Allow zone hvac to draw return air #8719

lgu1234 · 2021-04-16T13:28:44Z

Pull request overview

The new feature requests Zone HVAC objects to draw inlet air from return plenum and return duct. It should be pointed out that no return duct losses are calculated in Existing EnergyPlus, except for the AirflowNetwork model (beyond the topic for this new feature). Instead, light heat from return fraction is added to the return node after mixing. Therefore, light heat will be added into the drawn air for the scenario with return duct. There is no modification for the scenario with return plenum.

This new feature is applied to the system configuration only when a zone equipment and an AirLoop serve the same zone. The proposed IO modification will be made in the ZoneHVAC:EquipmentConnections object by adding a new field as Plenum or Return Air Node Name for the last position, so that no transition is needed for this new feature.

The feature request is GitHub Issue #8190 at #8190

Test files are attached here.

Pull Request Author

Add to this list or remove from it as applicable. This is a simple templated set of guidelines.

Title of PR should be user-synopsis style (clearly understandable in a standalone changelog context)
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Reviewer

This will not be exhaustively relevant to every PR.

lgu1234 · 2021-04-19T13:24:22Z

src/EnergyPlus/DataHeatBalance.hh

@@ -648,6 +648,7 @@ namespace DataHeatBalance {
        Real64 FractionReturnAirPlenTempCoeff1;
        Real64 FractionReturnAirPlenTempCoeff2;
        int ZoneReturnNum;        // zone return index (not the node number) for return heat gain
+        int ZoneExhaustNodeNum;   // Exhaust node number


Add a new variable to store zone exhaust node number in the Lights object

Why a single node number here? And why do the lights care what kind of node this is?

@mjwitte Although the Lights object does not care what kind of node is, this new feature only adds an additional exhaust node to share the return gain. The existing function only adds return heat gain into a single return node. If a user wants to have more return gain share, more Lights object may be listed.

lgu1234 · 2021-04-19T13:26:09Z

src/EnergyPlus/DataZoneEquipment.hh

@@ -265,6 +265,7 @@ namespace DataZoneEquipment {
        Array1D_bool FixedReturnFlow;    // true if return node is fixed and cannot be adjusted in CalcZoneReturnFlows
        Array1D_int ReturnNodePlenumNum; // number of the return plenum attached to this return node (zero if none)
        Array1D_int ReturnFlowBasisNode; // return air flow basis nodes
+        Array1D_int ReturnNodeExhaustNodeNum; // Exhaust node number flow to a corrsponding return node due to light heat gain


Add a new 1-D array to store exhaust node number in ZoneEquipConfig

I don't see why ReturnNodeExhaustNodeNum is necessary.

@mjwitte Since we allow multiple Lights objects in a single zone, it is possible there are multiple exhaust nodes in a single zone, so that an 1-D array is created. If not necessary, do you have any suggestions to store exhaust node information in ZoneEquipConfig?

lgu1234 · 2021-04-19T13:31:02Z

src/EnergyPlus/FanCoilUnits.cc

+                        ShowContinueError(state, "..FanCoil inlet node name = " + state.dataLoopNodes->NodeID(FanCoil(FanCoilNum).AirInNode));
+                        ErrorsFound = true;
+                    }
+                }


Allow FanCoil to accept an induced node of return plenum as an inlet node with ATMixer at the supply side, in addition to a zone exhaust node.

lgu1234 · 2021-04-19T13:36:15Z

src/EnergyPlus/FanCoilUnits.cc

+                        ShowContinueError(state,
+                                          "..Fan coil unit air inlet node name = " + state.dataLoopNodes->NodeID(FanCoil(FanCoilNum).AirInNode));
+                        ErrorsFound = true;
+                    }


Allow FanCoil to accept an induced node of return plenum as an inlet node without ATMixer, in addition to a zone exhaust node.

lgu1234 · 2021-04-19T13:38:23Z

src/EnergyPlus/InternalHeatGains.cc

+                            }
+                        } else {
+                            state.dataHeatBal->Lights(Loop).ZoneReturnNum = ZoneReturnNum;
+                        }


Allow Lights object to accept a NodeList as Return Air Heat Gain, in addition to return node name.

