Peak load time

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The LS-B Space Peak Load Components Report shows my peak cooling load
for a perimeter hotel room with windows occurring on Oct 2 at 5pm when
its 62F outside in new york city. I believe this is an error. My peak
heating load for this space appears correct occurring on jan 23 at 8am.
Solar radiation dominates the total space load at 75% of the total
cooling load. The overall building peak cooling load occurs on July 1
at 8pm when its 92F outside which appears correct. What do you think?

Mike Tobias PE

Tobias, Mike's picture
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Joined: 2011-10-02
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If this is a south-western facing room, this makes sense. For spaces with
alot of glass, peak cooling loads typically occur in the fall when the sun
sits lower in the sky. For a western or south-western facing room, at 5pm
in October, the sun is shining directly into the windows. With a 62 degree
outdoor air temperature, conductive losses are low, so the heat gained by
the space does not have a chance to leave (as it would in December, with
temperatures in the 30's). Solar gain trumps all other cooling loads in
spaces with large window areas. You could try modeling an alternative with
a really low SHGC glass, or exterior vertical shades and see how this
affects the peak.

While this is the peak space load, this may not be the peak coil load as
ventilation is not taken into account in the LS-B report (drives me crazy).
It all depends on whether ventilation air is conditioned before it arrives
at the terminal coils or not...

--
Karen

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Joined: 2011-09-30
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Mike:

Sun angle, sun angle, sun angle !!

You also didn't mention which way the guest tower was oriented, say as a
tall thin tower with facing directions dominating East and West. The
rest of your hotel is undoubtedly space where internal loads and outside
air are the primary load drivers. The guest rooms get a smidgen of OSA
and internal load driving it. October 2 in New York City could also be
an 80 DegF day as well.

I will bet on eQuest (or DOE-2).

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