Hi Matt,

I'm unsure if observing cooling behavior 12 months out of the year is
something to inherently be concerned about... year-round cooling is a
typical behavior for many buildings I've done in 4-season climates like
our own with significant 'core' zones -not cooling all of the time, but
there's almost always at least some in each month. The ordinary
heating/cooling distribution can however significantly change in other
climates (a Montana project I just did comes to mind...). If you're
unsure of what is normal, describe some of the project building
geometries and the climate/location, and often you'll find someone who
can let you know what they're used to observing regarding
heating/cooling behavior through the year.

Perhaps a helpful self-clarifying question for your situation is to
break it down a bit: You're observing system cooling operation during
all 12 months. Do you have internal/envelope loads that together call
for cooling every month? If so, this is not an indication that anything
was modeled incorrectly with your 2-pipe system. If anything, you
might have something entered incorrectly regarding the calculation your
internal/envelope loads - on the other hand there may be nothing wrong
with what you're observing per above.

That said, if you feel there is a system issue, do you mean 2-pipe in
the sense of a shared heating/cooling loop (i.e. you can't have unitary
equipment simultaneously in "heating" and "cooling" mode), or 2-pipe in
the sense of only one loop (say, chilled water with electric unitary
coils)?

PS: This is just a hunch, but if you have/develop a program-specific
question (equest?), you'll might get faster answers on that program's
mailing list - in any case you'll want to probably mention which program
you're using if you're using the [bldg-sim] list =).

NICK CATON, E.I.T.