HVACTemplate:VAV doesn't introduce Outdoor Air

asked 2017-10-14 03:48:48 -0600

2085 ●1 ●4 ●14

I am modelling the VAV with water cooled chiller.
I specify the Outdoor air flow rate in DesignSpecification:OutdoorAir as below

DesignSpecification:OutdoorAir,
Office_OA,               !- Name
Sum,                     !- Outdoor Air Method
0.00325,                 !- Outdoor Air Flow per Person {m3/s-person}
0.00039;                 !- Outdoor Air Flow per Zone Floor Area {m3/s-m2}

and refer this specification in HVACTemplate:Zone:VAV as below

HVACTemplate:Zone:VAV,
A_LZ_OfficeN,            !- Zone Name
A_LZ_Sys,                !- Template VAV System Name
Off_SP,                  !- Template Thermostat Name
autosize,                !- Supply Air Maximum Flow Rate {m3/s}
,                        !- Zone Heating Sizing Factor
,                        !- Zone Cooling Sizing Factor
Constant,                !- Zone Minimum Air Flow Input Method
0.4,                     !- Constant Minimum Air Flow Fraction
,                        !- Fixed Minimum Air Flow Rate {m3/s}
,                        !- Minimum Air Flow Fraction Schedule Name
DetailedSpecification,   !- Outdoor Air Method
0.00944,                 !- Outdoor Air Flow Rate per Person {m3/s}
,                        !- Outdoor Air Flow Rate per Zone Floor Area {m3/s-m2}
,                        !- Outdoor Air Flow Rate per Zone {m3/s}
None,                    !- Reheat Coil Type
,                        !- Reheat Coil Availability Schedule Name
Reverse,                 !- Damper Heating Action
,                        !- Maximum Flow per Zone Floor Area During Reheat {m3/s-m2}
,                        !- Maximum Flow Fraction During Reheat
,                        !- Maximum Reheat Air Temperature {C}
Office_OA,               !- Design Specification Outdoor Air Object Name for Control
,                        !- Supply Plenum Name
,                        !- Return Plenum Name
None,                    !- Baseboard Heating Type
,                        !- Baseboard Heating Availability Schedule Name
autosize,                !- Baseboard Heating Capacity {W}
SystemSupplyAirTemperature,  !- Zone Cooling Design Supply Air Temperature Input Method
12.8,                    !- Zone Cooling Design Supply Air Temperature {C}
11.11,                   !- Zone Cooling Design Supply Air Temperature Difference {deltaC}
SupplyAirTemperature,    !- Zone Heating Design Supply Air Temperature Input Method
50,                      !- Zone Heating Design Supply Air Temperature {C}
30;                      !- Zone Heating Design Supply Air Temperature Difference {deltaC}

However, checking the result Standard 62.1 Summarybelow, it seems that no Outdoor Air is introduced
image description

Can anyone tell me why and how I can fix this problem?

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2 Answers

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answered 2017-10-17 12:46:02 -0600

MJWitte

9740 ●6 ●10 http://www.gard.com/

The OA specification name is in the wrong field. It should be in a later field named "Design Specification Outdoor Air Object Name for Sizing". The OA spec for Sizing is copied into the expanded Sizing:Zone object and ultimately sets the minimum system OA flow rate. The field used in the question above, ""Design Specification Outdoor Air Object Name for Control" is for active control of the VAV damper minimum position to satisfy the zone OA requirement (this is a less common application).

HVACTemplate:Zone:VAV,
SPACE1-1,                !- Zone Name
VAV Sys 1,               !- Template VAV System Name
All Zones,               !- Template Thermostat Name
autosize,                !- Supply Air Maximum Flow Rate {m3/s}
,                        !- Zone Heating Sizing Factor
,                        !- Zone Cooling Sizing Factor
Constant,                !- Zone Minimum Air Flow Input Method
0.3,                     !- Constant Minimum Air Flow Fraction
,                        !- Fixed Minimum Air Flow Rate {m3/s}
,                        !- Minimum Air Flow Fraction Schedule Name
DetailedSpecification,   !- Outdoor Air Method
0.00,                    !- Outdoor Air Flow Rate per Person {m3/s}
0.0,                     !- Outdoor Air Flow Rate per Zone Floor Area {m3/s-m2}
0.0,                     !- Outdoor Air Flow Rate per Zone {m3/s}
HotWater,                !- Reheat Coil Type
,                        !- Reheat Coil Availability Schedule Name
Reverse,                 !- Damper Heating Action
,                        !- Maximum Flow per Zone Floor Area During Reheat {m3/s-m2}
,                        !- Maximum Flow Fraction During Reheat
,                        !- Maximum Reheat Air Temperature {C}
,                        !- Design Specification Outdoor Air Object Name for Control
,                        !- Supply Plenum Name
,                        !- Return Plenum Name
None,                    !- Baseboard Heating Type
,                        !- Baseboard Heating Availability Schedule Name
autosize,                !- Baseboard Heating Capacity {W}
SystemSupplyAirTemperature,  !- Zone Cooling Design Supply Air Temperature Input Method
,                        !- Zone Cooling Design Supply Air Temperature {C}
,                        !- Zone Cooling Design Supply Air Temperature Difference {deltaC}
SupplyAirTemperature,    !- Zone Heating Design Supply Air Temperature Input Method
50.0,                    !- Zone Heating Design Supply Air Temperature {C}
,                        !- Zone Heating Design Supply Air Temperature Difference {deltaC}
Office_OA;               !- Design Specification Outdoor Air Object Name for Sizing