If the Lights input is Return Air Heat Gain Node or NodeList Name then it should accept any number of nodes in the list. If there is a reason to limit it to a single return node and/or a single plenum induced air node, then there should be two input nodes for one node each. Why an Exhaust Node here? It should be a plenum induced air node, correct?

@mjwitte I can make a change for Light object to add one more field. In this scenario, I would like to have a sing return node vs. a single exhaust node to share return heat gain. Induced node is not for this application.

lgu1234 · 2021-04-19T14:22:03Z

src/EnergyPlus/UnitarySystem.cc

                        ShowContinueError(state,
                                          "Air Inlet Node " + loc_AirInNodeName +
                                              " name does not match any controlled zone exhaust node name. Check ZoneHVAC:EquipmentConnections "
                                              "object inputs.");
+                        ShowContinueError(state, "or Induced Air Outlet Node Name specified in AirLoopHVAC:ReturnPlenum object.");


Provide information to allow an induced node from ZonePlenum

lgu1234 · 2021-04-19T14:22:48Z

src/EnergyPlus/ZoneEquipmentManager.cc

+    int ActualZoneNum;        // Zone number
+    int ZoneNode;             // Node number of controlled zone
+    int ReturnNode;           // Node number of controlled zone's return air
+    int ReturnNodeExhaustNum; // Asscoaited exhaust node number, corresponding to the return node


Add an array to store ReturnExhaust node number

lgu1234 · 2021-04-19T14:23:50Z

src/EnergyPlus/ZoneEquipmentManager.cc

@@ -4958,6 +4963,9 @@ void CalcZoneLeavingConditions(EnergyPlusData &state, bool const FirstHVACIterat
                    } else {
                        state.dataLoopNodes->Node(ReturnNode).Temp = TempRetAir;
                    }
+                    if (ReturnNodeExhaustNum > 0 && state.dataLoopNodes->Node(ReturnNodeExhaustNum).MassFlowRate > 0.0 && QRetAir > 0.0) {
+                        state.dataLoopNodes->Node(ReturnNodeExhaustNum).Temp = TempRetAir;
+                    }


Assign node temperature after adding return heat to both nodes of return and zone exhaust.

lgu1234 · 2021-04-19T14:24:31Z

src/EnergyPlus/ZonePlenum.cc

+
+    return Nodefound;
+}
+


Ensure induced node is used as inlet node of zone equipment

lgu1234 · 2021-04-19T14:24:55Z

testfiles/CMakeLists.txt

@@ -212,6 +212,7 @@ add_simulation_test(IDF_FILE DOASDualDuctSchool.idf EPW_FILE USA_IL_Chicago-OHar
 add_simulation_test(IDF_FILE DOAToFanCoilInlet.idf EPW_FILE USA_IL_Chicago-OHare.Intl.AP.725300_TMY3.epw)
 add_simulation_test(IDF_FILE DOAToFanCoilSupply.idf EPW_FILE USA_IL_Chicago-OHare.Intl.AP.725300_TMY3.epw)
 add_simulation_test(IDF_FILE DOAToPTAC.idf EPW_FILE USA_FL_Miami.Intl.AP.722020_TMY3.epw)
+add_simulation_test(IDF_FILE DOAToPTAC_DrawReturnAir.idf EPW_FILE USA_FL_Miami.Intl.AP.722020_TMY3.epw)


Add a new example file for this new feature

lgu1234 · 2021-04-19T15:02:14Z

In addition to a new example file, five test files are provided for each of 5 zone equipment types:

FanCoilInlet_Test.txt
PTAC_Test.txt
PTHP_Test.txt
Unitary_Test.txt
UnitVentuilator_Test.txt

mjwitte

@lgu1234 This is a good start, but I have some questions below. If you would like to arrange a call next week to discuss, let me know.

