Unitary HVAC: Sensible Load Request

[FavaroP]

My goal is to simulate the behaviour of a building based on the electricity consumption of its centralised HVAC System. I could not find any actuator in the EMS to control a HVAC system knowing its electrical consumption (which, I believe, would be nice to have).

I decided to use the Sensible Load Request actuator for Unitary HVAC System instead. My problem is that I do not understand the behaviour of this actuator. In the documentation, two internal variables were said to help, the Unitary HVAC Design Heating Capacity and Unitary HVAC Design Cooling Capacity. How do these help? What is their connection to Sensible Load Request?
I also do not get why the output of those two variables is 220.95 W and 1 W, respectively, when I run my script. It does not make any sense in my case since the heating and cooling systems operates at several thousands of Watts during some time steps.

See output below (for one time step):

Reading Cooling:Electricity [Wh], value is: 0.0
Reading Heating:Electricity [Wh], value is: 2101.3916003111453
Reading Cooling:EnergyTransfer [Wh], value is: 0.0
Reading Heating:EnergyTransfer [Wh], value is: 2322.3397188553317
Reading System Sensible Heating [Wh], value is: 2435.445364296842
Reading US Design Cooling Capacity [W], value is: 1.0
Reading US Design Heating Capacity [W], value is: 220.94811855332142

So my questions are:

1. What exactly do the sensors Unitary HVAC Design Heating Capacity and Unitary HVAC Design Cooling Capacity return?
2. How do I manage the HVAC operation of a Unitary System with the Sensible Load Request actuator?
3. At which point of the time step should I insert the callback (e.g., callback_after_predictor_after_hvac_managers)?
4. Finally, do you see a better way to control HVAC system knowing its electricity consumption (and weather parameters)?

Thanks for your help!

[FavaroP]

I solve my issues. Here is what I discover and understood (correctly, I hope).

1. Unitary HVAC Design Heating Capacity and Unitary HVAC Design Cooling Capacityare internal variables. Therefore, make sure to use get_internal_variable_value().
2. Sensible Load Request sets the thermal load at which the Unitary Unit can operate, if it needs to, in order to reach the set point. So if it needs to heat the controlling zone in order for it to reach the heating setpoint, then it can only heat with the thermal load given in Sensible Load Request. The energy from the fan is included. It works at the system time step thus the system may turn on and generates the given load only during some sub time step of the zone time step.
3. I personally actuate at callback_begin_system_timestep_before_predictor and it works.
4. I have not found anything better.