[BLDG-SIM] %RH problem when modeling WSHP in EnergyPro 3.1 (DOE2 frontend)

[John Weale]

Hello, 

A co-worker has run into a problem with Energy Pro (a DOE2 front end that
gives results in a CA state approved format to meet code issues). I took a
look at the .inp files and am also stumped.  Here's the issue:

We are experiencing a problem when trying to compare a PTAC unit with
electric heat to a WSHP in EnergyPro 3.1 (uses DOE2.1E-110).  When
modeling the WSHP system, the SS-N (humidity scatter plot) shows the %RH
of the space residing in the range of 0-9 for over 7000 hours per year.
The climate is the San Francisco area, on a peninsula, so this humidity
range is just not really possible with a heat pump unit.  The Water Source
Heat Pump output shows a reasonable temperature scatter plot, but does not
indicate a massive amount of reheat (which would be needed to keep a room
at 70 while magically dehumidifying to 5% rh with a heat pump).  The same
building modeled with the PTAC unit stays between 40-50% RH for most of
the year (as expected in this climate).

We believe we have the units sized appropriately, and don't expect to see
such massive over-dehumidification.  Has anyone else run into this? Is
this a bug in DOE2?  Any thoughts on trusting the energy consumption
output?  I would think not on general principle, but the results are not
too outlandish, it shows the WSHP as 15-20% lower energy consumption than
the PTAC system with electric heat. 

Thank you for any suggestions,

John Weale


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