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HVAC system simulation

asked 2018-05-31 15:28:27 -0500

mfath's avatar

updated 2018-05-31 18:42:45 -0500


I am trying to model the HVAC system performance. I know all the internal loads and I have them applied as internal loads schedule. However, I do not have any idea about the cooling and Heating setpoint. The house is located in Austin, Texas. I changed the setpoint couple of times.

Finally since I saw extra performance from the HVAC system, I tried the following setpoints:

Heating setpoint: 74 F Cooling setpoint: 80 F

But still I have a really weak performance simulation for HVAC system. I uploaded the .CSV file of data which you can open in Dview. And also I uploaded the picture of results for some intervals in the following URL.

I would appreciate if you can help me with any suggestion.


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@M 108014 Could you explain some more what you mean by saying "But still I have a really weak performance simulation"? Is it you get high demand relative to real data or is it something else?

Avi's avatar Avi  ( 2018-05-31 22:20:43 -0500 )edit

@Avi I meant that I am not able to follow the trend of the experimental data that I have. If you look at the .csv file that I attached, there is a column that shows the measured total load and the simulated total load of the house. As shown also in the picture, these two are really far away because of the HVAC system since I know the internal loads and they are applied.

mfath's avatar mfath  ( 2018-05-31 22:43:05 -0500 )edit

@M 108014 could you post a link to your model?

Avi's avatar Avi  ( 2018-06-01 03:50:50 -0500 )edit

@Avi I uploaded the ,idf model which I am using. I would appreciate that if you can take a look into my model. Please consider that I have the ACH50 as a measured value from experiments. However, I am not sure about the wood stud and the thermal mass of the walls.

mfath's avatar mfath  ( 2018-06-01 10:01:44 -0500 )edit

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answered 2018-06-01 04:26:14 -0500

Avi's avatar

Without looking at your model I can recommend on checking the following:

  1. Make sure you set the right infiltration.
  2. Make sure that you set the right amount of outside Air.
  3. Use the right ground model. This one is a big gotcha since for small and medium building the ground coupling model can change results dramatically. You can read about it in my chained answer to that question.
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Asked: 2018-05-31 15:28:27 -0500

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Last updated: Jun 01 '18