Mike Kennedy's profile - activity

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2022-08-01 09:56:22 -0500	received badge	● Popular Question (source)
2018-05-05 15:33:25 -0500	received badge	● Supporter (source)
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2018-04-30 16:32:48 -0500	asked a question	How to stage autosized chillers How to stage autosized chillers Chiller Staging - Plant Loop Load Distribution Scheme - Chiller Control Scheme Questio
2018-04-19 18:14:39 -0500	edited answer	Calculating Power, Capacity, and COP from Chiller Curves Not sure whether this is all water under the bridge but I've found the reported cop to be 1 / ( 1/COPref * EIRfT * EIRfP
2018-04-19 13:37:01 -0500	edited answer	Calculating Power, Capacity, and COP from Chiller Curves Not sure whether this is all water under the bridge but I've found the reported cop to be 1 / ( 1/COPref * EIRfT * EIRfP
2018-04-19 13:03:01 -0500	answered a question	Calculating Power, Capacity, and COP from Chiller Curves Not sure whether this is all water under the bridge but I've found the reported cop to be COP ref * EIRfT * EIRfPLR / PL
2018-03-23 13:07:46 -0500	answered a question	What is the best way to model infliltration in a building? The Gowri approach (PNNL) is a wind only model and so clearly suspect especially in colder climates where stack effect i
2017-08-09 12:59:50 -0500	commented question	Which EnergyPlus VRF Model? The answer I was looking for was not what is in the manual but what peoples experience with the models are. After spend
2017-06-21 09:15:00 -0500	commented answer	Which EnergyPlus VRF Model? Thank you for this information. I had already read manual, Input-Output and Engineering. Perhaps my question is better s
2017-06-20 17:48:41 -0500	answered a question	Which EnergyPlus VRF Model? Thank you for this information. I had already read manual, Input-Output and Engineering. Perhaps my question is better
2017-06-16 14:16:09 -0500	asked a question	Which EnergyPlus VRF Model? Which EnergyPlus VRF Model? Does anybody have guidance on choosing which EnergyPlus VRF model to use?
2017-06-07 08:29:54 -0500	asked a question	zone user design airflow rate not used in system sizing zone user design airflow rate not used in system sizing For a single zone with a unitarysystem HVAC object, I'm using th
2017-05-12 13:21:23 -0500	received badge	● Teacher (source)
2017-05-12 12:13:00 -0500	answered a question	Modeling Code Compliant DX with Two-Speed Airflow Control I never did get this working in Version 8.6. Version 8.7 added a new fan model Fan:SystemModel that solves the issue.
2017-01-19 16:02:47 -0500	commented question	Economizer changes supply air set point and zone set point temperature SetpointManager:MixedAir controlling the mixed air setpoint node with a reference at the Supply equipment outlet node, and SetpointManager:SingleZone:Reheat with Room, !- Control Zone Name Room Air Node, !- Zone Node Name Room ATU Inlet Node, !- Zone Inlet Node Name
2017-01-19 13:32:13 -0500	received badge	● Editor (source)
2017-01-17 15:30:06 -0500	asked a question	Economizer changes supply air set point and zone set point temperature Using UnitarySystem, controller:outdoorair, and setpointmanager:MixedAir to model a constant volume single zone system serving a single zone. With NoEconomizer selected the cooling coil operates to meet the loop outlet set point and the connected zone is maintained at the cooling setpoint. Enabling the economizer causes the loop outlet set point is several degrees lower and the connected zone is maintained at the heating set point. I've looked at other input decks and it seems like the setPointmanager:mixedair is set up the way others have done. Is there an obvious missing manager? How should I go about debugging this issue? Update: The heating coil is not on. The only difference in the run input is the outdoor air controller has FixedDryBulb economizer in one case and no economizer in the other. The zone set point as reported by system node setpoint temperature is the same in both runs. A difference appears at the supply equipment outlet setpoint. In the NoEconomizer case this is set at a temperature that maintains the zone cooling setpoint, in the Economizer case it is lower and maintains the space temperature at the heating set point. If the heating set point is lowered then the economizer opens up. The input seems pretty standard and a few others have looked at it to no avail. Seems like some sort of interface issue between controller:outdoorair and unitarysystem but it could be I'm just confused by the various controllers. Update2: Before the fans turn on, the space temperature is above the cooling set point. Once the system starts, if no economizer is present and the system is at minimum air, the DX cooling is required to maintain the cooling set point. I don't understand why a modulating economizer would force the zone temperature below not only the cooling set point but the heating set point which is 5F lower, and why it would modulate to maintain the heating set point rather than the cooling set point. In a real system, the cooling signal would drop and the economizer shut down. Why would an economizer be controlled differently from the compressor which faithfully maintains the cooling set point? Is there a control that will limit this? Sorry if this is dense, it does feel like I'm missing some basic item in the controls.
