On 10.07.2014, at 17:21, "HJ wanghaojie630@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
Thanks Jean, i checked with it and it seems it does not provide any water flow even though the setpoint is higher than the node temeprature (heating). I recreate a airloop using Openstudio and now seems everything is fine. Maybe I accidentally changed something.... But now it seems to be working. Thanks again.
HJ
Check which node the Coil Controller is referencing and output the setpoint being set on that node. Output your mass flowrate and temperature water side for the coil.
2014-07-08 16:44 GMT+02:00 HJ wanghaojie630@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx>:
Thank you very much Annie. For the air flow rate in the airloop, I manage to get it right now. It is now correctly based on the ventilation requirement. I also made the change on the plant sizing delta T and VAV minimum airflow. But the problem I still have is that the heating coil does not seem to heating up the air at all.
This is extracted from design day:
Before Heating coil:-15.45871895 C After heating coil: -15.45599013 C
Even though my room temperature is much lower than my heating setpoint temperature.
I tried with only the dedicated outdoor air system in the model (without radiant system). E+ now will heat up the air a little bit, but still doesn't meet the central heating supply air temperature defined in sizing system. Is this because I used VAV with no reheat and sized by ventilation requirement? I dont have problem with traditional VAV with reheat to provide heating, cooling and ventilation. I only see this problem when I use VAV to supply ventilation air only and precondition it to 12.78 C.
Thanks again for you time.
These are my sizing zone and system information.
Sizing:Zone,
Thermal Zone 9, !- Zone or ZoneList Name
SupplyAirTemperature, !- Zone Cooling Design Supply Air Temperature Input Method
12.78, !- Zone Cooling Design Supply Air Temperature {C}
, !- Zone Cooling Design Supply Air Temperature Difference {deltaC}
SupplyAirTemperature, !- Zone Heating Design Supply Air Temperature Input Method
30.5556, !- Zone Heating Design Supply Air Temperature {C}
, !- Zone Heating Design Supply Air Temperature Difference {deltaC}
0.0085, !- Zone Cooling Design Supply Air Humidity Ratio {kgWater/kgDryAir}
0.008, !- Zone Heating Design Supply Air Humidity Ratio {kgWater/kgDryAir}
ASHRAE_189.1-2009 ClimateZone 4-8 SecondarySchool Library Ventilation, !- Design Specification Outdoor Air Object Name
, !- Zone Heating Sizing Factor
, !- Zone Cooling Sizing Factor
DesignDay, !- Cooling Design Air Flow Method
0, !- Cooling Design Air Flow Rate {m3/s}
0.000762, !- Cooling Minimum Air Flow per Zone Floor Area {m3/s-m2}
0, !- Cooling Minimum Air Flow {m3/s}
0, !- Cooling Minimum Air Flow Fraction
DesignDay, !- Heating Design Air Flow Method
, !- Heating Design Air Flow Rate {m3/s}
0.002032, !- Heating Maximum Air Flow per Zone Floor Area {m3/s-m2}
0.1415762, !- Heating Maximum Air Flow {m3/s}
0.3, !- Heating Maximum Air Flow Fraction
Thermal Zone 9 Design Spec Zone Air Dist; !- Design Specification Zone Air Distribution Object Name
!- =========== ALL OBJECTS IN CLASS: SIZING:SYSTEM ===========
Sizing:System,
VAV with Reheat, !- AirLoop Name
VentilationRequirement, !- Type of Load to Size On
Autosize, !- Design Outdoor Air Flow Rate {m3/s}
0, !- Minimum System Air Flow Ratio
12.78, !- Preheat Design Temperature {C}
0.008, !- Preheat Design Humidity Ratio {kgWater/kgDryAir}
12.78, !- Precool Design Temperature {C}
0.008, !- Precool Design Humidity Ratio {kgWater/kgDryAir}
12.78, !- Central Cooling Design Supply Air Temperature {C}
40, !- Central Heating Design Supply Air Temperature {C}
NonCoincident, !- Sizing Option
Yes, !- 100% Outdoor Air in Cooling
Yes, !- 100% Outdoor Air in Heating
0.0085, !- Central Cooling Design Supply Air Humidity Ratio {kgWater/kgDryAir}
0.008, !- Central Heating Design Supply Air Humidity Ratio {kgWater/kgDryAir}
DesignDay, !- Cooling Design Air Flow Method
, !- Cooling Design Air Flow Rate {m3/s}
DesignDay, !- Heating Design Air Flow Method
, !- Heating Design Air Flow Rate {m3/s}
ZoneSum; !- System Outdoor Air Method
Hi,
I model these systems a lot and so I took a quick look at your file. Two things struck me straight away
1. Plant sizing object has a delta T of 2.2°K on the hot water loop. This seems to me like a very small delta T for a hot water loop, mine is usually closer to 20°K
2. You have a VAV no reheat objectAirTerminal:SingleDuct:VAV:NoReheat,AT9, !- NameAlways On Discrete, !- Availability Schedule NameNode 180, !- Air Outlet Node NameNode 186, !- Air Inlet Node Nameautosize, !- Maximum Air Flow Rate {m3/s}Constant, !- Zone Minimum Air Flow Input Method0, !- Constant Minimum Air Flow Fraction, !- Fixed Minimum Air Flow Rate {m3/s}, !- Minimum Air Flow Fraction Schedule NameASHRAE_189.1-2009 ClimateZone 4-8 SecondarySchool Library Ventilation; !- Design Specification Outdoor Air Object Name
Which is asking that the minimum air flow input is constantly zero. Changing this value could help.
It might also help to change the rated inlet air temperature on your heating coils from 16.6°C to something much lower, that way the coils will size larger. It is also likely that
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