Create Rule23-17.md

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+# Airside System - Rule 23-17  
+
+**Schema Version:** 0.0.34  
+**Mandatory Rule:** TRUE   
+**Rule ID:** 23-1  
+**Rule Description:** System 2 and 4 - Electric air-source heat pumps shall shall be modeled to continue to operate while auxiliary heat is energized.  
+**Rule Assertion:** B-RMR = expected value  
+**Appendix G Section:** Section 23 Air-side  
+**90.1 Section Reference:** G3.1.3.1 Heat Pumps (Systems 2 and 4)  
+**Data Lookup:** None  
+**Evaluation Context:** HVAC System  
+
+**Applicability Checks:**  
+
+1. B-RMR is modeled with at least one air-side system that is Type-2, or 4  
+
+**Function Calls:**  
+
+1. get_baseline_system_types()
+2. baseline_system_type_compare()
+3. get_component_by_id()
+
+**Applicability Checks:**  
+- create a list of the target system types: `APPLICABLE_SYS_TYPES = [HVAC_SYS.SYS_2,HVAC_SYS.SYS_4]`
+- Get B-RMR system types: `baseline_system_types_dict = get_baseline_system_types(B-RMR)`
+
+- loop through the applicable system types: `for target_sys_type in APPLICABLE_SYS_TYPES:`
+    - and loop through the baseline_system_types_dict to check the system types of the baseline systems: `for system_type in baseline_system_types_dict:`
+        - do baseline_system_type_compare to determine whether the baseline_system_type is the applicable_system_type: `if((baseline_system_type_compare(system_type, target_sys_type, false)):`
+            - the systems in the list: baseline_system_types_dict[system_type] are sys-2 or 4 - loop through the list of systems: `for hvac_system_id in baseline_system_types_dict[system_type]:`
+            - `CONTINUE TO RULE LOGIC`
+            - otherwise, rule not applicable: `else: RULE_NOT_APPLICABLE`
+
+**Rule Logic:**  
+- get the hvac system from the hvac_system_id: `hvac_system = get_component_by_id(hvac_system_id)`
+- get the heating system: `heating_system = hvac_system.heating_system`
+- get the heatpump_low_shutoff_temperature = `heatpump_low_shutoff = heating_system.heatpump_low_shutoff_temperature`
+
+**Rule Assertion:**
+- Case 1: The heat pump low shutoff temperature equal to the flag of -999, which indicates that there is no low-temperature shutoff for the heatpump: `if heatpump_low_shutoff <= -999: PASS`
+- Case 2: all other cases: FAIL: `else: FAIL`
+
+**Notes:**
+1.  The minimum temperature is not finalized and is up for discussion.  Must coordinate with the note provided in the schema element: HeatingSystem.heatpump_low_shutoff_temperature
+
+**[Back](../_toc.md)**