Hi all,
I am preparing a model showing T-24 compliance that will also be
submitted for LEED. The model passes T-24. However, I have about 10
warnings saying some systems may have undersized cooling and some have
undersized heating. As long as it complies, do the warnings matter?
Will someone reviewer make me go back and try and change system sizing
to get rid of warning? Thank you!!
Amber Welsh, P.E.
How did you get the file to work in LEED? Does it have any plenums? The
LEED Compliance Analysis manual warns that you will have to go back and
manually size heating and cooling equipment. You may also have too many
hours outside of the throttling range and on LEED forms you need to explain
all warnings. So., I believe you should manually resize the equipment and
see what happens.
JAMES F. GEERS
Good afternoon Amber,
The warnings of "cooling (or heating ) may be undersized" are very
common (and often meaningless) warnings in eQuest, and the reviewers are
aware of this.
If the T24 compliance forms say that the building complies, then there
is no need to worry about these warnings.
If using ASHRAE compliance, as long as the unmet load hours are below
300 for each building, again, there is no need to worry. If there are
excessive unmet load hours, only then should you go back in and manually
increase the capacity of the appropriate coil as allowed in G3.1.2.2.
A word of caution: Increasing the coil capacity should only be employed
as a last resort for reducing the unmet load hours. It is important to
understand why the unmet load hours are showing up. There are many
sources of error in eQuest which result in unmet load hours which cannot
be corrected just by increasing the coil capacity. Often, mis-matched
schedules are the source of unmet load hours and increased coil sizes do
not reduce the number of unmet load hours.
A couple examples:
1. The temperature schedule setting is set to the occupied temperature
of 75F, but the fan is scheduled off that hour
2. The temperature schedule gradually increases the tstat setting to
mimic optimum start, but the OA schedule has full OA coming in during
that optimum start.
I hope this helps.
Regards,
Sheila Sagerer