Hi,
I put external light of 8.26 kW which is operating for 12 hours per day and
for 365 days in year. As per simple calculation, the energy consumption of
external lighting should be 8.26 kW X 12 Hours X 365 Days = 36179 kWh/annum.
However, when I run the model, I got 3046692 kWh/annum. I checked the
schedule and it is ok.
What could be wrong?
Rakesh
The external lighting entry is watts/square foot of floor area, not total watts.
Cheers,
Daniel Knapp, PhD, LEED? AP O+M
Hi Rakesh,
In wizards you are forced to enter exterior lighting in units of W/SF.
In detailed edits we can more intuitively enter the load in kW units.
In wizards, divide watts (8,260W in this case) by the area of the shell
under which you are defining the exterior lighting load - use the area
displayed in the zone/footprint definition screen for reference. Note
with multiple shells the resulting figure may seem otherwise entirely
arbitrary but this procedure will result in the correct lighting load
(slight deviations of rounding notwithstanding).
I would take care to define exterior lighting only once under (i.e.
under a single shell) if you have multiple shells. You may end up with
a multiplier on your external loads if you copy shells and forget to
turn them off after the first shell. If you wish to define
multiple/distinctly-scheduled exterior lighting loads, I would wait to
do that in detailed edits where it's (a) more intuitive and (b) you can
assign those distinct schedules.
~Nick
NICK CATON, P.E.
Hi Nick,
In detailed wizard, I entered exterior lighting load which is in kW. I am
attaching snapshot file of the same. I have also made schedule so that it
operates for 12 hours per day.
Is it correct?
Rakesh
Hi Rakesh,
Noting that you've entered 6.41 kW instead of 8.26 mentioned earlier, it
looks like you're using the correct detailed mode inputs.
I can't qualify whether 12 hrs every day is "correct" (a fair enough
approximation if everything is 100% photocell controlled*), but you've
recognized to assign a custom schedule as well so assuming that's put
together correctly (as described previously) you should find your annual
consumption to be 6.41*12*365 = 28,075 kWh
If it still turns out lower, I'd verify the schedule has accounted for
holidays/weekends and is in fact 100% for 12 hours daily.
~Nick
* PS: Those interested can create a set of photocell-based schedules to
import into their projects that will vary exterior lighting sensitive to
the changing day lengths over the year. I've posted instructions in a
thread that can be found within the archives. Search for
"PHOTOCELL-CTRL problem"
NICK CATON, P.E.