On 27.06.2014, at 19:33, "lmblanes@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
Dear Modellers
I am modelling an HVAC systems comprising
<-- Return Fan
Outdoor Air System + Heat Exchanger
---> PreHeating Coil --> Cooling Coil --> Humidifier --> Heating Coil --> Supply Fan
I am using a SetpointManager:OutdoorAirReset to set up the Air Supply temperature to the zone as follows:
SetpointManager:OutdoorAirReset,
Air Loop 1|SupplyAirTempManager_OutdoorAirReset, !- Name
Temperature, !- Control Variable
30, !- Setpoint at Outdoor Low Temperature {C}
0, !- Outdoor Low Temperature {C}
14, !- Setpoint at Outdoor High Temperature {C}
30, !- Outdoor High Temperature {C}
The Preheting Coil controls work fine. The Heating Coil and the Cooling Coil seem to be working Ok as per responding to the Thermal Zone Thermostat, which is set with a DualSetpoint thermostat (21-26deg.C).
However, I notice that the setpoint specified for the air supply temperature is rarely met, and for some reason, the air supply temperature oscilates during the year in a band between 23 deg. C and 16.5 deg. C. (see picture 1 black is the setpoint and blue is the actual air supply temperature). I have not specified in any place these 23 and 16.5 deg. C. Having a closer look, the air supply meet the setpoint during mostly the central part of the year while during winter the air supply temperature and the calculated setpoint also mirror-inverse each other (see picture 2). That looks like the Heating Coil is having some performance problems.
I also had a look to see if there was simultaneous heating and cooling (see picture 3). The cooling coil energy (pink) is following the request for increasing air supply temperature setpoint (black), but the real air supply temperature (blue) is falling down instead of increasing. There is no cooling (sky blue). So it looks to me contradictory as the temperature decreases when it should increase. There is no infiltration or ventilation objects. The zone equipment is an AirTerminal: SingleDuct: Uncontrolled. So I have no explanation about where this energy sink comes from.
Why is this behaviour happening? I guess there may be some capacity problems, but that contradicts the second picture. Has anyone encountered a similar problem? Why the system sticks to a deadband that isn't prescribed?
Thanks
Luis from Hibernia
<FCO_HVAC_Customized_mod_pump_variable Flow_V7.2_V810.idf>
<1_AirSupply and Setpoint closer winter.jpg>
<3_AirSupply_Setpoint_Heating_and_CoolingCoilEnergy.jpg>
<1_AirSupplyTemp and Setpoint.jpg>
__._,_.___
Posted by: "jeannieboef@xxxxxxxxx" <jeannieboef@xxxxxxxxx>
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
__,_._,___