Why the cooling load (Cooling Coil Total Cooling Rate) changes in EnergyPlus when the building is the same but different HVAC systems are used, even though the building load should theoretically remain constant

grasshopper honeybee
1

I am currently working with Energyplus and comparing the performance of different HVAC systems for the same building model

The building geometry, constructions, schedules, internal gains, and weather file are identical in all simulations. The only change between runs is the HVAC system type.

My understanding is that building cooling load should depend only on building properties (envelope, internal gains, infiltration, weather, etc.), so the cooling load should remain the same regardless of the HVAC system used.

However, when I check the Energyplus output variable:

Cooling Coil Total Cooling Rate

I observe that the values are different for the two HVAC systems.

My questions are:

  1. Should the cooling load be identical when the building model is the same but HVAC systems are different?
  2. Is Cooling Coil Total Cooling Rate actually the correct variable to represent the building cooling load, or does it include system effects such as control strategies, coil performance, or airflow differences?
  3. If I want to compare true building cooling load independent of HVAC**, which Energyplus output variable should I use?

Any clarification on how Energyplus separates building load vs system load would be greatly appreciated.