No one. So, if you combine similar rooms into one … it’s
reasonable, defensibly accurate and saves you time.
·
That said, you are absolutely right to consider zoning
carefully. A recent model of mine included several nominally identical
office floors, but one of those floors was occupied by an accounting firm that
worked very long hours in the early months of the year for tax preparation (and
the other floors did not share those long hours). That’s a very
good reason for making separate zones! I know you can think of other
examples. The point that I try to focus on for my own models is that an
energy model of most buildings cannot pretend that it’s too close
to the reality of actual operation. People always use and operate
buildings differently than we expect, not to mention never using or operating it
in the same way every day (or month, or year)!
I hope that is helpful (and not too long-winded).
The Building Performance Team
James V. Dirkes II, P.E., LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653
From: EnergyPlus_Support@xxxxxxxxxxxxxxx
[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of jeannieboef
Sent: Wednesday, March 03, 2010 9:14 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Re: Energy Plus - adding multiple fancoils
to zone in the idf
Dear James,
I was under the impression that there is a corrilation between fan size and
efficiency. One big fan's energy consumption surely can't be the same as many
small ones. As for zones, there really are cases where lighting, HVAC&R and
occupation types in one multifuction building force one to use many, many
zones. I generally don't try to make things harder than they are.
I was actually toying with the idea of creating a virtual zone (air for walls)
inside the normal zone, putting one Fancoil into it and then multiplying the
entire zone (zone multiplier).
Kind regards,
Jean
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx,
"James V Dirkes II, PE" <jvd2pe@...> wrote:
>
> Dear Jeannie,
>
>
>
> Perhaps you should consider reducing the number of zones and fancoils.
> Generally, a zone can be as large as you desire (e.g., many individual
rooms
> in the core of a floor) as long as it has the same occupancy hours, lighting
> density, people density, and orientation to the sun. Small differences for
> lighting and people density do not influence your results in any
significant
> way.
>
>
>
> Similarly, E+ does not care, or produce different results, if you assign
> one (very large) fan coil to the zone instead of 20 small fan coils. For
> your purposes, one large fan coil and a lesser number of zones makes it
> easier for you to create the model and probably reduces your run time a
lot.
>
>
>
> The Building Performance Team
> James V. Dirkes II, P.E., LEED AP
> 1631 Acacia Drive NW
> Grand Rapids, MI 49504
> 616 450 8653
>
>
>
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
On Behalf Of jeannieboef
> Sent: Wednesday, March 03, 2010 6:23 AM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Energy Plus - adding multiple fancoils to
zone
> in the idf
>
>
>
>
>
> I've just started going through the excersize of adding additional
fancoils
> to a zone.
>
> Each FC has to be defined.
>
> Each additional FC has to lie on it's own branch split from the plantloop
> demand side splitter (as only one splitter per loop is allowed).
>
> The same for the demand side mixer.
>
> And the Demand side branch list has to be updated with the extra branches.
>
> AND THAT'S JUST FOR HOT WATER...the same still goes for CW.
> ------------------------
> Even though all the fancoils may be the same!
>
> Is their no way to use a multiplier of sorts to only have to do this once?
> Or at least once per Fancoil type?
>
> I just had a project with hundreds of zones, each with up to 20 fancoils
> consisting of variants of 4 different types.
>
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