Another way to simplify this would be to create some common functions for:
1.int GetControlledZoneNum(EquipType, EquipName)
2. bool validateZoneHVACEquipInlet(CtrlZoneNum, inletNodeNum) which could call:
3. bool isZoneReturnNode(CtrlZoneNum, NodeNum)
4. bool isReturnPlenumInducedNode(NodeNum, &ReturnPlenumNum?)

Perhaps get this working for one equipment type first, then the same code changes can be implemented in the other equipment types.

mjwitte · 2021-05-07T18:47:06Z

idd/Energy+.idd.in

@@ -21153,13 +21153,14 @@ Lights,
       \units 1/K
       \minimum 0.0
       \default 0.0
-  A7 ; \field Return Air Heat Gain Node Name
+  A7 ; \field Return Air Heat Gain Node or NodeList Name


I don't see why the Lights object needs to care what kind of node(s) it is connected to. The function which calculates the the heat gain to the node can simply look at one or more nodes and allocated the heat gain from this lights object to the node(s) on a mass-flow weighted basis.

@mjwitte The current field input allows a single return node. The expansion allows a node list with a single return node and a single exhaust node to share the return heat gain.

@lgu1234 How about 2 node names here?
Return Air Heat Gain Node Name
Exhaust Heat Gain Node Name

@mjwitte I am OK with your suggestion. Therefore, A7 is kept as is. A8 will be added as Exhaust Heat Gain Node Name. Thanks.

mjwitte · 2021-05-07T18:47:14Z

src/EnergyPlus/DataHeatBalance.hh

@@ -648,6 +648,7 @@ namespace DataHeatBalance {
        Real64 FractionReturnAirPlenTempCoeff1;
        Real64 FractionReturnAirPlenTempCoeff2;
        int ZoneReturnNum;        // zone return index (not the node number) for return heat gain
+        int ZoneExhaustNodeNum;   // Exhaust node number


Why a single node number here? And why do the lights care what kind of node this is?

mjwitte · 2021-05-07T18:48:06Z

src/EnergyPlus/DataZoneEquipment.hh

@@ -265,6 +265,7 @@ namespace DataZoneEquipment {
        Array1D_bool FixedReturnFlow;    // true if return node is fixed and cannot be adjusted in CalcZoneReturnFlows
        Array1D_int ReturnNodePlenumNum; // number of the return plenum attached to this return node (zero if none)
        Array1D_int ReturnFlowBasisNode; // return air flow basis nodes
+        Array1D_int ReturnNodeExhaustNodeNum; // Exhaust node number flow to a corrsponding return node due to light heat gain


I don't see why ReturnNodeExhaustNodeNum is necessary.

mjwitte · 2021-05-07T19:03:20Z

src/EnergyPlus/FanCoilUnits.cc

+                    if (FanCoil(FanCoilNum).ControlZoneNum > 0) {
+                        for (NodeNum = 1; NodeNum <= state.dataZoneEquip->ZoneEquipConfig(FanCoil(FanCoilNum).ControlZoneNum).NumReturnNodes;
+                             ++NodeNum) {
+                            InletNodeFound = ZonePlenum::ValidateInducedNode(
+                                state, FanCoil(FanCoilNum).AirInNode, state.dataZoneEquip->ZoneEquipConfig(CtrlZone).ReturnNode(NodeNum));
+                            if (InletNodeFound) break;
+                        }
+                    }


This block is testing to see of one if a zone return node is connected to the same plenum as the induced air node? Is this necessary?
This would be more efficient if the full list state.dataZoneEquip->ZoneEquipConfig(CtrlZone).ReturnNode is passed to the function. Then the function can first search for a plenum that matches the induced air node, then run through the return node list checking for a match there.
Also, if this fails because the induced node happens to be connected to a different plenum that does not return from the same zone, then the error message below will be confusing.

