diff --git a/custom_components/simple_pid_controller/number.py b/custom_components/simple_pid_controller/number.py
index 2660add..b8cabeb 100644
--- a/custom_components/simple_pid_controller/number.py
+++ b/custom_components/simple_pid_controller/number.py
@@ -67,7 +67,7 @@
         "key": "sample_time",
         "unit": "s",
         "min": 0.01,
-        "max": 600.0,
+        "max": 6000.0,
         "step": 0.01,
         "default": 10.0,
         "entity_category": EntityCategory.CONFIG,
diff --git a/tests/test_number.py b/tests/test_number.py
index 91c1328..5d30d1b 100644
--- a/tests/test_number.py
+++ b/tests/test_number.py
@@ -222,3 +222,15 @@ async def test_control_number_step_defaults(hass, config_entry, desc):
     """Test that ControlParameterNumber falls back to DEFAULT_STEPS when no option is set."""
     num = ControlParameterNumber(hass, config_entry, desc)
     assert num._attr_native_step == DEFAULT_STEPS[desc["key"]]
+
+
+@pytest.mark.usefixtures("setup_integration")
+async def test_sample_time_allows_long_intervals(hass, config_entry):
+    """Sample time must allow long intervals for slow systems (issue #155)."""
+    desc = next(d for d in PID_NUMBER_ENTITIES if d["key"] == "sample_time")
+    assert desc["max"] >= 6000.0
+
+    num = PIDParameterNumber(hass, config_entry, desc)
+    num.async_write_ha_state = lambda: None
+    await num.async_set_native_value(6000.0)
+    assert num.native_value == 6000.0
diff --git a/tests/test_sensor.py b/tests/test_sensor.py
index d7c928a..a0e6ec7 100644
--- a/tests/test_sensor.py
+++ b/tests/test_sensor.py
@@ -420,4 +420,9 @@ async def test_update_pid_adjusts_update_interval(hass, config_entry, monkeypatc
     await coordinator.update_method()
     assert coordinator.update_interval == timedelta(seconds=sample_time)
 
+    # Long sample times for slow (inertial) systems, see issue #155
+    sample_time = 6000
+    await coordinator.update_method()
+    assert coordinator.update_interval == timedelta(seconds=sample_time)
+
     await async_unload_entry(hass, config_entry)