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How to add HeatExchanger:AirToAir:SensibleAndLatent with Supply Air Outlet Temperature Control to AirLoopHVAC:DedicatedOutdoorAirSystem

asked 2022-03-29 01:46:46 -0600

Keigo's avatar

updated 2022-10-12 21:17:57 -0600

I want to add HeatExchanger:AirToAir:SensibleAndLatent to AirLoopHVAC:DedicatedOutdoorAirSystem, but I have a problem. Let me explain using an ExampleFile SmallOffice_CentralDOAS.idf. I added HeatExchanger:AirToAir:SensibleAndLatent as illustrated below. Here is the revised idf file (V9-6-0). One more revision is that originally the OA Supply Fan was located in front of the heating coil i.e, blow-through configuration, but the Fan was changed after the cooling coil i.e., draw-through configuration.

image description

When I set Supply Air Outlet Temperature Control of HeatExchanger:AirToAir:SensibleAndLatent to "No", there is no error and the simulation completes sucsessflly. However, when I set Supply Air Outlet Temperature Control to "Yes", the following severe error occurs and the simulation terminates even though I add a temperature setpoint with SetpointManager:Scheduled.

   ** Severe  ** Missing temperature setpoint for HeatExchanger:AirToAir:SensibleAndLatent "HEX" :
   **   ~~~   **   use a Setpoint Manager to establish a setpoint at the supply air outlet node of the Heat Exchanger.
   **  Fatal  **  Previous condition causes program termination.

At first, the same error occurred in another energy model which was much more complecated, so I tested with the simple ExampleFile to clarify the cause.

I tried several things such as adding OutdoorAir:Mixer and Controller:OutdoorAir which are usually not required for AirLoopHVAC:DedicatedOutdoorAirSystem. I also tried changing SetpointManager:Scheduled to SetpointManager:MixedAir, but they were all in vein. Any suggestions?

I forgot to share my idf files. They are here. The version is V9-6-0.

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Still waiting for any advices. I cannnot enable Supply Air Outlet Temperature Control of HeatExchanger:AirToAir:SensibleAndLatent.

Keigo's avatar Keigo  ( 2022-07-14 03:31:51 -0600 )edit

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answered 2022-10-13 08:11:11 -0600

I do see a set point manager at the outlet of the HX. However, I do not see a set point at the AirLoopDOASSplitterInlet node.

  HEX-1-1 Heat Recovery Air Temp Manager,  !- Name
  Temperature,             !- Control Variable
  AirLoopDOASSplitterInlet,!- Reference Setpoint Node Name
  OA Supply Fan Inlet,     !- Fan Inlet Node Name
  AirLoopDOASSplitterInlet,!- Fan Outlet Node Name
  HEX Supply Air Outlet;   !- Setpoint Node or NodeList Name

Adding this set point manager did not correct the problem in V9.6.

  OA Air Temp Manager 20,   !- Name
  Temperature,             !- Control Variable
  OA Cooling Supply Air Temp Sch,  !- Schedule Name
  AirLoopDOASSplitterInlet;     !- Setpoint Node or NodeList Name

I updated this file to V22.2 and there is some other problem in the file that I have narrowed down to the DOAS air loop but not quite sure what the problem is.
The error (in the debugger) is ** Severe ** invalid vector subscript. This error is related to a bug where a HX in the DOAS air loop cannot autosize properly.

I corrected that problem and the simulation did run and now shows these errors with the set point managers.

** Warning ** SetpointManager:Scheduled="OA AIR TEMP MANAGER 1"
**   ~~~   ** ...setpoint node conflicts with another setpoint manager.
**   ~~~   ** ...conflicting setpoint manager = SetpointManager:MixedAir:"HEX-1-1 HEAT RECOVERY ECONOMIZER TEMP MANAGER"
**   ~~~   ** ...conflicting node name = OA SUPPLY FAN INLET
**   ~~~   ** ...control type variable = Temperature
** Severe  ** CalcMixedAirSetPoint: Missing reference temperature setpoint for Mixed Air Setpoint Manager HEX-1-1 HEAT RECOVERY AIR TEMP MANAGER
**   ~~~   ** Node Referenced =AIRLOOPDOASSPLITTERINLET
**   ~~~   **   use an additional Setpoint Manager with Control Variable = "Temperature" to establish a setpoint at this node.
** Severe  ** CalcMixedAirSetPoint: Missing reference temperature setpoint for Mixed Air Setpoint Manager HEX-1-1 HEAT RECOVERY ECONOMIZER TEMP MANAGER
**   ~~~   ** Node Referenced =AIRLOOPDOASSPLITTERINLET
**   ~~~   **   use an additional Setpoint Manager with Control Variable = "Temperature" to establish a setpoint at this node.
**  Fatal  ** Previous severe set point errors cause program termination

I added back in the set point manager for the AirLoopDOASSplitterInlet node (the SPM above) and the simulation runs successfully. I am not quite sure why adding this set point manager in V22.2 worked while trying this same correction in V9.6 did not. I do believe there is a problem with autosizing the HX in V9.6 and you will have difficulty getting this configuration to run in V9.6. I would suggest removing the HX from the DOAS air loop until this can be corrected.

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rraustad's avatar rraustad  ( 2022-10-13 08:51:52 -0600 )edit

One more thing. The invalid vector subscript error I got was in debug mode. When I run this file in V22.2 release the file runs (after fixing the missing SPM) but the HX sizes to 0. That has been corrected as part of the NREL issue process.

rraustad's avatar rraustad  ( 2022-10-13 09:12:33 -0600 )edit

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Asked: 2022-03-29 01:46:46 -0600

Seen: 479 times

Last updated: Oct 13 '22