@mjwitte If a full list of return node is passed as an argument, return node do loop will occur inside the function. Therefore, do loop will be needed in either outside function or inside function. I can make change. By the way, how can I place a full list of return nodes as a single argument?

mjwitte · 2021-05-07T19:09:42Z

src/EnergyPlus/InternalHeatGains.cc

+                            }
+                        } else {
+                            state.dataHeatBal->Lights(Loop).ZoneReturnNum = ZoneReturnNum;
+                        }


If the Lights input is Return Air Heat Gain Node or NodeList Name then it should accept any number of nodes in the list. If there is a reason to limit it to a single return node and/or a single plenum induced air node, then there should be two input nodes for one node each. Why an Exhaust Node here? It should be a plenum induced air node, correct?

mjwitte · 2021-05-07T19:29:34Z

src/EnergyPlus/FanCoilUnits.cc

+                    for (CtrlZone = 1; CtrlZone <= state.dataGlobal->NumOfZones; ++CtrlZone) {
+                        for (int Num = 1; Num <= state.dataZoneEquip->ZoneEquipList(CtrlZone).NumOfEquipTypes; ++Num) {
+                            if (UtilityRoutines::SameString(FanCoil(FanCoilNum).Name, state.dataZoneEquip->ZoneEquipList(CtrlZone).EquipName(Num)) &&
+                                UtilityRoutines::SameString(FanCoil(FanCoilNum).UnitType,
+                                                            state.dataZoneEquip->ZoneEquipList(CtrlZone).EquipType(Num))) {
+                                FanCoil(FanCoilNum).ControlZoneNum = CtrlZone;
+                                break;
+                            }
+                        }
+                        if (FanCoil(FanCoilNum).ControlZoneNum > 0) break;


If this search to set FanCoil(FanCoilNum).ControlZoneNum was done before all of the node checking, then the loops for CtrlZone could be eliminated.
Also, the inlet node checks are the same for ATMixer_SupplySide or no mixer, so this can be structured to avoid duplicate code.

@mjwitte I debug the code and found FanCoil(FanCoilNum).ControlZoneNum is not assigned. There is a section to get ControlZoneNum without a mixer. Therefore, this section code is needed.

I agree that the inlet node checks are duplicated. I am going to created a new function.

It would be better to always set ControlZoneNum before all of this connection checking. I don't think that would break anything else. So, this block can be moved higher up.

Yes, it can be done. However, this search is needed with ATMixer_SupplySide and an induced node is used as an inlet node. Therefore, this section is better to stay as is.

My point here is that I see three new loops over CtrlZone. It seems that one loop would be adequate.

lgu1234 · 2021-05-10T15:04:47Z

@mjwitte I checked code in UnitarySystem I modified. There is a do loop section:

                    for (int NodeNum = 1; NodeNum <= state.dataZoneEquip->ZoneEquipConfig(this->ControlZoneNum).NumReturnNodes; ++NodeNum) {
                        InducedNodeFound = ZonePlenum::ValidateInducedNode(
                            state, this->m_ATMixerSecNode, state.dataZoneEquip->ZoneEquipConfig(this->ControlZoneNum).ReturnNode(NodeNum));
                        if (InducedNodeFound) break;
                    }

This section can be consolidated as you suggested: bool isReturnPlenumInducedNode(NodeNum, &ReturnPlenumNum?)

