Peak_cool and cool_bal don't match

grasshopper honeybee
1

Hi all,

I would have expected the peak_cool output of the HB Peak Loads component to match up with the peak of the cool_bal, but it doesn’t:

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Can anyone please explain why?

2

from component:

peak_cool: A list of numbers that align with the input _rooms and ****correspond
            to the peak cooling of each room on the summer design day***** in Watts.
            Note that, for multi-room simulations, the individual room peaks may
            not be coincident, meaning that summing these values together won't
            give a correct sense of the size of cetral cooling equipment serving
            multiple rooms. For such equipment, the max of the cooling data
            collection should be used.

cool_bal: A list of data collections for the various terms of the sensible load
            balance that *****contribute to peak cooling on the summer design day*****. These
            can be plugged into the "LB Monthly Chart" component (with stack_ set
            to True) to visualize the terms contributing to the peak. Will be
            None unless run_bal_ is set to True.

from: eplusdocs
“”"
The heat balance algorithms used by EnergyPlus result in a single combined design load for a given zone and some, but not all, of the zone instantaneous heat gains. This section describes the estimation procedure for the three Component Loads Summary reports that shows an estimated breakdown of load components from each type of of heat gain for each zone. The three different reports are the Zone Component Loads Summary, the AirLoop Component Loads Summary and the Facility Component Loads Summary. The procedure described below is used for each zone and then the AirLoop and Facility level reports are generated by aggregating the results for the appropriate zones.

If the time of the peak load for each Zone for cooling exactly matches the time of the peak load for the AirLoop or Facility than the Estimated Cooling Peak Load Components will represent a sum of the values from the corresponding zones. Likewise the Estimated Heating Peak Load Components will add up for the AirLoop or Facility if the times of the heating peaks exactly match. This is not necessarily the case for Peak Conditions or the Engineering Checks tables. Since the sizing of Airloops is based on the system sizing they usually will be different than the sum of the corresonding zones.

The Estimated Cooling Peak Load Components and Estimated Heating Peak Load Components subtables of the Zone Component Loads Summary report contain values that are estimated and are not part of the normal heat balance algorithms used in the rest of EnergyPlus. In particular, the column described as Sensible-Delayed represents an estimate of the sensible load contributed at the peak time based on radiant contributions from various load components that have radiant portions in previous timesteps. The focus of this section will be on the Sensible-Delayed column.

The columns labeled Sensible-Instant, Sensible-Return Air, and Latent are directly computed for people, lights, equipment, refrigeration, water use equipment, HVAC equipment losses, power generation equipment, infiltration, zone ventilation and interzone mixing. For example, Lights objects have inputs for the fractions of the gains that are to return air, radiant, visible and the remainder is convected. In this case, the fraction to return air is reported in the Sensible Return Air column and the fraction that is convected is reported in the Sensible-Instant column.

At the time of the peak load, each surface in the zone is contributing a convective heat loss or heat gain depending on the inside surface temperature.
“”"

Note:
“”"
The Estimated Cooling Peak Load Components and Estimated Heating Peak Load Components subtables of the Zone Component Loads Summary report contain values that are estimated and are not part of the normal heat balance algorithms used in the rest of EnergyPlus. In particular, the column described as Sensible-Delayed represents an estimate of the sensible load contributed at the peak time based on radiant contributions from various load components that have radiant portions in previous timesteps. The focus of this section will be on the Sensible-Delayed column.
“”"

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