Availability Manager Hybrid Ventilation Control Status

asked 2017-04-12 18:36:41 -0500

Sriraj
53 ●3

updated 2017-04-13 10:52:13 -0500

As per the energyplus I/O reference, the output variable 'Availability Manager Hybrid Ventilation Control Status' reports three integer values: 0,1, and 2 denoting no hybrid ventilation control, whether natural ventilation is allowed, or not. However, the output result from a simulation shows the values range between 1 and 2 (1.1,1.858796296, 1.758333333, 1.716666667 etc.). Does it mean that there is a partial natural ventilation happening or denotes that there is a potential to naturally ventilate? I believe this should not be the case, as the output results has to just show a binary result in either 1 or 2. Could somebody please explain how this has to be understood? Thank you very much in advance.

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answered 2017-04-13 07:32:04 -0500

rraustad

13599 ●72 ●12 http://www.fsec.ucf.edu/

EnergyPlus can simulate shorter time steps than defined in the 'TimeStep' object.

Timestep, 4;

There are zone time steps, defined above using the TimeStep object, and there are system time steps that can be shorter than this down to 1 minute intervals. When the system time step is shorter than the zone time step the output reported during the system time step are averaged over the zone time step interval. To see the output reports at the system time step enter a time step frequency of detailed in the Output:Variable object.

Output:Variable,*,Site Outdoor Air Drybulb Temperature,detailed;

Using this method should show either a 0, 1 or 2 in the output reports.

To lock down the system time step use the ConvergenceLimits object.

ConvergenceLimits,
  N1 , \field Minimum System Timestep
    \units minutes
    \type integer
    \note 0 sets the minimum to the zone timestep (ref: Timestep)
    \note 1 is normal (ratchet down to 1 minute)
    \note setting greater than zone timestep (in minutes) will effectively set to zone timestep
    \minimum 0
    \maximum 60
  N2 , \field Maximum HVAC Iterations
    \type integer
    \default 20
    \minimum 1
  N3 , \field Minimum Plant Iterations
    \note Controls the minimum number of plant system solver iterations within a single HVAC iteration
    \note Larger values will increase runtime but might improve solution accuracy for complicated plant systems
    \note Complex plants include: several interconnected loops, heat recovery, thermal load following generators, etc.
    \type integer
    \default 2
    \minimum 1
  N4 ; \field Maximum Plant Iterations
    \note Controls the maximum number of plant system solver iterations within a single HVAC iteration
    \note Smaller values might decrease runtime but could decrease solution accuracy for complicated plant systems
    \type integer
    \default 8
    \minimum 2

ConvergenceLimits,
  4;

ConvergenceLimits,
  0; (to match what you have entered in the TimeStep object)

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Thank you very much for reply Richard. That pretty much solved the issue and moreover reminded me of an important element that I often tend to overlook.

best regards, Sriraj

Sriraj ( 2017-04-13 08:00:40 -0500 )edit

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answered 2021-09-24 10:58:45 -0500

yousra rashad
11 ●1

please i have the same question above and i do not understand the above answer

ConvergenceLimits, N1 , \field Minimum System Timestep \units minutes \type integer \note 0 sets the minimum to the zone timestep (ref: Timestep) \note 1 is normal (ratchet down to 1 minute) \note setting greater than zone timestep (in minutes) will effectively set to zone timestep \minimum 0 \maximum 60 N2 , \field Maximum HVAC Iterations \type integer \default 20 \minimum 1 N3 , \field Minimum Plant Iterations \note Controls the minimum number of plant system solver iterations within a single HVAC iteration \note Larger values will increase runtime but might improve solution accuracy for complicated plant systems \note Complex plants include: several interconnected loops, heat recovery, thermal load following generators, etc. \type integer \default 2 \minimum 1 N4 ; \field Maximum Plant Iterations \note Controls the maximum number of plant system solver iterations within a single HVAC iteration \note Smaller values might decrease runtime but could decrease solution accuracy for complicated plant systems \type integer \default 8 \minimum 2

ConvergenceLimits, 4;

this input where i can put it to generate the values (0, 1, 2) and without decimals (like 1.565 .... etc).

thanks

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@yousra rashad with ConvergenceLimits Minimum System Timestep = 4 minutes and zone time step set = 4, or 15 minutes, means the shortened system time step can be no smaller than 4 minutes. Users usually set Minimum System Timestep = 1 and let the program determine how short the system time step should be.

In your report variables use detailed and look at the results in eplusout.csv, you will see that at some times the time step is less than 15 minutes. At these times the system time step is shorter than the zone time step.

Output:Variable, SomeNodeName, System Node Temperature, detailed;