I would like to make changes in UnitarySystem first. As long as the change is OK, I can modify other modules. I would like to have a meeting. I am available either Thursday or Friday afternoon this week.

lgu1234 · 2021-05-12T19:06:46Z

@mjwitte I upload the code with a new common function for the FanCoil unit for review and comments. If OK, I hope to use this one as a starting point to generate more common functions in other modules.

mjwitte · 2021-05-13T18:14:20Z

src/EnergyPlus/FanCoilUnits.cc

+                        InletNodeFound = isReturnPlenumInducedNode(state,
+                                                                   FanCoil(FanCoilNum).AirInNode,
+                                                                   state.dataZoneEquip->ZoneEquipConfig(CtrlZone).NumReturnNodes,
+                                                                   state.dataZoneEquip->ZoneEquipConfig(CtrlZone).ReturnNode);


Looking at this more, isReturnPlenumInducedNode is not doing much. How about
ZonePlenum::ValidateInducedNode( state, InletNodeNum, state.dataZoneEquip->ZoneEquipConfig(CtrlZone).NumReturnNodes, state.dataZoneEquip->ZoneEquipConfig(CtrlZone).ReturnNode) right here. With the list of return nodes passed in, ValidateInducedNode can search the plenum induced air nodes first, then look for matching return node to plenum inlet node once the correct plenum is located.

lgu1234 · 2021-05-14T12:39:09Z

@mjwitte I revised the ZonePlenum::ValidateInducedNode function and uploaded the code. Please take a look to ensure the change is what you expect.

lgu1234 · 2021-05-17T12:27:29Z

src/EnergyPlus/FanCoilUnits.cc

+
+        FanCoil(FanCoilNum).ControlZoneNum = ControlZoneNum;
+    }
+


There are two places to find zone number. I consolidate two places as a common function based on search scenario. The other cases may not need to use the zone number.

mjwitte · 2021-05-17T19:44:13Z

src/EnergyPlus/ZonePlenum.cc

+                    for (InduceNodeCtr = 1; InduceNodeCtr <= state.dataZonePlenum->ZoneRetPlenCond(PlenumNum).NumInducedNodes; ++InduceNodeCtr) {
+                        if (InduceNodeNum == state.dataZonePlenum->ZoneRetPlenCond(PlenumNum).InducedNode(InduceNodeCtr)) {


If these lines are moved up after line 1389, then looking for the induced node first would be a little bit faster.

Done. Thanks.

lgu1234 · 2021-07-22T19:19:31Z

@mjwitte There is a warning in x86_64-MacOS-10.15-clang.

Could you let me know if this line can be removed or not?

mjwitte · 2021-07-22T19:24:13Z

@lgu1234 Yes, but it will be fixed when #8898 merges (deleted here). So, no need to fix it here.

Myoldmopar · 2021-07-22T19:58:17Z

when #8898 merges

Oh right, thanks for the reminder. Heading over there to merge now...

mjwitte

@lgu1234 Ran some tests with the new example file, with bad node names.
Invalid return node failed as expected.
Invalid exhaust node was just a warning - should be severe and stop.
Exhaust node not in the same zone was just a warning - should be severe and stop.
~~Exhaust node with blank return node - no warning at all.~~ This is ok.

mjwitte · 2021-07-23T21:17:00Z

Here are the test files.
8719-ZoneHVAC Return Air-TestNodeErrors.zip

mjwitte · 2021-07-23T21:54:22Z

Exhaust node with blank return node - no warning at all.
I forgot, this is valid, because blank will default to a valid return node if present. So this is ok.

Docs look good except a couple of warnings (see the file diffs page):

 Check warning on line 1029 in doc/input-output-reference/src/overview/group-unitary-equipment.tex

GitHub Actions
/ build
doc/input-output-reference/src/overview/group-unitary-equipment.tex#L1029
Label `field-supply-air-fan-operating-mode-schedule-name-4' multiply defined.

 Check warning on line 2263 in doc/input-output-reference/src/overview/group-zone-forced-air-units.tex

GitHub Actions
/ build
doc/input-output-reference/src/overview/group-zone-forced-air-units.tex#L2263
Label `field-supply-air-fan-operating-mode-schedule-name-4' multiply defined.

Looks like I never answered this question

Since we allow multiple Lights objects in a single zone, it is possible there are multiple exhaust nodes in a single zone, so that an 1-D array is created. If not necessary, do you have any suggestions to store exhaust node information in ZoneEquipConfig?

