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Just want to know if there are 100 FCU's in a building & follow one
schedule and have similar capacity. Do we need to model 100 FCU's? or any
other way to simplify it?
Assume thermal properties remain same for all.


cic at jci.com's picture
Joined: 2011-09-30
Reputation: 0

Hi Kathiresan!

If you have 100 spaces that you can state are identical in every
practical sense (think hard about envelope loads/orientation, interior
loads and scheduling),

And every FCU is identical in every practical sense (considering
capacity, part load curves, controls, scheduling, etc.),

And heat transfer between other interior spaces is not a big deal,

Then I'd propose the following wizard-centric approach:

1. Create 1 shell in the wizards to represent your typical space.

2. Define adiabatic surfaces for all footprint perimeters (see
attached post from last week), floor and roofs that are interior

3. Assign a shell multiplier of 100 (first shell screen in DD

4. When defining your HVAC system, enter any inputs you don't want
auto-sized by a factor of 100 (heating/cooling/CFM capacities). Specify
any non-capacity inputs (such as oversizing factors, rated efficiencies
and thermostat setpoints) as though you were defining a single unit.

What you'll get is a very trim, small model that handles the x100
multiplier very efficiently during the simulation. You'll have a single
system sized to handle all 100 spaces at once, riding the same set of
performance curves and operating under a single set of schedules. In
evaluating/refining your model, keep the factor of 100 in mind.
Example: if the system summary reports 180,000 CFM, an individual unit's
CFM is really (180,000/100)= 1,800 CFM.

I'd advise investing some of the time you would saved with this approach
to double-check any auto-sized pump/loop energies correctly reflect the
x100 FCU's. Also consider extra scrutiny for any library-sourced
performance curves used (if you aren't defining your own already), as a
small difference from reality can become a large one when dealing with a
x100 multiplier.

Best of luck!



Nick-Caton's picture
Joined: 2011-09-30
Reputation: 805