Energyplus Thermostat Setpoint=0?

asked 2020-03-24 07:52:31 -0600

Eko123

251 ●2 ●6

updated 2020-03-24 08:10:18 -0600

__AmirRoth__

4436 ●5 ●17 http://bleedinggreenna...

I have a question regarding the following error message:

  ** Severe  ** UpdateZoneSizing: Heating supply air temperature (calculated) within 2C of zone temperature
   **   ~~~   ** ...check zone thermostat set point and design supply air temperatures
   **   ~~~   ** ...zone name = B001
   **   ~~~   ** ...design heating load         = 0.00 W
   **   ~~~   ** ...thermostat set piont temp   = 0.000 C
   **   ~~~   ** ...zone temperature            = 17.808 C
   **   ~~~   ** ...supply air temperature      = 18.000 C
   **   ~~~   ** ...temperature difference      = 0.19246 C
   **   ~~~   ** ...calculated volume flow rate = 4390.79153 m3/s
   **   ~~~   ** ...calculated mass flow rate   = 4964.53310 kg/s

I am using ThermostatSetpoint:SingleHeating, ThermostatSetpoint:SingleCooling, ThermostatSetpoint:DualSetpoint. I've already checked all Schedules, they are all okay. There is no value which would lead to a thermostat Setpoint of 0°C. How do I solve this problem? Or do I have to use another thermostat object?

And I've got another question regarding the following error:

 ** Severe  ** InitConductionTransferFunctions: Found Material that is too thin and/or too highly conductive, material name = STEEl SHEET 3MM
   **   ~~~   ** High conductivity Material layers are not well supported for internal source constructions, material conductivity = 50.000 [W/m-K]
   **   ~~~   ** Material thermal diffusivity = 1.425E-005 [m2/s]
   **   ~~~   ** Material with this thermal diffusivity should have thickness > 0.19612 [m]

Is this a common issue with thin material? Can I just continue using this material or would this lead to bad results later on?

answered 2020-03-24 11:40:07 -0600

rraustad

13804 ●79 ●12 http://www.fsec.ucf.edu/

updated 2020-03-24 11:42:31 -0600

I am guessing that zone = B001 is a zone with a ThermostatSetpoint:SingleCooling object? If so, you can disregard the warning. If not I would like to see your input file. Click on my name for my email address.

Regarding the high conductivity material, the model checks the against a thickness threshold and then issues the warning you show. The thickness threshold is a function of the zone time step specified in the input file. You can check the math here to see how your material compares to the checks here and make adjustments as necessary.

Alpha = Conductivity(Layer) / (Density(Layer) * SpecificHeat(Layer));
if (Alpha > HighDiffusivityThreshold(=1E-5)) {
    DeltaTimestep = TimeStepZoneSec (= 60 * 60/Timestep);
    ThicknessThreshold = std::sqrt(Alpha * DeltaTimestep * 3.0);
    if (Material(CurrentLayer).Thickness < ThicknessThreshold) {

In your input file:

Timestep,4;

You can save the results you have now and make any changes necessary to eliminate the warning. Then compare your results to results without the warning to see if your results make sense.

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Comments

Yes the zone has a ThermostatSetpoint:SingleCooling linked to it. So this is just a common error while using this object?

Regarding the issue with the material I will do it as you suggested to see how the results change and if they make sense.

Eko123 ( 2020-03-25 04:24:41 -0600 )edit

Well, it is a common error for the time being, but I would add when that warning was created it wasn't noticed that there would be no heating set point temperature available for the ThermostatSetpoint:SingleCooling object. This was simply overlooked for this case. If I were to fix this I would not print that heating warning for the single cooling set point thermostat (so therefore disregard).

rraustad ( 2020-03-25 07:10:12 -0600 )edit

I have one more question on the ThermostatSetpoint:SingleCooling object. Could the error lead to more warnings regarding the cooling of the building? For example a warning like the one shown below.

** Warning ** ManageSizing: Calculated Cooling Design Air Flow Rate for System=RLT LOOP 1 is zero.
   **   ~~~   ** Check Sizing:Zone and ZoneControl:Thermostat inputs.

Eko123 ( 2020-04-01 02:18:58 -0600 )edit

If you have a cooling thermostat, then a warning that says cooling air flow rate = 0 would mean there is no cooling load. To test this plot the zone temperature and zone thermostat cooling set point temperature during the design days to see what is happening.

rraustad ( 2020-04-02 10:13:33 -0600 )edit

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