If multiple lights objects are present in the zone, it should be ok as long as the return node/exhaust node pair are the same node names. The internal heat gain tracking will add all of the gains to that return/exhaust node pair. But if LightsA reference ReturnNode1 and ExhaustNode1 and LightsB references ReturnNode1 and ExhaustNode2, I think the current code for lights will overwrite the exhaust node and only the last one will get the heat gain. This could be a valid case if there is more than one piece of equipment in the zone that is drawing from the return duct. So, this could be a vector which means a vector on each return node, which seems complicated.

Perhaps at this point, you should check if a given return node already has ReturnNodeExhaustNodeNum assigned then any additional Lights objects that reference it need to use the same exhaust node. Some notes about this should be added to the I/O Ref entry for the exhaust node. Also, add that any other return air heat gains (like from refrigetation equipment) on the same return node will impact the exhaust node as well.

Also, I don't see any Engineering Ref changes, but I can't find anyplace in the Engineering Ref that talks about return air heat gain. I thought there was some place in the docs that explained RetTempMax and how any load not added to the return air gets added to the zone, etc.

Myoldmopar · 2021-07-24T20:12:13Z

Docs look good except a couple of warnings (see the file diffs page):

If those are the same warnings that have appeared in other branches, I think I have them fixed in one of my branches. If that is a new warning or a new field entirely or anything, then yeah, that should be fixed here.

lgu1234 · 2021-07-26T13:05:14Z

@mjwitte I resolved doc warning by replacing `field-supply-air-fan-operating-mode-schedule-name-4' in doc/input-output-reference/src/overview/group-unitary-equipment.tex#L1029 by '{field-unitaryheatcool-supply-air-fan-operating-mode-schedule-name}'.

Instead of using number to show difference, I add the object name in the beginning of the field name.

lgu1234 · 2021-07-26T14:45:29Z

@mjwitte I uploaded code by addressing partial comments.

Remove warning from IO ref
Add severe errors based 4 test files

DOAToPTAC_DrawReturnAir-ExhNodeNotInZone-Annual.idf
Current: warning
** Warning ** GetInternalHeatGains: Lights="SPACE1-1 LIGHTS 1", invalid Exhaust Air Heat Gain Node Name =SPACE4-1 PTAC INLET
** ~~~ ** No matching Zone Exhaust Air Node found.

Action: Severe and stop
** Severe ** GetInternalHeatGains: Lights="SPACE1-1 LIGHTS 1", invalid Exhaust Air Heat Gain Node Name = SPACE4-1 PTAC INLET
** ~~~ ** No matching Zone Exhaust Air Node found.
** Fatal ** GetInternalHeatGains: Errors found in Getting Internal Gains Input, Program Stopped

DOAToPTAC_LightsZero-DrawReturnAir-BadExhNode-Annual.idf
Current: Warning
Action: Same severe error
** Severe ** GetInternalHeatGains: Lights="SPACE1-1 LIGHTS 1", invalid Exhaust Air Heat Gain Node Name = SPACE1-1 ABC TERMINAL MIXER SECONDARY INLET
** ~~~ ** No matching Zone Exhaust Air Node found.
** Fatal ** GetInternalHeatGains: Errors found in Getting Internal Gains Input, Program Stopped

DOAToPTAC_LightsZero-DrawReturnAir-BadReturnNode-Annual.idf
Current: Warning and Severe
** Severe ** GetInternalHeatGains: Lights="SPACE1-1 LIGHTS 1", invalid Return Air Heat Gain Node Name =SPACE1-1 XYZ RETURN OUTLET
** ~~~ ** No matching Zone Return Air Node found.
** Warning ** GetInternalHeatGains: Lights="SPACE1-1 LIGHTS 1", Exhaust Air Heat Gain Node Name =SPACE1-1 AIR TERMINAL MIXER SECONDARY INLET is not used
** ~~~ ** No matching Zone Return Air Node found. The Exhaust Node requires Return Node to work together
** Fatal ** GetInternalHeatGains: Errors found in Getting Internal Gains Input, Program Stopped

