System type development for cDXGF, cDXNH, cDXHP, cPVVG, cAVVG systems and related changes

[Justin-DeBlois]

• [x] Provide a concise description of the measure, bug, or feature. Submit one PR per measure.

  A. Changes needed to enable new system types

  1. Templates files in SWXX000-00 TRC System Types\X\cases\ with parameters assignments for cDXGF, cDXNH, cDXHP, cPVVG, cAVVG -cDXGF: Single zone packaged with gas furnace -cDXNH: Single zone packaged with no heat (appears to be new to eTRM) -cDXHP: Single zone packaged with HP -cPVVG: Single zone packaged variable volume with gas furnace -cAVVG: Multi-zone VAV with hot water coil, natural gas boilers, chilled water coil, air-cooled chiller -Parameters added in cases files to over-ride prototype defaults. The :main_oa_econ_max_temp parameter was added to the cohorts.csv file so that fixed DB temp economizer control could be used.

2. The codes files were modified to add Title 24 drybulb limit temperatures for each climate zone.

3. Enable ability to change prototypes with SZ default systems to MZ systems using hvac_config and main_hvac_type. The way all_zones was defined for the prototypes, changing main_hvac_type did not combine zones into one system and changing hvac_config resulted in conflicts. -Affects root.pxt files -Some hvac_config options would result in two hvac systems being assigned to zones if a system name is assigned both in all_zones and irregular_zones, and other similar conflicts.

4. Added "unitary_no_load_flow_method" parameter to parameterize the sizing method of the no load (minimum) flow for UnitarySystems with DX cooling. -Affects root.pxt (group "main_hvac_system"), hvac-zone.pxt and unitary.pxt files -Default is "SupplyAirFlowRate" which is the method previously hard-coded into unitary.pxt. -Changing to "FractionOfAutosizedCoolingValue" allows the minimum flow fraction to be defined, which was not working for systems with DX cooling when only using the sizing objects.

5. Added capability to model systems with no heat, for cDXNH system type. -Affects hvac-zone.pxt file -Only activated if atu_reheat_coil_type, heat_coil_type & sub_heat_type = "NONE" or nil

6. For cPVVG system type (packaged single zone variable volume gas furnace), UnitarySystem control_type = "SingleZoneVAV" works best. Added conditional logic to change to this method for single zone systems with fan_speed = "VARIABLE". -Affects unitary.pxt file -Activated for SZ systems with fan_speed = "VARIABLE".

B. Changes to min flow rate sizing

To determine minimum flow fraction based on the greater of ventilation requirement and minimum ratio. Currently for many configurations, ventilation rate is not being accounted for.

1. Added "cool_flow_min_frac" parameter. "cool_flow_min_frac" is the minimum flow ratio in cooling in the sizing:zone object, and in some cases is the no load flow fraction in the AirLoopHVAC:UnitarySystem object -Affects root.pxt (group "main_hvac_zone"), hvac-zone.pxt and unitary.pxt files -Differs from ATU_flow_min_frac because ATU_flow_min_frac is used at the AirTerminal object and if is not autosized, ATU_flow_min_frac overrides the ventilation requirement. -If ATU_flow_min_frac is Autosize and cool_flow_min_frac is defined, then the VAV minimum flow fraction will be the greater of the ventilation rate and cool_flow_min_frac. -cool_flow_min_frac has default "nil" and this change is not activated unless the parameter is defined by input.

2. Added parameter "design_spec_OA_name" to pass Design Specification OA object to ATU in order to size VAV minimum flowrate. -Affects hvac-zone.pxt, atu.pxt files -Activated by default

3. Added EMS logic to resolve the following EnergyPlus limitation: UnitarySystemSizing of the no load airflow does not account for ventilation rate when there is a DX coil, so in some cases the no load flow is less than the design ventilation rate. An EMS program is added to fix this for units configured with DX cooling, CONSTANT compressor speed and VARIABLE fan_speed. This may remain an issue for any Unitary systems with multispeed compressors, two-speed fans or other configurations. -Affects unitary.pxt file -Activated if cool_coil_type == "DX-AIR" && dx_comp_speed == "CONSTANT" && fan_speed == "VARIABLE" -EMS program runs after UnitarySizing. It reads the ventilation requirement and the min load flow rate. If the min load flow rate is less than the ventilation requirement, it assigns the ventilation requirement as the new min load flow rate.

• [x] For a new measure, attach a workbook named DEER_EnergyPlus_Modelkit_Measure_list_working.xlsx, containing only rows used for post-processing the measure. No new measure

• [x] Add comments in the code when necessary to facilitate the review process.

• [x] Add a comment before the added code, including the author's full name, company, and specifying if it's a bug fix, new measure, or feature.

• [x] For a new feature or bug, demonstrate the impact on energy consumption for selected cases with justification using plots and descriptions.

Change to default energy consumption:

A. New system types: Results showing the energy consumption for each new system and default system in the 2023 vintage, across CZ01, CZ12 and CZ15 and all prototypes. system-types-results-summary.csv

B. Minimum Flow/Ventilation: For the default system types the minimum flow rate is now set to be at least as high as the ventilation requirement. Testing the 2020 vintage in CZ01, CZ12 and CZ15: for some buildings (EPr, ERC, OfS etc) there is <1% change. For others with higher ventilation requirements, the low turndown was resulting in the building being underventilated and this change is significant. Asm shows a 70% increase in energy consumption. Four buildings show a >10% increase in energy consumption: Asm, MBT, MLI, RSD. Template_Changes_default_results-summary.xlsx

- [x] For a new measure, add a summary table showing total energy consumption per simulated case.

Edits: Feb 22,23: changed from cWVVG to cAVVG. Added efficiency values for existing building HVAC (e.g. COP, motor efficiency, etc.). Updated system-types-results-summary.csv. Removed some unintended changes to example folders.

[Justin-DeBlois]

Thank you for the provided template and prototype improvements. Below are a few comments on the suggested changes.

Regarding the cases with the system type cDXNH, I'm seeking clarification on whether they are intended to have no heating at all or this only applies specifically to the primary heating coils. Additionally, I couldn't locate the definition of this system type on the eTRM table. Could you please direct me to where it's defined?

Furthermore, since you updated cWVVG to cAVVG, please ensure that this change is reflected in section A of your Pull Request description as well.

Thanks for your review, I updated the pull request description.

The cDXNH system is not included in the eTRM. Lake Casco emailed a request to DEER Support to have it added, with more information. It is for systems with no heating at all.

[Justin-DeBlois]

@amine-lazrak I responded to your comments and updated the pull request.

[amine-lazrak]

@Justin-DeBlois one last thing: Since cDXNH models cases with no heating at all, the templates need to be updated to remove reheat coils as well. The way these cases are set up now only removes the main heating coil, I can still see significant space heating energy consumption.

[Justin-DeBlois]

@Justin-DeBlois one last thing: Since cDXNH models cases with no heating at all, the templates need to be updated to remove reheat coils as well. The way these cases are set up now only removes the main heating coil, I can still see significant space heating energy consumption.

The remaining heating is from the ALT and irregularzones systems, the cDXNH systems only serve the main group and don't have reheat coils.

[amine-lazrak]

Thank you for the updates, merging the branch now.