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EMS system actuator lag

asked 2018-06-01 16:19:01 -0500

EplusNewb's avatar

updated 2018-06-03 13:16:39 -0500


I am attempting to simulate a ducted VRF system using the EMS system, in order to validate a building model with experimental data. I am using individual terminal units in each conditioned zone, and setting inlet conditions and cooling rates to be the same for all of the simulated units which in reality are one ducted unit. The units are controlled based on the performance of the terminal unit in the zone corresponding to the zone in the actual building that has a thermostat. I am sensing the net cooling or heating provided by the coils, and using this to calculate the PLR according to the engineering reference manual. I then overwrite the PLR of the terminal units that correspond to supply ducts from the ducted unit to simulate the actual operation. I do all of this inside the HVAC simulation. The controls are almost working, but for some reason the actuators are timestep lagging by 1 timestep. I performed a line trace using the EDD, and am looking at detailed outputs. The line trace actually seems to indicate that the PLR should be overwritten in the appropriate timestep, so I am not sure what is causing the timestep lag.

I appreciate any help including suggesting any debugging methods that I could do beyond an EDD line trace.


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You may have already done this, but make sure you are using the correct EMS calling point. Chapter 6 of the EMS Application Guide has a good diagram.

aparker's avatar aparker  ( 2018-06-10 15:31:43 -0500 )edit

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answered 2018-06-28 14:56:34 -0500

updated 2018-06-28 14:57:44 -0500

This was answered in the helpdesk (Ticket 12851 with full input file), repeating answer here to close this out.

The primary problem here is that these zone thermostat actuators have no impact until the next call to the Predictor:

EnergyManagementSystem:Actuator, FC2_4_HEATSET, !- Name Office 1121, !- Actuated Component Unique Name Zone Temperature Control,!- Actuated Component Type Heating Setpoint; !- Actuated Component Control Type

So, any EMS program that sets these should use calling point BeginTimestepBeforePredictor. That's why there's a lag happening here

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Asked: 2018-06-01 16:19:01 -0500

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Last updated: Jun 28 '18