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Comments

Interesting that you can have 2 different OA specifications, one for sizing and one for the simulation.

rraustad ( 2017-10-17 12:50:12 -0600 )edit

What objects does the input for "Design Specification Outdoor Air Object Name for Control" populate upon expansion?

Molly Curtz ( 2017-10-18 09:54:48 -0600 )edit

@Molly Curtz The HVACTemplate:Zone:VAV "Design Specification Outdoor Air Object Name for Control" is copied into the "Design Specification Outdoor Air Object Name" field of AirTerminal:SingleDuct:VAV:Reheat or AirTerminal:SingleDuct:VAV:NoReheat.

MJWitte ( 2017-10-26 08:40:09 -0600 )edit

@rraustad The two fields came about because the HVACTemplate VAV objects originally had just the DSOA for Control field. If present, the VAV terminal unit raises the min flow to meet the OA requirement. If blank, the VAV terminal unit does not control for OA. Then when DSOA for sizing was added to all of the HVACTemplate:Zone:* objects, the VAV objects presented a problem. For better or worse, the decision at the time was to keep the existing field and add the new one for sizing. The other option would have been to change the existing field to some kind of Yes/No field VAV OA control.

MJWitte ( 2017-10-26 08:45:36 -0600 )edit

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answered 2017-10-14 06:43:58 -0600

rraustad

13804 ●79 ●12 http://www.fsec.ucf.edu/

updated 2017-10-14 07:34:29 -0600

It looks like there is a problem with using the design specification object in HVACTemplate:Zone:VAV. The design specification object name is not included in the Sizing:Zone object. Edit the *.expidf file using a text editor. Search for the Sizing:Zone objects and add the name of the DesignSpecification:OutdoorAir object in the correct field (field 10) . Then change the name of that file so it has the idf extension (e.g., MyFile.idf) and run the simulation. Or you could change the file name first and make this correction using the IDFEditor from EP-Launch.

Sizing:Zone,
  SPACE1-1,               !- Zone or ZoneList Name
  SupplyAirTemperature,   !- Zone Cooling Design Supply Air Temperature Input Method
  12.8,                   !- Zone Cooling Design Supply Air Temperature {C}
  11.11,                  !- Zone Cooling Design Supply Air Temperature Difference {delta C}
  SupplyAirTemperature,   !- Zone Heating Design Supply Air Temperature Input Method
  50.0,                   !- Zone Heating Design Supply Air Temperature {C}
  ,                       !- Zone Heating Design Supply Air Temperature Difference {delta C}
  0.008,                  !- Zone Cooling Design Supply Air Humidity Ratio {kg-H20/kg-air}
  0.008,                  !- Zone Heating Design Supply Air Humidity Ratio {kg-H2O/kg-air}
  Office_OA,                       !- 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}
  ,                       !- Cooling Minimum Air Flow per Zone Floor Area {m3/s-m2}
  ,                       !- Cooling Minimum Air Flow {m3/s}
  0,                      !- Cooling Minimum Air Flow Fraction {}
  DesignDay,              !- Heating Design Air Flow Method
  0,                      !- Heating Design Air Flow Rate {m3/s}
  ,                       !- Heating Maximum Air Flow per Zone Floor Area {m3/s-m2}
  ,                       !- Heating Maximum Air Flow {m3/s}
  0,                      !- Heating Maximum Air Flow Fraction {}
  ;                       !- Design Specification Zone Air Distribution Object Name