Action: All severe
** Severe ** GetInternalHeatGains: Lights="SPACE1-1 LIGHTS 1", invalid Return Air Heat Gain Node Name =SPACE1-1 XYZ RETURN OUTLET
** ~~~ ** No matching Zone Return Air Node found.
** Severe ** GetInternalHeatGains: Lights="SPACE1-1 LIGHTS 1", Exhaust Air Heat Gain Node Name =SPACE1-1 AIR TERMINAL MIXER SECONDARY INLET is not used
** ~~~ ** No matching Zone Return Air Node found. The Exhaust Node requires Return Node to work together
** Fatal ** GetInternalHeatGains: Errors found in Getting Internal Gains Input, Program Stopped

DOAToPTAC_LightsZero-DrawReturnAir-NoReturnNode-Annual.idf

No action is needed.

I am think of a case with multiple return nodes with the same exhaust node.

Do you provide an example file with multiple airloops to serve a single zone?

mjwitte · 2021-07-26T14:51:50Z

@lgu1234 For examples with 2 airloops (and 2 returns) for each zone, see House-2FurnaceAC-SequentialLoad.idf (and other House-2FurnaceAC-*.idf).

lgu1234 · 2021-07-30T19:37:45Z

@mjwitte I upload the code and document to address the rest of comments.

The new feature can handle multiple return nodes and referred to the same exhaust node in multiple Lights objects. The Engineering reference was revised to add how the node temperatures are calculated with 3 scenarios: Return node only, a pair of return and exhaust nodes, multiple return nodes and a single exhaust node. The corresponding unit test for the last scenario was added.

Enclosed is a test file for the last scenario.
DoubleLightsSingleExhaust.idf.txt

mjwitte

@lgu1234 Thanks for addressing comments and adding the engineering ref section.

mjwitte · 2021-08-03T01:08:59Z

...gineering-reference/src/simulation-models-encyclopedic-reference-003/zone-internal-gains.tex

+
+\(CpAir\) is the specific heat (J/kg)
+
+Although a single Lights object allows a return node and an exhasut node, it is possible to have multiple Lights objects with different return nodes and referrred to the same exhaust node. Therefore, the exhaust node will share return heat from different return nodes. The temperature rise at i-th return node is given below:


Typo: exhasut

This is not the scenario I was asking about. What would this mean physically for a single zonehvac unit to draw from 2 different return ducts? I'm not sure we should allow this combination.

I was asking about the reverse, where 2 different zoneHVAC units draw from the same return duct. At this point, I'm ok with not allowing that just so we can call this complete.

@mjwitte Thanks for finding typos. I corrected 4. I am going to upload the Eng. Ref.

I can remove the scenario for a single zonehvac unit to draw from 2 different return ducts. Please let me know if the scenario is removed or not.

lgu1234 · 2021-08-04T19:50:24Z

@mjwitte An error message was added if 2 different exhaust nodes draw from the same return node.

Enclosed is a test file.
SingleReturnDoubleExhaust.idf.txt

mjwitte · 2021-08-05T14:55:59Z

The new error check is correct when 2 different exhaust nodes are used with the same return node, as in SingleReturnDoubleExhaust.idf

But it should not be an error to use the same pair of exhaust node and return node multiples times. The internal gains tracking will sum the heat gains automatically. This file should run without error: DoubleLightsSingleExhaust-SingleReturn.idf.txt

…hts objects

lgu1234 · 2021-08-05T15:57:56Z

@mjwitte The code was changed and uploaded. No error is generated when the same return and exhaust nodes are used in two lights object.

mjwitte

Retested the new error messages and everything is working as expected. Will merge once CI finishes up.

mjwitte · 2021-08-05T21:26:15Z

Mac is green after the latest change. Merging.

