# Defining window properties using if-then statements

5 posts / 0 new

I'm trying to automatically adjust my window size based on a global
parameter called "Glazing Percentage". The width of the window is fixed
and the height is defined by the following expression:

4.47*(#PA("Glazing Percentage")/0.4)

However, a large glazing percentage leads to problems since the larger
window takes up space in the plenum. So I want to fix this by adjusting
the Y coordinate of the window. To do this, I tried creating the
following expression:

if (#PA("Glazing Percentage") == 0.4)
then #L("Y") = 4.37
else #L("Y") = 4.37 - (1.12*("#PA("Glazing Percentage) - 0.4))
endif

When glazing percentage is set to 0.4, the above expression sets Y to
0.00. As soon as I change it to says 0.5, eQuest crashes.
The math is correct, but there's something wrong with my syntax. Can

I've attached the pd2 and inp files for reference.

Thanks,
Luka

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Joined: 2011-09-30
Reputation: 0

Sorry, I fixed the typo in the expression. It should say:
if (#PA("Glazing Percentage") == 0.4)
then #L("Y") = 4.37
else #L("Y") = 4.37 - 1.12*(#PA("Glazing Percentage") - 0.4)
endif

And no, that didn't fix it.

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Joined: 2011-09-30
Reputation: 0

Ok I found my mistake.

It's unnecessary to use "#L("Y") " to define the value of Y. I think I
ended up getting into a circular reference problem.

The correct expressions is:
if (#PA("Glazing Percentage") == 0.4)
then 4.37
else 4.37 - 1.12*(#PA("Glazing Percentage") - 0.4)
endif

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Joined: 2011-09-30
Reputation: 0

For those that are on both the BLDG-SIM and this list, I apologize for
the repost...

Question on PIU vs. VAV systems in eQuest...

If a PIU system has only SVAV boxes and all other parameters are
identical, does the PIU act like a VAV in eQuest? Only changing the
system type in my model seems to have a significant impact on energy
usage and I can't track down why that is. The difference is significant
enough that with App. G System 7 VAV w/RH, the choice between PIU and
VAV has an effect on the number of points. Any thoughts would be
appreciated.

Thanks,

Matt

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Joined: 2011-09-30
Reputation: 0

Matt -
You may be observing the result of the different default for
"THERMOSTAT-TYPE" for zones served by each system. The default for VAVS
is "REVERSE-ACTION" while it is "PROPORTIONAL" for PIU. Take a look in
the DOE-2 documentation for descriptions of each of these and how this
property affects ZONE terminal unit and SYSTEM operation.

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Joined: 2011-09-30
Reputation: 200