2016-11-11 13:13:11 -0500	received badge	● Student (source)
2016-11-11 12:42:05 -0500	received badge	● Organizer (source)
2016-11-11 12:18:11 -0500	asked a question	Modeling Code Compliant DX with Two-Speed Airflow Control My goal is to model energy code required air flow control. Energy codes regulate over 5 ton single zone DX system flows as a fraction of design flow as follows: 66% during venting, 66% during low cooling, 100% during high cooling. Heating is not regulated but I believe it is typically 100% in gas furnace units. I thought this would be easy with the airloophvac:unitarysystem object but am stuck in a house of mirrors. Does anyone have suggestions for how this is supposed to be done? Or know of a good example. I did look up the 90.1 Determination models but they seem to use a large EMS program. What I'm doing that gets close: airloophvac:unitarysystem cooling design supply air flow rate method = SupplyAirFlowRate cooling design supply air flow rate = Autosize heating design supply air flow rate method = SupplyAirFlowRate heating design supply air flow rate = Autosize supply air flow rate method when no cooling or heating is required = SupplyAirFlowRate supply air flow rate when no cooling or heating is required = Autosize UnitarySystemPerformance:MultiSpeed, Single Mod Operation = Yes or No Heating Speed 1 Supply Air Flow Ratio = 1 Cooling Speed 1 Supply Air Flow Ratio = 0.66 Heating Speed 2 Supply Air Flow Ratio = 1 Cooling Speed 2 Supply Air Flow Ratio = 1 Coil:Cooling:DX:MultiSpeed, Rated Air Flow Rate, Speed 1 {m3/s} = Autosize Rated Air Flow Rate, Speed 2 {m3/s} = Autosize With the above inputs and single mode = Yes, the mass flow in low cooling is constant and 66% of the mass flow in heating, venting and high cooling. Fan runtime fraction is 1 and the fan power is reduced to account for the lower mass flow. Just as I would expect it. Only issue is the ventilation flow is at 100% With the above inputs and single mode = No, in heating and venting mode the mass flow is constant and the fan runtime is 1. In low cooling, the mass flow is constant and 66% but the fan runtime fraction is suddenly less than 1. is constant and 66% of the mass flow in heating, venting and high cooling. Fan runtime fraction is 1 and the fan power is reduced . I do not understand why the fan runtime is not 1. To get the reduced ventilation flow I was thinking I needed to set the following: airloophvac:unitarysystem Supply Air Flow Rate Method When No Cooling or Heating is Required = FractionOfAutosizedCoolingValue No Load Fraction of Autosized Cooling Supply Air Flow Rate = 0.66 But with this input the mass flow, fan runtime, and fan energy behave in unexpected ways. With single mode = Yes or No the heating mode mass flow is no longer constant and fan runtimes are less than 0. In ventilation mode the mass flow rate is constant just a few percent below the heating mode mass flow rate (rather than 0.66). The fan runtime is 0.66. The fan energy is a few percent below the heating mode ... (more)
2016-11-09 19:59:24 -0500	asked a question	How to model code compliant two speed fan New energy codes require two speed fans in many classes of HVAC equipment. The fan is supposed to run at no more than 66% of peak fan speed during low cooling and during ventilation hours. From what I can tell units that do this typically run at 100% during heating. I tried the AirLoopHVAC:UnitarySystem, Coil:Cooling:DX:MultiSpeed, UnitarySystemPerformance:MultiSpeed objects but have found that the unit runs at 100% flow during ventilation only hours. I looked at the PNNL 90.1 models and they have a 1200 line EMS routine to model the correct behavior including the economizer function. Can someone point to an easier way to get the fan to operation at 100% speed during heating, 66% during ventilation and low cooling, and 100% during high cooling? Thanks.
2016-11-09 19:59:24 -0500	commented answer	Fan power calculation for variable speed Fan:OnOff Okay now I get it. The reduced mass flow that results from reduced speed operation is already accounted for. The speed curve just adjusts for speed effect, not the reduced mass. To get a specific fan power response for a specific flow reduction, such as the base code requirement, we need to have a curve that modifies your blue line above. And in low speed operation the flow fraction is used as the fan run time fraction. (whether that is due to cycling or reduced speed operation)