lgu1234 added 2 commits April 16, 2021 09:24

Initial upload

ee18b36

Merge branch 'develop' into Allow-zone-HVAC-to-draw-return-air-New

d326548

lgu1234 added IDDChange Code changes impact the IDD file (cannot be merged after IO freeze) NewFeature Includes code to add a new feature to EnergyPlus labels Apr 16, 2021

lgu1234 added 2 commits April 16, 2021 13:29

Remove a warning

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Merge branch 'develop' into Allow-zone-HVAC-to-draw-return-air-New

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lgu1234 commented Apr 19, 2021

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lgu1234 mentioned this pull request Apr 19, 2021

Allow zone HVAC terminal units to draw return air from return air plenum and return duct #8453

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lgu1234 added 3 commits May 5, 2021 10:25

Merge branch 'develop' into Allow-zone-HVAC-to-draw-return-air-New

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lgu1234 added 2 commits May 12, 2021 15:02

Create a common function in FanCoil module

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Merge branch 'develop' into Allow-zone-HVAC-to-draw-return-air-New

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mjwitte reviewed May 13, 2021

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Revise a common function

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Generate a common function

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lgu1234 commented May 17, 2021

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mjwitte reviewed May 17, 2021

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lgu1234 added 4 commits May 19, 2021 14:36

Address comments

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Merge branch 'develop' into Allow-zone-HVAC-to-draw-return-air-New

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Correct a mistake

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Merge branch 'develop' into Allow-zone-HVAC-to-draw-return-air-New

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mjwitte added this to the EnergyPlus 9.6 IOFreeze milestone May 20, 2021

Move a common function into DataZoneEquipment

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mjwitte reviewed Jul 23, 2021

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lgu1234 added 2 commits July 26, 2021 10:34

Address partial comments

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Merge branch 'develop' into Allow-zone-HVAC-to-draw-return-air-New

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Clang format

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lgu1234 added 3 commits July 30, 2021 15:14

Address rest of comments

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Merge branch 'develop' into Allow-zone-HVAC-to-draw-return-air-New

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clang format

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mjwitte reviewed Aug 3, 2021

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lgu1234 added 2 commits August 4, 2021 08:58

Correct a typo

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Add an error message

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No error when same return and exhaust nodes are used in different Lig…

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…hts objects

mjwitte approved these changes Aug 5, 2021

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mjwitte merged commit 1a8e491 into develop Aug 5, 2021

mjwitte deleted the Allow-zone-HVAC-to-draw-return-air-New branch August 5, 2021 21:26

mjwitte mentioned this pull request Feb 15, 2022

Allow Zone HVAC Terminal Units to draw return air from return air plenum or an air branch off the return air duct #8190

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mjwitte mentioned this pull request Jun 17, 2022

AirloopHVAC:UnitarySystem uses outdoor air temperature to size water source dx cooling coils and incorrectly reports autosized supplemental heating coil capacity for CoolReheat control #9501

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20 tasks

		for (InduceNodeCtr = 1; InduceNodeCtr <= state.dataZonePlenum->ZoneRetPlenCond(PlenumNum).NumInducedNodes; ++InduceNodeCtr) {
		if (InduceNodeNum == state.dataZonePlenum->ZoneRetPlenCond(PlenumNum).InducedNode(InduceNodeCtr)) {


		\(CpAir\) is the specific heat (J/kg)

		Although a single Lights object allows a return node and an exhasut node, it is possible to have multiple Lights objects with different return nodes and referrred to the same exhaust node. Therefore, the exhaust node will share return heat from different return nodes. The temperature rise at i-th return node is given below:

Allow zone hvac to draw return air #8719

Allow zone hvac to draw return air #8719

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lgu1234 commented Apr 16, 2021 • edited by mjwitte

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lgu1234 commented Apr 19, 2021

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mjwitte commented Aug 5, 2021

lgu1234 commented Apr 16, 2021 •

edited by mjwitte

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