diff --git a/scripts/add_existing_baseyear.py b/scripts/add_existing_baseyear.py
index ff1a3e46..f67c38d9 100644
--- a/scripts/add_existing_baseyear.py
+++ b/scripts/add_existing_baseyear.py
@@ -420,13 +420,13 @@ def add_power_capacities_installed_before_baseyear(n, grouping_years, costs, bas
 
 
 def add_heating_capacities_installed_before_baseyear(
-    n,
-    baseyear,
-    grouping_years,
+    n: pypsa.Network,
+    baseyear: int,
+    grouping_years: list,
     cop: dict,
     time_dep_hp_cop: bool,
-    costs,
-    default_lifetime,
+    costs: pd.DataFrame,
+    default_lifetime: int,
     existing_heating: pd.DataFrame,
 ):
     """
@@ -500,7 +500,7 @@ def add_heating_capacities_installed_before_baseyear(
                     )
                     .to_pandas()
                     .reindex(index=n.snapshots)
-                    if options["time_dep_hp_cop"]
+                    if time_dep_hp_cop
                     else costs.at[costs_name, "efficiency"]
                 )
 
diff --git a/scripts/definitions/heat_system.py b/scripts/definitions/heat_system.py
index 2f305644..b907b0fe 100644
--- a/scripts/definitions/heat_system.py
+++ b/scripts/definitions/heat_system.py
@@ -212,6 +212,7 @@ class HeatSystem(Enum):
         """
         Generates the name for the heat pump costs based on the heat source and
         system.
+        Used to retrieve data from `technology-data <https://github.com/PyPSA/technology-data>`.
 
         Parameters
         ----------
@@ -230,6 +231,7 @@ class HeatSystem(Enum):
         """
         Generates the name for the resistive heater costs based on the heat
         system.
+        Used to retrieve data from `technology-data <https://github.com/PyPSA/technology-data>`.
 
         Returns
         -------
@@ -242,6 +244,7 @@ class HeatSystem(Enum):
     def gas_boiler_costs_name(self) -> str:
         """
         Generates the name for the gas boiler costs based on the heat system.
+        Used to retrieve data from `technology-data <https://github.com/PyPSA/technology-data>`.
 
         Returns
         -------
@@ -254,6 +257,7 @@ class HeatSystem(Enum):
     def oil_boiler_costs_name(self) -> str:
         """
         Generates the name for the oil boiler costs based on the heat system.
+        Used to retrieve data from `technology-data <https://github.com/PyPSA/technology-data>`.
 
         Returns
         -------
diff --git a/scripts/prepare_sector_network.py b/scripts/prepare_sector_network.py
index d9d0f6e3..585b3f25 100644
--- a/scripts/prepare_sector_network.py
+++ b/scripts/prepare_sector_network.py
@@ -1780,7 +1780,7 @@ def build_heat_demand(n):
         .unstack(level=1)
     )
 
-    sectors = ["residential", "services"]
+    sectors = [sector.value for sector in HeatSector]
     uses = ["water", "space"]
 
     heat_demand = {}
@@ -1808,10 +1808,21 @@ def build_heat_demand(n):
     return heat_demand
 
 
-def add_heat(n, costs, cop):
+def add_heat(n: pypsa.Network, costs: pd.DataFrame, cop: xr.DataArray):
+    """
+    Add heat sector to the network.
+
+    Parameters:
+        n (pypsa.Network): The PyPSA network object.
+        costs (pd.DataFrame): DataFrame containing cost information.
+        cop (xr.DataArray): DataArray containing coefficient of performance (COP) values.
+
+    Returns:
+        None
+    """
     logger.info("Add heat sector")
 
-    sectors = ["residential", "services"]
+    sectors = [sector.value for sector in HeatSector]
 
     heat_demand = build_heat_demand(n)
 
@@ -3113,27 +3124,23 @@ def add_industry(n, costs):
     if options["oil_boilers"]:
         nodes = pop_layout.index
 
-        for name in [
-            "residential rural",
-            "services rural",
-            "residential urban decentral",
-            "services urban decentral",
-        ]:
-            n.madd(
-                "Link",
-                nodes + f" {name} oil boiler",
-                p_nom_extendable=True,
-                bus0=spatial.oil.nodes,
-                bus1=nodes + f" {name} heat",
-                bus2="co2 atmosphere",
-                carrier=f"{name} oil boiler",
-                efficiency=costs.at["decentral oil boiler", "efficiency"],
-                efficiency2=costs.at["oil", "CO2 intensity"],
-                capital_cost=costs.at["decentral oil boiler", "efficiency"]
-                * costs.at["decentral oil boiler", "fixed"]
-                * options["overdimension_individual_heating"],
-                lifetime=costs.at["decentral oil boiler", "lifetime"],
-            )
+        for heat_system in HeatSystem:
+            if not heat_system == HeatSystem.URBAN_CENTRAL:
+                n.madd(
+                    "Link",
+                    nodes + f" {heat_system} oil boiler",
+                    p_nom_extendable=True,
+                    bus0=spatial.oil.nodes,
+                    bus1=nodes + f" {heat_system} heat",
+                    bus2="co2 atmosphere",
+                    carrier=f"{heat_system} oil boiler",
+                    efficiency=costs.at["decentral oil boiler", "efficiency"],
+                    efficiency2=costs.at["oil", "CO2 intensity"],
+                    capital_cost=costs.at["decentral oil boiler", "efficiency"]
+                    * costs.at["decentral oil boiler", "fixed"]
+                    * options["overdimension_individual_heating"],
+                    lifetime=costs.at["decentral oil boiler", "lifetime"],
+                )
 
     n.madd(
         "Link",