[Bldg-sim] Energy Recovery Wheels (ERV) and Chiller Run Hours

[John Forester]

Hello Bldg-Sim and eQuest Users,

 

I am having difficulty in eQuest V3.61 build 5653 (equivalent to 3.61e)
setting up an energy recovery wheel for an AHU with 60% min OA by design
serving typical offices/classrooms.  Without energy recovery, the chiller
run-hours seem reasonable (about 4,000 hrs) and I am getting very little
coincident cooling/heating in the winter months based on the SS-C report for
the AHU.  The AHU is set up with an enthalpy economizer and a min OA
schedule that is set to 0.001 for all hours to allow for economizer control
during night-cycle.  The AHU runs for 6,907 annual hours including 3,749
night cycle hours.  The zone thermostat type is proportional with a 2°F
throttling range.  All cooling and heating load hours are met and the
chiller does not operate at outside air temperatures lower than 48°F.

 

Once I enable the airside energy recovery (enthalpy wheel), the chiller
run-hours jump to nearly 7,400 hours and there are a significant amount of
coincident cooling/heating hours in all winter months.  The chilled water
loop control is set to demand (although I’ve tried a snap schedule resulting
in many unmet cooling hours).  I am controlling the ERV with the mixed air
temperature and an exhaust bypass.  I’ve tried scheduling the ERV to operate
at min OA and with a schedule matching the supply fan hours minus any
optimum start (-999) hours resulting in little change in the results.  I’ve
also tried the fixed setpoint control method (using MEP data for the make-up
air temperatures) with no success.

 

I can reduce the chiller run-time to about 4,600 hours with the ERV enabled
if I disable the night-cycle fan control option.  However, the unmet heating
and cooling hours become significant.  

 

>From what I can conclude through my trial and error approach is that
enabling night-cycle control also enables the ERV even with an On/Off
schedule calling for no ERV.  When the ERV is enabled, the chilled water
loop also becomes available to satisfy any cooling load that the ERV is
creating and operates down to the coldest hour.  I’m not sure if setting the
Min OA schedule of 0.001 (enable economizer) for all hours is affecting
whether or not the ERV is activated.

 

Any help with this control option or insight to the ERV calculations are
greatly appreciated.

 

 

 

 

John T. Forester, LEED AP
Demand Management Institute
35 Walnut Street
Wellesley, MA 02481
Phone: 781 431 1100 x14
Fax: 781 431 1109
email:  <mailto:jforester at dmiinc.comweb> jforester at dmiinc.com
web:  <http://www.dmiinc.com/> www.dmiinc.com

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20090202/9dd2003b/attachment.htm>