How to use the results of the predictor in EMS

asked 2017-01-24 11:16:33 -0600

JB Heritier's avatar

updated 2017-01-25 10:04:53 -0600

I am currently trying to simulate a on-off control, that would turn on only if the predicted load is higher than its nominal capacity.

I am using an EMS script for that, using the sensor Zone Predicted Sensible Load to Setpoint Heat Transfer Rate, with the Model Calling Point AfterPredictorAfterHVACManagers, as described in the example file EMSConstantVolumePurchasedAir

Until now, I am only sensing the value of the predictor, not actuating anything.

I am getting 3 different results for something I was hoping to be the same :

  • The ems sensor Zone Predicted Sensible Load to Setpoint Heat Transfer Rate
  • The report DistrictHeating:Facility
  • The normal report Output:Variable, *, Zone Predicted Sensible Load to Setpoint Heat Transfer Rate, timestep;

C:\fakepath\Output-1.png

I am pretty sure the difference between the two first is due to the mechanical ventilation loss (with HR) under normal conditions. But there is also a big difference when the thermostat setpoint is changed (+2°C)

How can someone get the real load during an EMS simulation?

And why is the last one (=sum of the two zones) that different from the two others?

edit retag flag offensive close merge delete

Comments

"And why is the last one (=sum of the two zones) that different from the two others?" If you do expect yellow+green to equate the two others, I think this is actually the case no?

Julien Marrec's avatar Julien Marrec  ( 2017-01-25 00:37:19 -0600 )edit

Not on the second time step : yellow + green = way more ! Even green by itself is above both. But I agree for the other timesteps.

JB Heritier's avatar JB Heritier  ( 2017-01-25 01:37:30 -0600 )edit

You may not be reporting stuff at the appropriate timestep here (is it at 'detailed'?). And this fringe peak could be the result of many things, including a rapid change in thermostat or something. I wouldn't read too much into it. Look at other days, see if there's a peak too, and if it's around 17:00 as well.

Julien Marrec's avatar Julien Marrec  ( 2017-01-25 01:44:30 -0600 )edit

For the difference between first two, you didn't explain why you expect it to be the same, nor what your HVAC system is like. I would expect it to be the same if you had IdealLoadsAirSystem in your building and nothing else.

Julien Marrec's avatar Julien Marrec  ( 2017-01-25 01:50:56 -0600 )edit
  • Yes, it is a result of a change of thermostat, as I explained. Every day at 17:00, there's the "same" peak difference with halved results. But I was still wondering how the real load (so the blue) could be predicted accurately.

  • Yes, my HVAC system is only IdealAirLoads, as I didn't explain ;) . It's an IdealAirLoads with heat recovery ventilation (80%). And I guess the difference between blue and red is the remaining 20% of cold air blowed in by the ventilation. Which I was expecting to be included in the predictor.

  • What do you mean by is it at 'detailed'?

JB Heritier's avatar JB Heritier  ( 2017-01-25 02:08:38 -0600 )edit